# Programar con gtkmm 3

## Introducción

### Este libro

Este libro explica conceptos clave sobre la API gtkmm de C++ para la creación de interfaces de usuario. También introduce los elementos principales de la interfaz de usuario («widgets»). A pesar de que se hace mención a las clases, constructores y métodos, estas no se explican en gran detalle. Por lo tanto, para obtener información completa sobre la API, diríjase a los enlaces en la documentación de referencia.

Este libro asume un buen entendimiento sobre C++, y cómo crear programas en C++.

Nos encantaría que nos informara sobre cualquier problema que encuentre aprendiendo gtkmm con este documento, y apreciaríamos cualquier información sobre mejoras en el mismo. Consulte la sección contribuir para obtener más información.

### gtkmm

gtkmm es un envoltorio de C++ para GTK+, una biblioteca usada para crear interfaces gráficas de usuario. Esta liberado bajo la licencia LGPL, para que pueda desarrollar software abierto, software gratuito o software comercial usando gtkmm sin comprar ninguna licencia.

gtkmm fue originalmente llamado gtk-- debido a que GTK+ ya tenía el signo + en el nombre. Sin embargo, debido a que -- no puede ser indexado fácilmente en los motores de búsqueda, el paquete fue generalmente llamado gtkmm, y eso fue con lo que nos quedamos.

#### ¿Por qué usar gtkmm en vez de GTK+?

gtkmm le permite escribir código usando técnicas normales de C++ tales como encapsulación, derivación y polimorfismo. Como programador de C++, probablemente ya se habrá dado cuenta de que esto conlleva a un código mas limpio y mejor organizado.

gtkmm es más seguro, por lo que el compilador puede detectar errores que sólo pudieran detectarse durante ejecución al usar C. Este uso de tipos específicos también hace la API más limpia debido a que puede ver qué tipos deberían usarse con sólo mirar la declaración de un método.

Se puede hacer uso de herencia para derivar nuevos widgets. Derivar nuevos widgets en código C GTK+ es tan complicado y propenso a errores que casi ningún codificador de C lo hace. Como programador en C++ usted sabe que la derivación es una técnica orientada a objetos esencial.

Pueden usarse instancias de miembros, simplificando la gestión de memoria. Todos los widgets C GTK+ son tratados usando punteros. Como programador en C++ usted sabe que los punteros deben evitarse siempre que sea posible.

gtkmm implica menos código en comparación con GTK+, el cual usa nombres de funciones prefijadas y muchos macros.

#### gtkmm comparado con Qt

Qt de Trolltech es el competidor más cercano de gtkmm, por lo que merece discusión.

Los desarrolladores de gtkmm tienden a preferir gtkmm antes que a Qt porque gtkmm es funcionalmente similar a C++. Qt se originó en un momento en que C++ y la biblioteca estándar no estaban estandarizados o bien no contaban con un buen soporte de los compiladores. Es por ello que en la actualidad se encuentran mucho material duplicado en la biblioteca estándar, tales como contenedores e información de tipo. Lo más relevante es que Trolltech ha modificado el lenguaje C + + para proporcionar señales, por lo que las clases de Qt no se pueden utilizar fácilmente con clases de otras bibliotecas. gtkmm fue capaz de utilizar C++ estándar para proporcionar señales sin necesidad de cambiar el lenguaje C++. Consulte las preguntas frecuentes para conocer las diferencias de manera detallada.

#### gtkmm es un envoltorio

gtkmm no es un kit de herramientas nativo de C++, pero si es un envoltorio C++ de un conjunto de herramientas de C. Esta separación de la interfaz e implementación tiene sus ventajas. Los desarrolladores de gtkmm pasan la mayor parte de su tiempo hablando sobre cómo gtkmm puede presentar una API lo mas clara posible, sin compromisos incómodos debido a oscuros detalles técnicos. Nosotros contribuimos un poco a al código fuente subyacente de GTK+, pero también lo hacen los programadores de C, los programadores de Perl, los programadores de Python, etc. Por ello, GTK+ se beneficia de una base de usuarios de mayor proporción que el lenguaje de herramientas específicas; hay más desarrolladores, más personas que prueban software en desarrollo, y más usuarios.

## Instalación

### Dependecias

Antes de intentar instalar gtkmm 3.0, probablemente deba instalar primero estos otros paquetes.

- libsigc++ 2.0

- GTK+ 3.0

- cairomm

- pangomm

- atkmm

Estas dependencias tienen sus propias dependencias, incluyendo las siguientes aplicaciones y bibliotecas:

- pkg-config

- glib

- ATK

- Pango

- cairo

- gdk-pixbuf

### Unix y Linux

#### Paquetes preconstruidos

Las versiones recientes de gtkmm se empaquetan en casi todas las distribuciones principales de Linux actualmente. Si usted utiliza Linux, es probable que pueda empezar a trabajar con gtkmm instalando el paquete desde el repositorio oficial para su distribución Linux. Las distribuciones que cuentan con gtkmm en sus repositorios son Debian, Ubuntu, Red Hat, Fedora, Mandriva, Suse, y muchas otras.

Los nombres de los paquetes de gtkmm varían de distribución en distribución (por ejemplo, libgtkmm3.0-dev en Debian y en Ubuntu o gtkmm30-devel en Red Hat Fedora), por lo que se recomienda consultar el nombre del paquete correcto en el gestor de paquetes de su distribución para instalarlo como lo haría con cualquier otro paquete.

Los nombres de los paquetes no cambiarán cuando se libere la nueva API/ABI compatible con versiones de gtkmm. De lo contrario, no sería una API/ABI compatible. Así que no se sorprenda, por ejemplo, de encontrar gtkmm 3.2 suministrado por el paquete libgtkmm3.0-dev de Debian.

#### Instalar desde las fuentes

Si su distribución no proporciona un paquete gtkmm pre-construido, o si desea instalar una versión diferente a la proporcionada por su distribución, también puede instalar gtkmm desde las fuentes. El código fuente para gtkmm se puede descargar desde .

Después de haber instalado todas las dependencias, descargue el código fuente de gtkmm, descomprímalo y cámbiese a la carpeta creada. gtkmm se puede construir e instalar con la siguiente secuencia de comandos:

    # ./configure
    # make
    # make install

Recuerde que en un sistema Unix o Linux, probablemente tendrá que ser `root` para instalar el software. El comando `su` le permitirá introducir la contraseña de `root`para tener el acceso de `root` temporalmente.

El script `configure` hará comprobaciones para asegurarse de que todas las dependencias necesarias ya están instaladas. Si le falta alguna dependencia, terminará y mostrará un error.

De manera predeterminada, gtkmm se instalará en la carpeta `/usr/local`, En algunos sistemas es posible que necesite instalar en una ubicación diferente. Por ejemplo, en sitemas Red Hat Linux puede utilizar la opción `--prefix` , de este modo:

    # ./configure --prefix=/usr

Debe tener mucho cuidado al instalar en prefijos estándar del sistema, como `/usr`. Las distribuciones de Linux instalan paquetes de software en `/usr`, por lo que instalar un paquete de fuentes en este prefijo puede corromper o crear un conflicto con el software instalado usando el sistema de gestión de paquetes de su distribución. De manera ideal, debería usar un prefijo separado para todo el software que instale desde las fuentes.

Si quiere ayudar al desarrollo de gtkmm o experimentar con nuevas características, puede instalar gtkmm desde git. La mayoría de los usuarios nunca tendrán que hacer esto, pero si está interesado en involucrarse directamente con el desarrollo de gtkmm, consulte el apéndice Trabajando con el código fuente de gtkmm.

### Microsoft Windows

GTK+ y gtkmm están diseñados para funcionar correctamente con Microsoft Windows, y los desarrolladores fomentan su uso en la plataforma win32. Sin embargo, Windows no tiene un sistema de instalación estándar para las bibliotecas de desarrollo. Si quiere obtener instrucciones y notas para una instalación específica de Windows consulte la página Instalación en Windows.

## Conceptos básicos

En este capítulo se presentan algunos de los aspectos más importantes de la codificación gtkmm. Que se validarán con un ejemplo de trabajo de código. Sin embargo, esta es sólo una pequeña muestra, por lo que es necesario leer otros capítulos para obtener más información importante.

Conocer C++ le ayudará con gtkmm como lo haría con cualquier otra biblioteca. A menos que se indique lo contrario, el comportamiento de las clases de gtkmm será como el de cualquier otra clase C++, de manera que podrá utilizar sus actuales técnicas de C++ con las clases de gtkmm.

### Ejemplo simple

Para iniciar nuestra introducción a gtkmm, vamos a empezar con el programa más simple posible. Este programa va a crear una ventana vacía de 200 x 200 píxeles.

Código fuente

File: `base.cc` (For use with gtkmm 3, not gtkmm 2)

    #include <gtkmm.h>

    int main(int argc, char *argv[])
    {
      Glib::RefPtr<Gtk::Application> app =
        Gtk::Application::create(argc, argv,
          "org.gtkmm.examples.base");

      Gtk::ApplicationWindow window;

      return app->run(window);
    }

Ahora se explicará cada línea del ejemplo

    #include <gtkmm.h>

Todos los programas gtkmm deben incluir ciertas cabeceras gtkmm: `gtkmm.h` incluye el kit completo de gtkmm. Esto no suele ser una buena idea, ya que incluye casi un megabyte de cabeceras, pero para programas sencillos, basta.

La siguiente línea:

    Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.examples.base");

crea un objeto `Gtk::Application`, almacenado en un puntero inteligente `RefPtr`. Esto es necesario en todas las aplicaciones gtkmm. El método «create()» de este objeto inicializa gtkmm y verifica los argumentos pasados a su aplicación en la línea de comandos, buscando opciones estándar tales como `-display`. Toma estos argumentos de la lista, dejándole cualquier cosa que no reconozca para que su aplicación la procese o la ignore. Esto asegura que todas las aplicaciones gtkmm acepten el mismo conjunto de argumentos estándar.

Las dos siguientes líneas de código crean y muestran una ventana:

    Gtk::Window window;

La última línea muestra la ventana y entra al bucle principal de gtkmm, que terminará cuando la ventana se cierre. Su función «main()» entonces retornará con un éxito apropiado o un código de error.

    return app->run(window);

Después de poner el código fuente en `simple.cc` puede compilar el programa anterior con gcc usando:

    g++ simple.cc -o simple `pkg-config gtkmm-3.0 --cflags --libs`

Tenga en cuenta que debe poner la invocación `pkg-config` entre apóstrofes. Los apóstrofes permite a la shell ejecutar el comando dentro de ellos, y utilizar la salida de comando como parte de la línea de comando.

### Cabeceras y enlazado

A pesar de que hemos mostrado el comando de compilación para el ejemplo simple, en realidad debería usar las herramientas automake y autoconf, como se describe en «Autoconf, Automake, Libtool», por G. V. Vaughan y otros. Los ejemplos utilizados en este libro se incluyen en el paquete gtkmm, con archivos de construcción apropiados, por lo que no mostraremos los comandos de construcción en el futuro. Sólo tendrá que encontrar la carpeta adecuada e introducir `make`.

Para simplificar la compilación, se usa `pkg-config`, que está presente en todas las instalaciones correctas de gtkmm. Este programa «sabe» qué opciones de compilación son necesarias para compilar los programas que usan gtkmm. La opción `--cflags` hace que `pkg-config` devuelva la lista de carpetas en las que el compilador buscará los archivos de cabecera; la opción `--libs` solicita la lista de bibliotecas a las que el compilador enlazará y las carpetas en las que encontrarlas. Intente ejecutarlo desde su intérprete de comandos para ver los resultados en su sistema.

Sin embargo, es aún más simple cuando se utiliza la macro `PKG_CHECK_MODULES()` en un archivo estándar configure.ac con autoconf y automake. Por ejemplo:

    PKG_CHECK_MODULES([MYAPP], [gtkmm-3.0 >= 3.0.0])

Esto comprueba la presencia de gtkmm y define MYAPP_LIBS y MYAPP_CFLAGS para su uso en los archivos Makefile.am.

gtkmm-3.0 es el nombre de la API estable actual. Hubo una API más antigua llamada gtkmm-2-4 que se instalará en paralelo cuando está disponible. Hubo varias versiones de gtkmm-2.4, tales como gtkmm 2.10 y habrá varias versiones de la API gtkmm-3.0. Tenga en cuenta que el nombre de la API no cambia para todas las versiones, porque esto implicaría una API incompatible y una ABI rota. Teóricamente, podría haber un futura API gtkmm-4.0 que se instalaría en paralelo con gtkmm-3.0 sin afectar las aplicaciones existentes.

Tenga en cuenta que si menciona módulos adicionales, además de gtkmm-3.0, deben estar separados por espacios, no por comas.

Openismus tiene más ayuda básica con automake y autoconf

### Widgets

Las aplicaciones gtkmm están compuestas por ventanas, estas a su vez contienen widgets, tales como botones y cuadros de texto. En algunos otros sistemas, los widgets se llaman «controles». Hay un objeto C++ en el código de la aplicación para cada widget contenido en las ventanas de una aplicación. Sólo debe llamar a un método de la clase widget para afectar al widget visible.

Los widgets se ordenan dentro de widgets contenedores como marcos y cuardenos de notas, en una jerarquía de widgets dentro de widgets. Algunos de estos widgets contenedores, como `Gtk::Grid` no son visibles: sólo existen para ordenar otros widgets. Aquí hay un código de ejemplo que añade dos widgets `Gtk::Button` a un widget contenedor `Gtk::Box`:

    m_box.pack_start(m_Button1);
    m_box.pack_start(m_Button2);

y aquí se muestra cómo agregar el `Gtk::Box`, conteniendo esos botones, a un `Gtk::Frame`, que tiene un cuadro y título visibles:

    m_frame.add(m_box);

La mayoría de los capítulos de este libro tratan de widgets específicos. Consulte la sección Widgets contenedores para obtener más detalles sobre de cómo agregar widgets a widgets contenedores.

Aunque se puede especificar el diseño y apariencia de las ventanas y widgets con código C++, es probable que resulte más conveniente usar `Glade` para el diseño de la interfaz de usuario y cargarlos en tiempo de ejecución con `Gtk::Builder`. Consulte el capítulo Glade y Gtk::Builder.

A pesar de que las instancias de widgets gtkmm tienen ámbito y duración de la misma manera que otras clases de C++, gtkmm tiene una característica opcional para ahorrar tiempo que verá en algunos de los ejemplos. `Gtk::manage()` le permite decir que un widget hijo es propiedad del contenedor en el que lo ubica. Esto le permite utilizar `new` en el widget, añadirlo al contenedor, y olvidarse de eliminarlo. Puede aprender más de las técnicas de gestión de memoria de gtkmm en el capítulo de gestión de memoria.

### Señales

gtkmm, como la mayoría de kits de herramientas de la IGU, está dirigido por eventos. Cuando ocurre un evento, como la pulsación de un botón del ratón sobre un widget, éste emitirá la señal apropiada. Cada widget puede emitir un conjunto de señales diferente. Para hacer que la pulsación de un botón resulte en una acción, establecemos un manejador de señales para atrapar la señal «clicked» del botón.

gtkmm usa la biblioteca libsigc++ para implementar señales. Aquí hay una línea de código de ejemplo que conecta una señal «clicked» de Gtk::Button a un manejador de señales llamado «on_button_clicked»:

    m_button1.signal_clicked().connect( sigc::mem_fun(*this,
      &HelloWorld::on_button_clicked) );

Para obtener información más detallada acerca de señales, consulte el apéndice.

Para obtener información acerca de la implementación de sus propias señales en vez de sólo conectar a las señales existentes de gtkmm, consulte el apéndice.

### Glib::ustring

Puede sorprenderle aprender que gtkmm no utiliza `std::string` en sus interfaces. En cambio, usa `Glib::ustring`, que es tan similar y discreto que en realidad puede pretender que cada Glib::ustring es un `std::string` e ignorar el resto de esta sección. Pero siga leyendo si quiere aplicar otros lenguajes además del inglés en su aplicación.

std::string utiliza 8 bits por carácter, pero 8 bits no son suficientes para codificar lenguajes como árabe, chino y japonés. A pesar de que las codificaciones de estos lenguajes ahora las ha especificado el Consorcio Unicode, los lenguajes C y C++ todavía no proporcionan ningún soporte Unicode estándar. GTK+ y GNOME eligen implementar Unicode usando UTF-8, y eso es lo que está envuelto en Glib::ustring. Proporciona casi exactamente la misma interfaz que std::string, además de conversiones automáticas desde y hacia std::string.

Uno de los beneficios de UTF-8 es que no necesita usarlo a menos que quiera, por lo que no necesita reconvertir todo su código de una vez. `std::string` todavía funcionará para cadenas de 7 bits ASCII. Pero cuando intente localizar su aplicación para lenguajes como chino, por ejemplo, empezará a ver errores extraños y posibles fallos. Entonces, todo lo que necesitará hacer es empezar a utilizar `Glib::ustring` en su lugar.

tenga en cuenta que UTF-8 no es compatible con codificaciones de 8 bits como ISO-8859-1. Por ejemplo, las diéresis alemanas no están en el rango ASCII y necesitan más de un byte en la codificación UTF-8. Si su código contiene cadenas literales de 8 bits, debe convertirlas a UTF-8 (por ejemplo, el saludo bávaro «Grüß Gott» sería «Gr\xC3\xBC\xC3\x9F Gott»).

Evite la aritmética de punteros al estilo C, y funciones como strlen(). En UTF-8, cada carácter podría necesitar entre 1 y 6 bytes, por lo que no es posible asumir que el próximo byte es otro carácter. `Glib::ustring` se ocupa de estos detalles, por lo que puede usar métodos como Glib::ustring::substr() y seguir pensando en términos de caracteres en vez de bytes.

A diferencia de la solución Unicode de Windows UCS-2, esto no requiere ninguna opción especial de compilación para procesar cadenas literales, y no resulta en que los ejecutables y bibliotecas Unicode sean incompatibles con las ASCII.

Referencia

Para obtener más información acerca de cómo proporcionar cadenas literales UTF-8, consulte la sección Internacionalización.

### Tipos intermedios

Algunas API relacionadas con gtkmm utilizan contenedores de datos intermedios, como `Glib::StringArrayHandle`, en vez de un contenedor específico estándar de C++ como `std::vector` o `std::list`, a pesar de que gtkmm en sí mismo ahora sólo usa `std::vector` desde gtkmm 3.0.

No declare estos tipos usted mismo. Utilice, en cambio, el contenedor estándar C++ que prefiera. glibmm hará la conversión. Aquí hay algunos de estos tipos intermedios:

- `Glib::StringArrayHandle` o `Glib::ArrayHandle<Glib::ustring>`: usan `std::vector<Glib::ustring>`, `std::list<Glib::ustring>`, `const char*[]`, etc.

- `Glib::ListHandle<Gtk::Widget*>`: usa `std::vector<Gtk::Widget*>`, `std::list<Gtk::Widget*>`, etc.

- `Glib::SListHandle<Gtk::Widget*>`: usa `std::vector<Gtk::Widget*>`, `std::list<Gtk::Widget*>`, etc.

### Mezclando las API de C y C++

Puede usar las API de C que no tengan todavía interfaces C++ convenientes. Generalmente no es un problema usar las API de C desde C++, y gtkmm le ayuda proporcionándole acceso al objeto C subyacente y una forma fácil de crear un objeto C++ envoltorio desde un objeto C, si la API de C también está basada en el sistema GObject.

Para usar una instancia de gtkmm con una función C que requiere una instancia GObject C, use la función `gobj()` para obtener un puntero a la instancia GObject subyacente. Por ejemplo

    Gtk::Button* button = new Gtk::Button("example");
    gtk_button_do_something_new(button->gobj());

Para obtener una instancia gtkmm desde una instancia C GObject, use la función Glib::wrap(). Por ejemplo

    GtkButton* cbutton = get_a_button();
    Gtk::Button* button = Glib::wrap(cbutton);

### «Hola mundo» en gtkmm

Ahora ha aprendido lo suficiente para ver un ejemplo real. De acuerdo con una antigua tradición de la informática, se introducirá la aplicación Hola Mundo en gtkmm:

Código fuente

File: `helloworld.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLE_HELLOWORLD_H
    #define GTKMM_EXAMPLE_HELLOWORLD_H

    #include <gtkmm/button.h>
    #include <gtkmm/window.h>

    class HelloWorld : public Gtk::Window
    {

    public:
      HelloWorld();
      virtual ~HelloWorld();

    protected:
      //Signal handlers:
      void on_button_clicked();

      //Member widgets:
      Gtk::Button m_button;
    };

    #endif // GTKMM_EXAMPLE_HELLOWORLD_H

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "helloworld.h"
    #include <gtkmm/application.h>

    int main (int argc, char *argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      HelloWorld helloworld;

      //Shows the window and returns when it is closed.
      return app->run(helloworld);
    }

File: `helloworld.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "helloworld.h"
    #include <iostream>

    HelloWorld::HelloWorld()
    : m_button("Hello World")   // creates a new button with label "Hello World".
    {
      // Sets the border width of the window.
      set_border_width(10);

      // When the button receives the "clicked" signal, it will call the
      // on_button_clicked() method defined below.
      m_button.signal_clicked().connect(sigc::mem_fun(*this,
                  &HelloWorld::on_button_clicked));

      // This packs the button into the Window (a container).
      add(m_button);

      // The final step is to display this newly created widget...
      m_button.show();
    }

    HelloWorld::~HelloWorld()
    {
    }

    void HelloWorld::on_button_clicked()
    {
      std::cout << "Hello World" << std::endl;
    }

Intente compilarla y ejecutarla antes de continuar. Debería ver algo así:

#### Hello World

Fascinante, ¿verdad? Examinemos el código. Primero, la clase `HelloWorld`:

    class HelloWorld : public Gtk::Window
    {

    public:
      HelloWorld();
      virtual ~HelloWorld();

    protected:
      //Signal handlers:
      virtual void on_button_clicked();

      //Member widgets:
      Gtk::Button m_button;
    };

Esta clase implementa la ventana «Hello World». Deriva de `Gtk::Window` y tiene un único `Gtk::Button` como miembro. Se eligió usar el constructor para realizar todo el trabajo de inicialización de la ventana, incluyendo establecer las señales. Aquí está, sin los comentarios:

    HelloWorld::HelloWorld()
    :
      m_button ("Hello World")
    {
      set_border_width(10);
      m_button.signal_clicked().connect(sigc::mem_fun(*this,
        &HelloWorld::on_button_clicked));
      add(m_button);.
      m_button.show();
    }

Tenga en cuenta que se ha usado una declaración de inicialización para darle al objeto `m_button` la etiqueta «Hello World».

A continuación, llamamos al método `set_border_width()` de la ventana. Esto establece el tamaño del espacio entre los lados de la ventana y el widget que contiene.

Luego, se le engancha un manejador de señales a la señal `clicked` de `m_button`. Esto imprime nuestro amigable saludo a `stdout`.

A continuación usamos el método `add()` de la ventana para situar el `m_button` en ella. (`add()` deriva de `Gtk::Container`, que se describe en el capítulo sobre widgets contenedores). El método `add()` ubica al widget en la ventana, pero no lo muestra. Los widgets de gtkmm siempre son invisibles cuando se crean: para mostrarlos, debe llamar a su método `show()`, que es lo que se hace en la siguiente línea.

Ahora eche un vistazo a la función `main()` del programa. Aquí está, sin comentarios:

    int main(int argc, char** argv)
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      HelloWorld helloworld;
      return app->run(helloworld);
    }

Primero, se instancia un objeto almacenado en un puntero inteligente `RefPtr` llamado `app`. Éste es del tipo `Gtk::Application`. Cada programa de gtkmm debe tener uno de estos. Le pasamos nuestros argumentos de línea de comandos a su método «create()». Toma los argumentos que quiere, y le deja el resto, como se ha descrito anteriormente.

A continuación, se crea un objeto de la clase `HelloWorld`, cuyo constructor no toma argumentos, pero todavía no es visible. Cuando se llama a Gtk::Application::run(), pasándole la ventana «helloworld», la muestra y comienza el bucle de eventos de gtkmm. Durante el bucle, gtkmm espera las acciones del usuario, y responde apropiadamente. Cuando el usuario cierre la ventana, «run()» retornará, haciendo que la última línea de nuestra función «main()» se ejecute. Entonces, la aplicación finalizará.

## Cambios en gtkmm 3

gtkmm-3.0 es una versión nueva de la API gtkmm que se instala en paralelo con la API gtkmm-2.4, más vieja. La última versión de la API gtkmm-2.4 fue gtkmm 2.24. gtkmm 3 no tiene diferencias fundamentales importantes con respecto a gtkmm 2, pero hace varios cambios pequeños que no fueron posibles mientras se mantenía la compatibilidad de los binarios. Si nunca ha usado la API gtkmm-2.4, entonces puede ignorar con seguridad este capítulo.

La biblioteca de gtkmm 3 se llama `libgtkmm-3.0`, en vez de `libgtkmm-2.4` e instala sus archivos de cabecera en una carpeta versionada similarmente, por lo que su verificación pkg-config debería buscar `gtkmm-3.0` en vez de `gtkmm-2.4`.

gtkmm 3 añadió algunas clases nuevas:

1. `Gtk::AppChooser`, `Gtk::AppChooserButton`, `Gtk::AppChooserDialog` permiten al usuario seleccionar una aplicación instalada para abrir un determinado tipo de contenido.

2. `Gtk::Grid` es un widget contenedor nuevo que eventualmente remplazará a `Gtk::Box`. Ordena a sus hijos de acuerdo a sus propiedades en lugar de sus propios detalles de disposición.

3. `Gtk::Switch` muestra los estados Encendido/Apagado más explícitamente que `Gtk::CheckBox`. Puede ser útil, por ejemplo, al permitir a los usuarios activar hardware.

gtkmm 3 también hizo varios cambios pequeños a la API, que probablemente encontrará cuando porte código que usaba gtkmm-2.4. Aquí hay una lista corta:

1. `Gtk::CellLayout`, usada por `Gtk::IconView`, `Gtk::TreeView::Column` y `Gtk::ComboBox` ahora tiene una `Gtk::CellArea`, que puede usarse para especificar más detalles acerca de cómo las `CellRenderer` se ordenan y alinean.

2. Gtk::ComboBox ahora deriva de CellLayout, permitiendo una disposición y alineación más fácil de sus `Gtk::CellRenderer`.

3. `Gtk::Adjustment`, `IconSet` y `Gdk::Cursor` se usan ahora a través de `Glib::RefPtr`.

4. `Gtk::Box`, `Gtk::ButtonBox`, `Gtk::IconView`, `Gtk::Paned`, `Gtk::ProgressBar`, `Gtk::ScaleButton`, `Gtk::Scrollbar` y `Gtk::Separator` ahora derivan de `Gtk::Orientable`, permitiendo especificar su orientación (vertical u horizontal) sin requerir el uso de una clase derivada como `Gtk::HBox`.

5. `Gtk::IconView`, `Gtk::TextView`, `Gtk::TreeView` y otros widgets derivan de Scrollable en vez de tener sus propios métodos como `get_vadjustment()` y su propia señal set_scroll_adjustments.

6. `Gtk::Style` y `Gtk::Rc` se quitaron y se reemplazaron por `Gtk::StyleContext`, y `Gtk::StyleProvider`, así como `Gtk::CssProvider`.

7. Widget::on_expose_event() se reemplazó por Widget::on_draw(), que asume que cairomm se usa para dibujar, a través del `Cairo::Context` provisto y no requiere que llame a `Cairo::Context::clip()`.

8. `Gdk::RGBA` reemplaza a `Color`, añadiendo un componente alfa para la opacidad. `Colormap` se eliminó, junto con su molesto uso para asignar colores.

9. `Gdk::Pixmap` y `Gdk::Bitmap` se eliminaron en favor de `Gdk::Pixbuf`.

10. `Gdk::Drawable` se quitó, y sus métodos se movieron a `Gdk::Window`.

11. Ahora se usa std::vector en muchos métodos en vez de los tipos intermedios *Handle para hacer a la API más clara.

Toda la API obsoleta se quitó en gtkmm 3.0, sin embargo, se marcarán más partes como obsoletas en versiones futuras.

Como un primer paso para portar su código fuente a gtkmm-3.0, probablemente deba asegurarse de que su aplicación se construye con la API obsoleta gtkmm-2.4 desactivada, definiendo una macro como GTK_DISABLE_DEPRECATED. Hay algunas macros de autotools que le pueden ayudar con esto mediante su definición opcional en tiempo de construcción. Consulte la página de la wiki de portar de gtkmm 3 para obtener más detalles.

## Botones

gtkmm proporciona cuatro tipos básicos de botones:

Pulsadores

- `Gtk::Button`. Botones estándar, normalmente marcados con una etiqueta o imagen. Presionar uno desencadena una acción. Consulte la sección botón.

Botones conmutables

- `Gtk::ToggleButton`. A diferencia de un botón normal, que baja y sube en la misma pulsación, un botón conmutable se queda abajo hasta que lo vuelve a presionar. Puede ser útil como conmutador de encendido/apagado. Consulte la sección botón conmutador.

Casillas de verificación

- `Gtk::CheckButton`. Estos actúan como botones conmutadores, pero muestran su estado en pequeños cuadrados, con su etiqueta a un lado. Los puede usar en la mayoría de las situaciones que requieren una configuración de encendido/apagado. Consulte la seccióncasilla de verificación.

Botones de radio

- `Gtk::RadioButton`. Su nombre proviene de los selectores de estación en las antiguas radios de coches. Estos botones se usan en grupos para opciones que se excluyen mutuamente. Pulsar uno de ellos hace que los otros botones de su grupo se apaguen. Son similares a las casillas de verificación (un pequeño widget con una etiqueta a un lado), pero normalmente se ven diferentes. Consulte la sección botón de radio.

Tenga en cuenta que, debido a sistema de tema de GTK+, las apariencia de estos widgets variará. En el caso de las casillas y de los botones de radio, variará considerablemente.

### Botón

#### Constructores

Hay dos maneras de crear un botón. Puede especificar una etiqueta en el constructor de `Gtk::Button`, o establecerla más tarde con `set_label()`.

Para definir un atajo para la navegación por teclado, ponga un guión bajo antes de uno de los caracteres y especifique `true` para el parámetro opcional `mnemonic`. Por ejemplo:

    Gtk::Button* pButton = new Gtk::Button("_Something", true);

Siempre que sea posible, debe usar elementos del almacén («stock»), para asegurar la consistencia con otras aplicaciones, y mejorar la apariencia de sus aplicaciones mediante los iconos. Por ejemplo,

    Gtk::Button* pButton = new Gtk::Button(Gtk::Stock::OK);

. Esto usará texto estándar, en todos los lenguajes, con atajos estándar, con un icono estándar.

`Gtk::Button` también es un contenedor, por lo que puede poner otro widget, como un `Gtk::Image` dentro de él.

Referencia

#### Ejemplo

Este ejemplo crea un botón con una imagen y una etiqueta.

##### ejemplo de botones

Código fuente

File: `buttons.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLE_BUTTONS_H
    #define GTKMM_EXAMPLE_BUTTONS_H

    #include <gtkmm/window.h>
    #include <gtkmm/button.h>

    class Buttons : public Gtk::Window
    {
    public:
      Buttons();
      virtual ~Buttons();

    protected:
      //Signal handlers:
      void on_button_clicked();

      //Child widgets:
      Gtk::Button m_button;
    };

    #endif //GTKMM_EXAMPLE_BUTTONS_H

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "buttons.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      Buttons buttons;

      //Shows the window and returns when it is closed.
      return app->run(buttons);
    }

File: `buttons.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "buttons.h"
    #include <iostream>

    Buttons::Buttons()
    {
      m_button.add_pixlabel("info.xpm", "cool button");

      set_title("Pixmap'd buttons!");
      set_border_width(10);

      m_button.signal_clicked().connect( sigc::mem_fun(*this,
                  &Buttons::on_button_clicked) );

      add(m_button);

      show_all_children();
    }

    Buttons::~Buttons()
    {
    }

    void Buttons::on_button_clicked()
    {
      std::cout << "The Button was clicked." << std::endl;
    }

#### Señales

El widget `Gtk::Button` tiene las siguientes señales, pero la mayor parte del tiempo sólo manejara la señal `clicked`:

`pressed`

- Emitida cuando se pulsa el botón.

`released`

- Emitida cuando se suelta el botón.

`clicked`

- Emitida cuando el botón se pulsa y se suelta.

`enter`

- Emitida cuando se mueve el puntero del ratón sobre el botón de la ventana.

`leave`

- Emitida cuando el puntero del ratón sale del botón de la ventana.

### Botón Conmutable

Los `ToggleButton` son como los `Button` normales, pero cuando se pulsan quedan activados, o presionados, hasta que se vuelvan a pulsar.

Para recuperar el estado de un `ToggleButton`, puede usar el método `get_active()`. Esto devuelve `true` si el botón está «abajo». También puede establecer el estado del botón conmutador con `set_active()`. Tenga en cuenta que, si hace esto, y el estado efectivamente cambia, hace que se emita la señal «clicked». Esto normalmente será lo que quiera.

Puede usar el método `toggled()` para conmutar el botón, en vez de forzarlo a estar arriba o abajo: esto conmuta el estado del botón, y hace que se emita la señal `toggled`.

`Gtk::ToggleButton` es más útil como clase base para las clases `Gtk::CheckButton` y `Gtk::RadioButton`.

Referencia

### Casilla de verificación

`Gtk::CheckButton` hereda de `Gtk::ToggleButton`. La única diferencia real entre ambos es la apariencia de `Gtk::CheckButton`. Puede verificar, establecer, y conmutar una casilla de verificación utilizando los mismos métodos miembro que para `Gtk::ToggleButton`.

Referencia

#### Ejemplo

##### Casilla de verificación

Código fuente

File: `examplewindow.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLE_BUTTONS_H
    #define GTKMM_EXAMPLE_BUTTONS_H

    #include <gtkmm/window.h>
    #include <gtkmm/checkbutton.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      void on_button_clicked();

      //Child widgets:
      Gtk::CheckButton m_button;
    };

    #endif //GTKMM_EXAMPLE_BUTTONS_H

File: `examplewindow.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <iostream>

    ExampleWindow::ExampleWindow()
    : m_button("something")
    {
      set_title("checkbutton example");
      set_border_width(10);

      m_button.signal_clicked().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_button_clicked) );

      add(m_button);

      show_all_children();
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_button_clicked()
    {
      std::cout << "The Button was clicked: state="
          << (m_button.get_active() ? "true" : "false")
          << std::endl;
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      ExampleWindow window;

      //Shows the window and returns when it is closed.
      return app->run(window);
    }

### Botón de radio

Al igual que las casillas de verificación, los botones de radio también heredan de `Gtk::ToggleButton`, pero trabajan en grupos, y sólo se puede seleccionar un un botón de radio en un grupo a la vez.

#### Grupos

Hay dos maneras de establecer un grupo de botones de radio. La primera manera es crear los botones, y establecer sus grupos luego. Sólo los dos primeros constructores se usan. En el siguiente ejemplo, se crea una clase de ventana nueva llamada `RadioButtons` y luego se ubican tres botones de radio en ella:

    class RadioButtons : public Gtk::Window
    {
    public:
        RadioButtons();

    protected:
        Gtk::RadioButton m_rb1, m_rb2, m_rb3;
    };

    RadioButtons::RadioButtons()
      : m_rb1("button1"),
        m_rb2("button2"),
        m_rb3("button3")
    {
        Gtk::RadioButton::Group group = m_rb1.get_group();
        m_rb2.set_group(group);
        m_rb3.set_group(group);
    }

Se indicó a gtkmm que colocase los tres `RadioButton` en el mismo grupo obteniéndolo con `get_group()` y usando `set_group()` para indicarle a los otros `RadioButton` que compartan ese grupo.

Tenga en cuenta que no puede simplemente hacer

    m_rb2.set_group(m_rb1.get_group()); //doesn't work

porque se modifica al grupo mediante `set_group()`, y por lo tanto, no es constante.

La segunda manera de establecer botones de radio es hacer primero un grupo y luego añadirle los botones a él. Aquí hay un ejemplo:

    class RadioButtons : public Gtk::Window
    {
    public:
        RadioButtons();
    };

    RadioButtons::RadioButtons()
    {
        Gtk::RadioButton::Group group;
        Gtk::RadioButton *m_rb1 = Gtk::manage(
          new Gtk::RadioButton(group,"button1"));
        Gtk::RadioButton *m_rb2 = manage(
          new Gtk::RadioButton(group,"button2"));
          Gtk::RadioButton *m_rb3 = manage(
            new Gtk::RadioButton(group,"button3"));
    }

Se creó un grupo nuevo simplemente declarando una variable, `group`, del tipo `Gtk::RadioButton::Group`. Luego, se hicieron tres botones de radio, usando un constructor para hacer que cada uno sea parte de `group`.

#### Métodos

Los `RadioButtons` están «apagados» cuando se crean; esto significa que cuando hace un grupo de ellos, primero estarán todos apagados. No olvide encender uno de ellos usando `set_active()`:

Referencia

#### Ejemplo

El siguiente ejemplo muestra el uso de `RadioButton`:

##### Botón de radio

Código fuente

File: `radiobuttons.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLE_RADIOBUTTONS_H
    #define GTKMM_EXAMPLE_RADIOBUTTONS_H

    #include <gtkmm/box.h>
    #include <gtkmm/window.h>
    #include <gtkmm/radiobutton.h>
    #include <gtkmm/separator.h>

    class RadioButtons : public Gtk::Window
    {
    public:
      RadioButtons();
      virtual ~RadioButtons();

    protected:
      //Signal handlers:
      void on_button_clicked();

      //Child widgets:
      Gtk::Box m_Box_Top, m_Box1, m_Box2;
      Gtk::RadioButton m_RadioButton1, m_RadioButton2, m_RadioButton3;
      Gtk::Separator m_Separator;
      Gtk::Button m_Button_Close;
    };

    #endif //GTKMM_EXAMPLE_RADIOBUTTONS_H

File: `radiobuttons.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "radiobuttons.h"

    RadioButtons::RadioButtons() :
      m_Box_Top(Gtk::ORIENTATION_VERTICAL),
      m_Box1(Gtk::ORIENTATION_VERTICAL, 10),
      m_Box2(Gtk::ORIENTATION_VERTICAL, 10),
      m_RadioButton1("button1"),
      m_RadioButton2("button2"),
      m_RadioButton3("button3"),
      m_Button_Close("close")
    {
      // Set title and border of the window
      set_title("radio buttons");
      set_border_width(0);

      // Put radio buttons 2 and 3 in the same group as 1:
      Gtk::RadioButton::Group group = m_RadioButton1.get_group();
      m_RadioButton2.set_group(group);
      m_RadioButton3.set_group(group);

      // Add outer box to the window (because the window
      // can only contain a single widget)
      add(m_Box_Top);

      //Put the inner boxes and the separator in the outer box:
      m_Box_Top.pack_start(m_Box1);
      m_Box_Top.pack_start(m_Separator);
      m_Box_Top.pack_start(m_Box2);

      // Set the inner boxes' borders
      m_Box2.set_border_width(10);
      m_Box1.set_border_width(10);

      // Put the radio buttons in Box1:
      m_Box1.pack_start(m_RadioButton1);
      m_Box1.pack_start(m_RadioButton2);
      m_Box1.pack_start(m_RadioButton3);

      // Set the second button active
      m_RadioButton2.set_active();

      // Put Close button in Box2:
      m_Box2.pack_start(m_Button_Close);

      // Make the button the default widget
      m_Button_Close.set_can_default();
      m_Button_Close.grab_default();

      // Connect the clicked signal of the button to
      // RadioButtons::on_button_clicked()
      m_Button_Close.signal_clicked().connect(sigc::mem_fun(*this,
                  &RadioButtons::on_button_clicked) );

      // Show all children of the window
      show_all_children();
    }

    RadioButtons::~RadioButtons()
    {
    }

    void RadioButtons::on_button_clicked()
    {
      hide(); //to close the application.
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "radiobuttons.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      RadioButtons buttons;

      //Shows the window and returns when it is closed.
      return app->run(buttons);
    }

## Widgets de Rango

`Gtk::Scale` y `Gtk::Scrollbar` heredan de `Gtk::Range` y comparten mucha funcionalidad. Contienen un «canal» y un «control deslizante» (a veces llamado «rueda» en otros entornos IGU). Deslizar el control con el puntero lo mueve dentro del canal, mientras que pulsar en el canal avanza al control deslizante hacia la ubicación de la pulsación, completamente o en una cantidad definida dependiendo del botón que se use. Este es el comportamiento normal de las barras de desplazamiento.

Como se explicará en la sección ajuste, todos los widgets del rango están asociados a un objeto `Adjustment`. Para cambiar los valores inferior, superior y actual del widget debe usar los métodos de su `Adjustment`, que puede obtenerlos con el método `get_adjustment()`. Los constructores predeterminados de los widgets `Range` crean un `Adjustment` automáticamente, o puede especificar un `Adjustment` existente, tal vez para compartirlo con otro widget. Consulte la sección ajuste para obtener más detalles.

Referencia

### Widgets de barras de desplazamiento

Estas son las barras de desplazamiento estándar. Sólo se deben ser usar para desplazar otro widget, como un `Gtk::Entry`, o un `Gtk::Viewport`, aunque generalmente es más fácil usar el widget `Gtk::ScrolledWindow` en la mayoría de los casos.

La orientación de una `Gtk::Scrollbar` puede ser horizontal o vertical.

Referencia

### Widgets de Escala

Los widgets `Gtk::Scale` (o «deslizadores») le permiten al usuario seleccionar y manipular visualmente un valor dentro de un rango específico. Puede usar uno, por ejemplo, para ajustar el nivel de ampliación en una previsualización de una imagen, o para controlar el brillo de un color, o especificar la cantidad de minutos de inactividad antes de que aparezca un salvapantallas.

Al igual que con las `Scrollbar`s, la orientación puede ser horizontal o vertical. El constructor predeterminado crea un `Adjustment` con todos sus valores establecidos a `0.0`. Esto no es útil, por lo que necesitará establecer algunos detalles del `Adjustment` para obtener un comportamiento significativo.

#### Métodos útiles

Los widgets `Scale` pueden mostrar su valor actual como un número junto al canal. De manera predeterminada muestran el valor, pero puede cambiar esto con el método `set_draw_value()`.

El valor mostrado en un widget de escala se redondea a un dígito decimal de manera predeterminada, como es el campo `value` en su `Gtk::Adjustment`. Puede cambiar esto con el método `set_digits()`.

Además, pueden dibujar el valor en diferentes posiciones relativas al canal, especificadas por el método `set_value_pos()`.

Referencia

### Políticas de Actualización

La política de actualización de un widget `Range` define en qué puntos durante la interacción del usuario cambiará el campo `value` de su `Gtk::Adjustment` y se emitirá la señal `value_changed`. Las políticas de actualización, que se establecen con el método `set_update_policy()`, son:

- `Gtk::UPDATE_CONTINUOUS`: esta es la predeterminada. Se emite la señal `value_changed` continuamente, es decir, siempre que el deslizador se mueva aunque sea sólo un poco.

- `Gtk::UPDATE_DISCONTINUOUS`: la señal `value_changed` sólo se emite una vez que el deslizador se detuvo y el usuario soltó el botón del ratón.

- `Gtk::UPDATE_DELAYED`: la señal `value_changed` se emite cuando el usuario suelta el botón del ratón, o si el deslizador deja de moverse por un corto período de tiempo.

### Ejemplo

Este ejemplo muestra una ventana con tres widgets de rango, todos conectados al mismo ajuste, junto con un par de controles para establecer algunos de los parámetros mencionados anteriormente y en la sección de ajustes, para que pueda ver cómo afectan la manera en la que estos widgets funcionan para el usuario.

#### Widgets de Rango

Código fuente

File: `examplewindow.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLE_RANGEWIDGETS_H
    #define GTKMM_EXAMPLE_RANGEWIDGETS_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      void on_checkbutton_toggled();
      void on_menu_position(Gtk::PositionType type);
      void on_adjustment1_value_changed();
      void on_adjustment2_value_changed();
      void on_button_quit();

      //Child widgets:
      Gtk::Box m_VBox_Top, m_VBox2, m_VBox_HScale;
      Gtk::Box m_HBox_Scales, m_HBox_Digits, m_HBox_PageSize;

      Glib::RefPtr<Gtk::Adjustment> m_adjustment, m_adjustment_digits, m_adjustment_pagesize;

      Gtk::Scale m_VScale;
      Gtk::Scale m_HScale, m_Scale_Digits, m_Scale_PageSize;

      Gtk::Separator m_Separator;

      Gtk::CheckButton m_CheckButton;

      Gtk::Scrollbar m_Scrollbar;

      Gtk::Menu m_Menu_Position;

      Gtk::Button m_Button_Quit;
    };

    #endif //GTKMM_EXAMPLE_RANGEWIDGETS_H

File: `examplewindow.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <iostream>

    ExampleWindow::ExampleWindow()
    :
      m_VBox_Top(Gtk::ORIENTATION_VERTICAL, 0),
      m_VBox2(Gtk::ORIENTATION_VERTICAL, 20),
      m_VBox_HScale(Gtk::ORIENTATION_VERTICAL, 10),
      m_HBox_Scales(Gtk::ORIENTATION_HORIZONTAL, 10),
      m_HBox_Digits(Gtk::ORIENTATION_HORIZONTAL, 10),
      m_HBox_PageSize(Gtk::ORIENTATION_HORIZONTAL, 10),

      // Value, lower, upper, step_increment, page_increment, page_size:
      // Note that the page_size value only makes a difference for
      // scrollbar widgets, and the highest value you'll get is actually
      // (upper - page_size).
      m_adjustment( Gtk::Adjustment::create(0.0, 0.0, 101.0, 0.1, 1.0, 1.0) ),
      m_adjustment_digits( Gtk::Adjustment::create(1.0, 0.0, 5.0, 1.0, 2.0) ),
      m_adjustment_pagesize( Gtk::Adjustment::create(1.0, 1.0, 101.0) ),

      m_VScale(m_adjustment, Gtk::ORIENTATION_VERTICAL),
      m_HScale(m_adjustment, Gtk::ORIENTATION_HORIZONTAL),
      m_Scale_Digits(m_adjustment_digits),
      m_Scale_PageSize(m_adjustment_pagesize),

      // A checkbutton to control whether the value is displayed or not:
      m_CheckButton("Display value on scale widgets", 0),

      // Reuse the same adjustment again.
      // Notice how this causes the scales to always be updated
      // continuously when the scrollbar is moved.
      m_Scrollbar(m_adjustment),

      m_Button_Quit("Quit")
    {
      set_title("range controls");
      set_default_size(300, 350);

      //VScale:
      m_VScale.set_digits(1);
      m_VScale.set_value_pos(Gtk::POS_TOP);
      m_VScale.set_draw_value();
      m_VScale.set_inverted(); // highest value at top

      //HScale:
      m_HScale.set_digits(1);
      m_HScale.set_value_pos(Gtk::POS_TOP);
      m_HScale.set_draw_value();

      add(m_VBox_Top);
      m_VBox_Top.pack_start(m_VBox2);
      m_VBox2.set_border_width(10);
      m_VBox2.pack_start(m_HBox_Scales);

      //Put VScale and HScale (above scrollbar) side-by-side.
      m_HBox_Scales.pack_start(m_VScale);
      m_HBox_Scales.pack_start(m_VBox_HScale);

      m_VBox_HScale.pack_start(m_HScale);

      //Scrollbar:
      m_VBox_HScale.pack_start(m_Scrollbar);

      //CheckButton:
      m_CheckButton.set_active();
      m_CheckButton.signal_toggled().connect( sigc::mem_fun(*this,
        &ExampleWindow::on_checkbutton_toggled) );
      m_VBox2.pack_start(m_CheckButton, Gtk::PACK_SHRINK);

      //Menus:
      Gtk::MenuItem* item = Gtk::manage(new Gtk::MenuItem("Top"));
      item->signal_activate().connect(
        sigc::bind(sigc::mem_fun(*this,
          &ExampleWindow::on_menu_position), Gtk::POS_TOP));
      m_Menu_Position.append(*item);

      item = Gtk::manage(new Gtk::MenuItem("Bottom"));
      item->signal_activate().connect(
        sigc::bind(sigc::mem_fun(*this,
          &ExampleWindow::on_menu_position), Gtk::POS_BOTTOM));
      m_Menu_Position.append(*item);

      item = Gtk::manage(new Gtk::MenuItem("Left"));
      item->signal_activate().connect(
        sigc::bind(sigc::mem_fun(*this,
          &ExampleWindow::on_menu_position), Gtk::POS_LEFT));
      m_Menu_Position.append(*item);

      item = Gtk::manage(new Gtk::MenuItem("Right"));
      item->signal_activate().connect(
        sigc::bind(sigc::mem_fun(*this,
          &ExampleWindow::on_menu_position), Gtk::POS_RIGHT));
      m_Menu_Position.append(*item);

      //Digits:
      m_HBox_Digits.pack_start(
        *Gtk::manage(new Gtk::Label("Scale Digits:", 0)), Gtk::PACK_SHRINK);
      m_Scale_Digits.set_digits(0);
      m_adjustment_digits->signal_value_changed().connect(sigc::mem_fun(*this,
        &ExampleWindow::on_adjustment1_value_changed));
      m_HBox_Digits.pack_start(m_Scale_Digits);

      //Page Size:
      m_HBox_PageSize.pack_start(
        *Gtk::manage(new Gtk::Label("Scrollbar Page Size:", 0)),
        Gtk::PACK_SHRINK);
      m_Scale_PageSize.set_digits(0);
      m_adjustment_pagesize->signal_value_changed().connect(sigc::mem_fun(*this,
        &ExampleWindow::on_adjustment2_value_changed));
      m_HBox_PageSize.pack_start(m_Scale_PageSize);

      m_VBox2.pack_start(m_HBox_Digits, Gtk::PACK_SHRINK);
      m_VBox2.pack_start(m_HBox_PageSize, Gtk::PACK_SHRINK);
      m_VBox_Top.pack_start(m_Separator, Gtk::PACK_SHRINK);
      m_VBox_Top.pack_start(m_Button_Quit, Gtk::PACK_SHRINK);

      m_Button_Quit.set_can_default();
      m_Button_Quit.grab_default();
      m_Button_Quit.signal_clicked().connect(sigc::mem_fun(*this,
        &ExampleWindow::on_button_quit));
      m_Button_Quit.set_border_width(10);

      show_all_children();
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_checkbutton_toggled()
    {
      m_VScale.set_draw_value(m_CheckButton.get_active());
      m_HScale.set_draw_value(m_CheckButton.get_active());
    }

    void ExampleWindow::on_menu_position(Gtk::PositionType postype)
    {
      m_VScale.set_value_pos(postype);
      m_HScale.set_value_pos(postype);
    }

    void ExampleWindow::on_adjustment1_value_changed()
    {
      const double val = m_adjustment_digits->get_value();
      m_VScale.set_digits((int)val);
      m_HScale.set_digits((int)val);
    }

    void ExampleWindow::on_adjustment2_value_changed()
    {
      const double val = m_adjustment_pagesize->get_value();
      m_adjustment->set_page_size(val);
      m_adjustment->set_page_increment(val);

      // Note that we don't have to emit the "changed" signal
      // because gtkmm does this for us.
    }

    void ExampleWindow::on_button_quit()
    {
      hide();
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      ExampleWindow window;

      //Shows the window and returns when it is closed.
      return app->run(window);
    }

## Widgets varios

### Etiqueta

Las etiquetas son el método principal para poner texto no editable en ventanas, por ejemplo, para poner un título junto a un widget `Entry`. Puede especificar el texto en el constructor, o más tarde con los métodos `set_text()` o `set_markup()`.

El ancho de la etiqueta se ajusta automáticamente. Puede producir etiquetas con varias líneas poniendo saltos de línea («\n») en la cadena de la etiqueta.

El texto de la etiqueta se puede justificar usando el método `set_justify()`. El widget también es capaz de ajustar el texto, lo que se puede activar con `set_line_wrap()`.

Gtk::Label soporta formateado simple, por ejemplo, permitiéndole hacer que el texto se vea en negrita, coloreado, o más grande. Puede hacer esto proporcionándole una cadena a `set_markup()`, usando la sintaxis de marcado de Pango. Por ejemplo, `<b>texto en negrita</b> y <s>texto tachado</s>` .

Referencia

#### Ejemplo

Abajo se muestra un ejemplo corto que ilustra estas funciones. Este ejemplo hace uso del widget «Marco» para demostrar mejor los estilos de etiquetas. (El widget «Marco» se explica en la sección Marco).

##### Etiqueta

Código fuente

File: `examplewindow.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:

      //Child widgets:
      Gtk::Box m_HBox;
      Gtk::Box m_VBox, m_VBox2;
      Gtk::Frame m_Frame_Normal, m_Frame_Multi, m_Frame_Left, m_Frame_Right,
        m_Frame_LineWrapped, m_Frame_FilledWrapped, m_Frame_Underlined;
      Gtk::Label m_Label_Normal, m_Label_Multi, m_Label_Left, m_Label_Right,
        m_Label_LineWrapped, m_Label_FilledWrapped, m_Label_Underlined;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <iostream>

    ExampleWindow::ExampleWindow()
    :
      m_HBox(Gtk::ORIENTATION_HORIZONTAL, 5),
      m_VBox(Gtk::ORIENTATION_VERTICAL, 5),
      m_VBox2(Gtk::ORIENTATION_VERTICAL, 5),
      m_Frame_Normal("Normal Label"),
      m_Frame_Multi("Multi-line Label"),
      m_Frame_Left("Left Justified Label"),
      m_Frame_Right("Right Justified Label"),
      m_Frame_LineWrapped("Line wrapped label"),
      m_Frame_FilledWrapped("Filled, wrapped label"),
      m_Frame_Underlined("Underlined label"),
      m_Label_Normal("_This is a Normal label", true),
      m_Label_Multi("This is a Multi-line label.\nSecond line\nThird line"),
      m_Label_Left("This is a Left-Justified\nMulti-line label.\nThird line"),
      m_Label_Right("This is a Right-Justified\nMulti-line label.\nThird line"),
      m_Label_Underlined("This label is underlined!\n"
              "This one is underlined in quite a funky fashion")
    {
      set_title("Label");
      set_border_width(5);

      add(m_HBox);

      m_HBox.pack_start(m_VBox, Gtk::PACK_SHRINK);

      m_Frame_Normal.add(m_Label_Normal);
      m_VBox.pack_start(m_Frame_Normal, Gtk::PACK_SHRINK);

      m_Frame_Multi.add(m_Label_Multi);
      m_VBox.pack_start(m_Frame_Multi, Gtk::PACK_SHRINK);

      m_Label_Left.set_justify(Gtk::JUSTIFY_LEFT);
      m_Frame_Left.add(m_Label_Left);
      m_VBox.pack_start(m_Frame_Left, Gtk::PACK_SHRINK);

      m_Label_Right.set_justify(Gtk::JUSTIFY_RIGHT);
      m_Frame_Right.add(m_Label_Right);
      m_VBox.pack_start(m_Frame_Right, Gtk::PACK_SHRINK);

      m_HBox.pack_start(m_VBox2, Gtk::PACK_SHRINK);

      m_Label_LineWrapped.set_text(
              "This is an example of a line-wrapped label.  It "
              /* add a big space to the next line to test spacing */
              "should not be taking up the entire             "
              "width allocated to it, but automatically "
              "wraps the words to fit.  "
              "The time has come, for all good men, to come to "
              "the aid of their party.  "
              "The sixth sheik's six sheep's sick.\n"
              "     It supports multiple paragraphs correctly, "
              "and  correctly   adds "
              "many          extra  spaces. ");
      m_Label_LineWrapped.set_line_wrap();
      m_Frame_LineWrapped.add(m_Label_LineWrapped);
      m_VBox2.pack_start(m_Frame_LineWrapped, Gtk::PACK_SHRINK);

      m_Label_FilledWrapped.set_text(
              "This is an example of a line-wrapped, filled label.  "
              "It should be taking "
              "up the entire              width allocated to it.  "
              "Here is a sentence to prove "
              "my point.  Here is another sentence. "
              "Here comes the sun, do de do de do.\n"
              "    This is a new paragraph.\n"
              "    This is another newer, longer, better "
              "paragraph.  It is coming to an end, "
              "unfortunately.");
      m_Label_FilledWrapped.set_justify(Gtk::JUSTIFY_FILL);
      m_Label_FilledWrapped.set_line_wrap();
      m_Frame_FilledWrapped.add(m_Label_FilledWrapped);
      m_VBox2.pack_start(m_Frame_FilledWrapped, Gtk::PACK_SHRINK);

      m_Label_Underlined.set_justify(Gtk::JUSTIFY_LEFT);
      m_Label_Underlined.set_pattern (
              "_________________________ _ _________ _ ______"
              "     __ _______ ___");
      m_Frame_Underlined.add(m_Label_Underlined);
      m_VBox2.pack_start(m_Frame_Underlined, Gtk::PACK_SHRINK);

      show_all_children();
    }

    ExampleWindow::~ExampleWindow()
    {
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      ExampleWindow window;

      //Shows the window and returns when it is closed.
      return app->run(window);
    }

### Entry

#### Uso simple

Los widgets de «entry» le permiten al usuario introducir texto. Puede cambiar el contenido con el método `set_text()`, y leer el contenido actual con el método `get_text()`.

Ocasionalmente querrá definir un widget `Entry` como sólo lectura. Esto se puede hacer pasándole `false` al método `set_editable()`.

Para introducir contraseñas, frases de paso, y otra información que no quiera que aparezca en la pantalla, llamar a `set_visibility` con `false` hará que el texto permanezca oculto.

You might want to be notified whenever the user types in a text entry widget. `Gtk::Entry` provides the `changed` signal for this purpose. It is emitted when the text in the widget changes. You can use it, for instance, to validate or filter the text the user types.

The `changed` signal is not emitted when the user presses the Enter key. If a pressed Enter key signals that the user has finished entering text, you probably want to be notified. For this purpose, use the `key_press_event` signal that `Gtk::Entry` inherits from `Gtk::Widget`. Moving the keyboard focus to another widget may also signal that the user has finished entering text. The `focus_out_event` signal can notify you when that happens. The ComboBox with an Entry section contains example programs that use these signals.

If you pass `true` to the `set_activates_default()` method, pressing Enter in the `Gtk::Entry` will activate the default widget for the window containing the `Gtk::Entry`. This is especially useful in dialog boxes. The default widget is usually one of the dialog buttons, which e.g. will close the dialog box. To set a widget as the default widget, use `Gtk::Widget::set_can_default()` and `Gtk::Widget::grab_default()`.

Referencia

##### Ejemplo simple de «Entry»

Este ejemplo usa `Gtk::Entry`. También tiene dos `CheckButton`, con los que puede conmutar las opciones «editable» y «visible».

###### Entry

Código fuente

File: `examplewindow.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      void on_checkbox_editable_toggled();
      void on_checkbox_visibility_toggled();
      void on_button_close();

      //Child widgets:
      Gtk::Box m_HBox;
      Gtk::Box m_VBox;
      Gtk::Entry m_Entry;
      Gtk::Button m_Button_Close;
      Gtk::CheckButton m_CheckButton_Editable, m_CheckButton_Visible;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <iostream>

    ExampleWindow::ExampleWindow()
    : m_VBox(Gtk::ORIENTATION_VERTICAL),
      m_Button_Close("Close"),
      m_CheckButton_Editable("Editable"),
      m_CheckButton_Visible("Visible")
    {
      set_size_request(200, 100);
      set_title("Gtk::Entry");

      add(m_VBox);

      m_Entry.set_max_length(50);
      m_Entry.set_text("hello");
      m_Entry.set_text(m_Entry.get_text() + " world");
      m_Entry.select_region(0, m_Entry.get_text_length());
      m_VBox.pack_start(m_Entry);

      // Note that add() can also be used instead of pack_xxx()
      m_VBox.add(m_HBox);

      m_HBox.pack_start(m_CheckButton_Editable);
      m_CheckButton_Editable.signal_toggled().connect( sigc::mem_fun(*this,
                  &ExampleWindow::on_checkbox_editable_toggled) );
      m_CheckButton_Editable.set_active(true);

      m_HBox.pack_start(m_CheckButton_Visible);
      m_CheckButton_Visible.signal_toggled().connect( sigc::mem_fun(*this,
                  &ExampleWindow::on_checkbox_visibility_toggled) );
      m_CheckButton_Visible.set_active(true);

      m_Button_Close.signal_clicked().connect( sigc::mem_fun(*this,
                  &ExampleWindow::on_button_close) );
      m_VBox.pack_start(m_Button_Close);
      m_Button_Close.set_can_default();
      m_Button_Close.grab_default();

      show_all_children();
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_checkbox_editable_toggled()
    {
      m_Entry.set_editable(m_CheckButton_Editable.get_active());
    }

    void ExampleWindow::on_checkbox_visibility_toggled()
    {
      m_Entry.set_visibility(m_CheckButton_Visible.get_active());
    }

    void ExampleWindow::on_button_close()
    {
      hide();
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      ExampleWindow window;

      //Shows the window and returns when it is closed.
      return app->run(window);
    }

#### Completado de «Entry»

Un widget `Entry` puede ofrecer una lista desplegable de opciones pre-existentes sobre la base de los primeros caracteres escritos por el usuario. Por ejemplo, un cuadro de diálogo de búsqueda podría sugerir el texto de búsquedas anteriores.

Para activar esta funcionalidad, cree un objeto `EntryCompletion` y proporcióneselo al widget `Entry` mediante el método `set_completion()`.

El `EntryCompletion` puede usar un `TreeModel` que contenga las entradas posibles, especificadas por `set_model()`. Luego llame a `set_text_column()` para especificar cuál de las columnas de su modelo debe usarse para las posibles entradas de texto.

Alternatively, if a complete list of possible entries would be too large or too inconvenient to generate, a callback slot may instead be specified with `set_match_func()`. This is also useful if you wish to match on a part of the string other than the start.

Referencia

##### Ejemplo de completado de «Entry»

Este ejemplo crea un `Gtk::EntryCompletion` y lo asocia a un widget `Gtk::Entry`. Se usan un `Gtk::TreeModel` de entradas posibles para el completado y algunas acciones adicionales.

###### Completado de «Entry»

Código fuente

File: `examplewindow.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      void on_button_close();

      void on_completion_action_activated(int index);

      //See the comment in the implementation:
      //bool on_completion_match(const Glib::ustring& key, const Gtk::TreeModel::const_iterator& iter);

      //Tree model columns, for the EntryCompletion's filter model:
      class ModelColumns : public Gtk::TreeModel::ColumnRecord
      {
      public:

        ModelColumns()
        { add(m_col_id); add(m_col_name); }

        Gtk::TreeModelColumn<unsigned int> m_col_id;
        Gtk::TreeModelColumn<Glib::ustring> m_col_name;
      };

      ModelColumns m_Columns;

      typedef std::map<int, Glib::ustring> type_actions_map;
      type_actions_map m_CompletionActions;

      //Child widgets:
      Gtk::Box m_HBox;
      Gtk::Box m_VBox;
      Gtk::Entry m_Entry;
      Gtk::Label m_Label;
      Gtk::Button m_Button_Close;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <iostream>

    ExampleWindow::ExampleWindow()
    : m_VBox(Gtk::ORIENTATION_VERTICAL),
      m_Label("Press a or b to see a list of possible completions and actions."),
      m_Button_Close("Close")
    {
      //set_size_request(200, 100);
      set_title("Gtk::EntryCompletion");

      add(m_VBox);
      m_VBox.pack_start(m_Entry, Gtk::PACK_SHRINK);

      m_VBox.pack_start(m_Label, Gtk::PACK_EXPAND_WIDGET);

      m_Button_Close.signal_clicked().connect( sigc::mem_fun(*this,
                  &ExampleWindow::on_button_close) );
      m_VBox.pack_start(m_Button_Close, Gtk::PACK_SHRINK);
      m_Button_Close.set_can_default();
      m_Button_Close.grab_default();

      //Add an EntryCompletion:
      Glib::RefPtr<Gtk::EntryCompletion> completion =
          Gtk::EntryCompletion::create();
      m_Entry.set_completion(completion);

      //Create and fill the completion's filter model
      Glib::RefPtr<Gtk::ListStore> refCompletionModel =
          Gtk::ListStore::create(m_Columns);
      completion->set_model(refCompletionModel);

      // For more complex comparisons, use a filter match callback, like this.
      // See the comment below for more details:
      //completion->set_match_func( sigc::mem_fun(*this,
                  //&ExampleWindow::on_completion_match) );

      //Fill the TreeView's model
      Gtk::TreeModel::Row row = *(refCompletionModel->append());
      row[m_Columns.m_col_id] = 1;
      row[m_Columns.m_col_name] = "Alan Zebedee";

      row = *(refCompletionModel->append());
      row[m_Columns.m_col_id] = 2;
      row[m_Columns.m_col_name] = "Adrian Boo";

      row = *(refCompletionModel->append());
      row[m_Columns.m_col_id] = 3;
      row[m_Columns.m_col_name] = "Bob McRoberts";

      row = *(refCompletionModel->append());
      row[m_Columns.m_col_id] = 4;
      row[m_Columns.m_col_name] = "Bob McBob";

      //Tell the completion what model column to use to
      //- look for a match (when we use the default matching, instead of
      //  set_match_func().
      //- display text in the entry when a match is found.
      completion->set_text_column(m_Columns.m_col_name);

      //Add actions to the completion:
      //These are just extra items shown at the bottom of the list of possible
      //completions.

      //Remember them for later.
      m_CompletionActions[0] = "Use Wizard";
      m_CompletionActions[1] = "Browse for Filename";

      for(type_actions_map::iterator iter = m_CompletionActions.begin();
              iter != m_CompletionActions.end(); ++iter)
      {
        int position = iter->first;
        Glib::ustring title = iter->second;
        completion->insert_action_text(title, position);
      }

      completion->signal_action_activated().connect( sigc::mem_fun(*this,
                  &ExampleWindow::on_completion_action_activated) );

      show_all_children();
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_button_close()
    {
      hide();
    }

    /* You can do more complex matching with a handler like this.
     * For instance, you could check for substrings inside the string instead of the start,
     * or you could look for the key in extra model columns as well as the model column that will be displayed.
     * The code here is not actually more complex - it's a reimplementation of the default behaviour.
     *
    bool ExampleWindow::on_completion_match(const Glib::ustring& key, const
            Gtk::TreeModel::const_iterator& iter)
    {
      if(iter)
      {
        Gtk::TreeModel::Row row = *iter;

        Glib::ustring::size_type key_length = key.size();
        Glib::ustring filter_string = row[m_Columns.m_col_name];

        Glib::ustring filter_string_start = filter_string.substr(0, key_length);
        //The key is lower-case, even if the user input is not.
        filter_string_start = filter_string_start.lowercase();

        if(key == filter_string_start)
          return true; //A match was found.
      }

      return false; //No match.
    }
    */

    void ExampleWindow::on_completion_action_activated(int index)
    {
      type_actions_map::iterator iter = m_CompletionActions.find(index);
      if(iter != m_CompletionActions.end()) //If it's in the map
      {
        Glib::ustring title = iter->second;
        std::cout << "Action selected: " << title << std::endl;
      }
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      ExampleWindow window;

      //Shows the window and returns when it is closed.
      return app->run(window);
    }

#### Iconos de «Entry»

Un widget `Entry` puede mostrar un icono al principio o al final del área del texto. Este icono se puede especificar por métodos como `set_icon_from_pixbuf()` o `set_icon_from_stock()`. Una aplicación puede responder al usuario que pulsa el icono manejando la señal `signal_icon_press`.

##### Ejemplo de icono de «Entry»

Este ejemplo muestra un widget `Gtk::Entry` con un icono de búsqueda del almacén, e imprime texto en la terminal cuando se pulsa el icono.

###### «Entry» con icono

Código fuente

File: `examplewindow.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      void on_icon_pressed(Gtk::EntryIconPosition icon_pos, const GdkEventButton* event);
      void on_button_close();

      //Child widgets:
      Gtk::Box m_VBox;
      Gtk::Entry m_Entry;
      Gtk::Button m_Button_Close;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <iostream>

    ExampleWindow::ExampleWindow()
    : m_VBox(Gtk::ORIENTATION_VERTICAL),
      m_Button_Close("Close")
    {
      set_title("Gtk::Entry");

      add(m_VBox);

      m_Entry.set_max_length(50);
      m_Entry.set_text("Hello world");
      m_VBox.pack_start(m_Entry, Gtk::PACK_SHRINK);

      m_Entry.set_icon_from_stock(Gtk::Stock::FIND);
      m_Entry.signal_icon_press().connect( sigc::mem_fun(*this, &ExampleWindow::on_icon_pressed) );

      m_Button_Close.signal_clicked().connect( sigc::mem_fun(*this,
                  &ExampleWindow::on_button_close) );
      m_VBox.pack_start(m_Button_Close, Gtk::PACK_SHRINK);
      m_Button_Close.set_can_default();
      m_Button_Close.grab_default();

      show_all_children();
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_icon_pressed(Gtk::EntryIconPosition /* icon_pos */, const GdkEventButton* /* event */)
    {
      std::cout << "Icon pressed." << std::endl;
    }

    void ExampleWindow::on_button_close()
    {
      hide();
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      ExampleWindow window;

      //Shows the window and returns when it is closed.
      return app->run(window);
    }

#### «Entry» de progreso

Un widget `Entry` puede mostrar una barra de progreso dentro del área del texto, bajo el texto introducido. La barra de progreso se mostrará si se llama a los métodos `set_progress_fraction()` o `set_progress_pulse_step()`.

##### Ejemplo de «Entry» de progreso

Este ejemplo muestra un widget `Gtk::Entry` con una barra de progreso.

###### «Entry» con barra de progreso

Código fuente

File: `examplewindow.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      bool on_timeout();
      void on_button_close();

      //Child widgets:
      Gtk::Box m_VBox;
      Gtk::Entry m_Entry;
      Gtk::Button m_Button_Close;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <iostream>

    ExampleWindow::ExampleWindow()
    : m_VBox(Gtk::ORIENTATION_VERTICAL),
      m_Button_Close("Close")
    {
      set_title("Gtk::Entry");

      add(m_VBox);

      m_Entry.set_max_length(50);
      m_Entry.set_text("Hello world");
      m_VBox.pack_start(m_Entry, Gtk::PACK_SHRINK);

      //Change the progress fraction every 0.1 second:
      Glib::signal_timeout().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_timeout),
        100
      );

      m_Button_Close.signal_clicked().connect( sigc::mem_fun(*this,
                  &ExampleWindow::on_button_close) );
      m_VBox.pack_start(m_Button_Close, Gtk::PACK_SHRINK);
      m_Button_Close.set_can_default();
      m_Button_Close.grab_default();

      show_all_children();
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    bool ExampleWindow::on_timeout()
    {
      static double fraction = 0;
      m_Entry.set_progress_fraction(fraction);

      fraction += 0.01;
      if(fraction > 1)
        fraction = 0;

      return true;
    }

    void ExampleWindow::on_button_close()
    {
      hide();
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      ExampleWindow window;

      //Shows the window and returns when it is closed.
      return app->run(window);
    }

### SpinButton

Un `SpinButton` permite al usuario seleccionar un valor de un rango de valores numéricos. Este tiene un widget «Entry» con botones de flechas en un lado. Al pulsar en los botones hace que el valor del «spin» suba y baje en toda la gama de valores posibles. El widget `Entry` también puede utilizarse para introducir un valor directamente.

El valor puede tener un número ajustable de decimales, y el tamaño del paso es configurable. Los `SpinButton` también tienen una característica de «auto-repetición»: mantener pulsada una de las flechas puede, opcionalmente, causar que el valor cambie más rápidamente cuanto más tiempo se mantenga pulsada la flecha.

Los `SpinButton` usan un objeto Adjustment para mantener la información del rango de valores. Los «SpinButton» usan estos atributos del «Adjustment» así:

- `value`: valor del «SpinButton»

- `lower`: valor mínimo del rango

- `upper`: valor máximo del rango

- `step_increment`: valor en el que se incrementa/decrementa cuando se presiona un botón con el botón 1 del ratón

- `page_increment`: valor en el que se incrementa/decrementa cuando se presiona un botón con el botón 2 del ratón

- `page_size`: no se usa

Además, el botón 3 del ratón se puede usar para saltar directamente a los valores `upper` o `lower`.

El `SpinButton` puede crear un `Adjustment` predeterminado, al que puede acceder mediante el método `get_adjustment()`, o puede especificar un `Adjustment` existente en el constructor.

#### Métodos

La cantidad de lugares decimales se puede alterar usando el método `set_digits()`.

Puede establecer el valor del «spinbutton» usando el método `set_value()`, y obtenerlo con `get_value()`.

El método `spin()` «gira» al `SpinButton`, como si se hubiera presionado una de sus flechas. Debe especificar un `Gtk::SpinType` para especificar la dirección de su posición nueva.

Para que el usuario no pueda introducir caracteres no numéricos al cuadro de entrada, pásele `true` al método `set_numeric()`.

Para que el `SpinButton` «salte» entre sus límites superior e inferior, use el método `set_wrap()`.

Para forzarlo a encajar en el `step_increment` más cercano, use `set_snap_to_ticks()`.

Puede modificar la política de actualización usando el método `set_update_policy()`, especificando `Gtk::UPDATE_ALWAYS` o `Gtk::UPDATE_IF_VALID`. `Gtk::UPDATE_ALWAYS` hace que el `SpinButton` ignore los errores encontrados cuando se convierte el texto en el cuadro de entrada a un valor numérico. Esta opción, por lo tanto, también le permite al `SpinButton` aceptar valores no numéricos. Puede forzar a una actualización inmediata usando el método `update()`.

Referencia

#### Ejemplo

Aquí hay un ejemplo de un `SpinButton` en acción:

##### SpinButton

Código fuente

File: `examplewindow.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      void on_checkbutton_snap();
      void on_checkbutton_numeric();
      void on_spinbutton_digits_changed();
      void on_button_close();

      enum enumValueFormats
      {
        VALUE_FORMAT_INT,
        VALUE_FORMAT_FLOAT
      };
      void on_button_getvalue(enumValueFormats display);

      //Child widgets:
      Gtk::Frame m_Frame_NotAccelerated, m_Frame_Accelerated;
      Gtk::Box m_HBox_NotAccelerated, m_HBox_Accelerated,
        m_HBox_Buttons;
      Gtk::Box m_VBox_Main, m_VBox, m_VBox_Day, m_VBox_Month, m_VBox_Year,
        m_VBox_Accelerated, m_VBox_Value, m_VBox_Digits;
      Gtk::Label m_Label_Day, m_Label_Month, m_Label_Year,
        m_Label_Value, m_Label_Digits,
        m_Label_ShowValue;
      Glib::RefPtr<Gtk::Adjustment> m_adjustment_day, m_adjustment_month, m_adjustment_year,
        m_adjustment_value, m_adjustment_digits;
      Gtk::SpinButton m_SpinButton_Day, m_SpinButton_Month, m_SpinButton_Year,
        m_SpinButton_Value, m_SpinButton_Digits;
      Gtk::CheckButton m_CheckButton_Snap, m_CheckButton_Numeric;
      Gtk::Button m_Button_Int, m_Button_Float, m_Button_Close;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <iostream>
    #include <cstdio>

    ExampleWindow::ExampleWindow()
    :
      m_Frame_NotAccelerated("Not accelerated"),
      m_Frame_Accelerated("Accelerated"),
      m_VBox_Main(Gtk::ORIENTATION_VERTICAL, 5),
      m_Label_Day("Day: "),
      m_Label_Month("Month: "),
      m_Label_Year("Year: "),
      m_Label_Value("Value: "),
      m_Label_Digits("Digits: "),
      m_adjustment_day( Gtk::Adjustment::create(1.0, 1.0, 31.0, 1.0, 5.0, 0.0) ),
      m_adjustment_month( Gtk::Adjustment::create(1.0, 1.0, 12.0, 1.0, 5.0, 0.0) ),
      m_adjustment_year( Gtk::Adjustment::create(1998.0, 0.0, 2100.0, 1.0, 100.0, 0.0) ),
      m_adjustment_value( Gtk::Adjustment::create(0.0, -10000.0, 10000.0, 0.5, 100.0, 0.0) ),
      m_adjustment_digits( Gtk::Adjustment::create(2.0, 1.0, 5.0, 1.0, 1.0, 0.0) ),
      m_SpinButton_Day(m_adjustment_day),
      m_SpinButton_Month(m_adjustment_month),
      m_SpinButton_Year(m_adjustment_year),
      m_SpinButton_Value(m_adjustment_value, 1.0, 2),
      m_SpinButton_Digits(m_adjustment_digits),
      m_CheckButton_Snap("Snap to 0.5-ticks"),
      m_CheckButton_Numeric("Numeric only input mode"),
      m_Button_Int("Value as Int"),
      m_Button_Float("Value as Float"),
      m_Button_Close("Close")
    {
      set_title("SpinButton");

      m_VBox_Main.set_border_width(10);
      add(m_VBox_Main);

      m_VBox_Main.pack_start(m_Frame_NotAccelerated);

      m_VBox.set_border_width(5);
      m_Frame_NotAccelerated.add(m_VBox);

      /* Day, month, year spinners */

      m_VBox.pack_start(m_HBox_NotAccelerated, Gtk::PACK_EXPAND_WIDGET, 5);

      m_Label_Day.set_alignment(Gtk::ALIGN_START);
      m_VBox_Day.pack_start(m_Label_Day);

      m_SpinButton_Day.set_wrap();

      m_VBox_Day.pack_start(m_SpinButton_Day);

      m_HBox_NotAccelerated.pack_start(m_VBox_Day, Gtk::PACK_EXPAND_WIDGET, 5);

      m_Label_Month.set_alignment(Gtk::ALIGN_START);
      m_VBox_Month.pack_start(m_Label_Month);

      m_SpinButton_Month.set_wrap();
      m_VBox_Month.pack_start(m_SpinButton_Month);

      m_HBox_NotAccelerated.pack_start(m_VBox_Month, Gtk::PACK_EXPAND_WIDGET, 5);

      m_Label_Year.set_alignment(Gtk::ALIGN_START);
      m_VBox_Year.pack_start(m_Label_Year);

      m_SpinButton_Year.set_wrap();
      m_SpinButton_Year.set_size_request(55, -1);
      m_VBox_Year.pack_start(m_SpinButton_Year);

      m_HBox_NotAccelerated.pack_start(m_VBox_Year, Gtk::PACK_EXPAND_WIDGET, 5);

      //Accelerated:
      m_VBox_Main.pack_start(m_Frame_Accelerated);

      m_VBox_Accelerated.set_border_width(5);
      m_Frame_Accelerated.add(m_VBox_Accelerated);

      m_VBox_Accelerated.pack_start(m_HBox_Accelerated, Gtk::PACK_EXPAND_WIDGET, 5);

      m_HBox_Accelerated.pack_start(m_VBox_Value, Gtk::PACK_EXPAND_WIDGET, 5);

      m_Label_Value.set_alignment(Gtk::ALIGN_START);
      m_VBox_Value.pack_start(m_Label_Value);

      m_SpinButton_Value.set_wrap();
      m_SpinButton_Value.set_size_request(100, -1);
      m_VBox_Value.pack_start(m_SpinButton_Value);

      m_HBox_Accelerated.pack_start(m_VBox_Digits, Gtk::PACK_EXPAND_WIDGET, 5);

      m_Label_Digits.set_alignment(Gtk::ALIGN_START);
      m_VBox_Digits.pack_start(m_Label_Digits);

      m_SpinButton_Digits.set_wrap();
      m_adjustment_digits->signal_value_changed().connect( sigc::mem_fun(*this,
                  &ExampleWindow::on_spinbutton_digits_changed) );

      m_VBox_Digits.pack_start(m_SpinButton_Digits);

      //CheckButtons:
      m_VBox_Accelerated.pack_start(m_CheckButton_Snap);
      m_CheckButton_Snap.set_active();
      m_CheckButton_Snap.signal_clicked().connect( sigc::mem_fun(*this,
                  &ExampleWindow::on_checkbutton_snap) );

      m_VBox_Accelerated.pack_start(m_CheckButton_Numeric);
      m_CheckButton_Numeric.set_active();
      m_CheckButton_Numeric.signal_clicked().connect( sigc::mem_fun(*this,
                  &ExampleWindow::on_checkbutton_numeric) );

      //Buttons:
      m_VBox_Accelerated.pack_start (m_HBox_Buttons, Gtk::PACK_SHRINK, 5);

      m_Button_Int.signal_clicked().connect( sigc::bind( sigc::mem_fun(*this,
                      &ExampleWindow::on_button_getvalue), VALUE_FORMAT_INT) );
      m_HBox_Buttons.pack_start(m_Button_Int, Gtk::PACK_EXPAND_WIDGET, 5);

      m_Button_Float.signal_clicked().connect( sigc::bind( sigc::mem_fun(*this,
                      &ExampleWindow::on_button_getvalue), VALUE_FORMAT_FLOAT) );
      m_HBox_Buttons.pack_start(m_Button_Float, Gtk::PACK_EXPAND_WIDGET, 5);

      m_VBox_Accelerated.pack_start(m_Label_ShowValue);
      m_Label_ShowValue.set_text("0");

      //Close button:
      m_Button_Close.signal_clicked().connect( sigc::mem_fun(*this,
                  &ExampleWindow::on_button_close) );
      m_VBox_Main.pack_start(m_Button_Close, Gtk::PACK_SHRINK);

      show_all_children();
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_button_close()
    {
      hide();
    }

    void ExampleWindow::on_checkbutton_snap()
    {
      m_SpinButton_Value.set_snap_to_ticks( m_CheckButton_Snap.get_active() );
    }

    void ExampleWindow::on_checkbutton_numeric()
    {
      m_SpinButton_Value.set_numeric( m_CheckButton_Numeric.get_active() );
    }

    void ExampleWindow::on_spinbutton_digits_changed()
    {
      m_SpinButton_Value.set_digits( m_SpinButton_Digits.get_value_as_int() );
    }

    void ExampleWindow::on_button_getvalue(enumValueFormats display)
    {
      gchar buf[32];

      if (display == VALUE_FORMAT_INT)
        sprintf (buf, "%d", m_SpinButton_Value.get_value_as_int());
      else
        sprintf (buf, "%0.*f", m_SpinButton_Value.get_digits(),
                m_SpinButton_Value.get_value());

      m_Label_ShowValue.set_text(buf);
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      ExampleWindow window;

      //Shows the window and returns when it is closed.
      return app->run(window);
    }

### ProgressBar

Las barras de progreso se usan para mostrar el estado de una operación en curso. Por ejemplo, una `ProgressBar` puede mostrar cuánto se ha completado de una tarea.

Para cambiar el valor mostrado, use el método `set_fraction()`, pasándole un «double» entre 0 y 1 para proporcionarle el porcentaje nuevo.

donde `percentage` es un número, de 0 a 1, indicando qué fracción de la barra debe llenarse.

Una `ProgressBar` es horizontal y de izquierda a derecha de manera predeterminada, pero se puede cambiar a una barra de progreso vertical mediante el uso del método `set_orientation()`.

Referencia

#### Modo de actividad

Además de indicar la cantidad de progreso que se ha completado, la barra de progreso también puede usarse para indicar que ocurre actividad; esto se realiza poniendo la barra en modo de actividad. En este modo, la barra de progreso muestra un pequeño rectángulo que se mueve hacia adelante y atrás. El modo de actividad es útil en las situaciones en las que el progreso de una operación no se puede calcular como un rango de valores (por ejemplo, cuando se recibe un archivo de tamaño desconocido).

Para hacer esto, debe llamar al método `pulse()` a intervalos regulares. También puede elegir el tamaño del paso con el método `set_pulse_step()`.

En el modo continuo, la barra de progreso también puede mostrar una cadena de texto configurable en su canal, usando el método `set_text()`.

#### Ejemplo

##### ProgressBar

Código fuente

File: `examplewindow.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      void on_checkbutton_text();
      void on_checkbutton_activity();
      void on_checkbutton_inverted();
      virtual bool on_timeout();
      void on_button_close();

      //Child widgets:
      Gtk::Box m_VBox;
      Gtk::Alignment m_Alignment;
      Gtk::Grid m_Grid;
      Gtk::ProgressBar m_ProgressBar;
      Gtk::Separator m_Separator;
      Gtk::CheckButton m_CheckButton_Text, m_CheckButton_Activity, m_CheckButton_Inverted;
      Gtk::Button m_Button_Close;

      int m_connection_id_timeout;
      bool m_bActivityMode;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <iostream>

    ExampleWindow::ExampleWindow()
    : m_VBox(Gtk::ORIENTATION_VERTICAL, 5),
      m_Alignment(0.5, 0.5, 0, 0),
      m_CheckButton_Text("Show text"),
      m_CheckButton_Activity("Activity mode"),
      m_CheckButton_Inverted("Right to Left"),
      m_Button_Close("Close"),
      m_bActivityMode(false)
    {
      set_resizable();
      set_title("Gtk::ProgressBar");

      m_VBox.set_border_width(10);
      add(m_VBox);

      m_VBox.pack_start(m_Alignment, Gtk::PACK_SHRINK, 5);
      m_Alignment.add(m_ProgressBar);
      m_ProgressBar.set_text("some text");
      m_ProgressBar.set_show_text(false);

      //Add a timer callback to update the value of the progress bar:
      m_connection_id_timeout = Glib::signal_timeout().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_timeout), 50 );

      m_VBox.pack_start(m_Separator, Gtk::PACK_SHRINK);
      m_VBox.pack_start(m_Grid);
      m_Grid.set_row_homogeneous(true);

      //Add a check button to select displaying of the trough text:
      m_Grid.attach(m_CheckButton_Text, 0, 0, 1, 1);
      m_CheckButton_Text.property_margin() = 5;
      m_CheckButton_Text.signal_clicked().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_checkbutton_text) );

      //Add a check button to toggle activity mode:
      m_Grid.attach(m_CheckButton_Activity, 0, 1, 1, 1);
      m_CheckButton_Activity.property_margin() = 5;
      m_CheckButton_Activity.signal_clicked().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_checkbutton_activity) );

      //Add a check button to select growth from left to right or from right to left:
      m_Grid.attach(m_CheckButton_Inverted, 0, 2, 1, 1);
      m_CheckButton_Inverted.property_margin() = 5;
      m_CheckButton_Inverted.signal_clicked().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_checkbutton_inverted) );

      //Add a button to exit the program.
      m_VBox.pack_start(m_Button_Close, Gtk::PACK_SHRINK);
      m_Button_Close.signal_clicked().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_button_close) );
      m_Button_Close.set_can_default();
      m_Button_Close.grab_default();

      show_all_children();
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_checkbutton_text()
    {
      const bool show_text = m_CheckButton_Text.get_active();
      m_ProgressBar.set_show_text(show_text);
    }

    void ExampleWindow::on_checkbutton_activity()
    {
      m_bActivityMode = m_CheckButton_Activity.get_active();

      if(m_bActivityMode)
        m_ProgressBar.pulse();
      else
        m_ProgressBar.set_fraction(0.0);
    }

    void ExampleWindow::on_checkbutton_inverted()
    {
      const bool inverted = m_CheckButton_Inverted.get_active();
      m_ProgressBar.set_inverted(inverted);
    }

    void ExampleWindow::on_button_close()
    {
      hide();
    }

    /* Update the value of the progress bar so that we get
     * some movement */
    bool ExampleWindow::on_timeout()
    {
      if(m_bActivityMode)
        m_ProgressBar.pulse();
      else
      {
        double new_val = m_ProgressBar.get_fraction() + 0.01;

        if(new_val > 1.0)
          new_val = 0.0;

        //Set the new value:
        m_ProgressBar.set_fraction(new_val);
      }

      //As this is a timeout function, return true so that it
      //continues to get called
      return true;
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      ExampleWindow window;

      //Shows the window and returns when it is closed.
      return app->run(window);
    }

### InfoBar

Una `InfoBar` puede mostrar pequeños elementos de información o hacer preguntas breves. A diferencia de un `Dialog`, aparece encima de la ventana actual en vez de en una ventana nueva. Su API es muy similar a la del Gtk::Dialog.

Referencia

#### Ejemplo

##### InfoBar

Código fuente

File: `examplewindow.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      void on_infobar_response(int response);
      void on_button_quit();
      void on_button_clear();
      void on_textbuffer_changed();

      //Child widgets:
      Gtk::Box m_VBox;

      Gtk::ScrolledWindow m_ScrolledWindow;
      Gtk::TextView m_TextView;

      Glib::RefPtr<Gtk::TextBuffer> m_refTextBuffer;

      Gtk::InfoBar m_InfoBar;
      Gtk::Label m_Message_Label;

      Gtk::ButtonBox m_ButtonBox;
      Gtk::Button m_Button_Quit, m_Button_Clear;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"

    ExampleWindow::ExampleWindow()
    : m_VBox(Gtk::ORIENTATION_VERTICAL, 6),
      m_Button_Quit(Gtk::Stock::QUIT),
      m_Button_Clear("Clear")
    {
      set_title("Gtk::InfoBar example");
      set_border_width(6);
      set_default_size(400, 200);

      add(m_VBox);

      // Add the message label to the InfoBar:
      Gtk::Container* infoBarContainer =
        dynamic_cast<Gtk::Container*>(m_InfoBar.get_content_area());
      if (infoBarContainer)
        infoBarContainer->add(m_Message_Label);

      // Add an ok button to the InfoBar:
      m_InfoBar.add_button(Gtk::Stock::OK, 0);

      // Add the InfoBar to the vbox:
      m_VBox.pack_start(m_InfoBar, Gtk::PACK_SHRINK);

      // Create the buffer and set it for the TextView:
      m_refTextBuffer = Gtk::TextBuffer::create();
      m_TextView.set_buffer(m_refTextBuffer);

      // Add the TreeView, inside a ScrolledWindow:
      m_ScrolledWindow.add(m_TextView);

      // Show the scrollbars only when they are necessary:
      m_ScrolledWindow.set_policy(Gtk::POLICY_AUTOMATIC, Gtk::POLICY_AUTOMATIC);

      m_VBox.pack_start(m_ScrolledWindow);

      // Add button box:
      m_VBox.pack_start(m_ButtonBox, Gtk::PACK_SHRINK);

      m_ButtonBox.pack_start(m_Button_Clear, Gtk::PACK_SHRINK);
      m_ButtonBox.pack_start(m_Button_Quit, Gtk::PACK_SHRINK);
      m_ButtonBox.set_spacing(6);
      m_ButtonBox.set_layout(Gtk::BUTTONBOX_END);

      // Connect signals:
      m_InfoBar.signal_response().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_infobar_response) );
      m_Button_Quit.signal_clicked().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_button_quit) );
      m_Button_Clear.signal_clicked().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_button_clear) );
      m_refTextBuffer->signal_changed().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_textbuffer_changed) );

      show_all_children();

      // Keep the InfoBar hidden until a message needs to be shown:
      m_InfoBar.hide();

      // Make the clear button insensitive until text is typed in the buffer.  When
      // the button is sensitive and it is pressed, the InfoBar is displayed with a
      // message.
      m_Button_Clear.set_sensitive(false);
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_infobar_response(int)
    {
      // Clear the message and hide the info bar:
      m_Message_Label.set_text("");
      m_InfoBar.hide();
    }

    void ExampleWindow::on_button_quit()
    {
      hide();
    }

    void ExampleWindow::on_button_clear()
    {
      m_refTextBuffer->set_text("");
      m_Message_Label.set_text("Cleared the text.");
      m_InfoBar.set_message_type(Gtk::MESSAGE_INFO);
      m_InfoBar.show();
    }

    void ExampleWindow::on_textbuffer_changed()
    {
      m_Button_Clear.set_sensitive(m_refTextBuffer->size() > 0);
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      ExampleWindow window;
      //Shows the window and returns when it is closed.
      return app->run(window);
    }

### Consejos

Los consejos son pequeñas ventanas de información que aparecen cuando deja su puntero sobre un widget por unos segundos. Use `set_tooltip_text()` para establecer una cadena nueva como consejo en cualquier `Widget`. Los `Gtk::ToolItem` no son `Widget`s, pero tienen el mismo método por convenio. `Gtk::Tooltip` es para un uso de los consejos más avanzado, como mostrar una imagen junto al texto.

Referencia de widgets

Referencia de consejos

#### Ejemplo

##### Consejo

Código fuente

File: `examplewindow.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:

      ExampleWindow();
      virtual ~ExampleWindow();

    protected:

      //Methods:
      void prepare_textview();
      void connect_signals();

      //Signal handlers:
      void on_markup_checkbutton_click();
      bool on_textview_query_tooltip(int x, int y, bool keyboard_tooltip, const Glib::RefPtr<Gtk::Tooltip>& tooltip);
      bool on_button_query_tooltip(int x, int y, bool keyboard_tooltip, const Glib::RefPtr<Gtk::Tooltip>& tooltip);

      //Child widgets:
      Gtk::Box m_vbox;

      Gtk::CheckButton m_checkbutton;
      Gtk::Label m_label;

      Gtk::ScrolledWindow m_scrolled_window;
      Gtk::TextView m_text_view;
      Glib::RefPtr<Gtk::TextBuffer> m_ref_text_buffer;
      Glib::RefPtr<Gtk::TextTag> m_ref_bold_tag;

      Gtk::Button m_button;
      Gtk::Window m_button_tooltip_window;

    };

    #endif // GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"

    #include <vector>

    const Glib::ustring app_title = "gtkmm tooltips example";
    const Glib::ustring non_markedup_tip = "A tooltip without markup.";
    const Glib::ustring markedup_tip = "<i>Markup</i> in a tooltip.";

    ExampleWindow::ExampleWindow()
      :
      m_vbox(Gtk::ORIENTATION_VERTICAL, 3),
      m_checkbutton("Click to alternate markup in tooltip"),
      m_label("A label"),
      m_button("Custom widget in tooltip window"),
      m_button_tooltip_window(Gtk::WINDOW_POPUP)
    {
      //Set up window and the top-level container:
      set_title(app_title);
      set_border_width(10);

      add(m_vbox);

      //Check button with markup in tooltip:
      m_checkbutton.set_tooltip_text(non_markedup_tip);
      m_vbox.pack_start(m_checkbutton, Gtk::PACK_SHRINK);

      //Label:
      m_label.set_tooltip_text("Another tooltip");
      m_vbox.pack_start(m_label, Gtk::PACK_SHRINK);

      //Textview:
      prepare_textview();

      //Button:
      // set_tooltip_window(), like set_tooltip_text(),
      // will call set_has_tooltip() for us.
      m_button.set_tooltip_window(m_button_tooltip_window);
      m_vbox.pack_start(m_button, Gtk::PACK_SHRINK);

      //Button's custom tooltip window:
      m_button_tooltip_window.set_default_size(250, 30);
      Gtk::Label* label =
        Gtk::manage(new Gtk::Label("A label in a custom tooltip window"));
      label->show();
      m_button_tooltip_window.add(*label);

      connect_signals();

      show_all_children();
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::prepare_textview()
    {
      Gtk::TextIter iter;
      std::vector< Glib::RefPtr<Gtk::TextTag> > tags;

      //Set up a scrolled window:
      m_scrolled_window.add(m_text_view);
      m_scrolled_window.set_policy(Gtk::POLICY_AUTOMATIC, Gtk::POLICY_AUTOMATIC);
      m_vbox.pack_start(m_scrolled_window);

      //Create a text buffer with some text:
      m_ref_text_buffer = Gtk::TextBuffer::create();

      iter = m_ref_text_buffer->end();
      m_ref_text_buffer->insert(iter, "Hover over the text ");

      //Insert some text with a tag.
      //In the tooltip signal handler below, we will show a tooltip
      //when mouse pointer is above this tagged text.
      m_ref_bold_tag = m_ref_text_buffer->create_tag("bold");
      m_ref_bold_tag->set_property("weight", Pango::WEIGHT_BOLD);

      tags.push_back(m_ref_bold_tag);

      iter = m_ref_text_buffer->end();
      m_ref_text_buffer->insert_with_tags(iter, "in bold", tags);

      iter = m_ref_text_buffer->end();
      m_ref_text_buffer->insert(iter, " to see its' tooltip");

      m_text_view.set_buffer(m_ref_text_buffer);

      m_text_view.set_size_request(320, 50);

      //When only connecting to the query-tooltip signal, and not using any
      //of set_tooltip_text(), set_tooltip_markup() or set_tooltip_window(),
      //we need to explicitly tell GTK+ that the widget has a tooltip which
      //we'll show.
      m_text_view.set_has_tooltip();
    }

    void ExampleWindow::connect_signals()
    {
      m_checkbutton.signal_clicked().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_markup_checkbutton_click));

      m_text_view.signal_query_tooltip().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_textview_query_tooltip));

      m_button.signal_query_tooltip().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_button_query_tooltip));
    }

    void ExampleWindow::on_markup_checkbutton_click()
    {
      if (m_checkbutton.get_active() == true)
      {
        m_checkbutton.set_tooltip_markup(markedup_tip);
      }
      else
      {
        m_checkbutton.set_tooltip_markup(non_markedup_tip);
      }
    }

    bool ExampleWindow::on_textview_query_tooltip(int x, int y, bool keyboard_tooltip, const Glib::RefPtr<Gtk::Tooltip>& tooltip)
    {
      Gtk::TextIter iter;

      if (keyboard_tooltip)
      {
        int offset = m_ref_text_buffer->property_cursor_position().get_value();
        iter = m_ref_text_buffer->get_iter_at_offset(offset);
      }
      else
      {
        int mouse_x, mouse_y, trailing;
        m_text_view.window_to_buffer_coords(Gtk::TEXT_WINDOW_TEXT,
                                            x, y, mouse_x, mouse_y);
        m_text_view.get_iter_at_position(iter, trailing, mouse_x, mouse_y);
      }

      //Show a tooltip if the cursor or mouse pointer is over the text
      //with the specific tag:
      if (iter.has_tag(m_ref_bold_tag))
      {
        tooltip->set_markup("<b>Information</b> attached to a text tag");
        tooltip->set_icon_from_stock (Gtk::Stock::INFO, Gtk::ICON_SIZE_MENU);
      }
      else
      {
        return false;
      }

      return true;
    }

    bool ExampleWindow::on_button_query_tooltip(int, int, bool, const Glib::RefPtr<Gtk::Tooltip>&)
    {
      //We already have a custom window ready, just return true to show it:
      return true;
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      ExampleWindow window;

      //Shows the window and returns when it is closed.
      return app->run(window);
    }

## Widgets contenedores

Todos los widgets contenedores derivan de `Gtk::Container`, no siempre directamente. Algunos widgets contenedores, como `Gtk::Grid` pueden contener varios widgets hijos, por lo que típicamente tienen interfaces más complejas. Otros, como `Gtk::Frame` contienen sólo un widget hijo.

### Contenedor de un sólo elemento

Los contenedores de un sólo elemento derivan de `Gtk::Bin`, que proporciona los métodos `add()` y `remove()` para el widget hijo. Tenga en cuenta que `Gtk::Button` y `Gtk::Window` son, técnicamente, contenedores de un sólo elemento, pero ya se ha hablado de ellos anteriormente.

También se habla del widget `Gtk::Paned`, que le permite dividir una ventana en dos «paneles» separados. El widget, en realidad, contiene dos widgets hijos, pero el número es fijo, por lo que parece apropiado.

#### Marco

Los cuadros pueden encerrar un grupo de widgets dentro de una caja, con un título opcional. Por ejemplo, tal vez quiera poner un grupo de `RadioButton` o `CheckButton` en un `Frame`.

Referencia

##### Ejemplo

###### Marco

Código fuente

File: `examplewindow.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:

      //Child widgets:
      Gtk::Frame m_Frame;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"

    ExampleWindow::ExampleWindow()
    {
     /* Set some window properties */
      set_title("Frame Example");
      set_size_request(300, 300);

      /* Sets the border width of the window. */
      set_border_width(10);

      add(m_Frame);

      /* Set the frames label */
      m_Frame.set_label("Gtk::Frame Widget");

      /* Align the label at the right of the frame */
      //m_Frame.set_label_align(Gtk::ALIGN_END, Gtk::ALIGN_START);

      /* Set the style of the frame */
      m_Frame.set_shadow_type(Gtk::SHADOW_ETCHED_OUT);

      show_all_children();
    }

    ExampleWindow::~ExampleWindow()
    {
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      ExampleWindow window;

      //Shows the window and returns when it is closed.
      return app->run(window);
    }

#### Con paneles

Se pueden usar paneles para dividir un widget en dos mitades, separadas por un divisor móvil. Las dos mitades (paneles) pueden orientarse tanto horizontal (lado a lado) como verticalmente (uno encima de otro).

A diferencia de los otros widgets en esta sección, los paneles no contienen un widget hijo, sino dos, uno en cada panel. Por lo tanto, debe usar los métodos `add1()` y `add2()` en vez de `add()`.

Puede ajustar la posición del divisor usando el método `set_position()`, y probablemente lo necesite.

Referencia

##### Ejemplo

###### Con paneles

Código fuente

File: `messageslist.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLE_MESSAGESLIST_H
    #define GTKMM_EXAMPLE_MESSAGESLIST_H

    #include <gtkmm.h>

    class MessagesList: public Gtk::ScrolledWindow
    {
    public:
      MessagesList();
      virtual ~MessagesList();

      class ModelColumns : public Gtk::TreeModel::ColumnRecord
      {
      public:

        ModelColumns()
        { add(m_col_text); }

        Gtk::TreeModelColumn<Glib::ustring> m_col_text;
      };

      ModelColumns m_Columns;

    protected:
      Glib::RefPtr<Gtk::ListStore> m_refListStore; //The Tree Model.
      Gtk::TreeView m_TreeView; //The Tree View.
    };
    #endif //GTKMM_EXAMPLE_MESSAGESLIST_H

File: `messagetext.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLE_MESSAGETEXT_H
    #define GTKMM_EXAMPLE_MESSAGETEXT_H

    #include <gtkmm.h>

    class MessageText : public Gtk::ScrolledWindow
    {
    public:
      MessageText();
      virtual ~MessageText();

      void insert_text();

    protected:
      Gtk::TextView m_TextView;
    };

    #endif //GTKMM_EXAMPLE_MESSAGETEXT_H

File: `examplewindow.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include "messageslist.h"
    #include "messagetext.h"
    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:

      //Child widgets:
      Gtk::Paned m_VPaned;
      MessagesList m_MessagesList;
      MessageText m_MessageText;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `messagetext.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "messagetext.h"

    MessageText::MessageText()
    {
      set_policy(Gtk::POLICY_AUTOMATIC, Gtk::POLICY_AUTOMATIC);

      add(m_TextView);
      insert_text();

      show_all_children();
    }

    MessageText::~MessageText()
    {
    }

    void MessageText::insert_text()
    {
      Glib::RefPtr<Gtk::TextBuffer> refTextBuffer = m_TextView.get_buffer();

      Gtk::TextBuffer::iterator iter = refTextBuffer->get_iter_at_offset(0);
      refTextBuffer->insert(iter,
        "From: pathfinder@nasa.gov\n"
        "To: mom@nasa.gov\n"
        "Subject: Made it!\n"
        "\n"
        "We just got in this morning. The weather has been\n"
        "great - clear but cold, and there are lots of fun sights.\n"
        "Sojourner says hi. See you soon.\n"
        " -Path\n");
    }

File: `messageslist.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "messageslist.h"
    #include <sstream>

    MessagesList::MessagesList()
    {
      /* Create a new scrolled window, with scrollbars only if needed */
      set_policy(Gtk::POLICY_AUTOMATIC, Gtk::POLICY_AUTOMATIC);

      add(m_TreeView);

      /* create list store */
      m_refListStore = Gtk::ListStore::create(m_Columns);

      m_TreeView.set_model(m_refListStore);

      /* Add some messages to the window */
      for(int i = 0; i < 10; ++i)
      {
        std::ostringstream text;
        text << "message #" << i;

        Gtk::TreeModel::Row row = *(m_refListStore->append());
        row[m_Columns.m_col_text] = text.str();
      }

      //Add the Model's column to the View's columns:
      m_TreeView.append_column("Messages", m_Columns.m_col_text);

      show_all_children();
    }

    MessagesList::~MessagesList()
    {
    }

File: `examplewindow.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"

    ExampleWindow::ExampleWindow()
    : m_VPaned(Gtk::ORIENTATION_VERTICAL)
    {
      set_title ("Paned Windows");
      set_border_width(10);
      set_default_size(450, 400);

      /* Add a vpaned widget to our toplevel window */
      add(m_VPaned);

      /* Now add the contents of the two halves of the window */
      m_VPaned.add1(m_MessagesList);
      m_VPaned.add2(m_MessageText);

      show_all_children();
    }

    ExampleWindow::~ExampleWindow()
    {
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      ExampleWindow window;

      //Shows the window and returns when it is closed.
      return app->run(window);
    }

#### ScrolledWindow

Los widgets `ScrolledWindow` crean un área desplazable. Puede insertar cualquier tipo de widget en una ventana `ScrolledWindow`, y será accesible sin importar su tamaño mediante el uso de barras de desplazamiento. Tenga en cuenta que `ScrolledWindow` no es un `Gtk::Window`, a pesar del nombre ligeramente confuso.

Las ventanas desplazables tienen políticas de desplazamiento que determinan si se muestran las `Scrollbar` o no. Las políticas se pueden establecer mediante el método `set_policy()`. La política puede ser `Gtk::POLICY_AUTOMATIC` o `Gtk::POLICY_ALWAYS`. `Gtk::POLICY_AUTOMATIC` hace que la ventana desplazable muestre la barra de desplazamiento sólo si el widget contenido es más grande que el área visible. `Gtk::POLICY_ALWAYS` hace que la barra de desplazamiento se muestre siempre.

Referencia

##### Ejemplo

Aquí hay un ejemplo simple que incluye 100 botones conmutadores en una ventana ScrolledWindow. Intente redimensionar la ventana para ver reaccionar a las barras de desplazamiento.

###### ScrolledWindow

Código fuente

File: `examplewindow.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Dialog
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      void on_button_close();

      //Child widgets:
      Gtk::ScrolledWindow m_ScrolledWindow;
      Gtk::Grid m_Grid;
      Gtk::Button m_Button_Close;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <cstdio>

    ExampleWindow::ExampleWindow()
    : m_Button_Close("Close")
    {
      set_title("Gtk::ScrolledWindow example");
      set_border_width(0);
      set_size_request(300, 300);

      m_ScrolledWindow.set_border_width(10);

      /* the policy is one of Gtk::POLICY AUTOMATIC, or Gtk::POLICY_ALWAYS.
       * Gtk::POLICY_AUTOMATIC will automatically decide whether you need
       * scrollbars, whereas Gtk::POLICY_ALWAYS will always leave the scrollbars
       * there.  The first one is the horizontal scrollbar, the second,
       * the vertical. */
      m_ScrolledWindow.set_policy(Gtk::POLICY_AUTOMATIC, Gtk::POLICY_ALWAYS);

      get_content_area()->pack_start(m_ScrolledWindow);

      /* set the spacing to 10 on x and 10 on y */
      m_Grid.set_row_spacing(10);
      m_Grid.set_column_spacing(10);

      /* pack the grid into the scrolled window */
      m_ScrolledWindow.add(m_Grid);

      /* this simply creates a grid of toggle buttons
       * to demonstrate the scrolled window. */
      for(int i = 0; i < 10; i++)
      {
         for(int j = 0; j < 10; j++)
         {
            char buffer[32];
            sprintf(buffer, "button (%d,%d)\n", i, j);
            Gtk::Button* pButton = Gtk::manage(new Gtk::ToggleButton(buffer));
            m_Grid.attach(*pButton, i, j, 1, 1);
         }
      }

      /* Add a "close" button to the bottom of the dialog */
      m_Button_Close.signal_clicked().connect( sigc::mem_fun(*this,
                  &ExampleWindow::on_button_close));

      /* this makes it so the button is the default. */
      m_Button_Close.set_can_default();

      Gtk::Box* pBox = get_action_area();
      if(pBox)
        pBox->pack_start(m_Button_Close);

      /* This grabs this button to be the default button. Simply hitting
       * the "Enter" key will cause this button to activate. */
      m_Button_Close.grab_default();

      show_all_children();
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_button_close()
    {
      hide();
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      ExampleWindow window;

      //Shows the window and returns when it is closed.
      return app->run(window);
    }

#### AspectFrame

El widget `AspectFrame` se ve como un widget `Frame`, pero fuerza la relación de aspecto (la razón entre la altura y el ancho) del widget hijo, añadiendo espacio adicional de ser necesario. Por ejemplo, esto le permitiría mostrar una fotografía sin permitirle al usuario distorsionarla horizontal o verticalmente cuando la redimensione.

Referencia

##### Ejemplo

El siguiente programa usa un `Gtk::AspectFrame` para presentar un área de dibujo cuya relación de aspecto siempre es 2:1, sin importar cómo el usuario redimensiona la ventana superior.

###### AspectFrame

Código fuente

File: `examplewindow.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:

      //Child widgets:
      Gtk::AspectFrame m_AspectFrame;
      Gtk::DrawingArea m_DrawingArea;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"

    ExampleWindow::ExampleWindow()
    : m_AspectFrame("2x1", /* label */
        Gtk::ALIGN_CENTER, /* center x */
        Gtk::ALIGN_CENTER, /* center y */
        2.0, /* xsize/ysize = 2 */
        false /* ignore child's aspect */)
    {
      set_title("Aspect Frame");
      set_border_width(10);

      // Add a child widget to the aspect frame */
      // Ask for a 200x200 window, but the AspectFrame will give us a 200x100
      // window since we are forcing a 2x1 aspect ratio */
      m_DrawingArea.set_size_request(200, 200);
      m_AspectFrame.add(m_DrawingArea);

      // Add the aspect frame to our toplevel window:
      add(m_AspectFrame);

      show_all_children();
    }

    ExampleWindow::~ExampleWindow()
    {
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      ExampleWindow window;

      //Shows the window and returns when it is closed.
      return app->run(window);
    }

#### Alignment

El widget `Alignment` le permite poner un widget en una posición y tamaño relativos al tamaño del widget `Alignment` en sí. Por ejemplo, puede usarse para centrar un widget.

Debe especificar las características del `Alignment` al constructor, o al método `set()`. En particular, no notará ningún efecto a menos que especifique un número distinto a 1.0 para los parámetros `xscale` e `yscale`, porque 1.0 simplemente significa que el widget se expandirá hasta cubrir todo el espacio disponible.

Referencia

##### Ejemplo

Este ejemplo alinea a la derecha un botón en una ventana mediante el uso de un widget `Alignment`.

###### Alignment

Código fuente

File: `examplewindow.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      void on_button_clicked();

      //Child widgets:
      Gtk::Alignment m_Alignment;
      Gtk::Button m_Button;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"

    ExampleWindow::ExampleWindow()
    : m_Alignment(Gtk::ALIGN_END, Gtk::ALIGN_CENTER, 0.0, 0.0),
      m_Button("Close")
    {
      set_title("Gtk::Alignement");
      set_border_width(10);
      set_default_size(200, 50);

      add(m_Alignment);

      m_Alignment.add(m_Button);

      m_Button.signal_clicked().connect( sigc::mem_fun(*this,
                  &ExampleWindow::on_button_clicked) );

      show_all_children();
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_button_clicked()
    {
      hide();
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      ExampleWindow window;

      //Shows the window and returns when it is closed.
      return app->run(window);
    }

Consulte la sección ProgressBar para ver otro ejemplo que usa un `Alignment`.

### Widgets de elementos múltiples

Los widgets de elementos múltiples heredan de `Gtk::Container`; al igual que con `Gtk::Bin`, use los métodos `add()` y `remove()` para añadir y eliminar widgets contenedores. A diferencia de `Gtk::Bin::remove()`, sin embargo, el método `remove()` para `Gtk::Container` toma un argumento, especificando qué widget eliminar.

#### Empaquetado

Probablemente ya haya notado que las ventanas de gtkmm parecen «elásticas»: normalmente pueden estirarse de muchas maneras diferentes. Esto es así por el sistema de empaquetado de widgets.

Muchos conjuntos de herramientas de la IGU le requieren ubicar precisamente widgets en una ventana, utilizando posicionamiento absoluto, a menudo usando un editor visual. Esto lleva a muchos problemas:

- Los widgets no se reordenar cuando la ventana se redimensiona. Algunos se esconden cuando las ventanas se hacen más pequeñas, y aparece un montón de espacio sin utilizar cuando la ventana se agranda.

- Es imposible predecir la cantidad de espacio necesaria para texto después de que se ha traducido a otros idiomas, o se ha mostrado en otra tipografía. En Unix, también es imposible anticipar los efectos de cada tema y gestor de ventanas.

- Cambiar la disposición de una ventana «al vuelo» para, por ejemplo, hacer que algunos widgets adicionales aparezcan, es complejo. Requiere un cálculo tedioso de la posición de cada widget.

gtkmm usa el sistema de empaquetado para resolver estos problemas. En lugar de especificar el tamaño y posición de cada widget en la ventana, puede ordenar sus widgets en filas, columnas, y/o tablas. gtkmm puede dimensionar su ventana automáticamente, de acuerdo a los tamaños de los widgets que contiene. A su vez, los tamaños de los widgets se determinan por la cantidad de texto que contienen, los tamaños máximo y mínimo que especifique, y/o cómo ha pedido que se comparta el espacio disponible entre los diferentes conjuntos de widgets. Puede perfeccionar su disposición especificando las distancias entre bordes y los valores de centrado de cada widget. gtkmm, entonces, usa toda esta información para redimensionar y reposicionar todo suave y sensiblemente cuando el usuario manipula la ventana.

gtkmm ordena los widgets jerárquicamente, usando contenedores. Un widget contenedor contiene a otros widgets. La mayoría de los widgets de gtkmm son contenedores. Las ventanas, las pestañas de los cuadernos y los botones son todos widgets contenedores. Hay dos formas de contenedores: de un sólo hijo, que descienden todos de `Gtk::Bin`, y de múltiples hijos, que descienden de `Gtk::Container`. La mayoría de los widgets en gtkmm descienden de `Gtk::Bin`, incluyendo `Gtk::Window`.

Sí, es correcto: una ventana sólo puede contener un widget. Entonces, ¿cómo puede usar una ventana para algo útil? Poniendo un contenedor de múltiples hijos en la ventana. Los widgets contenedores más útiles son `Gtk::Grid` y `Gtk::Box`.

- `Gtk::Grid` ordena sus widgets hijos en filas y columnas. Use `attach()`, `attach_next_to()` y `add()` para insertar widgets hijos.

- `Gtk::Box` ordena a sus widgets hijos vertical u horizontalmente. Use `pack_start()` y `pack_end()` para insertar widgets hijos.

Hay muchos más contenedores, de los que también se hablará.

Si nunca ha usado un kit de herramientas de empaquetado antes, puede llevar algo de tiempo acostumbrarse a él. Probablemente encuentre, sin embargo, que no necesita editores de formularios visuales tanto como con otros kits de herramientas.

#### Un «Hola mundo» mejorado

Eche un vistazo a un `helloworld` ligeramente mejorado, mostrando lo que ha aprendido.

##### Hola mundo 2

Código fuente

File: `helloworld.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLE_HELLOWORLD_H
    #define GTKMM_EXAMPLE_HELLOWORLD_H

    #include <gtkmm/box.h>
    #include <gtkmm/button.h>
    #include <gtkmm/window.h>

    class HelloWorld : public Gtk::Window
    {
    public:
      HelloWorld();
      virtual ~HelloWorld();

    protected:

      // Signal handlers:
      // Our new improved on_button_clicked(). (see below)
      void on_button_clicked(Glib::ustring data);

      // Child widgets:
      Gtk::Box m_box1;
      Gtk::Button m_button1, m_button2;
    };

    #endif // GTKMM_EXAMPLE_HELLOWORLD_H

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "helloworld.h"
    #include <gtkmm/application.h>

    int main (int argc, char *argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      HelloWorld helloworld;

      //Shows the window and returns when it is closed.
      return app->run(helloworld);
    }

File: `helloworld.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "helloworld.h"
    #include <iostream>

    HelloWorld::HelloWorld()
    : m_button1("Button 1"),
      m_button2("Button 2")
    {
      // This just sets the title of our new window.
      set_title("Hello Buttons!");

      // sets the border width of the window.
      set_border_width(10);

      // put the box into the main window.
      add(m_box1);

      // Now when the button is clicked, we call the "on_button_clicked" function
      // with a pointer to "button 1" as it's argument
      m_button1.signal_clicked().connect(sigc::bind<Glib::ustring>(
                  sigc::mem_fun(*this, &HelloWorld::on_button_clicked), "button 1"));

      // instead of gtk_container_add, we pack this button into the invisible
      // box, which has been packed into the window.
      // note that the pack_start default arguments are Gtk::EXPAND | Gtk::FILL, 0
      m_box1.pack_start(m_button1);

      // always remember this step, this tells GTK that our preparation
      // for this button is complete, and it can be displayed now.
      m_button1.show();

      // call the same signal handler with a different argument,
      // passing a pointer to "button 2" instead.
      m_button2.signal_clicked().connect(sigc::bind<-1, Glib::ustring>(
                  sigc::mem_fun(*this, &HelloWorld::on_button_clicked), "button 2"));

      m_box1.pack_start(m_button2);

      // Show the widgets.
      // They will not really be shown until this Window is shown.
      m_button2.show();
      m_box1.show();
    }

    HelloWorld::~HelloWorld()
    {
    }

    // Our new improved signal handler.  The data passed to this method is
    // printed to stdout.
    void HelloWorld::on_button_clicked(Glib::ustring data)
    {
      std::cout << "Hello World - " << data << " was pressed" << std::endl;
    }

Después de haber construido y ejecutado este programa, pruebe a redimensionar la ventana para observar su comportamiento. Además, pruebe modificar las opciones a `pack_start()` mientras lee la sección Cajas.

#### Cajas

La mayor parte del empaquetado usa cajas como en el ejemplo anterior. Éstas son contenedores invisibles en los que podemos empaquetar a nuestros widgets. Cuando se empaquetan los widgets en una caja horizontal, los objetos se insertan horizontalmente de izquierda a derecha o de derecha a izquierda dependiendo de si se usó `pack_start()` o `pack_end()`. En una caja vertical, los widgets se empaquetan de arriba a abajo o viceversa. Puede usar cualquier combinación de cajas dentro o al lado de otras cajas para crear el efecto deseado.

##### Añadir widgets

###### Opciones de empaquetado por hijo

Los métodos `pack_start()` y `pack_end()` ponen widgets dentro de estos contenedores. El método `pack_start()` empezará arriba, y seguirá hacia abajo en una `Box` de orientación vertical, o empaquetará de izquierda a derecha en una `Box` de orientación horizontal. `pack_end()` hará lo contrario, empaquetando de abajo hacia arriba o de derecha a izquierda. Usar estos métodos le permite justificar a derecha o izquierda a sus widgets. Se usará `pack_start()` en la mayoría de los ejemplos.

Hay muchas opciones que determinan cómo se empaquetan los widgets, y esto puede resultar confuso al principio. Si tiene dificultades, entonces a veces es una buena idea jugar con el diseñador de IGU glade para ver qué es posible. Incluso, tal vez decida usar la API de Gtk::Builder para cargar su IGU en tiempo de ejecución.

Básicamente, hay cinco estilos diferentes, como se muestra en esta imagen.

###### Caja de empaquetado 1

Cada línea contiene una `Box` horizontal con varios botones. Cada uno de los botones en una línea está empaquetado en la `Box`, con los mismos argumentos pasados al método `pack_start()`.

Esta es la declaración del método `pack_start()`.

    void pack_start(Gtk::Widget& child,
                    PackOptions options = PACK_EXPAND_WIDGET,
                    guint padding = 0);

El primer argumento es el widget que está empaquetando. En el ejemplo estos son todos los `Button`.

El argumento `options` puede tomar una de estas tres opciones:

- `PACK_SHRINK`: el espacio se contrae al tamaño del widget hijo. El widget usará el espacio justo y necesario, y nunca se expandirá.

- `PACK_EXPAND_PADDING`: se rellena espacio adicional. Los widgets se espacian de manera similar, pero sus tamaños no cambiarán: en su lugar, habrá espacio vacío.

- `PACK_EXPAND_WIDGET`: se usa espacio adicional incrementando el tamaño del widget hijo, sin cambiar la cantidad de espacio entre los widgets.

El argumento `padding` especifica el ancho de un área adicional en el borde para dejar alrededor del widget empaquetado.

Referencia

###### Opciones de empaquetado por contenedor

Aquí está el constructor de los widgets de caja:

    Gtk::Box(bool homogeneous = false, int spacing = 0);

Pasarle `true` a `homogeneous` hará que todos los widgets contenidos sean del mismo tamaño. `spacing` es el número (mínimo) de píxeles que dejar entre cada widget.

¿Cuál es la diferencia entre el espaciado (establecido cuando se crea la caja) y el relleno (establecido cuando se empaquetan los elementos)? El espaciado se añade entre objetos, y el relleno a cada lado del widget. La siguiente figura debería aclararlo:

###### Caja de empaquetado 2

##### Ejemplo

Aquí está el código fuente del ejemplo que produjo las capturas de pantalla anteriores. Cuando ejecute este ejemplo, proporcione un número entre 1 y 3 como opción de línea de comandos, para ver las diferentes opciones de empaquetado en acción.

Código fuente

File: `packbox.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLE_PACKBOX_H
    #define GTKMM_EXAMPLE_PACKBOX_H

    #include <gtkmm.h>

    class PackBox : public Gtk::Box
    {
    public:
      PackBox(bool homogeneous, int spacing, Gtk::PackOptions, int padding = 0);
      virtual ~PackBox();

    protected:
      Gtk::Button m_button1, m_button2, m_button3;
      Gtk::Button* m_pbutton4;

      char padstr[80];
    };

    #endif //GTKMM_EXAMPLE_PACKBOX_H

File: `examplewindow.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>
    #include "packbox.h"

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow(int which);
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      void on_button_quit_clicked();

      //Child widgets:
      Gtk::Button m_button;
      Gtk::Box m_box1;
      Gtk::Box m_boxQuit;
      Gtk::Button m_buttonQuit;

      Gtk::Label m_Label1, m_Label2;

      Gtk::Separator m_seperator1, m_seperator2, m_seperator3, m_seperator4, m_seperator5;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 3, not gtkmm 2)

    #include <iostream>
    #include "examplewindow.h"

    ExampleWindow::ExampleWindow(int which)
    : m_box1(Gtk::ORIENTATION_VERTICAL),
      m_buttonQuit("Quit")
    {
      set_title("Gtk::Box example");

      PackBox *pPackBox1, *pPackBox2, *pPackBox3, *pPackBox4, *pPackBox5;

      switch(which)
      {
        case 1:
        {
          m_Label1.set_text("Gtk::Box(Gtk::ORIENTATION_HORIZONTAL, 0);");

          // Align the label to the left side.  We'll discuss this function and
          // others in the section on Widget Attributes.
          m_Label1.set_alignment(Gtk::ALIGN_START, Gtk::ALIGN_START);

          // Pack the label into the vertical box (vbox box1).  Remember that
          // widgets added to a vbox will be packed one on top of the other in
          // order.
          m_box1.pack_start(m_Label1, Gtk::PACK_SHRINK);

          // Create a PackBox - homogeneous = false, spacing = 0,
          // options = Gtk::PACK_SHRINK, padding = 0
          pPackBox1 = Gtk::manage(new PackBox(false, 0, Gtk::PACK_SHRINK));
          m_box1.pack_start(*pPackBox1, Gtk::PACK_SHRINK);

          // Create a PackBox - homogeneous = false, spacing = 0,
          // options = Gtk::PACK_EXPAND_PADDING, padding = 0
          pPackBox2 = Gtk::manage(new PackBox(false, 0, Gtk::PACK_EXPAND_PADDING));
          m_box1.pack_start(*pPackBox2, Gtk::PACK_SHRINK);

          // Create a PackBox - homogeneous = false, spacing = 0,
          // options = Gtk::PACK_EXPAND_WIDGET, padding = 0
          pPackBox3 = Gtk::manage(new PackBox(false, 0, Gtk::PACK_EXPAND_WIDGET));
          m_box1.pack_start(*pPackBox3, Gtk::PACK_SHRINK);

          // pack the separator into the vbox.  Remember each of these
          // widgets are being packed into a vbox, so they'll be stacked
          // vertically.
          m_box1.pack_start(m_seperator1, Gtk::PACK_SHRINK, 5);

          // create another new label, and show it.
          m_Label2.set_text("Gtk::Box(Gtk::ORIENTATION_HORIZONTAL, 0);");
          m_Label2.set_alignment(Gtk::ALIGN_START, Gtk::ALIGN_START);
          m_box1.pack_start(m_Label2, Gtk::PACK_SHRINK);

          // Args are: homogeneous, spacing, options, padding
          pPackBox4 = Gtk::manage(new PackBox(true, 0, Gtk::PACK_EXPAND_PADDING));
          m_box1.pack_start(*pPackBox4, Gtk::PACK_SHRINK);

          // Args are: homogeneous, spacing, options, padding
          pPackBox5 = Gtk::manage(new PackBox(true, 0, Gtk::PACK_EXPAND_WIDGET));
          m_box1.pack_start(*pPackBox5, Gtk::PACK_SHRINK);

          m_box1.pack_start(m_seperator2, Gtk::PACK_SHRINK, 5);

          break;
        }

        case 2:
        {

          m_Label1.set_text("Gtk::Box(Gtk::ORIENTATION_HORIZONTAL, 10);");
          m_Label1.set_alignment(Gtk::ALIGN_START, Gtk::ALIGN_START);
          m_box1.pack_start(m_Label1, Gtk::PACK_SHRINK);

          pPackBox1 = Gtk::manage(new PackBox(false, 10, Gtk::PACK_EXPAND_PADDING));
          m_box1.pack_start(*pPackBox1, Gtk::PACK_SHRINK);

          pPackBox2 = Gtk::manage(new PackBox(false, 10, Gtk::PACK_EXPAND_WIDGET));
          m_box1.pack_start(*pPackBox2, Gtk::PACK_SHRINK);

          m_box1.pack_start(m_seperator1, Gtk::PACK_SHRINK, 5);

          m_Label2.set_text("Gtk::Box(Gtk::ORIENTATION_HORIZONTAL, 0);");
          m_Label2.set_alignment(Gtk::ALIGN_START, Gtk::ALIGN_START);
          m_box1.pack_start(m_Label2, Gtk::PACK_SHRINK);

          pPackBox3 = Gtk::manage(new PackBox(false, 0, Gtk::PACK_SHRINK, 10));
          m_box1.pack_start(*pPackBox3, Gtk::PACK_SHRINK);

          pPackBox4 = Gtk::manage(new PackBox(false, 0, Gtk::PACK_EXPAND_WIDGET, 10));
          m_box1.pack_start(*pPackBox4, Gtk::PACK_SHRINK);

          m_box1.pack_start(m_seperator2, Gtk::PACK_SHRINK, 5);

          break;
        }

        case 3:
        {
          // This demonstrates the ability to use Gtk::Box::pack_end() to
          // right justify widgets.  First, we create a new box as before.
          pPackBox1 = Gtk::manage(new PackBox(false, 0, Gtk::PACK_SHRINK));

          // create the label that will be put at the end.
          m_Label1.set_text("end");

          // pack it using pack_end(), so it is put on the right side
          // of the PackBox.
          pPackBox1->pack_end(m_Label1, Gtk::PACK_SHRINK);

          m_box1.pack_start(*pPackBox1, Gtk::PACK_SHRINK);

          // this explicitly sets the separator to 400 pixels wide by 5 pixels
          // high.  This is so the hbox we created will also be 400 pixels wide,
          // and the "end" label will be separated from the other labels in the
          // hbox.  Otherwise, all the widgets in the hbox would be packed as
          // close together as possible.
          m_seperator1.set_size_request(400, 5);

          // pack the separator into ourselves
          m_box1.pack_start(m_seperator1, Gtk::PACK_SHRINK, 5);

          break;
        }

        default:
        {
          std::cerr << "Unexpected command-line option." << std::endl;
          break;
        }
      }

      // Connect the signal to hide the window:
      m_buttonQuit.signal_clicked().connect( sigc::mem_fun(*this,
                  &ExampleWindow::on_button_quit_clicked) );

      // pack the button into the quitbox.
      // The last 2 arguments to Box::pack_start are: options, padding.
      m_boxQuit.pack_start(m_buttonQuit, Gtk::PACK_EXPAND_PADDING);
      m_box1.pack_start(m_boxQuit, Gtk::PACK_SHRINK);

      // pack the vbox (box1) which now contains all our widgets, into the
      // main window.
      add(m_box1);

      show_all_children();
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_button_quit_clicked()
    {
      hide();
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/application.h>
    #include <iostream>
    #include <cstdlib>

    using std::atoi;

    int main(int argc, char *argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      if(argc != 2)
      {
        std::cerr << "usage: packbox num, where num is 1, 2, or 3." << std::endl;
        return 1;
      }

      ExampleWindow window( atoi(argv[1]) );
      return app->run(window); //Shows the window and returns when it is closed.
    }

File: `packbox.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "packbox.h"
    #include <cstdio> //For sprintf().

    PackBox::PackBox(bool homogeneous, int spacing, Gtk::PackOptions options,
            int padding)
    : Gtk::Box(Gtk::ORIENTATION_HORIZONTAL, spacing),
      m_button1("box.pack_start("),
      m_button2("button,"),
      m_button3((options == Gtk::PACK_SHRINK) ? "Gtk::PACK_SHRINK" :
                ((options == Gtk::PACK_EXPAND_PADDING) ?
                 "Gtk::PACK_EXPAND_PADDING" : "Gtk::PACK_EXPAND_WIDGET"))
    {
      set_homogeneous(homogeneous);

      pack_start(m_button1, options, padding);
      pack_start(m_button2, options, padding);
      pack_start(m_button3, options, padding);

      sprintf(padstr, "%d);", padding);

      m_pbutton4 = new Gtk::Button(padstr);
      pack_start(*m_pbutton4, options, padding);
    }

    PackBox::~PackBox()
    {
      delete m_pbutton4;
    }

#### Cajas de Botones

Las cajas de botones son una manera conveniente de ordenar rápidamente un grupo de botones. Su orientación puede ser tanto horizontal como vertical.

Las `ButtonBox` ayudan a hacer que las aplicaciones aparezcan consistentes porque usan opciones estándar, como espaciado entre botones y empaquetado.

Los botones se añaden a una `ButtonBox` con el método `add()`.

Las cajas de botones soportan varios estilos de disposición. Puede obtener y modificar el estilo usando `get_layout()` y `set_layout()`.

Referencia

##### Ejemplo

###### ButtonBox

Código fuente

File: `examplebuttonbox.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLE_BUTTONBOX_H
    #define GTKMM_EXAMPLE_BUTTONBOX_H

    #include <gtkmm.h>

    class ExampleButtonBox : public Gtk::Frame
    {
    public:
      ExampleButtonBox(bool horizontal,
           const Glib::ustring& title,
           gint spacing,
           Gtk::ButtonBoxStyle layout);

    protected:
      Gtk::Button m_Button_OK, m_Button_Cancel, m_Button_Help;
    };

    #endif //GTKMM_EXAMPLE_BUTTONBOX_H

File: `examplewindow.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      void on_button_clicked();

      //Child widgets:
      Gtk::Box m_VBox_Main, m_VBox;
      Gtk::Box m_HBox;
      Gtk::Frame m_Frame_Horizontal, m_Frame_Vertical;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplebuttonbox.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplebuttonbox.h"

    ExampleButtonBox::ExampleButtonBox(bool horizontal,
           const Glib::ustring& title,
           gint spacing,
           Gtk::ButtonBoxStyle layout)
    : Gtk::Frame(title),
      m_Button_OK("OK"),
      m_Button_Cancel("Cancel"),
      m_Button_Help("Help")
    {
      Gtk::ButtonBox* bbox = 0;

      if(horizontal)
        bbox = Gtk::manage( new Gtk::ButtonBox(Gtk::ORIENTATION_HORIZONTAL) );
      else
        bbox = Gtk::manage( new Gtk::ButtonBox(Gtk::ORIENTATION_VERTICAL) );

      bbox->set_border_width(5);

      add(*bbox);

      /* Set the appearance of the Button Box */
      bbox->set_layout(layout);
      bbox->set_spacing(spacing);

      bbox->add(m_Button_OK);
      bbox->add(m_Button_Cancel);
      bbox->add(m_Button_Help);
    }

File: `examplewindow.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include "examplebuttonbox.h"

    ExampleWindow::ExampleWindow()
    : m_VBox_Main(Gtk::ORIENTATION_VERTICAL),
      m_VBox(Gtk::ORIENTATION_VERTICAL),
      m_Frame_Horizontal("Horizontal Button Boxes"),
      m_Frame_Vertical("Vertical Button Boxes")
    {
      set_title("Gtk::ButtonBox");
      add(m_VBox_Main);

      m_VBox_Main.pack_start(m_Frame_Horizontal, Gtk::PACK_EXPAND_WIDGET, 10);

      //The horizontal ButtonBoxes:
      m_VBox.set_border_width(10);
      m_Frame_Horizontal.add(m_VBox);

      m_VBox.pack_start(*Gtk::manage(
                  new ExampleButtonBox(true, "Spread (spacing 40)", 40,
                      Gtk::BUTTONBOX_SPREAD)),
              Gtk::PACK_EXPAND_WIDGET, 0);

      m_VBox.pack_start(*Gtk::manage(
                  new ExampleButtonBox(true, "Edge (spacing 30)", 30,
                      Gtk::BUTTONBOX_EDGE)),
              Gtk::PACK_EXPAND_WIDGET, 5);

      m_VBox.pack_start(*Gtk::manage(
                  new ExampleButtonBox(true, "Start (spacing 20)", 20,
                      Gtk::BUTTONBOX_START)),
              Gtk::PACK_EXPAND_WIDGET, 5);

      m_VBox.pack_start(*Gtk::manage(
                  new ExampleButtonBox(true, "end (spacing 10)", 10,
                      Gtk::BUTTONBOX_END)),
              Gtk::PACK_EXPAND_WIDGET, 5);

      //The vertical ButtonBoxes:
      m_VBox_Main.pack_start(m_Frame_Vertical, Gtk::PACK_EXPAND_WIDGET, 10);

      m_HBox.set_border_width(10);
      m_Frame_Vertical.add(m_HBox);

      m_HBox.pack_start(*Gtk::manage(
                  new ExampleButtonBox(false, "Spread (spacing 5)", 5,
                      Gtk::BUTTONBOX_SPREAD)),
              Gtk::PACK_EXPAND_WIDGET, 0);

      m_HBox.pack_start(*Gtk::manage(
                  new ExampleButtonBox(false, "Edge (spacing 30)", 30,
                      Gtk::BUTTONBOX_EDGE)),
              Gtk::PACK_EXPAND_WIDGET, 5);

      m_HBox.pack_start(*Gtk::manage(
                  new ExampleButtonBox(false, "Start (spacing 20)", 20,
                      Gtk::BUTTONBOX_START)),
              Gtk::PACK_EXPAND_WIDGET, 5);

      m_HBox.pack_start(*Gtk::manage(new ExampleButtonBox(false, "End (spacing 10)",
                      10, Gtk::BUTTONBOX_END)),
              Gtk::PACK_EXPAND_WIDGET, 5);

      show_all_children();
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_button_clicked()
    {
      hide();
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      ExampleWindow window;

      //Shows the window and returns when it is closed.
      return app->run(window);
    }

#### Grid

Un `Grid` establece dinámicamente widgets hijos en filas y columnas. No es necesario especificar las dimensiones de la red en el constructor.

Los widgets hijos pueden abarcar múltiples filas o columnas, usando `attach()`, o añadirse a un widget existente dentro de la cuadrícula con `attach_next_to()`. Se puede establecer que las filas o columnas individuales de la cuadrícula tengan una altura o ancho uniforme con `set_row_homogeneous()` y `set_column_homogeneous()`.

Puede establecer las propiedades margin y expand de los `Widget` hijos para controlar su espaciado y comportamiento cuando se redimensiona la cuadrícula.

Referencia

##### Ejemplo

Este ejemplo crea una ventana con tres botones en una cuadrícula. Los dos primeros botones están en la fila superior, de izquierda a derecha. Se ha añadido un tercer botón bajo el primer botón, en una nueva fila más abajo, abarcando dos columnas.

###### Grid

Código fuente

File: `examplewindow.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    private:
      // Signal handlers:
      void on_button_quit();
      void on_button_numbered(const Glib::ustring& data);

      // Child widgets:
      Gtk::Grid m_grid;
      Gtk::Button m_button_1, m_button_2, m_button_quit;
    };

    #endif /* GTKMM_EXAMPLEWINDOW_H */

File: `examplewindow.cc` (For use with gtkmm 3, not gtkmm 2)

    #include <iostream>
    #include "examplewindow.h"

    ExampleWindow::ExampleWindow()
    : m_button_1("button 1"),
      m_button_2("button 2"),
      m_button_quit("Quit")
    {
      set_title("Gtk::Grid");
      set_border_width(12);

      add(m_grid);

      m_grid.add(m_button_1);
      m_grid.add(m_button_2);
      m_grid.attach_next_to(m_button_quit, m_button_1, Gtk::POS_BOTTOM, 2, 1);

      m_button_1.signal_clicked().connect(
        sigc::bind<Glib::ustring>( sigc::mem_fun(*this,
          &ExampleWindow::on_button_numbered), "button 1") );
      m_button_2.signal_clicked().connect(
        sigc::bind<Glib::ustring>( sigc::mem_fun(*this,
          &ExampleWindow::on_button_numbered), "button 2") );

      m_button_quit.signal_clicked().connect(sigc::mem_fun(*this,
        &ExampleWindow::on_button_quit) );

      show_all_children();
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_button_quit()
    {
      hide();
    }

    void
    ExampleWindow::on_button_numbered(const Glib::ustring& data)
    {
      std::cout << data << " was pressed" << std::endl;
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      ExampleWindow window;

      // Shows the window and returns when it is closed.
      return app->run(window);
    }

#### Tabla

`Gtk::Table` permite poner widgets en una cuadrícula, de manera similar a `Gtk::Grid`.

`Gtk::Table` se marcó como obsoleto en gtkmm 3.4 y no se debe usar en el código nuevo. Use `Gtk::Grid` en su lugar.

#### Cuaderno

Un `Notebook` tiene un conjunto de `páginas` apiladas, cada una de ellas contiene widgets. Las `pestañas` etiquetadas permiten al usuario seleccionar las páginas. Los `Notebook` permiten colocar varios conjuntos de widgets en un espacio reducido, mostrando sólo una página a la vez. Por ejemplo, se utilizan a menudo en los diálogos de preferencias.

Use los métodos `append_page()`, `prepend_page()` e `insert_page()` para añadir páginas con pestañas al `Notebook`, proporcionándoles el widget hijo y el nombre de la pestaña.

Para descubrir la página visible actual, use el método `get_current_page()`. Esto devuelve el número de página. Después llame a `get_nth_page()` con ese número le dará un puntero al widget hijo en sí.

Para cambiar la página seleccionada mediante programación, use el método `set_current_page()`.

Referencia

##### Ejemplo

###### Cuaderno

Código fuente

File: `examplewindow.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      void on_button_quit();
      void on_notebook_switch_page(Gtk::Widget* page, guint page_num);

      //Child widgets:
      Gtk::Box m_VBox;
      Gtk::Notebook m_Notebook;
      Gtk::Label m_Label1, m_Label2;

      Gtk::ButtonBox m_ButtonBox;
      Gtk::Button m_Button_Quit;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 3, not gtkmm 2)

    #include <iostream>
    #include "examplewindow.h"

    ExampleWindow::ExampleWindow()
    : m_VBox(Gtk::ORIENTATION_VERTICAL),
      m_Label1("Contents of tab 1"),
      m_Label2("Contents of tab 2"),
      m_Button_Quit("Quit")
    {
      set_title("Gtk::Notebook example");
      set_border_width(10);
      set_default_size(400, 200);

      add(m_VBox);

      //Add the Notebook, with the button underneath:
      m_Notebook.set_border_width(10);
      m_VBox.pack_start(m_Notebook);
      m_VBox.pack_start(m_ButtonBox, Gtk::PACK_SHRINK);

      m_ButtonBox.pack_start(m_Button_Quit, Gtk::PACK_SHRINK);
      m_Button_Quit.signal_clicked().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_button_quit) );

      //Add the Notebook pages:
      m_Notebook.append_page(m_Label1, "First");
      m_Notebook.append_page(m_Label2, "Second");

      m_Notebook.signal_switch_page().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_notebook_switch_page) );

      show_all_children();
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_button_quit()
    {
      hide();
    }

    void ExampleWindow::on_notebook_switch_page(Gtk::Widget* /* page */, guint page_num)
    {
      std::cout << "Switched to tab with index " << page_num << std::endl;

      //You can also use m_Notebook.get_current_page() to get this index.
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      ExampleWindow window;

      //Shows the window and returns when it is closed.
      return app->run(window);
    }

#### Asistente

Un `Assistant` divide una operación compleja en pasos. Cada paso es una página, conteniendo una cabecera, un widget hijo, y un área de acción. El área de acción del asistente tiene botones de navegación que se actualizan automáticamente dependiendo del tipo de la página, establecido con `set_page_type()`.

Use los métodos `append_page()`, `prepend_page` e `insert_page()` para añadirle páginas al `Assistant`, proporcionándole el widget hijo por cada página.

Para determinar la página actualmente visible, use el método `get_current_page()` y pásele el resultado a `get_nth_page()`, que le devuelve un puntero al widget en sí. Para cambiar mediante programación la página actual, use el método `set_current_page()`.

Para establecer el título de una página, use el método `set_page_title()`. Las imágenes de cabecera y de lado de una página se pueden establecer con los métodos `set_page_header_image()` y `set_page_side_image()`.

Para añadir widgets al área de acción, use el método `add_action_widget()`. Serán empaquetados junto a los botones predeterminados. Use el método `remove_action_widget()` para borrar los widgets.

Referencia

##### Ejemplo

###### Asistente

Código fuente

File: `exampleassistant.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLEASSISTANT_H
    #define GTKMM_EXAMPLEASSISTANT_H

    #include <gtkmm.h>

    class ExampleAssistant : public Gtk::Assistant
    {
    public:
      ExampleAssistant();
      virtual ~ExampleAssistant();

      void get_result(bool& check_state, Glib::ustring& entry_text);

    private:
      // Signal handlers:
      void on_assistant_apply();
      void on_assistant_cancel();
      void on_assistant_close();
      void on_assistant_prepare(Gtk::Widget* widget);
      void on_entry_changed();

      // Member functions:
      void print_status();

      // Child widgets:
      Gtk::Box m_box;
      Gtk::Label m_label1, m_label2;
      Gtk::CheckButton m_check;
      Gtk::Entry m_entry;
    };

    #endif /* GTKMM_EXAMPLEASSISTANT_H */

File: `examplewindow.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include "exampleassistant.h"
    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    private:
      // Signal handlers:
      void on_button_clicked();
      void on_assistant_apply();

      // Child widgets:
      Gtk::Grid m_grid;
      Gtk::Button m_button;
      Gtk::Label m_label1, m_label2;
      Gtk::CheckButton m_check;
      Gtk::Entry m_entry;
      ExampleAssistant m_assistant;
    };

    #endif /* GTKMM_EXAMPLEWINDOW_H */

File: `examplewindow.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include "exampleassistant.h"

    ExampleWindow::ExampleWindow()
    : m_button("Show the assistant"),
      m_label1("State of assistant checkbutton:"),
      m_label2("Contents of assistant entry:")
    {
      set_title("Gtk::Assistant example");
      set_border_width(12);

      m_grid.set_row_homogeneous(true);

      m_grid.attach(m_button, 0, 0, 2, 1);
      m_button.set_hexpand(true);
      m_button.set_valign(Gtk::ALIGN_CENTER);

      m_grid.attach(m_label1, 0, 1, 1, 1);
      m_label1.set_alignment(0.0, 0.5);

      m_grid.attach(m_label2, 0, 2, 1, 1);
      m_label2.set_alignment(0.0, 0.5);

      m_grid.attach(m_check, 1, 1, 1, 1);
      m_check.set_halign(Gtk::ALIGN_START);

      m_grid.attach(m_entry, 1, 2, 1, 1);
      m_entry.set_hexpand(true);

      add(m_grid);

      m_button.signal_clicked().connect(sigc::mem_fun(*this,
        &ExampleWindow::on_button_clicked));
      m_assistant.signal_apply().connect(sigc::mem_fun(*this,
        &ExampleWindow::on_assistant_apply));

      m_check.set_sensitive(false);
      m_entry.set_sensitive(false);

      show_all_children();
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_assistant_apply()
    {
      bool check_state;
      Glib::ustring entry_text;

      m_assistant.get_result(check_state, entry_text);
      m_check.set_active(check_state);
      m_entry.set_text(entry_text);
    }

    void ExampleWindow::on_button_clicked()
    {
      m_assistant.show();
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      ExampleWindow window;

      // Shows the window and returns when it is closed.
      return app->run(window);
    }

File: `exampleassistant.cc` (For use with gtkmm 3, not gtkmm 2)

    #include <iostream>
    #include "exampleassistant.h"

    ExampleAssistant::ExampleAssistant()
    : m_box(Gtk::ORIENTATION_HORIZONTAL, 12),
      m_label1("Type text to allow the assistant to continue:"),
      m_label2("Confirmation page"),
      m_check("Optional extra information")
    {
      set_title("Gtk::Assistant example");
      set_border_width(12);
      set_default_size(400, 300);

      m_box.pack_start(m_label1);
      m_box.pack_start(m_entry);

      append_page(m_box);
      append_page(m_check);
      append_page(m_label2);

      set_page_title(*get_nth_page(0), "Page 1");
      set_page_title(*get_nth_page(1), "Page 2");
      set_page_title(*get_nth_page(2), "Confirmation");

      set_page_complete(m_check, true);
      set_page_complete(m_label2, true);

      set_page_type(m_box, Gtk::ASSISTANT_PAGE_INTRO);
      set_page_type(m_label2, Gtk::ASSISTANT_PAGE_CONFIRM);

      signal_apply().connect(sigc::mem_fun(*this,
        &ExampleAssistant::on_assistant_apply));
      signal_cancel().connect(sigc::mem_fun(*this,
        &ExampleAssistant::on_assistant_cancel));
      signal_close().connect(sigc::mem_fun(*this,
        &ExampleAssistant::on_assistant_close));
      signal_prepare().connect(sigc::mem_fun(*this,
        &ExampleAssistant::on_assistant_prepare));

      m_entry.signal_changed().connect(sigc::mem_fun(*this,
        &ExampleAssistant::on_entry_changed));

      show_all_children();
    }

    ExampleAssistant::~ExampleAssistant()
    {
    }

    void ExampleAssistant::get_result(bool& check_state, Glib::ustring& entry_text)
    {
      check_state = m_check.get_active();
      entry_text = m_entry.get_text();
    }

    void ExampleAssistant::on_assistant_apply()
    {
      std::cout << "Apply was clicked";
      print_status();
    }

    void ExampleAssistant::on_assistant_cancel()
    {
      std::cout << "Cancel was clicked";
      print_status();
      hide();
    }

    void ExampleAssistant::on_assistant_close()
    {
      std::cout << "Assistant was closed";
      print_status();
      hide();
    }

    void ExampleAssistant::on_assistant_prepare(Gtk::Widget* /* widget */)
    {
      set_title(Glib::ustring::compose("Gtk::Assistant example (Page %1 of %2)",
        get_current_page() + 1, get_n_pages()));
    }

    void ExampleAssistant::on_entry_changed()
    {
      // The page is only complete if the entry contains text.
      if(m_entry.get_text_length())
        set_page_complete(m_box, true);
      else
        set_page_complete(m_box, false);
    }

    void ExampleAssistant::print_status()
    {
      std::cout << ", entry contents: \"" << m_entry.get_text()
        << "\", checkbutton status: " << m_check.get_active() << std::endl;
    }

## El widget TreeView

El widget `Gtk::TreeView` puede contener listas o árboles de datos, en columnas.

### El modelo

Cada `Gtk::TreeView` tiene un `Gtk::Model` asociado que contiene los datos mostrados por el `TreeView` Varios `Gtk::TreeView` puede usar el mismo `Gtk::TreeModel`. Por ejemplo, esto le permite mostrar y editar los mismos datos de 2 formas diferentes al mismo tiempo. O las 2 vistas pueden mostrar diferentes columnas de los mismos modelos de datos, de la misma manera que dos consultas SQL (o «vistas») pueden mostrar diferentes campos de la misma tabla de la base de datos.

A pesar de que, teóricamente, puede implementar su propio modelo, normalmente usará las clases de los modelos `ListStore` o `TreeStore`.

Referencia

#### ListStore, para filas

El `ListStore` contiene filas simples de datos, y ninguna fila tiene hijos.

##### TreeView - ListStore

Referencia

#### TreeStore, para una jerarquía

El `TreeStore` contiene filas de datos, y cada fila puede tener filas hijas.

##### TreeView - TreeStore

Referencia

#### Columnas del modelo

La clase `TreeModelColumnRecord` se usa para rastrear a las columnas y sus tipos de datos. Añádale instancias `TreeModelColumn` al `ColumnRecord` y luego use esas `TreeModelColumn` cuando establezca u obtenga los datos en las filas del modelo. Probablemente encuentre conveniente derivar un `TreeModelColumnRecord` que tenga a sus instancias `TreeModelColumn` como datos miembro.

    class ModelColumns : public Gtk::TreeModelColumnRecord
    {
    public:

      ModelColumns()
        { add(m_col_text); add(m_col_number); }

      Gtk::TreeModelColumn<Glib::ustring> m_col_text;
      Gtk::TreeModelColumn<int> m_col_number;
    };

    ModelColumns m_Columns;

Especifique el `ColumnRecord` cuando cree el modelo, así:

    Glib::RefPtr<Gtk::ListStore> refListStore =
        Gtk::ListStore::create(m_Columns);

Tenga en cuenta que la instancia (como m_Columns aquí) normalmente no debe ser estática, porque a menudo se necesita instanciarla después de haber instanciado a glibmm.

#### Añadir filas

Añadir filas al modelo con los métodos `append()`, `prepend()`, o `insert()`.

    Gtk::TreeModel::iterator iter = m_refListStore->append();

Puede desreferenciar al iterador para obtener la fila:

    Gtk::TreeModel::Row row = *iter;

##### Añadiendo filas secundarias

Los modelos `Gtk::TreeStore` pueden tener elementos hijos. Añádalos con los métodos `append()`, `prepend()`, o `insert()`, así:

    Gtk::TreeModel::iterator iter_child =
        m_refListStore->append(row.children());

#### Configurar los valores

Puede usar la sobrecarga de `operator[]` para establecer los datos de una columna particular en la fila, especificando la `TreeModelColumn` que se usó para crear el modelo.

    row[m_Columns.m_col_text] = "sometext";

#### Obtener los valores

Puede usar la sobrecarga `operator[]` para obtener los datos de una columna particular en una fila, especificando la `TreeModelColumn` que se usó para crear el modelo.

    Glib::ustring strText = row[m_Columns.m_col_text];
    int number = row[m_Columns.m_col_number];

El compilador le hará saber si usa un tipo inapropiado. Por ejemplo, esto generaría un error de compilación:

    //compiler error - no conversion from ustring to int.
    int number = row[m_Columns.m_col_text];

#### Columnas «ocultas»

Puede querer asociar datos adicionales a cada fila. Si es así, sólo añádalos como una columa del modelo, pero no se los añada a la vista.

### La vista

La vista es el widget en sí (`Gtk::TreeView`) que muestra los datos del modelo (`Gtk::TreeModel`) y le permite al usuario interactuar con él. La vista puede mostrar todas las columnas del modelo, o sólo algunas, y puede mostrarlas de varias maneras.

Referencia

#### Usar un modelo

Puede especificar un `Gtk::TreeModel` cuando construye la `Gtk::TreeView`, o puede usar el método `set_model()`, así:

    m_TreeView.set_model(m_refListStore);

#### Añadir columnas a la vista

Puede usar el método `append_column()` para decirle a la vista que debe mostrar ciertas columnas del modelo, en cierto orden, con un cierto título de columna.

    m_TreeView.append_column("Messages", m_Columns.m_col_text);

Cuando use esta simple sobrecarga `append_column()`, el `TreeView` mostrará los datos del modelo con un `CellRenderer` apropiado. Por ejemplo, las cadenas y los números se muestran en un simple widget `Gtk::Entry`, y los booleanos en un `Gtk::CheckButton`. Esto es normalmente lo que necesita. Para otros tipos de columnas, debe conectar un retorno de llamada que convierta su tipo en una cadena representativa, con `TreeViewColumn::set_cell_data_func()`; o derivar un `CellRenderer` personalizado. Tenga en cuenta que no se soporta el tipo «(unsigned) short» de manera predeterminada: puede usar como tipo de columna «(unsigned) int» o «(unsigned) long» en su lugar.

#### Más de una columna del modelo por columna de la vista

Para reproducir más de una columna del modelo en una columna de vista, necesita crear el widget `TreeView::Column` manualmente, y usar `pack_start()` para añadirle las columnas del modelo.

Entonces, use `append_column()` para añadirle la columna de vista a la vista. Tenga en cuenta que `Gtk::View::append_column()` se sobrecarga para aceptar un widget `Gtk::View::Column`, o sólo el `TreeModelColumn` del cual genera un widget `Gtk::View::Column` apropiado.

Aquí hay algo de código de ejemplo de `demos/gtk-demo/example_stockbrowser.cc`, que tiene un icono pixbuf y un nombre de texto en la misma columna:

    Gtk::TreeView::Column* pColumn =
        Gtk::manage( new Gtk::TreeView::Column("Symbol") );

    // m_columns.icon and m_columns.symbol are columns in the model.
    // pColumn is the column in the TreeView:
    pColumn->pack_start(m_columns.icon, false); //false = don't expand.
    pColumn->pack_start(m_columns.symbol);

    m_TreeView.append_column(*pColumn);

#### Especificar los detalles del CellRenderer

Los `CellRenderer` predeterminados y su comportamiento predeterminado normalmente serán suficientes, pero quizás necesite ocasionalmente un control más preciso. Por ejemplo, este código de ejemplo de `demos/gtk-demo/example_treestore.cc` construye manualmente un widget `Gtk::CellRenderer` y le indica que procese los datos de varias columnas de modelo a través de varios aspectos de su apariencia.

    Gtk::CellRendererToggle* pRenderer =
        Gtk::manage( new Gtk::CellRendererToggle() );
    int cols_count = m_TreeView.append_column("Alex", *pRenderer);
    Gtk::TreeViewColumn* pColumn = m_TreeView.get_column(cols_count-1);
    if(pColumn)
    {
      pColumn->add_attribute(pRenderer->property_active(),
          m_columns.alex);
      pColumn->add_attribute(pRenderer->property_visible(),
          m_columns.visible);
      pColumn->add_attribute(pRenderer->property_activatable(),
          m_columns.world);

También puede conectarle señales a un `CellRenderer` para detectar las acciones del usuario. Por ejemplo:

    Gtk::CellRendererToggle* pRenderer =
        Gtk::manage( new Gtk::CellRendererToggle() );
    pRenderer->signal_toggled().connect(
        sigc::bind( sigc::mem_fun(*this,
            &Example_TreeView_TreeStore::on_cell_toggled), m_columns.dave)
    );

#### Celdas editables

##### Celdas editables guardadas automáticamente.

El usuario puede editar las celdas en una `TreeView` directamente. Para permitir esto, use los métodos `Gtk::TreeView` `insert_column_editable()` y `append_column_editable()` en lugar de `insert_column()` y `append_column()`. Cuando estas celdas se editen, los nuevos valores se guardarán inmediatamente en el modelo. Tenga en cuenta que estos métodos son plantillas que sólo se pueden instanciar para tipos de columnas simples como `Glib::ustring`, int, y long.

##### Implementación de la lógica personalizada para celdas editables.

Sin embargo, tal vez no quiera que se almacenen los valores nuevos inmediatamente. Por ejemplo, tal vez quiera restringir la entrada a ciertos caracteres o rangos de valores.

Para lograr esto, debe usar los métodos `Gtk::TreeView` `insert_column()` y `append_column()` normales, y luego usar `get_column_cell_renderer()` para obtener el `Gtk::CellRenderer` que usa esa columna.

Entonces, convierta ese `Gtk::CellRenderer*` al `CellRenderer` específico que espera, para que pueda usar la API específica.

Por ejemplo, para un CellRendererText, establecería la propiedad editable de la celda a «true», así:

    cell.property_editable() = true;

Para un CellRendererToggle, establecería la propiedad activable en su lugar.

Entonces, puede conectar la señal «edited» apropiada. Por ejemplo, conectarlo a `Gtk::CellRendererText::signal_edited()`, o a `Gtk::CellRendererToggle::signal_toggled()`. Si la columna contiene más de un `CellRenderer`, entonces tendrá que usar `Gtk::TreeView::get_column()` y luego llamar a `get_cell_renderers()` en esa columna de la vista.

En su manejador de señales, debe examinar el valor nuevo y luego almacenarlo en el modelo, si eso es lo apropiado para su aplicación.

### Iterar sobre las filas del modelo

`Gtk::TreeModel` proporciona un contenedor de sus hijos al estilo de las bibliotecas C++ estándar, a través del método `children()`. Puede usar los incrementos del iterador familiares de los métodos `begin()` y `end()`.

    typedef Gtk::TreeModel::Children type_children; //minimise code length.
    type_children children = refModel->children();
    for(type_children::iterator iter = children.begin();
        iter != children.end(); ++iter)
    {
      Gtk::TreeModel::Row row = *iter;
      //Do something with the row - see above for set/get.
    }

#### Fila hija

Cuando usa un `Gtk::TreeStore`, las filas pueden tener filas hijas, que a su vez pueden tener sus propios hijos. Use `Gtk::TreeModel::Row::children()` para obtener el contenedor de las `Row` hijas:

    Gtk::TreeModel::Children children = row.children();

### La selección

Para descubrir qué filas ha seleccionado el usuario, obtenga el objeto `Gtk::TreeView::Selection` del `TreeView`, así:

    Glib::RefPtr<Gtk::TreeSelection> refTreeSelection =
        m_TreeView.get_selection();

#### Selección única o múltiple

De manera predeterminada, sólo se pueden seleccionar filas únicas, pero puede permitir la selección múltiple estableciendo el modo, así:

    refTreeSelection->set_mode(Gtk::SELECTION_MULTIPLE);

#### Las filas seleccionadas

Para la selección simple, puede simplemente llamar `get_selected()`, así:

    TreeModel::iterator iter = refTreeSelection->get_selected();
    if(iter) //If anything is selected
    {
      TreeModel::Row row = *iter;
      //Do something with the row.
    }

Para la selección múltiple, debe definir una devolución de llamada, y pasársela a `selected_foreach()`, `selected_foreach_path()`, o `selected_foreach_iter()`, así:

    refTreeSelection->selected_foreach_iter(
        sigc::mem_fun(*this, &TheClass::selected_row_callback) );

    void TheClass::selected_row_callback(
        const Gtk::TreeModel::iterator& iter)
    {
      TreeModel::Row row = *iter;
      //Do something with the row.
    }

#### La señal «changed»

Para responder a la pulsación del usuario en una fila o un rango de filas, conéctese a la señal así:

    refTreeSelection->signal_changed().connect(
        sigc::mem_fun(*this, &Example_StockBrowser::on_selection_changed)
    );

#### Evitar la selección de la fila

Tal vez, el usuario no deba ser capaz de seleccionar todos los elementos en su lista o árbol. Por ejemplo, en gtk-demo, puede seleccionar una demostración para ver su código fuente, pero no tiene ningún sentido seleccionar una categoría de demostraciones.

Para controlar qué filas pueden seleccionarse, use el método `set_select_function()`, proporcionándole una devolución de llamada `sigc::slot`. Por ejemplo:

    m_refTreeSelection->set_select_function( sigc::mem_fun(*this,
        &DemoWindow::select_function) );

Y luego

    bool DemoWindow::select_function(
        const Glib::RefPtr<Gtk::TreeModel>& model,
        const Gtk::TreeModel::Path& path, bool)
    {
      const Gtk::TreeModel::iterator iter = model->get_iter(path);
      return iter->children().empty(); // only allow leaf nodes to be selected
    }

#### Cambiar la selección

Para cambiar la selección, especifique un `Gtk::TreeModel::iterator` o un `Gtk::TreeModel::Row`, así:

    Gtk::TreeModel::Row row = m_refModel->children()[5]; //The fifth row.
    if(row)
      refTreeSelection->select(row);

o

    Gtk::TreeModel::iterator iter = m_refModel->children().begin()
    if(iter)
      refTreeSelection->select(iter);

### Ordenar

Los modelos de árbol estándar (`TreeStore` y `ListStore`) derivan de `TreeSortable`, por lo que ofrecen funciones de ordenación. Por ejemplo, llame a `set_sort_column()` para ordenar el modelo por la columna especificada. O, proporcione una función de retorno de llamada a `set_sort_func()` para implementar un algoritmo de ordenación más complejo.

Referencia de TreeSortable

#### Ordenación al pulsar en columnas

Para que un usuario pueda pulsar en la cabecera de una columna de un `TreeView` para ordenar el contenido del `TreeView`, llame a `Gtk::TreeViewModel::set_sort_column()`, proporcionando al modelo la columna por la que se deba ordenar cuando se pulse sobre la cabecera. Por ejemplo:

    Gtk::TreeView::Column* pColumn = treeview.get_column(0);
    if(pColumn)
      pColumn->set_sort_column(m_columns.m_col_id);

#### Vistas ordenadas independientemente del mismo modelo

El `TreeView` ya le permite mostrar al mismo `TreeModel` en dos widgets `TreeView`. Si necesita que uno de estos «TreeView» ordene el modelo de manera diferente al otro, entonces use un `TreeModelSort` en lugar de solo, por ejemplo, `Gtk::TreeViewModel::set_sort_column()`. `TreeModelSort` es un modelo que contiene a otro modelo, presentando una versión ordenada de ese modelo. Por ejemplo, puede añadir una versión ordenada de un modelo a un `TreeView` así:

    Glib::RefPtr<Gtk::TreeModelSort> sorted_model =
        Gtk::TreeModelSort::create(model);
    sorted_model->set_sort_column(columns.m_col_name, Gtk::SORT_ASCENDING);
    treeview.set_model(sorted_model);

Tenga en cuenta, sin embargo, que el «TreeView» le proporcionará iteradores al modelo ordenado. Debe convertirlos a iteradores del modelo hijo subyacente para llevar a cabo acciones en ese modelo. Por ejemplo:

    void ExampleWindow::on_button_delete()
    {
      Glib::RefPtr<Gtk::TreeSelection> refTreeSelection =
          m_treeview.get_selection();
      if(refTreeSelection)
      {
        Gtk::TreeModel::iterator sorted_iter =
            m_refTreeSelection->get_selected();
        if(sorted_iter)
        {
          Gtk::TreeModel::iterator iter =
              m_refModelSort->convert_iter_to_child_iter(sorted_iter);
          m_refModel->erase(iter);
        }
      }
    }

Referencia de TreeModelSort

### Arrastrar y soltar

`Gtk::TreeView` ya implementa un simple «arrastrar y soltar» cuando se usa con los modelos `Gtk::ListStore` o `Gtk::TreeStore`. Si es necesario, también le permite implementar un comportamiento más complejo cuando se arrastran y sueltan los elementos, usando la API de Arrastrar y soltar normal.

#### Filas reordenables

Si llama a `Gtk::TreeView::set:reorderable`, entonces se podrán mover los elementos de su «TreeView» dentro del «TreeView» en sí. Esto se demuestra en el ejemplo `TreeStore`.

Sin embargo, esto no le permite ningún control acerca de qué elementos pueden arrastrarse, ni dónde pueden soltarse. Si necesita ese control adicional, puede crear un `Gtk::TreeModel` derivado de `Gtk::TreeStore` o `Gtk::ListStore` y sobrecargar los métodos virtuales `Gtk::TreeDragSource::row_draggable()` y `Gdk::TreeDragDest::row_drop_possible()`. Puede examinar los `Gtk::TreeModel::Path` proporcionados y permitir o no arrastrar y soltar devolviendo `true` o `false`.

Esto se demuestra en el ejemplo «drag_and_drop».

### Menú contextual emergente

Mucha gente necesita implementar menús contextuales del botón derecho para los `TreeView`, por lo que se explicará cómo hacerlo para ahorrarle tiempo. Excepto uno o dos puntos, es muy parecido a un menú contextual normal, tal como se describe en el capítulo acerca de menús.

#### Manejar `button_press_event`

Para detectar la pulsación del botón derecho del ratón, debe manejar la señal `button_press_event`, y verificar exactamente qué botón se ha pulsado. Dado que el `TreeView` normalmente maneja esta señal por completo, necesitará sobrecargar el manejador de señales predeterminado en una clase `TreeView` derivada o bien usar el método `connect_notify()` en lugar de `connect()`. Probablemente también quiera llamar al manejador predeterminado antes de hacer nada más, para que la pulsación derecha haga que se seleccione la fila primero.

Esto queda demostrado en el ejemplo del menú emergente personalizado.

### Ejemplos

#### ListStore

Este ejemplo tiene un widget `Gtk::TreeView`, con un modelo `Gtk::ListStore`.

##### TreeView - ListStore

Código fuente

File: `examplewindow.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      void on_button_quit();

      //Tree model columns:
      class ModelColumns : public Gtk::TreeModel::ColumnRecord
      {
      public:

        ModelColumns()
        { add(m_col_id); add(m_col_name); add(m_col_number); add(m_col_percentage);}

        Gtk::TreeModelColumn<unsigned int> m_col_id;
        Gtk::TreeModelColumn<Glib::ustring> m_col_name;
        Gtk::TreeModelColumn<short> m_col_number;
        Gtk::TreeModelColumn<int> m_col_percentage;
      };

      ModelColumns m_Columns;

      //Child widgets:
      Gtk::Box m_VBox;

      Gtk::ScrolledWindow m_ScrolledWindow;
      Gtk::TreeView m_TreeView;
      Glib::RefPtr<Gtk::ListStore> m_refTreeModel;

      Gtk::ButtonBox m_ButtonBox;
      Gtk::Button m_Button_Quit;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 3, not gtkmm 2)

    #include <iostream>
    #include "examplewindow.h"

    ExampleWindow::ExampleWindow()
    : m_VBox(Gtk::ORIENTATION_VERTICAL),
      m_Button_Quit("Quit")
    {
      set_title("Gtk::TreeView (ListStore) example");
      set_border_width(5);
      set_default_size(400, 200);

      add(m_VBox);

      //Add the TreeView, inside a ScrolledWindow, with the button underneath:
      m_ScrolledWindow.add(m_TreeView);

      //Only show the scrollbars when they are necessary:
      m_ScrolledWindow.set_policy(Gtk::POLICY_AUTOMATIC, Gtk::POLICY_AUTOMATIC);

      m_VBox.pack_start(m_ScrolledWindow);
      m_VBox.pack_start(m_ButtonBox, Gtk::PACK_SHRINK);

      m_ButtonBox.pack_start(m_Button_Quit, Gtk::PACK_SHRINK);
      m_ButtonBox.set_border_width(5);
      m_ButtonBox.set_layout(Gtk::BUTTONBOX_END);
      m_Button_Quit.signal_clicked().connect( sigc::mem_fun(*this,
                  &ExampleWindow::on_button_quit) );

      //Create the Tree model:
      m_refTreeModel = Gtk::ListStore::create(m_Columns);
      m_TreeView.set_model(m_refTreeModel);

      //Fill the TreeView's model
      Gtk::TreeModel::Row row = *(m_refTreeModel->append());
      row[m_Columns.m_col_id] = 1;
      row[m_Columns.m_col_name] = "Billy Bob";
      row[m_Columns.m_col_number] = 10;
      row[m_Columns.m_col_percentage] = 15;

      row = *(m_refTreeModel->append());
      row[m_Columns.m_col_id] = 2;
      row[m_Columns.m_col_name] = "Joey Jojo";
      row[m_Columns.m_col_number] = 20;
      row[m_Columns.m_col_percentage] = 40;

      row = *(m_refTreeModel->append());
      row[m_Columns.m_col_id] = 3;
      row[m_Columns.m_col_name] = "Rob McRoberts";
      row[m_Columns.m_col_number] = 30;
      row[m_Columns.m_col_percentage] = 70;

      //Add the TreeView's view columns:
      //This number will be shown with the default numeric formatting.
      m_TreeView.append_column("ID", m_Columns.m_col_id);
      m_TreeView.append_column("Name", m_Columns.m_col_name);

      m_TreeView.append_column_numeric("Formatted number", m_Columns.m_col_number,
              "%010d" /* 10 digits, using leading zeroes. */);

      //Display a progress bar instead of a decimal number:
      Gtk::CellRendererProgress* cell = Gtk::manage(new Gtk::CellRendererProgress);
      int cols_count = m_TreeView.append_column("Some percentage", *cell);
      Gtk::TreeViewColumn* pColumn = m_TreeView.get_column(cols_count - 1);
      if(pColumn)
      {
        pColumn->add_attribute(cell->property_value(), m_Columns.m_col_percentage);
      }

      //Make all the columns reorderable:
      //This is not necessary, but it's nice to show the feature.
      //You can use TreeView::set_column_drag_function() to more
      //finely control column drag and drop.
      for(guint i = 0; i < 2; i++)
      {
        Gtk::TreeView::Column* pColumn = m_TreeView.get_column(i);
        pColumn->set_reorderable();
      }

      show_all_children();
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_button_quit()
    {
      hide();
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      ExampleWindow window;

      //Shows the window and returns when it is closed.
      return app->run(window);
    }

#### TreeStore

Este ejemplo es muy similar al ejemplo del `ListStore`, pero usa el modelo `Gtk::TreeStore` en su lugar, y le añade hijos a las filas.

##### TreeView - TreeStore

Código fuente

File: `examplewindow.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      void on_button_quit();
      void on_treeview_row_activated(const Gtk::TreeModel::Path& path, Gtk::TreeViewColumn* column);

      //Tree model columns:
      class ModelColumns : public Gtk::TreeModel::ColumnRecord
      {
      public:

        ModelColumns()
        { add(m_col_id); add(m_col_name); }

        Gtk::TreeModelColumn<int> m_col_id;
        Gtk::TreeModelColumn<Glib::ustring> m_col_name;
      };

      ModelColumns m_Columns;

      //Child widgets:
      Gtk::Box m_VBox;

      Gtk::ScrolledWindow m_ScrolledWindow;
      Gtk::TreeView m_TreeView;
      Glib::RefPtr<Gtk::TreeStore> m_refTreeModel;

      Gtk::ButtonBox m_ButtonBox;
      Gtk::Button m_Button_Quit;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 3, not gtkmm 2)

    #include <iostream>
    #include "examplewindow.h"

    ExampleWindow::ExampleWindow()
    : m_VBox(Gtk::ORIENTATION_VERTICAL),
      m_Button_Quit("Quit")
    {
      set_title("Gtk::TreeView (TreeStore) example");
      set_border_width(5);
      set_default_size(400, 200);

      add(m_VBox);

      //Add the TreeView, inside a ScrolledWindow, with the button underneath:
      m_ScrolledWindow.add(m_TreeView);

      //Only show the scrollbars when they are necessary:
      m_ScrolledWindow.set_policy(Gtk::POLICY_AUTOMATIC, Gtk::POLICY_AUTOMATIC);

      m_VBox.pack_start(m_ScrolledWindow);
      m_VBox.pack_start(m_ButtonBox, Gtk::PACK_SHRINK);

      m_ButtonBox.pack_start(m_Button_Quit, Gtk::PACK_SHRINK);
      m_ButtonBox.set_border_width(5);
      m_ButtonBox.set_layout(Gtk::BUTTONBOX_END);
      m_Button_Quit.signal_clicked().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_button_quit) );

      //Create the Tree model:
      m_refTreeModel = Gtk::TreeStore::create(m_Columns);
      m_TreeView.set_model(m_refTreeModel);

      //All the items to be reordered with drag-and-drop:
      m_TreeView.set_reorderable();

      //Fill the TreeView's model
      Gtk::TreeModel::Row row = *(m_refTreeModel->append());
      row[m_Columns.m_col_id] = 1;
      row[m_Columns.m_col_name] = "Billy Bob";

      Gtk::TreeModel::Row childrow = *(m_refTreeModel->append(row.children()));
      childrow[m_Columns.m_col_id] = 11;
      childrow[m_Columns.m_col_name] = "Billy Bob Junior";

      childrow = *(m_refTreeModel->append(row.children()));
      childrow[m_Columns.m_col_id] = 12;
      childrow[m_Columns.m_col_name] = "Sue Bob";

      row = *(m_refTreeModel->append());
      row[m_Columns.m_col_id] = 2;
      row[m_Columns.m_col_name] = "Joey Jojo";

      row = *(m_refTreeModel->append());
      row[m_Columns.m_col_id] = 3;
      row[m_Columns.m_col_name] = "Rob McRoberts";

      childrow = *(m_refTreeModel->append(row.children()));
      childrow[m_Columns.m_col_id] = 31;
      childrow[m_Columns.m_col_name] = "Xavier McRoberts";

      //Add the TreeView's view columns:
      m_TreeView.append_column("ID", m_Columns.m_col_id);
      m_TreeView.append_column("Name", m_Columns.m_col_name);

      //Connect signal:
      m_TreeView.signal_row_activated().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_treeview_row_activated) );

      show_all_children();
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_button_quit()
    {
      hide();
    }

    void ExampleWindow::on_treeview_row_activated(const Gtk::TreeModel::Path& path,
            Gtk::TreeViewColumn* /* column */)
    {
      Gtk::TreeModel::iterator iter = m_refTreeModel->get_iter(path);
      if(iter)
      {
        Gtk::TreeModel::Row row = *iter;
        std::cout << "Row activated: ID=" << row[m_Columns.m_col_id] << ", Name="
            << row[m_Columns.m_col_name] << std::endl;
      }
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      ExampleWindow window;

      //Shows the window and returns when it is closed.
      return app->run(window);
    }

#### Celdas editables

Este ejemplo es idéntico al del `ListStore`, pero usa `TreeView::append_column_editable()` en lugar de `TreeView::append_column()`.

##### TreeView: celdas editables

Código fuente

File: `examplewindow.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      void on_button_quit();

      void treeviewcolumn_validated_on_cell_data(Gtk::CellRenderer* renderer, const Gtk::TreeModel::iterator& iter);
      void cellrenderer_validated_on_editing_started(Gtk::CellEditable* cell_editable, const Glib::ustring& path);
      void cellrenderer_validated_on_edited(const Glib::ustring& path_string, const Glib::ustring& new_text);

      //Tree model columns:
      class ModelColumns : public Gtk::TreeModel::ColumnRecord
      {
      public:

        ModelColumns()
        { add(m_col_id); add(m_col_name); add(m_col_foo); add(m_col_number); add(m_col_number_validated); }

        Gtk::TreeModelColumn<unsigned int> m_col_id;
        Gtk::TreeModelColumn<Glib::ustring> m_col_name;
        Gtk::TreeModelColumn<bool> m_col_foo;
        Gtk::TreeModelColumn<int> m_col_number;
        Gtk::TreeModelColumn<int> m_col_number_validated;
      };

      ModelColumns m_Columns;

      //Child widgets:
      Gtk::Box m_VBox;

      Gtk::ScrolledWindow m_ScrolledWindow;
      Gtk::TreeView m_TreeView;
      Glib::RefPtr<Gtk::ListStore> m_refTreeModel;

      Gtk::ButtonBox m_ButtonBox;
      Gtk::Button m_Button_Quit;

      //For the validated column:
      //You could also use a CellRendererSpin or a CellRendererProgress:
      Gtk::CellRendererText m_cellrenderer_validated;
      Gtk::TreeView::Column m_treeviewcolumn_validated;
      bool m_validate_retry;
      Glib::ustring m_invalid_text_for_retry;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 3, not gtkmm 2)

    #include <iostream>
    #include <cstdio>
    #include <cstdlib>
    #include "examplewindow.h"

    using std::sprintf;
    using std::strtol;

    ExampleWindow::ExampleWindow()
    : m_VBox(Gtk::ORIENTATION_VERTICAL),
      m_Button_Quit("Quit"),
      m_validate_retry(false)
    {
      set_title("Gtk::TreeView Editable Cells example");
      set_border_width(5);
      set_default_size(400, 200);

      add(m_VBox);

      //Add the TreeView, inside a ScrolledWindow, with the button underneath:
      m_ScrolledWindow.add(m_TreeView);

      //Only show the scrollbars when they are necessary:
      m_ScrolledWindow.set_policy(Gtk::POLICY_AUTOMATIC, Gtk::POLICY_AUTOMATIC);

      m_VBox.pack_start(m_ScrolledWindow);
      m_VBox.pack_start(m_ButtonBox, Gtk::PACK_SHRINK);

      m_ButtonBox.pack_start(m_Button_Quit, Gtk::PACK_SHRINK);
      m_ButtonBox.set_border_width(5);
      m_ButtonBox.set_layout(Gtk::BUTTONBOX_END);
      m_Button_Quit.signal_clicked().connect( sigc::mem_fun(*this,
                  &ExampleWindow::on_button_quit) );

      //Create the Tree model:
      m_refTreeModel = Gtk::ListStore::create(m_Columns);
      m_TreeView.set_model(m_refTreeModel);

      //Fill the TreeView's model
      Gtk::TreeModel::Row row = *(m_refTreeModel->append());
      row[m_Columns.m_col_id] = 1;
      row[m_Columns.m_col_name] = "Billy Bob";
      row[m_Columns.m_col_foo] = true;
      row[m_Columns.m_col_number] = 10;

      row = *(m_refTreeModel->append());
      row[m_Columns.m_col_id] = 2;
      row[m_Columns.m_col_name] = "Joey Jojo";
      row[m_Columns.m_col_foo] = true;
      row[m_Columns.m_col_number] = 20;

      row = *(m_refTreeModel->append());

      row[m_Columns.m_col_id] = 3;
      row[m_Columns.m_col_name] = "Rob McRoberts";
      row[m_Columns.m_col_foo] = false;
      row[m_Columns.m_col_number] = 30;

      //Add the TreeView's view columns:
      //We use the *_editable convenience methods for most of these,
      //because the default functionality is enough:
      m_TreeView.append_column_editable("ID", m_Columns.m_col_id);
      m_TreeView.append_column_editable("Name", m_Columns.m_col_name);
      m_TreeView.append_column_editable("foo", m_Columns.m_col_foo);
      m_TreeView.append_column_numeric_editable("foo", m_Columns.m_col_number,
              "%010d");

      //For this column, we create the CellRenderer ourselves, and connect our own
      //signal handlers, so that we can validate the data that the user enters, and
      //control how it is displayed.
      m_treeviewcolumn_validated.set_title("validated (<10)");
      m_treeviewcolumn_validated.pack_start(m_cellrenderer_validated);
      m_TreeView.append_column(m_treeviewcolumn_validated);

      //Tell the view column how to render the model values:
      m_treeviewcolumn_validated.set_cell_data_func(m_cellrenderer_validated,
              sigc::mem_fun(*this,
                  &ExampleWindow::treeviewcolumn_validated_on_cell_data) );

      //Make the CellRenderer editable, and handle its editing signals:
      m_cellrenderer_validated.property_editable() = true;

      m_cellrenderer_validated.signal_editing_started().connect(
              sigc::mem_fun(*this,
            &ExampleWindow::cellrenderer_validated_on_editing_started) );

      m_cellrenderer_validated.signal_edited().connect( sigc::mem_fun(*this,
                  &ExampleWindow::cellrenderer_validated_on_edited) );

      //If this was a CellRendererSpin then you would have to set the adjustment:
      //m_cellrenderer_validated.property_adjustment() = m_spin_adjustment;

      show_all_children();
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_button_quit()
    {
      hide();
    }

    void ExampleWindow::treeviewcolumn_validated_on_cell_data(
            Gtk::CellRenderer* /* renderer */,
            const Gtk::TreeModel::iterator& iter)
    {
      //Get the value from the model and show it appropriately in the view:
      if(iter)
      {
        Gtk::TreeModel::Row row = *iter;
        int model_value = row[m_Columns.m_col_number_validated];

        //This is just an example.
        //In this case, it would be easier to use append_column_editable() or
        //append_column_numeric_editable()
        char buffer[32];
        sprintf(buffer, "%d", model_value);

        Glib::ustring view_text = buffer;
        m_cellrenderer_validated.property_text() = view_text;
      }
    }

    void ExampleWindow::cellrenderer_validated_on_editing_started(
            Gtk::CellEditable* cell_editable, const Glib::ustring& /* path */)
    {
      //Start editing with previously-entered (but invalid) text,
      //if we are allowing the user to correct some invalid data.
      if(m_validate_retry)
      {
        //This is the CellEditable inside the CellRenderer.
        Gtk::CellEditable* celleditable_validated = cell_editable;

        //It's usually an Entry, at least for a CellRendererText:
        Gtk::Entry* pEntry = dynamic_cast<Gtk::Entry*>(celleditable_validated);
        if(pEntry)
        {
          pEntry->set_text(m_invalid_text_for_retry);
          m_validate_retry = false;
          m_invalid_text_for_retry.clear();
        }
      }

    }

    void ExampleWindow::cellrenderer_validated_on_edited(
            const Glib::ustring& path_string,
            const Glib::ustring& new_text)
    {
      Gtk::TreePath path(path_string);

      //Convert the inputed text to an integer, as needed by our model column:
      char* pchEnd = 0;
      int new_value = strtol(new_text.c_str(), &pchEnd, 10);

      if(new_value > 10)
      {
        //Prevent entry of numbers higher than 10.

        //Tell the user:
        Gtk::MessageDialog dialog(*this,
                "The number must be less than 10. Please try again.",
                false, Gtk::MESSAGE_ERROR);
        dialog.run();

        //Start editing again, with the bad text, so that the user can correct it.
        //A real application should probably allow the user to revert to the
        //previous text.

        //Set the text to be used in the start_editing signal handler:
        m_invalid_text_for_retry = new_text;
        m_validate_retry = true;

        //Start editing again:
        m_TreeView.set_cursor(path, m_treeviewcolumn_validated,
                m_cellrenderer_validated, true /* start_editing */);
      }
      else
      {
        //Get the row from the path:
        Gtk::TreeModel::iterator iter = m_refTreeModel->get_iter(path);
        if(iter)
        {
          Gtk::TreeModel::Row row = *iter;

          //Put the new value in the model:
          row[m_Columns.m_col_number_validated] = new_value;
        }
      }
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      ExampleWindow window;

      //Shows the window and returns when it is closed.
      return app->run(window);
    }

#### Arrastrar y soltar

Este ejemplo es muy parecido al ejemplo del `TreeStore`, pero tiene dos columnas adicionales que indican si la fila se puede arrastrar, y si puede recibir filas arrastradas y soltadas. Usa un `Gtk::TreeStore` derivado, que sobrecarga las funciones virtuales como se describe en la sección TreeView: arrastrar y soltar.

##### TreeView: arrastrar y soltar

Código fuente

File: `treemodel_dnd.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLE_TREEMODEL_DND_H
    #define GTKMM_EXAMPLE_TREEMODEL_DND_H

    #include <gtkmm.h>

    class TreeModel_Dnd : public Gtk::TreeStore
    {
    protected:
      TreeModel_Dnd();

    public:

      //Tree model columns:
      class ModelColumns : public Gtk::TreeModel::ColumnRecord
      {
      public:

        ModelColumns()
        { add(m_col_id); add(m_col_name); add(m_col_draggable); add(m_col_receivesdrags); }

        Gtk::TreeModelColumn<int> m_col_id;
        Gtk::TreeModelColumn<Glib::ustring> m_col_name;
        Gtk::TreeModelColumn<bool> m_col_draggable;
        Gtk::TreeModelColumn<bool> m_col_receivesdrags;
      };

      ModelColumns m_Columns;

      static Glib::RefPtr<TreeModel_Dnd> create();

    protected:
      //Overridden virtual functions:
      virtual bool row_draggable_vfunc(const Gtk::TreeModel::Path& path) const;
      virtual bool row_drop_possible_vfunc(const Gtk::TreeModel::Path& dest, const Gtk::SelectionData& selection_data) const;

    };

    #endif //GTKMM_EXAMPLE_TREEMODEL_DND_H

File: `examplewindow.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>
    #include "treemodel_dnd.h"

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      void on_button_quit();

      //Child widgets:
      Gtk::Box m_VBox;

      Gtk::ScrolledWindow m_ScrolledWindow;
      Gtk::TreeView m_TreeView;
      Glib::RefPtr<TreeModel_Dnd> m_refTreeModel;

      Gtk::ButtonBox m_ButtonBox;
      Gtk::Button m_Button_Quit;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `treemodel_dnd.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "treemodel_dnd.h"
    #include <iostream>

    TreeModel_Dnd::TreeModel_Dnd()
    {
      //We can't just call Gtk::TreeModel(m_Columns) in the initializer list
      //because m_Columns does not exist when the base class constructor runs.
      //And we can't have a static m_Columns instance, because that would be
      //instantiated before the gtkmm type system.
      //So, we use this method, which should only be used just after creation:
      set_column_types(m_Columns);
    }

    Glib::RefPtr<TreeModel_Dnd> TreeModel_Dnd::create()
    {
      return Glib::RefPtr<TreeModel_Dnd>( new TreeModel_Dnd() );
    }

    bool
    TreeModel_Dnd::row_draggable_vfunc(const Gtk::TreeModel::Path& path) const
    {
      // Make the value of the "draggable" column determine whether this row can
      // be dragged:

      //TODO: Add a const version of get_iter to TreeModel:
      TreeModel_Dnd* unconstThis = const_cast<TreeModel_Dnd*>(this);
      const_iterator iter = unconstThis->get_iter(path);
      //const_iterator iter = get_iter(path);
      if(iter)
      {
        Row row = *iter;
        bool is_draggable = row[m_Columns.m_col_draggable];
        return is_draggable;
      }

      return Gtk::TreeStore::row_draggable_vfunc(path);
    }

    bool
    TreeModel_Dnd::row_drop_possible_vfunc(const Gtk::TreeModel::Path& dest,
            const Gtk::SelectionData& selection_data) const
    {
      //Make the value of the "receives drags" column determine whether a row can be
      //dragged into it:

      //dest is the path that the row would have after it has been dropped:
      //But in this case we are more interested in the parent row:
      Gtk::TreeModel::Path dest_parent = dest;
      bool dest_is_not_top_level = dest_parent.up();
      if(!dest_is_not_top_level || dest_parent.empty())
      {
        //The user wants to move something to the top-level.
        //Let's always allow that.
      }
      else
      {
        //Get an iterator for the row at this path:
        //We must unconst this. This should not be necessary with a future version
        //of gtkmm.
        //TODO: Add a const version of get_iter to TreeModel:
        TreeModel_Dnd* unconstThis = const_cast<TreeModel_Dnd*>(this);
        const_iterator iter_dest_parent = unconstThis->get_iter(dest_parent);
        //const_iterator iter_dest_parent = get_iter(dest);
        if(iter_dest_parent)
        {
          Row row = *iter_dest_parent;
          bool receives_drags = row[m_Columns.m_col_receivesdrags];
          return receives_drags;
        }
      }

      //You could also examine the row being dragged (via selection_data)
      //if you must look at both rows to see whether a drop should be allowed.
      //You could use
      //TODO: Add const version of get_from_selection_data(): Glib::RefPtr<const
      //Gtk::TreeModel> refThis = Glib::RefPtr<const Gtk::TreeModel>(this);
      //
      //Glib::RefPtr<Gtk::TreeModel> refThis =
      //Glib::RefPtr<Gtk::TreeModel>(const_cast<TreeModel_Dnd*>(this));
      //refThis->reference(); //, true /* take_copy */)
      //Gtk::TreeModel::Path path_dragged_row;
      //Gtk::TreeModel::Path::get_from_selection_data(selection_data, refThis,
      //path_dragged_row);

      return Gtk::TreeStore::row_drop_possible_vfunc(dest, selection_data);
    }

File: `examplewindow.cc` (For use with gtkmm 3, not gtkmm 2)

    #include <iostream>
    #include "examplewindow.h"

    ExampleWindow::ExampleWindow()
    : m_VBox(Gtk::ORIENTATION_VERTICAL),
      m_Button_Quit(Gtk::Stock::QUIT)
    {
      set_title("Gtk::TreeView (Drag and Drop) example");
      set_border_width(5);
      set_default_size(400, 200);

      add(m_VBox);

      //Add the TreeView, inside a ScrolledWindow, with the button underneath:
      m_ScrolledWindow.add(m_TreeView);

      //Only show the scrollbars when they are necessary:
      m_ScrolledWindow.set_policy(Gtk::POLICY_AUTOMATIC, Gtk::POLICY_AUTOMATIC);

      m_VBox.pack_start(m_ScrolledWindow);
      m_VBox.pack_start(m_ButtonBox, Gtk::PACK_SHRINK);

      m_ButtonBox.pack_start(m_Button_Quit, Gtk::PACK_SHRINK);
      m_ButtonBox.set_border_width(5);
      m_ButtonBox.set_layout(Gtk::BUTTONBOX_END);
      m_Button_Quit.signal_clicked().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_button_quit) );

      //Create the Tree model:
      //Use our derived model, which overrides some Gtk::TreeDragDest and
      //Gtk::TreeDragSource virtual functions:
      //The columns are declared in the overridden TreeModel.
      m_refTreeModel = TreeModel_Dnd::create();
      m_TreeView.set_model(m_refTreeModel);

      //Enable Drag-and-Drop of TreeView rows:
      //See also the derived TreeModel's *_vfunc overrides.
      m_TreeView.enable_model_drag_source();
      m_TreeView.enable_model_drag_dest();

      //Fill the TreeView's model
      Gtk::TreeModel::Row row = *(m_refTreeModel->append());
      row[m_refTreeModel->m_Columns.m_col_id] = 1;
      row[m_refTreeModel->m_Columns.m_col_name] = "Billy Bob";
      row[m_refTreeModel->m_Columns.m_col_draggable] = true;
      row[m_refTreeModel->m_Columns.m_col_receivesdrags] = true;

      Gtk::TreeModel::Row childrow = *(m_refTreeModel->append(row.children()));
      childrow[m_refTreeModel->m_Columns.m_col_id] = 11;
      childrow[m_refTreeModel->m_Columns.m_col_name] = "Billy Bob Junior";
      childrow[m_refTreeModel->m_Columns.m_col_draggable] = true;
      childrow[m_refTreeModel->m_Columns.m_col_receivesdrags] = true;

      childrow = *(m_refTreeModel->append(row.children()));
      childrow[m_refTreeModel->m_Columns.m_col_id] = 12;
      childrow[m_refTreeModel->m_Columns.m_col_name] = "Sue Bob";
      childrow[m_refTreeModel->m_Columns.m_col_draggable] = true;
      childrow[m_refTreeModel->m_Columns.m_col_receivesdrags] = true;

      row = *(m_refTreeModel->append());
      row[m_refTreeModel->m_Columns.m_col_id] = 2;
      row[m_refTreeModel->m_Columns.m_col_name] = "Joey Jojo";
      row[m_refTreeModel->m_Columns.m_col_draggable] = true;
      row[m_refTreeModel->m_Columns.m_col_receivesdrags] = true;

      row = *(m_refTreeModel->append());
      row[m_refTreeModel->m_Columns.m_col_id] = 3;
      row[m_refTreeModel->m_Columns.m_col_name] = "Rob McRoberts";
      row[m_refTreeModel->m_Columns.m_col_draggable] = true;
      row[m_refTreeModel->m_Columns.m_col_receivesdrags] = true;

      childrow = *(m_refTreeModel->append(row.children()));
      childrow[m_refTreeModel->m_Columns.m_col_id] = 31;
      childrow[m_refTreeModel->m_Columns.m_col_name] = "Xavier McRoberts";
      childrow[m_refTreeModel->m_Columns.m_col_draggable] = true;
      childrow[m_refTreeModel->m_Columns.m_col_receivesdrags] = true;

      //Add the TreeView's view columns:
      m_TreeView.append_column("ID", m_refTreeModel->m_Columns.m_col_id);
      m_TreeView.append_column("Name", m_refTreeModel->m_Columns.m_col_name);
      m_TreeView.append_column_editable("Draggable",
              m_refTreeModel->m_Columns.m_col_draggable);
      m_TreeView.append_column_editable("Receives Drags",
              m_refTreeModel->m_Columns.m_col_receivesdrags);

      show_all_children();
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_button_quit()
    {
      hide();
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      ExampleWindow window;

      //Shows the window and returns when it is closed.
      return app->run(window);
    }

#### Menú contextual emergente

Este ejemplo es muy parecido al ejemplo del `ListStore`, pero deriva un `TreeView` personalizado para sobrecargar al `button_press_event`, y también encapsular al código del modelo de árbol en la clase derivada. Consulte la sección TreeView: menú contextual emergente.

##### TreeView: menú de contexto emergente

Código fuente

File: `treeview_withpopup.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLE_TREEVIEW_WITHPOPUP_H
    #define GTKMM_EXAMPLE_TREEVIEW_WITHPOPUP_H

    #include <gtkmm.h>

    class TreeView_WithPopup : public Gtk::TreeView
    {
    public:
      TreeView_WithPopup();
      virtual ~TreeView_WithPopup();

    protected:
      // Override Signal handler:
      // Alternatively, use signal_button_press_event().connect_notify()
      virtual bool on_button_press_event(GdkEventButton *ev);

      //Signal handler for popup menu items:
      void on_menu_file_popup_generic();

      //Tree model columns:
      class ModelColumns : public Gtk::TreeModel::ColumnRecord
      {
      public:

        ModelColumns()
        { add(m_col_id); add(m_col_name); }

        Gtk::TreeModelColumn<unsigned int> m_col_id;
        Gtk::TreeModelColumn<Glib::ustring> m_col_name;
      };

      ModelColumns m_Columns;

      //The Tree model:
      Glib::RefPtr<Gtk::ListStore> m_refTreeModel;

      Gtk::Menu m_Menu_Popup;
    };

    #endif //GTKMM_EXAMPLE_TREEVIEW_WITHPOPUP_H

File: `examplewindow.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>
    #include "treeview_withpopup.h"

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      void on_button_quit();

      //Child widgets:
      Gtk::Box m_VBox;

      Gtk::ScrolledWindow m_ScrolledWindow;
      TreeView_WithPopup m_TreeView;

      Gtk::ButtonBox m_ButtonBox;
      Gtk::Button m_Button_Quit;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `treeview_withpopup.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "treeview_withpopup.h"
    #include <iostream>

    TreeView_WithPopup::TreeView_WithPopup()
    {
      //Create the Tree model:
      m_refTreeModel = Gtk::ListStore::create(m_Columns);
      set_model(m_refTreeModel);

      //Fill the TreeView's model
      Gtk::TreeModel::Row row = *(m_refTreeModel->append());
      row[m_Columns.m_col_id] = 1;
      row[m_Columns.m_col_name] = "right-click on this";

      row = *(m_refTreeModel->append());
      row[m_Columns.m_col_id] = 2;
      row[m_Columns.m_col_name] = "or this";

      row = *(m_refTreeModel->append());
      row[m_Columns.m_col_id] = 3;
      row[m_Columns.m_col_name] = "or this, for a popup context menu";

      //Add the TreeView's view columns:
      append_column("ID", m_Columns.m_col_id);
      append_column("Name", m_Columns.m_col_name);

      //Fill popup menu:
      Gtk::MenuItem* item = Gtk::manage(new Gtk::MenuItem("_Edit", true));
      item->signal_activate().connect(
        sigc::mem_fun(*this, &TreeView_WithPopup::on_menu_file_popup_generic) );
      m_Menu_Popup.append(*item);

      item = Gtk::manage(new Gtk::MenuItem("_Process", true));
      item->signal_activate().connect(
        sigc::mem_fun(*this, &TreeView_WithPopup::on_menu_file_popup_generic) );
      m_Menu_Popup.append(*item);

      item = Gtk::manage(new Gtk::MenuItem("_Remove", true));
      item->signal_activate().connect(
        sigc::mem_fun(*this, &TreeView_WithPopup::on_menu_file_popup_generic) );
      m_Menu_Popup.append(*item);

      m_Menu_Popup.accelerate(*this);
      m_Menu_Popup.show_all(); //Show all menu items when the menu pops up

    #ifndef GLIBMM_DEFAULT_SIGNAL_HANDLERS_ENABLED
      signal_button_press_event()
        .connect(sigc::mem_fun(*this, &TreeView_WithPopup::on_button_press_event), false);
    #endif
    }

    TreeView_WithPopup::~TreeView_WithPopup()
    {
    }

    bool TreeView_WithPopup::on_button_press_event(GdkEventButton* event)
    {
      bool return_value = false;

      //Call base class, to allow normal handling,
      //such as allowing the row to be selected by the right-click:
      return_value = TreeView::on_button_press_event(event);

      //Then do our custom stuff:
      if( (event->type == GDK_BUTTON_PRESS) && (event->button == 3) )
      {
        m_Menu_Popup.popup(event->button, event->time);
      }

      return return_value;
    }

    void TreeView_WithPopup::on_menu_file_popup_generic()
    {
      std::cout << "A popup menu item was selected." << std::endl;

      Glib::RefPtr<Gtk::TreeView::Selection> refSelection = get_selection();
      if(refSelection)
      {
        Gtk::TreeModel::iterator iter = refSelection->get_selected();
        if(iter)
        {
          int id = (*iter)[m_Columns.m_col_id];
          std::cout << "  Selected ID=" << id << std::endl;
        }
      }
    }

File: `examplewindow.cc` (For use with gtkmm 3, not gtkmm 2)

    #include <iostream>
    #include "examplewindow.h"

    ExampleWindow::ExampleWindow()
    : m_VBox(Gtk::ORIENTATION_VERTICAL),
      m_Button_Quit("Quit")
    {
      set_title("Gtk::TreeView (ListStore) example");
      set_border_width(5);
      set_default_size(400, 200);

      add(m_VBox);

      //Add the TreeView, inside a ScrolledWindow, with the button underneath:
      m_ScrolledWindow.add(m_TreeView);

      //Only show the scrollbars when they are necessary:
      m_ScrolledWindow.set_policy(Gtk::POLICY_AUTOMATIC, Gtk::POLICY_AUTOMATIC);

      m_VBox.pack_start(m_ScrolledWindow);
      m_VBox.pack_start(m_ButtonBox, Gtk::PACK_SHRINK);

      m_ButtonBox.pack_start(m_Button_Quit, Gtk::PACK_SHRINK);
      m_ButtonBox.set_border_width(5);
      m_ButtonBox.set_layout(Gtk::BUTTONBOX_END);
      m_Button_Quit.signal_clicked().connect( sigc::mem_fun(*this,
                  &ExampleWindow::on_button_quit) );

      show_all_children();
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_button_quit()
    {
      hide();
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      ExampleWindow window;

      //Shows the window and returns when it is closed.
      return app->run(window);
    }

## Cajas combinadas

The `ComboBox` widget offers a list (or tree) of choices in a dropdown menu. If appropriate, it can show extra information about each item, such as text, a picture, a checkbox, or a progress bar. The `ComboBox` widget usually restricts the user to the available choices, but it can optionally have an `Entry`, allowing the user to enter arbitrary text if none of the available choices are suitable.

Un `TreeModel` proporciona la lista, y las columnas de este modelo se añaden a la vista del «ComboBox» con el método `ComboBox::pack_start()`. Esto proporciona flexibilidad y seguridad de tipos en tiempo de compilación, pero la clase `ComboBoxText` proporciona una especialización más simple basada en texto en caso de que no se requiera la flexibilidad.

Referencia

### El modelo

The model for a ComboBox can be defined and filled exactly as for a `TreeView`. For instance, you might derive a ComboBox class with one integer and one text column, like so:

    ModelColumns()
    { add(m_col_id); add(m_col_name); }

      Gtk::TreeModelColumn<int> m_col_id;
      Gtk::TreeModelColumn<Glib::ustring> m_col_name;
    };

    ModelColumns m_columns;

After appending rows to this model, you should provide the model to the `ComboBox` with the `set_model()` method. Then use the `pack_start()` or `pack_end()` methods to specify what columns will be displayed in the ComboBox. As with the TreeView you may either use the default cell renderer by passing the `TreeModelColumn` to the pack methods, or you may instantiate a specific `CellRenderer` and specify a particular mapping with either `add_attribute()` or `set_cell_data_func()`. Note that these methods are in the `CellLayout` base class.

### El elemento elegido

Para descubrir si qué elemento seleccionó el usuario, de un «ComboBox», llame a `ComboBox::get_active()`. Esto devuelve un `TreeModel::iterator` que puede desreferenciar a una `Row` para leer los valores de sus columnas. Por ejemplo, puede leer el valor de ID de un entero del modelo, incluso a pesar de que ha seleccionado mostrar sólo la descripción legible por los humanos en el «Combo». Por ejemplo:

    Gtk::TreeModel::iterator iter = m_Combo.get_active();
    if(iter)
    {
      Gtk::TreeModel::Row row = *iter;

      //Get the data for the selected row, using our knowledge
      //of the tree model:
      int id = row[m_Columns.m_col_id];
      set_something_id_chosen(id); //Your own function.
    }
    else
      set_nothing_chosen(); //Your own function.

### Responder a los cambios

You might need to react to every change of selection in the ComboBox, for instance to update other widgets. To do so, you should handle the `changed` signal. For instance:

    m_combo.signal_changed().connect( sigc::mem_fun(*this,
          &ExampleWindow::on_combo_changed) );

### Ejemplo completo

#### ComboBox

Código fuente

File: `examplewindow.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm/window.h>
    #include <gtkmm/comboboxtext.h>
    #include <gtkmm/liststore.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      void on_combo_changed();

      //Tree model columns:
      class ModelColumns : public Gtk::TreeModel::ColumnRecord
      {
      public:

        ModelColumns()
        { add(m_col_id); add(m_col_name); }

        Gtk::TreeModelColumn<int> m_col_id;
        Gtk::TreeModelColumn<Glib::ustring> m_col_name;
      };

      ModelColumns m_Columns;

      //Child widgets:
      Gtk::ComboBox m_Combo;
      Glib::RefPtr<Gtk::ListStore> m_refTreeModel;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/stock.h>
    #include <iostream>

    ExampleWindow::ExampleWindow()
    {
      set_title("ComboBox example");

      //Create the Tree model:
      //m_refTreeModel = Gtk::TreeStore::create(m_Columns);
      m_refTreeModel = Gtk::ListStore::create(m_Columns);
      m_Combo.set_model(m_refTreeModel);

      //Fill the ComboBox's Tree Model:
      Gtk::TreeModel::Row row = *(m_refTreeModel->append());
      row[m_Columns.m_col_id] = 1;
      row[m_Columns.m_col_name] = "Billy Bob";
      /*
      Gtk::TreeModel::Row childrow = *(m_refTreeModel->append(row.children()));
      childrow[m_Columns.m_col_id] = 11;
      childrow[m_Columns.m_col_name] = "Billy Bob Junior";

      childrow = *(m_refTreeModel->append(row.children()));
      childrow[m_Columns.m_col_id] = 12;
      childrow[m_Columns.m_col_name] = "Sue Bob";
      */

      row = *(m_refTreeModel->append());
      row[m_Columns.m_col_id] = 2;
      row[m_Columns.m_col_name] = "Joey Jojo";

      row = *(m_refTreeModel->append());
      row[m_Columns.m_col_id] = 3;
      row[m_Columns.m_col_name] = "Rob McRoberts";

      /*
      childrow = *(m_refTreeModel->append(row.children()));
      childrow[m_Columns.m_col_id] = 31;
      childrow[m_Columns.m_col_name] = "Xavier McRoberts";
      */

      //Add the model columns to the Combo (which is a kind of view),
      //rendering them in the default way:
      m_Combo.pack_start(m_Columns.m_col_id);
      m_Combo.pack_start(m_Columns.m_col_name);

      //Add the ComboBox to the window.
      add(m_Combo);

      //Connect signal handler:
      m_Combo.signal_changed().connect( sigc::mem_fun(*this, &ExampleWindow::on_combo_changed) );

      show_all_children();
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_combo_changed()
    {
      Gtk::TreeModel::iterator iter = m_Combo.get_active();
      if(iter)
      {
        Gtk::TreeModel::Row row = *iter;
        if(row)
        {
          //Get the data for the selected row, using our knowledge of the tree
          //model:
          int id = row[m_Columns.m_col_id];
          Glib::ustring name = row[m_Columns.m_col_name];

          std::cout << " ID=" << id << ", name=" << name << std::endl;
        }
      }
      else
        std::cout << "invalid iter" << std::endl;
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      ExampleWindow window;

      //Shows the window and returns when it is closed.
      return app->run(window);
    }

### Ejemplo de texto simple

#### ComboBoxText

Código fuente

File: `examplewindow.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm/window.h>
    #include <gtkmm/comboboxtext.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      void on_combo_changed();

      //Child widgets:
      Gtk::ComboBoxText m_Combo;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/stock.h>
    #include <iostream>

    ExampleWindow::ExampleWindow()
    {
      set_title("ComboBoxText example");

      //Fill the combo:
      m_Combo.append("something");
      m_Combo.append("something else");
      m_Combo.append("something or other");

      add(m_Combo);

      //Connect signal handler:
      m_Combo.signal_changed().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_combo_changed) );

      show_all_children();
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_combo_changed()
    {
      Glib::ustring text = m_Combo.get_active_text();
      if(!(text.empty()))
        std::cout << "Combo changed: " << text << std::endl;
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      ExampleWindow window;

      //Shows the window and returns when it is closed.
      return app->run(window);
    }

### «ComboBox» con una entrada

A `ComboBox` may contain an `Entry` widget for entering of arbitrary text, by specifying `true` for the constructor's `has_entry` parameter.

#### La columna de texto

So that the `Entry` can interact with the drop-down list of choices, you must specify which of your model columns is the text column, with `set_entry_text_column()`. For instance:

    m_combo.set_entry_text_column(m_columns.m_col_name);

Cuando seleccione una opción de la lista desplegable, el valor de esta columna se pondrá en el widget `Entry`.

#### La entrada

Because the user may enter arbitrary text, an active model row isn't enough to tell us what text the user has entered. Therefore, you should retrieve the `Entry` widget with the `ComboBox::get_entry()` method and call `get_text()` on that.

#### Responder a los cambios

When the user enters arbitrary text, it may not be enough to connect to the `changed` signal, which is emitted for every typed character. It is not emitted when the user presses the Enter key. Pressing the Enter key or moving the keyboard focus to another widget may signal that the user has finished entering text. To be notified of these events, connect to the `Entry`'s `key_press_event` and `focus_out_event` signals, like so

    Gtk::Entry* entry = m_Combo.get_entry();
    if (entry)
    {
      // The Entry shall receive key-press events and focus-out events.
      entry->add_events(Gdk::KEY_PRESS_MASK | Gdk::FOCUS_CHANGE_MASK);

      // Alternatively you can connect to m_Combo.signal_changed().
      entry->signal_changed().connect(sigc::mem_fun(*this,
        &ExampleWindow::on_entry_changed) );

      // This signal handler must be called before the default signal handler,
      // or else it will not be called, if the default signal handler returns true.
      entry->signal_key_press_event().connect(sigc::mem_fun(*this,
        &ExampleWindow::on_entry_key_press_event), /* after= */ false );

      entry->signal_focus_out_event().connect(sigc::mem_fun(*this,
        &ExampleWindow::on_entry_focus_out_event) );
    }

The `changed` signals of `ComboBox` and `Entry` are both emitted for every change. It doesn't matter which one you connect to. But only `Entry`'s `key_press_event` and `focus_out_event` signals are useful here.

In `key_press_event`'s signal handler you must check which key has been pressed, e.g. like so

    bool ExampleWindow::on_entry_key_press_event(GdkEventKey* event)
    {
      Gtk::Entry* entry = m_Combo.get_entry();
      if (entry)
      {
        if (event->keyval == GDK_KEY_Return ||
            event->keyval == GDK_KEY_ISO_Enter ||
            event->keyval == GDK_KEY_KP_Enter)
        {
          input_finished(); //Your own function.
          return true;
        }
      }
      return false;
    }

X events are described in more detail in the Keyboard Events chapter and the X Event signals section in the appendix.

#### Ejemplo completo

##### «ComboBox» con una entrada

Código fuente

File: `examplewindow.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm/window.h>
    #include <gtkmm/combobox.h>
    #include <gtkmm/liststore.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      void on_entry_changed();
      bool on_entry_key_press_event(GdkEventKey* event);
      bool on_entry_focus_out_event(GdkEventFocus* event);

      //Signal connection:
      sigc::connection m_ConnectionFocusOut;

      //Tree model columns:
      class ModelColumns : public Gtk::TreeModel::ColumnRecord
      {
      public:

        ModelColumns()
        { add(m_col_id); add(m_col_name); }

        Gtk::TreeModelColumn<Glib::ustring> m_col_id; //The data to choose - this must be text.
        Gtk::TreeModelColumn<Glib::ustring> m_col_name;
      };

      ModelColumns m_Columns;

      //Child widgets:
      Gtk::ComboBox m_Combo;
      Glib::RefPtr<Gtk::ListStore> m_refTreeModel;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/stock.h>
    #include <iostream>

    ExampleWindow::ExampleWindow()
    : m_Combo(true /* has_entry */)
    {
      set_title("ComboBox example");

      //Create the Tree model:
      //m_refTreeModel = Gtk::TreeStore::create(m_Columns);
      m_refTreeModel = Gtk::ListStore::create(m_Columns);
      m_Combo.set_model(m_refTreeModel);

      //Fill the ComboBox's Tree Model:
      Gtk::TreeModel::Row row = *(m_refTreeModel->append());
      row[m_Columns.m_col_id] = "1";
      row[m_Columns.m_col_name] = "Billy Bob";
      /*
      Gtk::TreeModel::Row childrow = *(m_refTreeModel->append(row.children()));
      childrow[m_Columns.m_col_id] = 11;
      childrow[m_Columns.m_col_name] = "Billy Bob Junior";

      childrow = *(m_refTreeModel->append(row.children()));
      childrow[m_Columns.m_col_id] = 12;
      childrow[m_Columns.m_col_name] = "Sue Bob";
      */

      row = *(m_refTreeModel->append());
      row[m_Columns.m_col_id] = "2";
      row[m_Columns.m_col_name] = "Joey Jojo";

      row = *(m_refTreeModel->append());
      row[m_Columns.m_col_id] = "3";
      row[m_Columns.m_col_name] = "Rob McRoberts";

      /*
      childrow = *(m_refTreeModel->append(row.children()));
      childrow[m_Columns.m_col_id] = 31;
      childrow[m_Columns.m_col_name] = "Xavier McRoberts";
      */

      //Add the model columns to the Combo (which is a kind of view),
      //rendering them in the default way:
      //This is automatically rendered when we use set_entry_text_column().
      //m_Combo.pack_start(m_Columns.m_col_id);
      m_Combo.pack_start(m_Columns.m_col_name);

      m_Combo.set_entry_text_column(m_Columns.m_col_id);

      //Add the ComboBox to the window.
      add(m_Combo);

      //Connect signal handlers:
      Gtk::Entry* entry = m_Combo.get_entry();
      if (entry)
      {
        // The Entry shall receive key-press events and focus-out events.
        entry->add_events(Gdk::KEY_PRESS_MASK | Gdk::FOCUS_CHANGE_MASK);
        // Alternatively you can connect to m_Combo.signal_changed().
        entry->signal_changed().connect(sigc::mem_fun(*this,
          &ExampleWindow::on_entry_changed) );
        // This signal handler must be called before the default signal handler,
        // or else it will not be called, if the default signal handler returns true.
        entry->signal_key_press_event().connect(sigc::mem_fun(*this,
          &ExampleWindow::on_entry_key_press_event), false );
        m_ConnectionFocusOut = entry->signal_focus_out_event().
          connect(sigc::mem_fun(*this, &ExampleWindow::on_entry_focus_out_event) );
      }
      else
        std::cout << "No Entry ???" << std::endl;

      show_all_children();
    }

    ExampleWindow::~ExampleWindow()
    {
      // The focus_out signal may be emitted while m_Combo is being destructed.
      // The signal handler can generate critical messages, if it's called when
      // m_Combo has been partly destructed.
      m_ConnectionFocusOut.disconnect();
    }

    void ExampleWindow::on_entry_changed()
    {
      Gtk::Entry* entry = m_Combo.get_entry();
      if (entry)
      {
        std::cout << "on_entry_changed(): Row=" << m_Combo.get_active_row_number()
          << ", ID=" << entry->get_text() << std::endl;
      }
    }

    bool ExampleWindow::on_entry_key_press_event(GdkEventKey* event)
    {
      Gtk::Entry* entry = m_Combo.get_entry();
      if (entry)
      {
        if (event->keyval == GDK_KEY_Return ||
            event->keyval == GDK_KEY_ISO_Enter ||
            event->keyval == GDK_KEY_KP_Enter)
        {
          std::cout << "on_entry_key_press_event(): Row=" << m_Combo.get_active_row_number()
          << ", ID=" << entry->get_text() << std::endl;
          return true;
        }
      }
      return false;
    }

    bool ExampleWindow::on_entry_focus_out_event(GdkEventFocus* /* event */)
    {
      Gtk::Entry* entry = m_Combo.get_entry();
      if (entry)
      {
        std::cout << "on_entry_focus_out_event(): Row=" << m_Combo.get_active_row_number()
          << ", ID=" << entry->get_text() << std::endl;
        return true;
      }
      return false;
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      ExampleWindow window;

      //Shows the window and returns when it is closed.
      return app->run(window);
    }

#### Ejemplo de texto simple

##### «ComboBoxText» con una entrada

Código fuente

File: `examplewindow.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm/window.h>
    #include <gtkmm/comboboxtext.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      void on_combo_changed();
      bool on_entry_key_press_event(GdkEventKey* event);
      bool on_entry_focus_out_event(GdkEventFocus* event);

      //Signal connection:
      sigc::connection m_ConnectionFocusOut;

      //Child widgets:
      Gtk::ComboBoxText m_Combo;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/stock.h>
    #include <iostream>

    ExampleWindow::ExampleWindow()
    : m_Combo(true /* has_entry */)
    {
      set_title("ComboBoxText example");

      //Fill the combo:
      m_Combo.append("something");
      m_Combo.append("something else");
      m_Combo.append("something or other");

      add(m_Combo);

      //Connect signal handlers:
      Gtk::Entry* entry = m_Combo.get_entry();
      // Alternatively you can connect to entry->signal_changed().
      m_Combo.signal_changed().connect(sigc::mem_fun(*this,
        &ExampleWindow::on_combo_changed) );
      if (entry)
      {
        // The Entry shall receive key-press events and focus-out events.
        entry->add_events(Gdk::KEY_PRESS_MASK | Gdk::FOCUS_CHANGE_MASK);
        // This signal handler must be called before the default signal handler,
        // or else it will not be called, if the default signal handler returns true.
        entry->signal_key_press_event().connect(sigc::mem_fun(*this,
          &ExampleWindow::on_entry_key_press_event), false );
        m_ConnectionFocusOut = entry->signal_focus_out_event().
          connect(sigc::mem_fun(*this, &ExampleWindow::on_entry_focus_out_event) );
      }
      else
        std::cout << "No Entry ???" << std::endl;

      m_Combo.property_has_frame() = false;
      show_all_children();
    }

    ExampleWindow::~ExampleWindow()
    {
      // The focus_out signal may be emitted while m_Combo is being destructed.
      // The signal handler can generate critical messages, if it's called when
      // m_Combo has been partly destructed.
      m_ConnectionFocusOut.disconnect();
    }

    void ExampleWindow::on_combo_changed()
    {
      std::cout << "on_combo_changed(): Row=" << m_Combo.get_active_row_number()
        << ", Text=" << m_Combo.get_active_text() << std::endl;
    }

    bool ExampleWindow::on_entry_key_press_event(GdkEventKey* event)
    {
      if (event->keyval == GDK_KEY_Return ||
          event->keyval == GDK_KEY_ISO_Enter ||
          event->keyval == GDK_KEY_KP_Enter)
      {
        std::cout << "on_entry_key_press_event(): Row=" << m_Combo.get_active_row_number()
          << ", Text=" << m_Combo.get_active_text() << std::endl;
        return true;
      }
      return false;
    }

    bool ExampleWindow::on_entry_focus_out_event(GdkEventFocus* /* event */)
    {
      std::cout << "on_entry_focus_out_event(): Row=" << m_Combo.get_active_row_number()
        << ", Text=" << m_Combo.get_active_text() << std::endl;
      return true;
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      ExampleWindow window;

      //Shows the window and returns when it is closed.
      return app->run(window);
    }

## TextView

El widget `TextView` puede usarse para mostrar y editar grandes cantidades de texto formateado. Al igual que el `TreeView`, tiene un diseño modelo/vista. En este caso, el `TextBuffer` es el modelo.

### El búfer

`Gtk::TextBuffer` es el modelo que contiene los datos del `Gtk::TextView`, al igual que el `Gtk::TreeModel` usado por `Gtk::TreeView`. Esto permite a dos o más `Gtk::TreeView` compartir el mismo `TextBuffer`, y permite mostrar esos búferes de texto de una manera ligeramente diferente. O bien, puede mantener varios `Gtk::TextBuffer` y elegir mostrar cada uno en distintas ocasiones en el mismo widget `GtK::TextView`.

El `TextView` crea su propio `TextBuffer` predeterminado, al que puede acceder mediante el método `get_buffer()`.

Referencia

#### Iteradores

#### Etiquetas y formateado

##### Etiquetas

Para especificar que algún texto en el búfer deba tener un formato especial, defina una etiqueta que contenta esa información de formato, y luego aplíquela a la región de texto. Por ejemplo, para definir la etiqueta y sus propiedades:

    Glib::RefPtr<Gtk::TextBuffer::Tag> refTagMatch =
        Gtk::TextBuffer::Tag::create();
    refTagMatch->property_background() = "orange";

Puede especificar un nombre para la clase `Tag` cuando use el método `create()`, pero no es necesario.

La clase `Tag` tiene muchas otras propiedades.

Referencia

##### TagTable

Cada `Gtk::TextBuffer` usa una `Gtk::TextBuffer::TagTable`, que contiene las `Tag` para ese búfer. Dos o más `TextBuffer` pueden compartir la misma `TagTable`. Cuando cree las `Tag`, añádalas a la `TagTable`. Por ejemplo:

    Glib::RefPtr<Gtk::TextBuffer::TagTable> refTagTable =
        Gtk::TextBuffer::TagTable::create();
    refTagTable->add(refTagMatch);
    //Hopefully a future version of gtkmm will have a set_tag_table() method,
    //for use after creation of the buffer.
    Glib::RefPtr<Gtk::TextBuffer> refBuffer =
        Gtk::TextBuffer::create(refTagTable);

También puede usar `get_tag_table()` para obtener, y tal vez modificar, la `TagTable` predeterminada del `TextBuffer` en lugar de crear una explícitamente.

Referencia

##### Aplicar etiquetas

Si ha creado una `Tag` y la ha añadido a la `TagTable`, podrá aplicarle esa etiqueta a parte del `TextBuffer`, para que una parte del texto se muestre con ese formato. Puede definir el inicio y el fin del rango de texto especificando `Gtk::TextBuffer::iterator`. Por ejemplo:

    refBuffer->apply_tag(refTagMatch, iterRangeStart, iterRangeStop);

O puede especificar la etiqueta cuando inserta el texto por primera vez: refBuffer->insert_with_tag(iter, "Some text", refTagMatch);

Puede aplicar más de una `Tag` al mismo texto, usando `apply_tag()` más de una vez, o usando `insert_with_tags()`. Las `Tag` podrían especificar valores diferentes para las mismas propiedades, pero puede resolver estos conflictos usando `Tag::set_priority()`.

#### Marcas

Generalmente se invalidan los iteradores del `TextBuffer` cuando el texto cambia, pero puede usar una `Gtk::TextBuffer::Mark` para recordar una posición en estas situaciones. Por ejemplo,

    Glib::RefPtr<Gtk::TextBuffer::Mark> refMark =
        refBuffer->create_mark(iter);

Puede entonces usar el método `get_iter()` más tarde para crear un iterador para la posición nueva de la `Mark`.

Hay dos clases `Mark` incorporadas: `insert` y `select_bound`, a las que puede acceder con los métodos `get_insert()` y `get_selection_bound()` del `TextBuffer`.

Referencia

#### La vista

Como se mencionó anteriormente, cada `TextView` tiene un `TextBuffer`, y uno o más `TextView` pueden compartir el mismo `TextBuffer`.

Al igual que con el `TreeView`, probablemente deba poner su `TextView` dentro de una `ScrolledWindow` para permitirle al usuario ver y mover toda el área de texto con barras de desplazamiento.

Referencia

##### Formato predeterminado

Los `TextView` tienen varios métodos que le permiten cambiar la presentación del búfer de esta vista particular. Algunos de estos pueden anularse por los `Gtk::TextTag` en el búfer, si especifican las mismas cosas. Por ejemplo, `set_left_margin()`, `set_right_margin()`, `set_indent()`, etc.

##### Desplazamiento

`Gtk::TextView` tiene varios métodos `scroll_to_*()`. Estos le permiten asegurarse de que una parte particular del búfer de texto es visible. Por ejemplo, la característica «Encontrar» de su aplicación podría usar `Gtk::TextView::scroll_to_iter()` para mostrar el texto encontrado.

### Widgets y ChildAnchors

Puede empotrar widgets, como `Gtk::Button` en el texto. Cada widget hijo necesitará un `ChildAnchor`. Los «ChildAnchor» están asociados a los `iterators`. Por ejemplo, para crear un «ChildAnchor» en una posición particular, use `Gtk::TextBuffer::create_child_anchor()`:

    Glib::RefPtr<Gtk::TextChildAnchor> refAnchor =
        refBuffer->create_child_anchor(iter);

Luego, para añadir un widget en esa posición, use `Gtk::TextView::add_child_at_anchor()`:

    m_TextView.add_child_at_anchor(m_Button, refAnchor);

Referencia

### Ejemplos

#### Ejemplo simple

##### TextView

Código fuente

File: `examplewindow.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:

      void fill_buffers();

      //Signal handlers:
      void on_button_quit();
      void on_button_buffer1();
      void on_button_buffer2();

      //Child widgets:
      Gtk::Box m_VBox;

      Gtk::ScrolledWindow m_ScrolledWindow;
      Gtk::TextView m_TextView;

      Glib::RefPtr<Gtk::TextBuffer> m_refTextBuffer1, m_refTextBuffer2;

      Gtk::ButtonBox m_ButtonBox;
      Gtk::Button m_Button_Quit, m_Button_Buffer1, m_Button_Buffer2;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"

    ExampleWindow::ExampleWindow()
    : m_VBox(Gtk::ORIENTATION_VERTICAL),
      m_Button_Quit(Gtk::Stock::QUIT),
      m_Button_Buffer1("Use buffer 1"),
      m_Button_Buffer2("Use buffer 2")
    {
      set_title("Gtk::TextView example");
      set_border_width(5);
      set_default_size(400, 200);

      add(m_VBox);

      //Add the TreeView, inside a ScrolledWindow, with the button underneath:
      m_ScrolledWindow.add(m_TextView);

      //Only show the scrollbars when they are necessary:
      m_ScrolledWindow.set_policy(Gtk::POLICY_AUTOMATIC, Gtk::POLICY_AUTOMATIC);

      m_VBox.pack_start(m_ScrolledWindow);

      //Add buttons:
      m_VBox.pack_start(m_ButtonBox, Gtk::PACK_SHRINK);

      m_ButtonBox.pack_start(m_Button_Buffer1, Gtk::PACK_SHRINK);
      m_ButtonBox.pack_start(m_Button_Buffer2, Gtk::PACK_SHRINK);
      m_ButtonBox.pack_start(m_Button_Quit, Gtk::PACK_SHRINK);
      m_ButtonBox.set_border_width(5);
      m_ButtonBox.set_spacing(5);
      m_ButtonBox.set_layout(Gtk::BUTTONBOX_END);

      //Connect signals:
      m_Button_Quit.signal_clicked().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_button_quit) );
      m_Button_Buffer1.signal_clicked().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_button_buffer1) );
      m_Button_Buffer2.signal_clicked().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_button_buffer2) );

      fill_buffers();
      on_button_buffer1();

      show_all_children();
    }

    void ExampleWindow::fill_buffers()
    {
      m_refTextBuffer1 = Gtk::TextBuffer::create();
      m_refTextBuffer1->set_text("This is the text from TextBuffer #1.");

      m_refTextBuffer2 = Gtk::TextBuffer::create();
      m_refTextBuffer2->set_text(
              "This is some alternative text, from TextBuffer #2.");

    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_button_quit()
    {
      hide();
    }

    void ExampleWindow::on_button_buffer1()
    {
      m_TextView.set_buffer(m_refTextBuffer1);
    }

    void ExampleWindow::on_button_buffer2()
    {
      m_TextView.set_buffer(m_refTextBuffer2);
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      ExampleWindow window;

      //Shows the window and returns when it is closed.
      return app->run(window);
    }

## Menús y barras de herramientas

Hay API específicas para los menús y las barras de herramientas, pero usualmente debe tratarlas juntas, usando el `UIManager` para definir `Action` que puede ordenar en menús y barras de herramientas. De esta forma, puede manejar la activación de la acción en lugar de responder a los elementos del menú y las barras de herramientas separadamente. Y puede activar o desactivar tanto el elemento del menú como el de la barra de herramientas a través de la acción.

Esto implica el uso de las clases `Gtk::ActionGroup`, `Gtk::Action`, y `UIManager`, todas las cuales deben instanciarse a través de sus métodos `create()`, que devuelven `RefPtr`.

### Acciones

Primero cree las `Action`s y añádaselas a un `ActionGroup`, con `ActionGroup::add()`.

Los argumentos de `Action::create()` especifican el nombre de la acción y cómo aparecerá en los menús y las barras de herramientas. Use elementos del almacén donde sea posible para que no necesite especificar etiquetas, atajos, iconos ni consejos, y para poder usar traducciones preexistentes.

También puede especificar un manejador de señales cuando llame a `ActionGroup::add()`. Se llamará a este manejador de señales cuando se active la acción a través de un elemento del menú o un botón de la barra de herramientas.

Tenga en cuenta que debe especificar acciones para submenús así como para elementos del menú.

Por ejemplo:

    m_refActionGroup = Gtk::ActionGroup::create();

    m_refActionGroup->add( Gtk::Action::create("MenuFile", "_File") );
    m_refActionGroup->add( Gtk::Action::create("New", Gtk::Stock::NEW),
      sigc::mem_fun(*this, &ExampleWindow::on_action_file_new) );
    m_refActionGroup->add( Gtk::Action::create("ExportData", "Export Data"),
      sigc::mem_fun(*this, &ExampleWindow::on_action_file_open) );
    m_refActionGroup->add( Gtk::Action::create("Quit", Gtk::Stock::QUIT),
      sigc::mem_fun(*this, &ExampleWindow::on_action_file_quit) );

Tenga en cuenta que aquí es donde se especifican los nombres de las acciones como las verán los usuarios en los menús y las barras de herramientas. Por lo tanto, aquí es donde debe hacer las cadenas traducibles, poniéndolas dentro de la macro _(). Cuando use los elementos de Gtk::Stock, las traducciones estarán disponibles automáticamente, por supuesto.

### UIManager

A continuación debe crear un `UIManager` y añadirle el `ActionGroup` con `insert_action_group()`. En este punto, también es una buena idea decirle a la ventana madre que responda a los atajos del teclado especificados, usando `add_accel_group()`.

Por ejemplo,

    Glib::RefPtr<Gtk::UIManager> m_refUIManager =
        Gtk::UIManager::create();
    m_refUIManager->insert_action_group(m_refActionGroup);
    add_accel_group(m_refUIManager->get_accel_group());

Luego, puede definir la distribución visible real de los menús y las barras de herramientas, y añadírsela al `UIManager`. Esta «cadena de IU» usa un formato XML, en el que debe mencionar los nombre de las acciones que ya ha creado. Por ejemplo:

    Glib::ustring ui_info =
        "<ui>"
        "  <menubar name='MenuBar'>"
        "    <menu action='MenuFile'>"
        "      <menuitem action='New'/>"
        "      <menuitem action='Open'/>"
        "      <separator/>"
        "      <menuitem action='Quit'/>"
        "    </menu>"
        "    <menu action='MenuEdit'>"
        "      <menuitem action='Cut'/>"
        "      <menuitem action='Copy'/>"
        "      <menuitem action='Paste'/>"
        "    </menu>"
        "  </menubar>"
        "  <toolbar  name='ToolBar'>"
        "    <toolitem action='Open'/>"
        "    <toolitem action='Quit'/>"
        "  </toolbar>"
        "</ui>";

    m_refUIManager->add_ui_from_string(ui_info);

Recuerde que estos nombres son sólo identificadores que se usaron cuando se crearon las acciones. No son el texto que el usuario verá en los menús y barras de herramientas. Se han proporcionado esos nombres legibles por el humano cuando se crearon las acciones.

Para instanciar una `Gtk::MenuBar` o una `Gtk::Toolbar`, a la que en realidad puede mostrar, debe usar el método `UIManager::get_widget()`, y luego añadirle el widget a un contenedor. Por ejemplo:

    Gtk::Widget* pMenubar = m_refUIManager->get_widget("/MenuBar");
    pBox->add(*pMenuBar, Gtk::PACK_SHRINK);

### Menús emergentes

Normalmente, simplemente se añaden los `Menus` a la ventana, pero también pueden mostrarse temporalmente como resultado de una pulsación del botón del ratón. Por ejemplo, se puede mostrar un menú contextual cuando el usuario pulsa el botón derecho de su ratón.

La distribución de la IU para un menú emergente debe usar el nodo `popup`. Por ejemplo:

    Glib::ustring ui_info =
        "<ui>"
        "  <popup name='PopupMenu'>"
        "    <menuitem action='ContextEdit'/>"
        "    <menuitem action='ContextProcess'/>"
        "    <menuitem action='ContextRemove'/>"
        "  </popup>"
        "</ui>";

    m_refUIManager->add_ui_from_string(ui_info);

To show the popup menu, use `Gtk::Menu`'s `popup()` method, providing the button identifier and the time of activation, as provided by the `button_press_event` signal, which you will need to handle anyway. For instance:

    bool ExampleWindow::on_button_press_event(GdkEventButton* event)
    {
      if( (event->type == GDK_BUTTON_PRESS) &&
          (event->button == 3) )
      {
        m_Menu_Popup->popup(event->button, event->time);
        return true; //It has been handled.
      }
      else
        return false;
    }

### Ejemplos

#### Ejemplo de menú principal

##### Menú principal

Código fuente

File: `examplewindow.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      void on_menu_file_new_generic();
      void on_menu_file_quit();
      void on_menu_others();

      void on_menu_choices_one();
      void on_menu_choices_two();

      //Child widgets:
      Gtk::Box m_Box;

      Glib::RefPtr<Gtk::UIManager> m_refUIManager;
      Glib::RefPtr<Gtk::ActionGroup> m_refActionGroup;
      Glib::RefPtr<Gtk::RadioAction> m_refChoiceOne, m_refChoiceTwo;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/stock.h>
    #include <iostream>

    ExampleWindow::ExampleWindow()
    : m_Box(Gtk::ORIENTATION_VERTICAL)
    {
      set_title("main menu example");
      set_default_size(200, 200);

      add(m_Box); // put a MenuBar at the top of the box and other stuff below it.

      //Create actions for menus and toolbars:
      m_refActionGroup = Gtk::ActionGroup::create();

      //File|New sub menu:
      m_refActionGroup->add(Gtk::Action::create("FileNewStandard",
                  Gtk::Stock::NEW, "_New", "Create a new file"),
              sigc::mem_fun(*this, &ExampleWindow::on_menu_file_new_generic));

      m_refActionGroup->add(Gtk::Action::create("FileNewFoo",
                  Gtk::Stock::NEW, "New Foo", "Create a new foo"),
              sigc::mem_fun(*this, &ExampleWindow::on_menu_file_new_generic));

      m_refActionGroup->add(Gtk::Action::create("FileNewGoo",
                  Gtk::Stock::NEW, "_New Goo", "Create a new goo"),
              sigc::mem_fun(*this, &ExampleWindow::on_menu_file_new_generic));

      //File menu:
      m_refActionGroup->add(Gtk::Action::create("FileMenu", "File"));
      //Sub-menu.
      m_refActionGroup->add(Gtk::Action::create("FileNew", Gtk::Stock::NEW));
      m_refActionGroup->add(Gtk::Action::create("FileQuit", Gtk::Stock::QUIT),
              sigc::mem_fun(*this, &ExampleWindow::on_menu_file_quit));

      //Edit menu:
      m_refActionGroup->add(Gtk::Action::create("EditMenu", "Edit"));
      m_refActionGroup->add(Gtk::Action::create("EditCopy", Gtk::Stock::COPY),
              sigc::mem_fun(*this, &ExampleWindow::on_menu_others));
      m_refActionGroup->add(Gtk::Action::create("EditPaste", Gtk::Stock::PASTE),
              sigc::mem_fun(*this, &ExampleWindow::on_menu_others));
      m_refActionGroup->add(Gtk::Action::create("EditSomething", "Something"),
              Gtk::AccelKey("<control><alt>S"),
              sigc::mem_fun(*this, &ExampleWindow::on_menu_others));

      //Choices menu, to demonstrate Radio items
      m_refActionGroup->add( Gtk::Action::create("ChoicesMenu", "Choices") );
      Gtk::RadioAction::Group group_userlevel;
      m_refChoiceOne = Gtk::RadioAction::create(group_userlevel, "ChoiceOne", "One");
      m_refActionGroup->add(m_refChoiceOne,
              sigc::mem_fun(*this, &ExampleWindow::on_menu_choices_one) );
      m_refChoiceTwo = Gtk::RadioAction::create(group_userlevel, "ChoiceTwo", "Two");
      m_refActionGroup->add(m_refChoiceTwo,
              sigc::mem_fun(*this, &ExampleWindow::on_menu_choices_two) );

      //Help menu:
      m_refActionGroup->add( Gtk::Action::create("HelpMenu", "Help") );
      m_refActionGroup->add( Gtk::Action::create("HelpAbout", Gtk::Stock::HELP),
              sigc::mem_fun(*this, &ExampleWindow::on_menu_others) );

      m_refUIManager = Gtk::UIManager::create();
      m_refUIManager->insert_action_group(m_refActionGroup);

      add_accel_group(m_refUIManager->get_accel_group());

      //Layout the actions in a menubar and toolbar:
      Glib::ustring ui_info =
            "<ui>"
            "  <menubar name='MenuBar'>"
            "    <menu action='FileMenu'>"
            "      <menu action='FileNew'>"
            "        <menuitem action='FileNewStandard'/>"
            "        <menuitem action='FileNewFoo'/>"
            "        <menuitem action='FileNewGoo'/>"
            "      </menu>"
            "      <separator/>"
            "      <menuitem action='FileQuit'/>"
            "    </menu>"
            "    <menu action='EditMenu'>"
            "      <menuitem action='EditCopy'/>"
            "      <menuitem action='EditPaste'/>"
            "      <menuitem action='EditSomething'/>"
            "    </menu>"
            "    <menu action='ChoicesMenu'>"
            "      <menuitem action='ChoiceOne'/>"
            "      <menuitem action='ChoiceTwo'/>"
            "    </menu>"
            "    <menu action='HelpMenu'>"
            "      <menuitem action='HelpAbout'/>"
            "    </menu>"
            "  </menubar>"
            "  <toolbar  name='ToolBar'>"
            "    <toolitem action='FileNewStandard'/>"
            "    <toolitem action='FileQuit'/>"
            "  </toolbar>"
            "</ui>";

      try
      {
        m_refUIManager->add_ui_from_string(ui_info);
      }
      catch(const Glib::Error& ex)
      {
        std::cerr << "building menus failed: " <<  ex.what();
      }

      //Get the menubar and toolbar widgets, and add them to a container widget:
      Gtk::Widget* pMenubar = m_refUIManager->get_widget("/MenuBar");
      if(pMenubar)
        m_Box.pack_start(*pMenubar, Gtk::PACK_SHRINK);

      Gtk::Widget* pToolbar = m_refUIManager->get_widget("/ToolBar") ;
      if(pToolbar)
        m_Box.pack_start(*pToolbar, Gtk::PACK_SHRINK);

      show_all_children();
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_menu_file_quit()
    {
      hide(); //Closes the main window to stop the app->run().
    }

    void ExampleWindow::on_menu_file_new_generic()
    {
       std::cout << "A File|New menu item was selected." << std::endl;
    }

    void ExampleWindow::on_menu_others()
    {
      std::cout << "A menu item was selected." << std::endl;
    }

    void ExampleWindow::on_menu_choices_one()
    {
      Glib::ustring message;
      if(m_refChoiceOne->get_active())
        message = "Choice 1 was selected.";
      else
        message = "Choice 1 was deselected";

      std::cout << message << std::endl;
    }

    void ExampleWindow::on_menu_choices_two()
    {
      Glib::ustring message;
      if(m_refChoiceTwo->get_active())
        message = "Choice 2 was selected.";
      else
        message = "Choice 2 was deselected";

      std::cout << message << std::endl;
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      ExampleWindow window;

      //Shows the window and returns when it is closed.
      return app->run(window);
    }

#### Ejemplo de menú emergente

##### Menú emergente

Código fuente

File: `examplewindow.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      virtual bool on_button_press_event(GdkEventButton* event);
      void on_menu_file_popup_generic();

      //Child widgets:
      Gtk::Box m_Box;
      Gtk::EventBox m_EventBox;
      Gtk::Label m_Label;

      Glib::RefPtr<Gtk::UIManager> m_refUIManager;
      Glib::RefPtr<Gtk::ActionGroup> m_refActionGroup;

      Gtk::Menu* m_pMenuPopup;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/stock.h>
    #include <iostream>

    ExampleWindow::ExampleWindow()
    : m_Box(Gtk::ORIENTATION_VERTICAL),
      m_Label("Right-click to see the popup menu."),
      m_pMenuPopup(0)
      /* m_Image(Gtk::Stock::DIALOG_QUESTION, Gtk::ICON_SIZE_MENU) */
    {
      set_title("popup example");
      set_default_size(200, 200);

      add(m_Box);

      //Add an event box that can catch button_press events:
      m_Box.pack_start(m_EventBox);
      m_EventBox.signal_button_press_event().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_button_press_event) );

      m_EventBox.add(m_Label);

      //Create actions:

      //Fill menu:

      m_refActionGroup = Gtk::ActionGroup::create();

      //File|New sub menu:
      //These menu actions would normally already exist for a main menu, because a
      //context menu should not normally contain menu items that are only available
      //via a context menu.
      m_refActionGroup->add(Gtk::Action::create("ContextMenu", "Context Menu"));

      m_refActionGroup->add(Gtk::Action::create("ContextEdit", "Edit"),
              sigc::mem_fun(*this, &ExampleWindow::on_menu_file_popup_generic));

      m_refActionGroup->add(Gtk::Action::create("ContextProcess", "Process"),
              Gtk::AccelKey("<control>P"),
              sigc::mem_fun(*this, &ExampleWindow::on_menu_file_popup_generic));

      m_refActionGroup->add(Gtk::Action::create("ContextRemove", "Remove"),
              sigc::mem_fun(*this, &ExampleWindow::on_menu_file_popup_generic));

      //TODO:
      /*
        //Add a ImageMenuElem:
        menulist.push_back( Gtk::Menu_Helpers::ImageMenuElem("_Something", m_Image,
          sigc::mem_fun(*this, &ExampleWindow::on_menu_file_popup_generic) ) ) ;
      */

      m_refUIManager = Gtk::UIManager::create();
      m_refUIManager->insert_action_group(m_refActionGroup);

      add_accel_group(m_refUIManager->get_accel_group());

      //Layout the actions in a menubar and toolbar:
      Glib::ustring ui_info =
            "<ui>"
            "  <popup name='PopupMenu'>"
            "    <menuitem action='ContextEdit'/>"
            "    <menuitem action='ContextProcess'/>"
            "    <menuitem action='ContextRemove'/>"
            "  </popup>"
            "</ui>";

      try
      {
        m_refUIManager->add_ui_from_string(ui_info);
      }
      catch(const Glib::Error& ex)
      {
        std::cerr << "building menus failed: " <<  ex.what();
      }

      //Get the menu:
      m_pMenuPopup = dynamic_cast<Gtk::Menu*>(
              m_refUIManager->get_widget("/PopupMenu"));
      if(!m_pMenuPopup)
        g_warning("menu not found");

      show_all_children();
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_menu_file_popup_generic()
    {
       std::cout << "A popup menu item was selected." << std::endl;
    }

    bool ExampleWindow::on_button_press_event(GdkEventButton* event)
    {
      if( (event->type == GDK_BUTTON_PRESS) && (event->button == 3) )
      {
        if(m_pMenuPopup)
          m_pMenuPopup->popup(event->button, event->time);

        return true; //It has been handled.
      }
      else
        return false;
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      ExampleWindow window;

      //Shows the window and returns when it is closed.
      return app->run(window);
    }

## ToolPalette

Una `ToolPalette` es similar a una `Toolbar`, pero puede contener una rejilla de elementos categorizados en grupos. El usuario puede ocultar o expandir cada grupo. Al igual que en una barra de herramientas, los elementos pueden aparecer sólo como iconos, como sólo texto, o en forma de iconos con el texto.

The `ToolPalette`'s items might be dragged or simply activated. For instance, the user might drag objects to a canvas to create new items there. Or the user might click an item to activate a certain brush size in a drawing application.

`ToolItemGroup`s should be added to the tool pallete via the base class's `Gtk::Container::add()` method, for instance like so:

    Gtk::ToolItemGroup* group_brushes =
      Gtk::manage(new Gtk::ToolItemGroup("Brushes"));
    m_ToolPalette.add(*group_brushes);

`Gtk::ToolItem`s can then be added to the group. For instance, like so:

    Gtk::ToolButton* button = Gtk::manage(new Gtk::ToolButton(icon, "Big"));
    button->set_tooltip_text("Big Brush);
    group_brushes->insert(*button);

You might then handle the `ToolButton`'s `clicked` signal. Alternatively, you could allow the item to be dragged to another widget, by calling `Gtk::ToolPalette::add_drag_dest()` and then using `Gtk::ToolPalette::get_drag_item()` in the other widget's `drag_data_received` signal handler.

Referencia de ToolPalette

Referencia de ToolItemGroup

Referencia de ToolItem

### Arrastrar y soltar

Call `add_drag_dest()` to allow items or groups to be dragged from the tool palette to a particular destination widget. You can then use `get_drag_item()` to discover which ToolItem or ToolItemGroup is being dragged. You can use `dynamic_cast` to discover whether is it an item or a group. For instance, you might use this in your `drag_data_received` signal handler, to add a dropped item, or to show a suitable icon while dragging.

See the Drag and Drop chapter for general advice about Drag and Drop with gtkmm.

### Ejemplo de ToolPalette

This example adds a `ToolPalette` and a `DrawingArea` to a window and allows the user to drag icons from the tool palette to the drawing area. The tool palette contains several groups of items. The combo boxes allow the user to change the style and orientation of the tool palette.

#### ToolPalette

Código fuente

File: `canvas.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLE_CANVAS_H
    #define GTKMM_EXAMPLE_CANVAS_H

    #include <gtkmm.h>

    // This little canvas class is only here
    // because gtkmm does not have a canvas class yet.
    // Applications should probably use GooCanvas::Canvas (goocanvasmm) instead.
    class Canvas : public Gtk::DrawingArea
    {
    public:
      Canvas();
      virtual ~Canvas();

    private:

      class CanvasItem
      {
      public:
        CanvasItem(Gtk::Widget* canvas, Gtk::ToolButton* button, double x, double y)
        {
          const Gtk::StockID stock_id(button->get_stock_id());
          this->pixbuf = canvas->render_icon_pixbuf(stock_id, Gtk::ICON_SIZE_DIALOG);
          this->x = x;
          this->y = y;
        }

        Glib::RefPtr<Gdk::Pixbuf> pixbuf;
        double x, y;
      };

      void item_draw(const CanvasItem *item,
        const Cairo::RefPtr<Cairo::Context>& cr,
        bool preview);

      virtual bool on_draw(const Cairo::RefPtr<Cairo::Context>& cr);
      virtual void on_drag_data_received(const Glib::RefPtr<Gdk::DragContext>& context,
        int x, int y, const Gtk::SelectionData& selection_data, guint info, guint time);
      virtual bool on_drag_motion(const Glib::RefPtr<Gdk::DragContext>& context, int x, int y, guint time);
      virtual bool on_drag_drop(const Glib::RefPtr<Gdk::DragContext>& context, int x, int y, guint time);
      virtual void on_drag_leave(const Glib::RefPtr<Gdk::DragContext>& context, guint time);

      bool m_drag_data_requested_for_drop; //So we know what to do in on_drag_data_received().
      CanvasItem* m_drop_item;

      typedef std::vector<CanvasItem*> type_vec_items;
      type_vec_items m_canvas_items;
    };

    #endif //GTKMM_EXAMPLE_CANVAS_H

File: `examplewindow.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>
    #include "canvas.h"

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    private:

      void load_stock_items();
      void load_toggle_items();
      void load_special_items();

      //Signal handlers:
      void on_combo_orientation_changed();
      void on_combo_style_changed();

      //Tree model columns:
      class ModelColumnsOrientation : public Gtk::TreeModel::ColumnRecord
      {
      public:

        ModelColumnsOrientation()
        { add(m_col_value); add(m_col_name); }

        Gtk::TreeModelColumn<Gtk::Orientation> m_col_value;
        Gtk::TreeModelColumn<Glib::ustring> m_col_name;
      };

      ModelColumnsOrientation m_ColumnsOrientation;

      //Tree model columns:
      class ModelColumnsStyle : public Gtk::TreeModel::ColumnRecord
      {
      public:

        ModelColumnsStyle()
        { add(m_col_value); add(m_col_name); }

        Gtk::TreeModelColumn<int> m_col_value; //We use int to also allow -1
        Gtk::TreeModelColumn<Glib::ustring> m_col_name;
      };

      ModelColumnsStyle m_ColumnsStyle;

      //Child widgets:
      Gtk::Box m_VBox;
      Gtk::Box m_HBox;
      Gtk::ComboBox m_ComboOrientation;
      Glib::RefPtr<Gtk::ListStore> m_refTreeModelOrientation;
      Gtk::ComboBox m_ComboStyle;
      Glib::RefPtr<Gtk::ListStore> m_refTreeModelStyle;
      Gtk::ToolPalette m_ToolPalette;
      Gtk::ScrolledWindow m_ScrolledWindowPalette;
      Gtk::ScrolledWindow m_ScrolledWindowCanvas;
      Canvas m_Canvas;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"

    static bool sort_predicate(const Gtk::StockID& a, const Gtk::StockID& b)
    {
      return a.get_string() < b.get_string();
    }

    void ExampleWindow::load_stock_items()
    {
      Gtk::ToolItemGroup* group_af =
        Gtk::manage(new Gtk::ToolItemGroup("Stock Icons (A-F)"));
      m_ToolPalette.add(*group_af);
      Gtk::ToolItemGroup* group_gn =
        Gtk::manage(new Gtk::ToolItemGroup("Stock Icons (G-N)"));
      m_ToolPalette.add(*group_gn);
      Gtk::ToolItemGroup* group_or =
        Gtk::manage(new Gtk::ToolItemGroup("Stock Icons (O-R)"));
      m_ToolPalette.add(*group_or);
      Gtk::ToolItemGroup* group_sz =
        Gtk::manage(new Gtk::ToolItemGroup("Stock Icons (S-Z)"));
      m_ToolPalette.add(*group_sz);

      // Obtain the IDs of all stock items:
      typedef std::vector<Gtk::StockID> type_vecIDs;
      type_vecIDs vecIDs = Gtk::Stock::get_ids();

      std::sort(vecIDs.begin(), vecIDs.end(), &sort_predicate);

      Gtk::ToolItemGroup* group = 0;

      // Iterate through them, populating the ListStore as appropriate:
      for(type_vecIDs::const_iterator iterIDs = vecIDs.begin(); iterIDs != vecIDs.end(); ++iterIDs)
      {
        const Gtk::StockID& stockid = *iterIDs;
        const Glib::ustring str = stockid.get_string();
        if(str.size() < 4)
          continue;

        switch(str[4])
        {
          case 'a':
            group = group_af;
            break;
          case 'g':
            group = group_gn;
            break;
          case 'o':
            group = group_or;
            break;
          case 's':
            group = group_sz;
            break;
          default:
            //Use the previous group
            //(They are sorted.)
            break;
        }

        if(!group)
          continue;

        Gtk::ToolButton* button = Gtk::manage(new Gtk::ToolButton(stockid));
        button->set_tooltip_text(str);
        button->set_is_important();
        group->insert(*button);

        Gtk::StockItem stockitem;
        if(!Gtk::StockItem::lookup(stockid, stockitem) ||
          stockitem.get_label().empty())
            button->set_label(str);
      }
    }

    void ExampleWindow::load_toggle_items()
    {
      Gtk::ToolItemGroup* group =
        Gtk::manage(new Gtk::ToolItemGroup("Radio Item"));
      m_ToolPalette.add(*group);

      Gtk::RadioToolButton::Group radio_group;

      for(int i = 1; i <= 10; ++i)
      {
        const Glib::ustring label = Glib::ustring::compose("#%1", i);
        Gtk::RadioToolButton* button = Gtk::manage(new Gtk::RadioToolButton());
        button->set_group(radio_group);
        button->set_label(label);

        group->insert(*button);
      }
    }

    static Gtk::ToolItem* create_entry_item(const Glib::ustring& text)
    {
      Gtk::Entry* entry = Gtk::manage(new Gtk::Entry());
      entry->set_text(text);
      entry->set_width_chars(5);

      Gtk::ToolItem* item = Gtk::manage(new Gtk::ToolItem());
      item->add(*entry);

      return item;
    }

    void ExampleWindow::load_special_items()
    {
      Gtk::ToolItemGroup* group = Gtk::manage(new Gtk::ToolItemGroup());

      Gtk::Button *label_button = Gtk::manage(new Gtk::Button("Advanced Features"));
      label_button->show();
      group->set_label_widget(*label_button);
      m_ToolPalette.add(*group);

      Gtk::ToolItem* item = create_entry_item ("homogeneous=false");
      group->insert(*item);
      //TODO: Add Gtk::Container::set_child_property().
      gtk_container_child_set (GTK_CONTAINER (group->gobj()), GTK_WIDGET (item->gobj()),
                               "homogeneous", FALSE, NULL);

      item = create_entry_item ("homogeneous=FALSE, expand=TRUE");
      group->insert(*item);
      gtk_container_child_set (GTK_CONTAINER (group->gobj()), GTK_WIDGET (item->gobj()),
                               "homogeneous", FALSE, "expand", TRUE,
                               NULL);

      item = create_entry_item ("homogeneous=FALSE, expand=TRUE, fill=FALSE");
      group->insert(*item);
      gtk_container_child_set (GTK_CONTAINER (group->gobj()), GTK_WIDGET (item->gobj()),
                               "homogeneous", FALSE, "expand", TRUE,
                               "fill", FALSE, NULL);

      item = create_entry_item ("homogeneous=FALSE, expand=TRUE, new-row=TRUE");
      group->insert(*item);
      gtk_container_child_set (GTK_CONTAINER (group->gobj()), GTK_WIDGET (item->gobj()),
                               "homogeneous", FALSE, "expand", TRUE,
                               "new-row", TRUE, NULL);

      item = Gtk::manage(new Gtk::ToolButton(Gtk::Stock::GO_UP));
      item->set_tooltip_text("Show on vertical palettes only");
      group->insert(*item);
      item->set_visible_horizontal(false);

      item = Gtk::manage(new Gtk::ToolButton(Gtk::Stock::GO_FORWARD));
      item->set_tooltip_text("Show on horizontal palettes only");
      group->insert(*item);
      item->set_visible_vertical(false);

      item = Gtk::manage(new Gtk::ToolButton(Gtk::Stock::FULLSCREEN));
      item->set_tooltip_text("Expanded this item");
      group->insert(*item);
      gtk_container_child_set (GTK_CONTAINER (group->gobj()), GTK_WIDGET (item->gobj()),
                               "homogeneous", FALSE,
                               "expand", TRUE,
                               NULL);

      item = Gtk::manage(new Gtk::ToolButton(Gtk::Stock::HELP));
      item->set_tooltip_text("A regular item");
      group->insert(*item);
    }

    ExampleWindow::ExampleWindow()
    : m_VBox(Gtk::ORIENTATION_VERTICAL, 6),
      m_HBox(Gtk::ORIENTATION_HORIZONTAL, 6)
    {
      set_title("Gtk::ToolPalette example");
      set_size_request(600, 600);
      set_border_width(6);

      add(m_VBox);

      //The Orientation ComboBox:
      m_refTreeModelOrientation = Gtk::ListStore::create(m_ColumnsOrientation);
      Gtk::TreeModel::Row row = *(m_refTreeModelOrientation->append());
      row[m_ColumnsOrientation.m_col_value] = Gtk::ORIENTATION_HORIZONTAL;
      row[m_ColumnsOrientation.m_col_name] = "Horizontal";\
      row = *(m_refTreeModelOrientation->append());
      row[m_ColumnsOrientation.m_col_value] = Gtk::ORIENTATION_VERTICAL;
      row[m_ColumnsOrientation.m_col_name] = "Vertical";
      m_ComboOrientation.set_model(m_refTreeModelOrientation);
      m_VBox.pack_start(m_ComboOrientation, Gtk::PACK_SHRINK);
      m_ComboOrientation.pack_start(m_ColumnsOrientation.m_col_name);
      m_ComboOrientation.signal_changed().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_combo_orientation_changed) );
      m_ComboOrientation.set_active(row);

      //The Style ComboBox:
      m_refTreeModelStyle = Gtk::ListStore::create(m_ColumnsStyle);
      row = *(m_refTreeModelStyle->append());
      row[m_ColumnsStyle.m_col_value] = Gtk::TOOLBAR_TEXT;
      row[m_ColumnsStyle.m_col_name] = "Text";\
      row = *(m_refTreeModelStyle->append());
      row[m_ColumnsStyle.m_col_value] = Gtk::TOOLBAR_BOTH;
      row[m_ColumnsStyle.m_col_name] = "Both";
      row = *(m_refTreeModelStyle->append());
      row[m_ColumnsStyle.m_col_value] = Gtk::TOOLBAR_BOTH_HORIZ;
      row[m_ColumnsStyle.m_col_name] = "Both: Horizontal";
      row = *(m_refTreeModelStyle->append());
      row[m_ColumnsStyle.m_col_value] = Gtk::TOOLBAR_ICONS;
      row[m_ColumnsStyle.m_col_name] = "Icons";
      row = *(m_refTreeModelStyle->append());
      row[m_ColumnsStyle.m_col_value] = -1; // A custom meaning for this demo.
      row[m_ColumnsStyle.m_col_name] = "Default";
      m_ComboStyle.set_model(m_refTreeModelStyle);
      m_VBox.pack_start(m_ComboStyle, Gtk::PACK_SHRINK);
      m_ComboStyle.pack_start(m_ColumnsStyle.m_col_name);
      m_ComboStyle.signal_changed().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_combo_style_changed) );
      m_ComboStyle.set_active(row);

      //Add and fill the ToolPalette:
      load_stock_items();
      load_toggle_items();
      load_special_items();

      m_VBox.pack_start(m_HBox, Gtk::PACK_EXPAND_WIDGET);

      m_ScrolledWindowPalette.set_policy(Gtk::POLICY_NEVER, Gtk::POLICY_AUTOMATIC);
      m_ScrolledWindowPalette.set_border_width(6);
      m_ScrolledWindowPalette.add(m_ToolPalette);
      m_HBox.pack_start(m_ScrolledWindowPalette);

      on_combo_orientation_changed();

      m_ScrolledWindowCanvas.set_policy(Gtk::POLICY_AUTOMATIC, Gtk::POLICY_ALWAYS);
      m_ScrolledWindowCanvas.set_border_width(6);
      m_ScrolledWindowCanvas.add(m_Canvas);
      m_ScrolledWindowCanvas.set_size_request(200, -1);
      m_HBox.pack_start(m_ScrolledWindowCanvas);

      m_ToolPalette.add_drag_dest(m_Canvas,
        Gtk::DEST_DEFAULT_HIGHLIGHT, Gtk::TOOL_PALETTE_DRAG_ITEMS, Gdk::ACTION_COPY);

      show_all_children();
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_combo_orientation_changed()
    {
      Gtk::TreeModel::iterator iter = m_ComboOrientation.get_active();
      if(!iter)
        return;

      Gtk::TreeModel::Row row = *iter;
      const Gtk::Orientation value = row[m_ColumnsOrientation.m_col_value];

      m_ToolPalette.set_orientation(value);

      if(value == Gtk::ORIENTATION_HORIZONTAL)
        m_ScrolledWindowPalette.set_policy(Gtk::POLICY_AUTOMATIC, Gtk::POLICY_NEVER);
      else
        m_ScrolledWindowPalette.set_policy(Gtk::POLICY_NEVER, Gtk::POLICY_AUTOMATIC);
    }

    void ExampleWindow::on_combo_style_changed()
    {
      Gtk::TreeModel::iterator iter = m_ComboStyle.get_active();
      if(!iter)
        return;

      Gtk::TreeModel::Row row = *iter;
      const int value = row[m_ColumnsStyle.m_col_value];

      if(value == -1)
        m_ToolPalette.unset_style();
      else
        m_ToolPalette.set_style((Gtk::ToolbarStyle)value);
    }

File: `canvas.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "canvas.h"
    #include <iostream>

    Canvas::Canvas()
    : m_drag_data_requested_for_drop(false),
      m_drop_item()
    {
      set_app_paintable();
    }

    Canvas::~Canvas()
    {
      while(!m_canvas_items.empty())
      {
        type_vec_items::iterator iter = m_canvas_items.begin();
        CanvasItem* item = *iter;
        delete item;
        m_canvas_items.erase(iter);
      }

      if(m_drop_item)
        delete m_drop_item;
    }

    void Canvas::item_draw(const CanvasItem *item,
      const Cairo::RefPtr<Cairo::Context>& cr,
      bool preview)
    {
      if(!item || !item->pixbuf)
        return;

      const double cx = item->pixbuf->get_width();
      const double cy = item->pixbuf->get_height();

      Gdk::Cairo::set_source_pixbuf(cr,
        item->pixbuf,
        item->x - cx * 0.5, item->y - cy * 0.5);

      if(preview)
        cr->paint_with_alpha(0.6);
      else
        cr->paint();
    }

    bool Canvas::on_draw(const Cairo::RefPtr<Cairo::Context>& cr)
    {
      cr->set_source_rgb(1.0, 1.0, 1.0);
      const Gtk::Allocation allocation = get_allocation();
      cr->rectangle(0, 0, allocation.get_width(), allocation.get_height());
      cr->fill();

      for(type_vec_items::iterator iter = m_canvas_items.begin();
        iter != m_canvas_items.end(); ++iter )
      {
        item_draw(*iter, cr, false);
      }

      if(m_drop_item)
        item_draw (m_drop_item, cr, true);

      return true;
    }

    bool Canvas::on_drag_motion(const Glib::RefPtr<Gdk::DragContext>& context,
      int x, int y, guint time)
    {
      m_drag_data_requested_for_drop = false; //It's for drag-motion instead.

      if(m_drop_item)
      {
        // We already have a drop indicator so just update its position.

        m_drop_item->x = x;
        m_drop_item->y = y;

        queue_draw();
        context->drag_status(Gdk::ACTION_COPY, time);
      }
      else
      {
        // Request DnD data for creating a drop indicator.
        // This will cause on_drag_data_received() to be called.
        const Glib::ustring target = drag_dest_find_target(context);

        if (target.empty())
          return false;

        drag_get_data(context, target, time);
      }

      Gtk::DrawingArea::on_drag_motion(context, x, y, time);
      return true;
    }

    void Canvas::on_drag_data_received(const Glib::RefPtr<Gdk::DragContext>& context, int x, int y, const Gtk::SelectionData& selection_data, guint info, guint time)
    {
      // Find the tool button which is the source of this DnD operation.
      Gtk::Widget* widget = drag_get_source_widget(context);

      Gtk::ToolPalette* drag_palette = dynamic_cast<Gtk::ToolPalette*>(widget);
      while(widget && !drag_palette)
      {
        widget = widget->get_parent();
        drag_palette = dynamic_cast<Gtk::ToolPalette*>(widget);
      }

      Gtk::ToolItem* drag_item = 0;
      if(drag_palette)
        drag_item = drag_palette->get_drag_item(selection_data);

      // Create a drop indicator when a tool button was found:
      Gtk::ToolButton* button = dynamic_cast<Gtk::ToolButton*>(drag_item);
      if(!button)
        return;

      if(m_drop_item)
      {
        delete m_drop_item;
        m_drop_item = 0;
      }

      CanvasItem* item = new CanvasItem(this, button, x, y);

      if(m_drag_data_requested_for_drop)
      {
        m_canvas_items.push_back(item);

        // Signal that the item was accepted and then redraw.
        context->drag_finish(true /* success */, false /* del */, time);
      }
      else
      {
        m_drop_item = item;

        // We are getting this data due to a request in drag_motion,
        // rather than due to a request in drag_drop, so we are just
        // supposed to call gdk_drag_status (), not actually paste in
        // the data.
        context->drag_status(Gdk::ACTION_COPY, time);
      }

      queue_draw();

      Gtk::DrawingArea::on_drag_data_received(context, x, y, selection_data, info, time);
    }

    bool Canvas::on_drag_drop(const Glib::RefPtr<Gdk::DragContext>& context, int /* x */, int /* y */, guint time)
    {
      // Request DnD data for creating a dopped item.
      // This will cause on_drag_data_received() to be called.
      const Glib::ustring target = drag_dest_find_target(context);

      if (target.empty())
        return false;

      m_drag_data_requested_for_drop = true;
      drag_get_data(context, target, time);

      return true;
    }

    void Canvas::on_drag_leave(const Glib::RefPtr<Gdk::DragContext>& context, guint time)
    {
      //This signal is emitted to clean up the item used for drag-motion,
      //either when the cursor moves out of the widget or when we drop.

      if(!m_drop_item)
        return;

      delete m_drop_item;
      m_drop_item = 0;

      queue_draw();

      Gtk::DrawingArea::on_drag_leave(context, time);
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      ExampleWindow window;

      //Shows the window and returns when it is closed.
      return app->run(window);
    }

## Ajustes

gtkmm has various widgets that can be visually adjusted using the mouse or the keyboard, such as the `Range` widgets (described in the Range Widgets section). There are also a few widgets that display some adjustable part of a larger area, such as the `Viewport` widget. These widgets have `Gtk::Adjustment` objects that express this common part of their API.

So that applications can react to changes, for instance when a user moves a scrollbar, `Gtk::Adjustment` has a `changed` signal. You can then use the `get_changed()` method to discover the new value.

### Crear un ajuste

The `Gtk::Adjustment` constructor is as follows:

    Gtk::Adjustment(float value,
                    float lower,
                    float upper,
                    float step_increment = 1,
                    float page_increment = 10,
                    float page_size = 0);

The `value` argument is the initial value of the adjustment, usually corresponding to the topmost or leftmost position of an adjustable widget. The `lower` and `upper` arguments specifies the possible range of values which the adjustment can hold. The `step_increment` argument specifies the smaller of the two increments by which the user can change the value, while the `page_increment` is the larger one. The `page_size` argument usually corresponds somehow to the visible area of a panning widget. The `upper` argument is used to represent the bottom most or right most coordinate in a panning widget's child.

### Using Adjustments the Easy Way

The adjustable widgets can be roughly divided into those which use and require specific units for these values, and those which treat them as arbitrary numbers.

The group which treats the values as arbitrary numbers includes the `Range` widgets (`Scrollbar` and `Scale`), the `ScaleButton` widget, and the `SpinButton` widget. These widgets are typically "adjusted" directly by the user with the mouse or keyboard. They will treat the `lower` and `upper` values of an adjustment as a range within which the user can manipulate the adjustment's `value`. By default, they will only modify the `value` of an adjustment.

The other group includes the `Viewport` widget and the `ScrolledWindow` widget. All of these widgets use pixel values for their adjustments. These are also typically adjusted indirectly using scrollbars. While all widgets which use adjustments can either create their own adjustments or use ones you supply, you'll generally want to let this particular category of widgets create its own adjustments.

If you share an adjustment object between a Scrollbar and a TextView widget, manipulating the scrollbar will automagically adjust the TextView widget. You can set it up like this:

    // creates its own adjustments
    Gtk::TextView textview;
    // uses the newly-created adjustment for the scrollbar as well
    Gtk::Scrollbar vscrollbar (textview.get_vadjustment(), Gtk::ORIENTATION_VERTICAL);

### Adjustment Internals

OK, you say, that's nice, but what if I want to create my own handlers to respond when the user adjusts a `Range` widget or a `SpinButton`. To access the value of a `Gtk::Adjustment`, you can use the `get_value()` and `set_value()` methods:

As mentioned earlier, `Gtk::Adjustment` can emit signals. This is, of course, how updates happen automatically when you share an `Adjustment` object between a `Scrollbar` and another adjustable widget; all adjustable widgets connect signal handlers to their adjustment's `value_changed` signal, as can your program.

So, for example, if you have a `Scale` widget, and you want to change the rotation of a picture whenever its value changes, you would create a signal handler like this:

    void cb_rotate_picture (Gtk::Widget *picture)
    {
      picture->set_rotation (adj->value);
    ...

and connect it to the scale widget's adjustment like this:

    adj.value_changed.connect(sigc::bind<Widget*>(sigc::mem_fun(*this,
        &cb_rotate_picture), picture));

What if a widget reconfigures the `upper` or `lower` fields of its `Adjustment`, such as when a user adds more text to a text widget? In this case, it emits the `changed` signal.

`Range` widgets typically connect a handler to this signal, which changes their appearance to reflect the change - for example, the size of the slider in a scrollbar will grow or shrink in inverse proportion to the difference between the `lower` and `upper` values of its `Adjustment`.

You probably won't ever need to attach a handler to this signal, unless you're writing a new type of range widget.

    adjustment->changed();

## Widgets Without X-Windows

Some Widgets do not have an associated X-Window, so they therefore do not receive X events. This means that the signals described in the X event signals section will not be emitted. If you want to capture events for these widgets you can use a special container called `Gtk::EventBox`, which is described in the EventBox section.

Aquí hay una lista de estos widgets

    Gtk::Alignment
    Gtk::Arrow
    Gtk::AspectFrame
    Gtk::Bin
    Gtk::Box
    Gtk::Button
    Gtk::CheckButton
    Gtk::Fixed
    Gtk::Frame
    Gtk::Grid
    Gtk::Image
    Gtk::Label
    Gtk::MenuItem
    Gtk::Notebook
    Gtk::Paned
    Gtk::RadioButton
    Gtk::Range
    Gtk::ScrolledWindow
    Gtk::Separator
    Gtk::Table (deprecated from gtkmm version 3.4)
    Gtk::Toolbar

These widgets are mainly used for decoration or layout, so you won't often need to capture events on them. They are intended to have no X-Window in order to improve performance.

### EventBox

Some gtkmm widgets don't have associated X windows; they draw on their parents' windows. Because of this, they cannot receive events. Also, if they are incorrectly sized, they don't clip, so you can get messy overwriting etc. To receive events on one of these widgets, you can it inside an `EventBox` widget and then call `Gtk::Widget::set_events()` on the EventBox before showing it.

Although the name `EventBox` emphasises the event-handling method, the widget can also be used for clipping (and more; see the example below).

The constructor for `Gtk::EventBox` is:

    Gtk::EventBox();

Se puede agregar un widget hijo a `EventBox` utilizando:

    event_box.add(child_widget);

Referencia

#### Ejemplo

The following example demonstrates both uses of an `EventBox` - a label is created that is clipped to a small box, and set up so that a mouse-click on the label causes the program to exit. Resizing the window reveals varying amounts of the label.

##### EventBox

Código fuente

File: `examplewindow.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      virtual bool on_eventbox_button_press(GdkEventButton* event);

      //Child widgets:
      Gtk::EventBox m_EventBox;
      Gtk::Label m_Label;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"

    ExampleWindow::ExampleWindow()
    : m_Label("Click here to quit, quit, quit, quit, quit")
    {
      set_title ("EventBox");
      set_border_width(10);

      add(m_EventBox);

      m_EventBox.add(m_Label);

      //Clip the label short:
      m_Label.set_size_request(110, 20);

      //And bind an action to it:
      m_EventBox.set_events(Gdk::BUTTON_PRESS_MASK);
      m_EventBox.signal_button_press_event().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_eventbox_button_press) );

      m_EventBox.set_tooltip_text("Click me!");

      show_all_children();
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    bool ExampleWindow::on_eventbox_button_press(GdkEventButton*)
    {
      hide();
      return true;
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      ExampleWindow window;

      //Shows the window and returns when it is closed.
      return app->run(window);
    }

## Diálogos

Dialogs are used as secondary windows, to provide specific information or to ask questions. `Gtk::Dialog` windows contain a few pre-packed widgets to ensure consistency, and a `run()` method which blocks until the user dismisses the dialog.

There are several derived `Dialog` classes which you might find useful. `Gtk::MessageDialog` is used for most simple notifications. But at other times you might need to derive your own dialog class to provide more complex functionality.

To pack widgets into a custom dialog, you should pack them into the `Gtk::Box`, available via `get_content_area()`. To just add a `Button` to the bottom of the `Dialog`, you could use the `add_button()` method.

The `run()` method returns an `int`. This may be a value from the `Gtk::ResponseType` if the user closed the button by clicking a standard button, or it could be the custom response value that you specified when using `add_button()`.

Referencia

### MessageDialog

`MessageDialog` is a convenience class, used to create simple, standard message dialogs, with a message, an icon, and buttons for user response. You can specify the type of message and the text in the constructor, as well as specifying standard buttons via the `Gtk::ButtonsType` enum.

Referencia

#### Ejemplo

##### MessageDialog

Código fuente

File: `examplewindow.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      void on_button_info_clicked();
      void on_button_question_clicked();

      //Child widgets:
      Gtk::ButtonBox m_ButtonBox;
      Gtk::Button m_Button_Info, m_Button_Question;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/messagedialog.h>
    #include <iostream>

    ExampleWindow::ExampleWindow()
    : m_ButtonBox(Gtk::ORIENTATION_VERTICAL),
      m_Button_Info("Show Info MessageDialog"),
      m_Button_Question("Show Question MessageDialog")
    {
      set_title("Gtk::MessageDialog example");

      add(m_ButtonBox);

      m_ButtonBox.pack_start(m_Button_Info);
      m_Button_Info.signal_clicked().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_button_info_clicked) );

      m_ButtonBox.pack_start(m_Button_Question);
      m_Button_Question.signal_clicked().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_button_question_clicked) );

      show_all_children();
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_button_info_clicked()
    {
      Gtk::MessageDialog dialog(*this, "This is an INFO MessageDialog");
      dialog.set_secondary_text(
              "And this is the secondary text that explains things.");

      dialog.run();
    }

    void ExampleWindow::on_button_question_clicked()
    {
      Gtk::MessageDialog dialog(*this, "This is a QUESTION MessageDialog",
              false /* use_markup */, Gtk::MESSAGE_QUESTION,
              Gtk::BUTTONS_OK_CANCEL);
      dialog.set_secondary_text(
              "And this is the secondary text that explains things.");

      int result = dialog.run();

      //Handle the response:
      switch(result)
      {
        case(Gtk::RESPONSE_OK):
        {
          std::cout << "OK clicked." << std::endl;
          break;
        }
        case(Gtk::RESPONSE_CANCEL):
        {
          std::cout << "Cancel clicked." << std::endl;
          break;
        }
        default:
        {
          std::cout << "Unexpected button clicked." << std::endl;
          break;
        }
      }
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      ExampleWindow window;

      //Shows the window and returns when it is closed.
      return app->run(window);
    }

### FileChooserDialog

The `FileChooserDialog` is suitable for use with "Open" or "Save" menu items.

Most of the useful member methods for this class are actually in the `Gtk::FileChooser` base class.

Referencia

#### Ejemplo

##### Selector de archivos

Código fuente

File: `examplewindow.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      void on_button_file_clicked();
      void on_button_folder_clicked();

      //Child widgets:
      Gtk::ButtonBox m_ButtonBox;
      Gtk::Button m_Button_File, m_Button_Folder;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <iostream>

    ExampleWindow::ExampleWindow()
    : m_ButtonBox(Gtk::ORIENTATION_VERTICAL),
      m_Button_File("Choose File"),
      m_Button_Folder("Choose Folder")
    {
      set_title("Gtk::FileSelection example");

      add(m_ButtonBox);

      m_ButtonBox.pack_start(m_Button_File);
      m_Button_File.signal_clicked().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_button_file_clicked) );

      m_ButtonBox.pack_start(m_Button_Folder);
      m_Button_Folder.signal_clicked().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_button_folder_clicked) );

      show_all_children();
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_button_folder_clicked()
    {
      Gtk::FileChooserDialog dialog("Please choose a folder",
              Gtk::FILE_CHOOSER_ACTION_SELECT_FOLDER);
      dialog.set_transient_for(*this);

      //Add response buttons the the dialog:
      dialog.add_button(Gtk::Stock::CANCEL, Gtk::RESPONSE_CANCEL);
      dialog.add_button("Select", Gtk::RESPONSE_OK);

      int result = dialog.run();

      //Handle the response:
      switch(result)
      {
        case(Gtk::RESPONSE_OK):
        {
          std::cout << "Select clicked." << std::endl;
          std::cout << "Folder selected: " << dialog.get_filename()
              << std::endl;
          break;
        }
        case(Gtk::RESPONSE_CANCEL):
        {
          std::cout << "Cancel clicked." << std::endl;
          break;
        }
        default:
        {
          std::cout << "Unexpected button clicked." << std::endl;
          break;
        }
      }
    }

    void ExampleWindow::on_button_file_clicked()
    {
      Gtk::FileChooserDialog dialog("Please choose a file",
              Gtk::FILE_CHOOSER_ACTION_OPEN);
      dialog.set_transient_for(*this);

      //Add response buttons the the dialog:
      dialog.add_button(Gtk::Stock::CANCEL, Gtk::RESPONSE_CANCEL);
      dialog.add_button(Gtk::Stock::OPEN, Gtk::RESPONSE_OK);

      //Add filters, so that only certain file types can be selected:

      Glib::RefPtr<Gtk::FileFilter> filter_text = Gtk::FileFilter::create();
      filter_text->set_name("Text files");
      filter_text->add_mime_type("text/plain");
      dialog.add_filter(filter_text);

      Glib::RefPtr<Gtk::FileFilter> filter_cpp = Gtk::FileFilter::create();
      filter_cpp->set_name("C/C++ files");
      filter_cpp->add_mime_type("text/x-c");
      filter_cpp->add_mime_type("text/x-c++");
      filter_cpp->add_mime_type("text/x-c-header");
      dialog.add_filter(filter_cpp);

      Glib::RefPtr<Gtk::FileFilter> filter_any = Gtk::FileFilter::create();
      filter_any->set_name("Any files");
      filter_any->add_pattern("*");
      dialog.add_filter(filter_any);

      //Show the dialog and wait for a user response:
      int result = dialog.run();

      //Handle the response:
      switch(result)
      {
        case(Gtk::RESPONSE_OK):
        {
          std::cout << "Open clicked." << std::endl;

          //Notice that this is a std::string, not a Glib::ustring.
          std::string filename = dialog.get_filename();
          std::cout << "File selected: " <<  filename << std::endl;
          break;
        }
        case(Gtk::RESPONSE_CANCEL):
        {
          std::cout << "Cancel clicked." << std::endl;
          break;
        }
        default:
        {
          std::cout << "Unexpected button clicked." << std::endl;
          break;
        }
      }
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      ExampleWindow window;

      //Shows the window and returns when it is closed.
      return app->run(window);
    }

### ColorChooserDialog

The `ColorChooserDialog` allows the user to choose a color. The `ColorButton` opens a color selection dialog when it is clicked.

Referencia

#### Ejemplo

##### ColorChooserDialog

Código fuente

File: `examplewindow.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      void on_color_button_color_set();
      void on_button_dialog_clicked();

      //Child widgets:
      Gtk::Box m_VBox;
      Gtk::ColorButton m_ColorButton;
      Gtk::Button m_Button_Dialog;
      Gtk::DrawingArea m_DrawingArea; //To show the color.

      Gdk::RGBA m_Color;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <iostream>

    ExampleWindow::ExampleWindow()
    : m_VBox(Gtk::ORIENTATION_VERTICAL, 5),
      m_Button_Dialog("Choose Color")
    {
      set_title("Gtk::ColorChooserDialog example");
      set_default_size(200, 200);

      add(m_VBox);

      m_VBox.pack_start(m_ColorButton, Gtk::PACK_SHRINK);
      m_ColorButton.signal_color_set().connect(sigc::mem_fun(*this,
        &ExampleWindow::on_color_button_color_set) );

      m_VBox.pack_start(m_Button_Dialog, Gtk::PACK_SHRINK);
      m_Button_Dialog.signal_clicked().connect(sigc::mem_fun(*this,
        &ExampleWindow::on_button_dialog_clicked) );

      //Set start color:
      m_Color.set_red(0.0);
      m_Color.set_green(0.0);
      m_Color.set_blue(1.0);
      m_Color.set_alpha(1.0); //opaque
      m_ColorButton.set_rgba(m_Color);

      m_DrawingArea.override_background_color(m_Color);

      m_VBox.pack_start(m_DrawingArea);

      show_all_children();
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_color_button_color_set()
    {
      //Store the chosen color, and show it:
      m_Color = m_ColorButton.get_rgba();
      m_DrawingArea.override_background_color(m_Color);
    }

    void ExampleWindow::on_button_dialog_clicked()
    {
      Gtk::ColorChooserDialog dialog("Please choose a color");
      dialog.set_transient_for(*this);

      //Get the previously selected color:
      dialog.set_rgba(m_Color);

      const int result = dialog.run();

      //Handle the response:
      switch(result)
      {
        case Gtk::RESPONSE_OK:
        {
          //Store the chosen color, and show it:
          m_Color = dialog.get_rgba();
          m_ColorButton.set_rgba(m_Color);
          m_DrawingArea.override_background_color(m_Color);
          break;
        }
        case Gtk::RESPONSE_CANCEL:
        {
          std::cout << "Cancel clicked." << std::endl;
          break;
        }
        default:
        {
          std::cout << "Unexpected button clicked: " << result << std::endl;
          break;
        }
      }
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      ExampleWindow window;

      //Shows the window and returns when it is closed.
      return app->run(window);
    }

### FontChooserDialog

The `FontChooserDialog` allows the user to choose a font. The `FontButton` opens a font chooser dialog when it is clicked.

Referencia

#### Ejemplo

##### FontChooserDialog

Código fuente

File: `examplewindow.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      void on_font_button_font_set();
      void on_button_dialog_clicked();

      //Child widgets:
      Gtk::ButtonBox m_ButtonBox;
      Gtk::FontButton m_FontButton;
      Gtk::Button m_Button_Dialog;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <iostream>

    ExampleWindow::ExampleWindow()
    : m_ButtonBox(Gtk::ORIENTATION_VERTICAL),
      m_FontButton("Sans 10"),
      m_Button_Dialog("Choose Font")
    {
      set_title("Gtk::FontChooserDialog example");

      add(m_ButtonBox);

      m_ButtonBox.pack_start(m_FontButton);
      m_FontButton.set_use_font(true);
      m_FontButton.set_use_size(true);
      m_FontButton.signal_font_set().connect(sigc::mem_fun(*this,
        &ExampleWindow::on_font_button_font_set) );

      m_ButtonBox.pack_start(m_Button_Dialog);
      m_Button_Dialog.signal_clicked().connect(sigc::mem_fun(*this,
        &ExampleWindow::on_button_dialog_clicked) );
      show_all_children();
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_font_button_font_set()
    {
      Glib::ustring font_name = m_FontButton.get_font_name();
      std::cout << "Font chosen: " << font_name << std::endl;
    }

    void ExampleWindow::on_button_dialog_clicked()
    {
      Gtk::FontChooserDialog dialog("Please choose a font", *this);

      //Get the previously selected font name from the FontButton:
      dialog.set_font(m_FontButton.get_font_name());

      int result = dialog.run();

      //Handle the response:
      switch(result)
      {
        case Gtk::RESPONSE_OK:
        {
          Glib::ustring font_name = dialog.get_font();
          std::cout << "Font chosen: " << font_name << std::endl;
          m_FontButton.set_font_name(font_name);
          break;
        }
        case Gtk::RESPONSE_CANCEL:
        {
          std::cout << "Cancel clicked." << std::endl;
          break;
        }
        default:
        {
          std::cout << "Unexpected button clicked: " << result << std::endl;
          break;
        }
      }
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      ExampleWindow window;

      //Shows the window and returns when it is closed.
      return app->run(window);
    }

## El widget de área de dibujo

The `DrawingArea` widget is a blank window that gives you the freedom to create any graphic you desire. Along with that freedom comes the responsibility to handle draw signals on the widget. When a widget is first shown, or when it is covered and then uncovered again it needs to redraw itself. Most widgets have code to do this, but the DrawingArea does not, allowing you to write your own draw signal handler to determine how the contents of the widget will be drawn. This is most often done by overriding the virtual `on_draw()` member function.

GTK+ uses the Cairo drawing API. With gtkmm, you may use the cairomm C++ API for cairo.

You can draw very sophisticated shapes using Cairo, but the methods to do so are quite basic. Cairo provides methods for drawing straight lines, curved lines, and arcs (including circles). These basic shapes can be combined to create more complex shapes and paths which can be filled with solid colors, gradients, patterns, and other things. In addition, Cairo can perform complex transformations, do compositing of images, and render antialiased text.

### Cairo y Pango

Although Cairo can render text, it's not meant to be a replacement for Pango. Pango is a better choice if you need to perform more advanced text rendering such as wrapping or ellipsizing text. Drawing text with Cairo should only be done if the text is part of a graphic.

In this section of the tutorial, we'll cover the basic Cairo drawing model, describe each of the basic drawing elements in some detail (with examples), and then present a simple application that uses Cairo to draw a custom clock widget.

### El modelo de dibujo de Cairo

The basic concept of drawing in Cairo involves defining 'invisible' paths and then stroking or filling them to make them visible.

To do any drawing in gtkmm with Cairo, you must first create a `Cairo::Context` object. This class holds all of the graphics state parameters that describe how drawing is to be done. This includes information such as line width, color, the surface to draw to, and many other things. This allows the actual drawing functions to take fewer arguments to simplify the interface. In gtkmm, a `Cairo::Context` is created by calling the `Gdk::Window::create_cairo_context()` function. Since Cairo contexts are reference-counted objects, this function returns a `Cairo::RefPtr<Cairo::Context>` object.

The following example shows how to set up a Cairo context with a foreground color of red and a width of 2. Any drawing functions that use this context will use these settings.

    Gtk::DrawingArea myArea;
    Cairo::RefPtr<Cairo::Context> myContext = myArea.get_window()->create_cairo_context();
    myContext->set_source_rgb(1.0, 0.0, 0.0);
    myContext->set_line_width(2.0);

Each `Cairo::Context` is associated with a particular `Gdk::Window`, so the first line of the above example creates a `Gtk::DrawingArea` widget and the second line uses its associated `Gdk::Window` to create a `Cairo::Context` object. The final two lines change the graphics state of the context.

There are a number of graphics state variables that can be set for a Cairo context. The most common context attributes are color (using `set_source_rgb()` or `set_source_rgba()` for translucent colors), line width (using `set_line_width()`), line dash pattern (using `set_dash()`), line cap style (using `set_line_cap()`), and line join style (using `set_line_join()`), and font styles (using `set_font_size()`, `set_font_face()` and others). There are many other settings as well, such as transformation matrices, fill rules, whether to perform antialiasing, and others. For further information, see the cairomm API documentation.

The current state of a `Cairo::Context` can be saved to an internal stack of saved states and later be restored to the state it was in when you saved it. To do this, use the `save()` method and the `restore()` method. This can be useful if you need to temporarily change the line width and color (or any other graphics setting) in order to draw something and then return to the previous settings. In this situation, you could call `Cairo::Context::save()`, change the graphics settings, draw the lines, and then call `Cairo::Context::restore()` to restore the original graphics state. Multiple calls to `save()` and `restore()` can be nested; each call to `restore()` restores the state from the matching paired `save()`.

It is good practice to put all modifications to the graphics state between `save()`/`restore()` function calls. For example, if you have a function that takes a `Cairo::Context` reference as an argument, you might implement it as follows:

    void doSomething(const Cairo::RefPtr<Cairo::Context>& context, int x)
    {
        context->save();
        // change graphics state
        // peform drawing operations
        context->restore();
    }

The virtual `on_draw()` method provides a Cairo context that you shall use for drawing in the `Gtk::DrawingArea` widget. It is not necessary to save and restore this Cairo context in `on_draw()`.

### Dibujar Lineas Rectas

Now that we understand the basics of the Cairo graphics library, we're almost ready to start drawing. We'll start with the simplest of drawing elements: the straight line. But first you need to know a little bit about Cairo's coordinate system. The origin of the Cairo coordinate system is located in the upper-left corner of the window with positive x values to the right and positive y values going down.

Since the Cairo graphics library was written with support for multiple output targets (the X window system, PNG images, OpenGL, etc), there is a distinction between user-space and device-space coordinates. The mapping between these two coordinate systems defaults to one-to-one so that integer values map roughly to pixels on the screen, but this setting can be adjusted if desired. Sometimes it may be useful to scale the coordinates so that the full width and height of a window both range from 0 to 1 (the 'unit square') or some other mapping that works for your application. This can be done with the `Cairo::Context::scale()` function.

#### Ejemplo

In this example, we'll construct a small but fully functional gtkmm program and draw some lines into the window. The lines are drawn by creating a path and then stroking it. A path is created using the functions `Cairo::Context::move_to()` and `Cairo::Context::line_to()`. The function `move_to()` is similar to the act of lifting your pen off of the paper and placing it somewhere else -- no line is drawn between the point you were at and the point you moved to. To draw a line between two points, use the `line_to()` function.

After you've finished creating your path, you still haven't drawn anything visible yet. To make the path visible, you must use the function `stroke()` which will stroke the current path with the line width and style specified in your `Cairo::Context` object. After stroking, the current path will be cleared so that you can start on your next path.

Many Cairo drawing functions have a `_preserve()` variant. Normally drawing functions such as `clip()`, `fill()`, or `stroke()` will clear the current path. If you use the `_preserve()` variant, the current path will be retained so that you can use the same path with the next drawing function.

##### Área de dibujo: líneas

Código fuente

File: `myarea.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLE_MYAREA_H
    #define GTKMM_EXAMPLE_MYAREA_H

    #include <gtkmm/drawingarea.h>

    class MyArea : public Gtk::DrawingArea
    {
    public:
      MyArea();
      virtual ~MyArea();

    protected:
      //Override default signal handler:
      virtual bool on_draw(const Cairo::RefPtr<Cairo::Context>& cr);
    };

    #endif // GTKMM_EXAMPLE_MYAREA_H

File: `myarea.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "myarea.h"
    #include <cairomm/context.h>

    MyArea::MyArea()
    {
    }

    MyArea::~MyArea()
    {
    }

    bool MyArea::on_draw(const Cairo::RefPtr<Cairo::Context>& cr)
    {
      Gtk::Allocation allocation = get_allocation();
      const int width = allocation.get_width();
      const int height = allocation.get_height();

      // coordinates for the center of the window
      int xc, yc;
      xc = width / 2;
      yc = height / 2;

      cr->set_line_width(10.0);

      // draw red lines out from the center of the window
      cr->set_source_rgb(0.8, 0.0, 0.0);
      cr->move_to(0, 0);
      cr->line_to(xc, yc);
      cr->line_to(0, height);
      cr->move_to(xc, yc);
      cr->line_to(width, yc);
      cr->stroke();

      return true;
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "myarea.h"
    #include <gtkmm/application.h>
    #include <gtkmm/window.h>

    int main(int argc, char** argv)
    {
       Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

       Gtk::Window win;
       win.set_title("DrawingArea");

       MyArea area;
       win.add(area);
       area.show();

       return app->run(win);
    }

This program contains a single class, `MyArea`, which is a subclass of `Gtk::DrawingArea` and contains an `on_draw()` member function. This function is called whenever the image in the drawing area needs to be redrawn. It is passed a `Cairo::RefPtr` pointer to a `Cairo::Context` that we use for the drawing. The actual drawing code sets the color we want to use for drawing by using `set_source_rgb()` which takes arguments defining the Red, Green, and Blue components of the desired color (valid values are between 0 and 1). After setting the color, we created a new path using the functions `move_to()` and `line_to()`, and then stroked this path with `stroke()`.

##### Dibujar con coordenadas relativas

In the example above we drew everything using absolute coordinates. You can also draw using relative coordinates. For a straight line, this is done with the function `Cairo::Context::rel_line_to()`.

#### Estilos de línea

In addition to drawing basic straight lines, there are a number of things that you can customize about a line. You've already seen examples of setting a line's color and width, but there are others as well.

If you've drawn a series of lines that form a path, you may want them to join together in a certain way. Cairo offers three different ways to join lines together: Miter, Bevel, and Round. These are show below:

##### Different join types in Cairo

The line join style is set using the function `Cairo::Context::set_line_join()`.

Line ends can have different styles as well. The default style is for the line to start and stop exactly at the destination points of the line. This is called a Butt cap. The other options are Round (uses a round ending, with the center of the circle at the end point) or Square (uses a squared ending, with the center of the square at the end point). This setting is set using the function `Cairo::Context::set_line_cap()`.

There are other things you can customize as well, including creating dashed lines and other things. For more information, see the Cairo API documentation.

#### Drawing thin lines

If you try to draw one pixel wide lines, you may notice that the line sometimes comes up blurred and wider than it ought to be. This happens because Cairo will try to draw from the selected position, to both sides (half to each), so if you're positioned right on the intersection of the pixels, and want a one pixel wide line, Cairo will try to use half of each adjacent pixel, which isn't possible (a pixel is the smallest unit possible). This happens when the width of the line is an odd number of pixels (not just one pixel).

The trick is to position in the middle of the pixel where you want the line to be drawn, and thus guaranteeing you get the desired results. See Cairo FAQ.

##### Drawing Area - Thin Lines

Código fuente

File: `myarea.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLE_MYAREA_H
    #define GTKMM_EXAMPLE_MYAREA_H

    #include <gtkmm/drawingarea.h>

    class MyArea : public Gtk::DrawingArea
    {
    public:
      MyArea();
      virtual ~MyArea();

      void fix_lines(bool fix = true);
      void force_redraw();

    protected:
      //Override default signal handler:
      virtual bool on_draw(const Cairo::RefPtr<Cairo::Context>& cr);

    private:
      double m_fix;
    };

    #endif // GTKMM_EXAMPLE_MYAREA_H

File: `examplewindow.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm/window.h>
    #include <gtkmm/grid.h>
    #include <gtkmm/checkbutton.h>
    #include "myarea.h"

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      void on_button_toggled();

    private:
      Gtk::Grid m_Container;
      MyArea m_Area_Lines;
      Gtk::CheckButton m_Button_FixLines;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `myarea.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "myarea.h"

    MyArea::MyArea()
    : m_fix (0)
    {
      set_size_request (200, 100);
    }

    MyArea::~MyArea()
    {
    }

    bool MyArea::on_draw(const Cairo::RefPtr<Cairo::Context>& cr)
    {
      Gtk::Allocation allocation = get_allocation();
      const int width = allocation.get_width();
      const int height = allocation.get_height();

      cr->set_line_width(1.0);

      // draw one line, every two pixels
      // without the 'fix', you won't notice any space between the lines,
      // since each one will occupy two pixels (width)
      for (int i = 0; i < width; i += 2)
      {
        cr->move_to(i + m_fix, 0);
        cr->line_to(i + m_fix, height);
      }

      cr->stroke();

      return true;
    }

    // Toogle between both values (0 or 0.5)
    void MyArea::fix_lines(bool fix)
    {
      // to get the width right, we have to draw in the middle of the pixel
      m_fix = fix ? 0.5 : 0.0;

      force_redraw();
    }

    // force the redraw of the image
    void MyArea::force_redraw()
    {
      Glib::RefPtr<Gdk::Window> win = get_window();
      if (win)
      {
        Gdk::Rectangle r(0, 0, get_allocation().get_width(), get_allocation().get_height());
        win->invalidate_rect(r, false);
      }
    }

File: `examplewindow.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"

    ExampleWindow::ExampleWindow()
    : m_Button_FixLines("Fix lines")
    {
      set_title("Thin lines example");

      m_Container.set_orientation(Gtk::ORIENTATION_HORIZONTAL);

      m_Container.add(m_Area_Lines);
      m_Container.add(m_Button_FixLines);

      add(m_Container);

      m_Button_FixLines.signal_toggled().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_button_toggled));

      // Synchonize the drawing in m_Area_Lines with the state of the toggle button.
      on_button_toggled();

      show_all_children();
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_button_toggled()
    {
      m_Area_Lines.fix_lines(m_Button_FixLines.get_active());
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char* argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      ExampleWindow window;

      //Shows the window and returns when it is closed.
      return app->run(window);
    }

### Dibujar líneas curvas

In addition to drawing straight lines Cairo allows you to easily draw curved lines (technically a cubic Bézier spline) using the `Cairo::Context::curve_to()` and `Cairo::Context::rel_curve_to()` functions. These functions take coordinates for a destination point as well as coordinates for two 'control' points. This is best explained using an example, so let's dive in.

#### Ejemplo

This simple application draws a curve with Cairo and displays the control points for each end of the curve.

##### Área de dibujo: líneas

Código fuente

File: `myarea.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLE_MYAREA_H
    #define GTKMM_EXAMPLE_MYAREA_H

    #include <gtkmm/drawingarea.h>

    class MyArea : public Gtk::DrawingArea
    {
    public:
      MyArea();
      virtual ~MyArea();

    protected:
      //Override default signal handler:
      virtual bool on_draw(const Cairo::RefPtr<Cairo::Context>& cr);
    };

    #endif // GTKMM_EXAMPLE_MYAREA_H

File: `myarea.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "myarea.h"
    #include <cairomm/context.h>

    MyArea::MyArea()
    {
    }

    MyArea::~MyArea()
    {
    }

    bool MyArea::on_draw(const Cairo::RefPtr<Cairo::Context>& cr)
    {
      Gtk::Allocation allocation = get_allocation();
      const int width = allocation.get_width();
      const int height = allocation.get_height();

      double x0=0.1, y0=0.5, // start point
             x1=0.4, y1=0.9,  // control point #1
             x2=0.6, y2=0.1,  // control point #2
             x3=0.9, y3=0.5;  // end point

      // scale to unit square (0 to 1 width and height)
      cr->scale(width, height);

      cr->set_line_width(0.05);
      // draw curve
      cr->move_to(x0, y0);
      cr->curve_to(x1, y1, x2, y2, x3, y3);
      cr->stroke();
      // show control points
      cr->set_source_rgba(1, 0.2, 0.2, 0.6);
      cr->move_to(x0, y0);
      cr->line_to (x1, y1);
      cr->move_to(x2, y2);
      cr->line_to (x3, y3);
      cr->stroke();

      return true;
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "myarea.h"
    #include <gtkmm/application.h>
    #include <gtkmm/window.h>

    int main(int argc, char** argv)
    {
       Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

       Gtk::Window win;
       win.set_title("DrawingArea");

       MyArea area;
       win.add(area);
       area.show();

       return app->run(win);
    }

The only difference between this example and the straight line example is in the `on_draw()` function, but there are a few new concepts and functions introduced here, so let's examine them briefly.

We make a call to `Cairo::Context::scale()`, passing in the width and height of the drawing area. This scales the user-space coordinate system such that the width and height of the widget are both equal to 1.0 'units'. There's no particular reason to scale the coordinate system in this case, but sometimes it can make drawing operations easier.

The call to `Cairo::Context::curve_to()` should be fairly self-explanatory. The first pair of coordinates define the control point for the beginning of the curve. The second set of coordinates define the control point for the end of the curve, and the last set of coordinates define the destination point. To make the concept of control points a bit easier to visualize, a line has been draw from each control point to the end-point on the curve that it is associated with. Note that these control point lines are both translucent. This is achieved with a variant of `set_source_rgb()` called `set_source_rgba()`. This function takes a fourth argument specifying the alpha value of the color (valid values are between 0 and 1).

### Dibujar arcos y círculos

With Cairo, the same function is used to draw arcs, circles, or ellipses: `Cairo::Context::arc()`. This function takes five arguments. The first two are the coordinates of the center point of the arc, the third argument is the radius of the arc, and the final two arguments define the start and end angle of the arc. All angles are defined in radians, so drawing a circle is the same as drawing an arc from 0 to 2 * M_PI radians. An angle of 0 is in the direction of the positive X axis (in user-space). An angle of M_PI/2 radians (90 degrees) is in the direction of the positive Y axis (in user-space). Angles increase in the direction from the positive X axis toward the positive Y axis. So with the default transformation matrix, angles increase in a clockwise direction. (Remember that the positive Y axis points downwards.)

To draw an ellipse, you can scale the current transformation matrix by different amounts in the X and Y directions. For example, to draw an ellipse with center at `x`, `y` and size `width`, `height`:

    context->save();
    context->translate(x, y);
    context->scale(width / 2.0, height / 2.0);
    context->arc(0.0, 0.0, 1.0, 0.0, 2 * M_PI);
    context->restore();

#### Ejemplo

Here's an example of a simple program that draws an arc, a circle and an ellipse into a drawing area.

##### Área de dibujo: arcos

Código fuente

File: `myarea.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLE_MYAREA_H
    #define GTKMM_EXAMPLE_MYAREA_H

    #include <gtkmm/drawingarea.h>

    class MyArea : public Gtk::DrawingArea
    {
    public:
      MyArea();
      virtual ~MyArea();

    protected:
      //Override default signal handler:
      virtual bool on_draw(const Cairo::RefPtr<Cairo::Context>& cr);
    };

    #endif // GTKMM_EXAMPLE_MYAREA_H

File: `myarea.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "myarea.h"
    #include <cairomm/context.h>
    #include <cmath>

    MyArea::MyArea()
    {
    }

    MyArea::~MyArea()
    {
    }

    bool MyArea::on_draw(const Cairo::RefPtr<Cairo::Context>& cr)
    {
      // This is where we draw on the window
      Gtk::Allocation allocation = get_allocation();
      const int width = allocation.get_width();
      const int height = allocation.get_height();
      const int lesser = MIN(width, height);

      // coordinates for the center of the window
      int xc, yc;
      xc = width / 2;
      yc = height / 2;

      cr->set_line_width(lesser * 0.02);  // outline thickness changes
                                          // with window size

      // first draw a simple unclosed arc
      cr->save();
      cr->arc(width / 3.0, height / 4.0, lesser / 4.0, -(M_PI / 5.0), M_PI);
      cr->close_path();   // line back to start point
      cr->set_source_rgb(0.0, 0.8, 0.0);
      cr->fill_preserve();
      cr->restore();  // back to opaque black
      cr->stroke();   // outline it

      // now draw a circle
      cr->save();
      cr->arc(xc, yc, lesser / 4.0, 0.0, 2.0 * M_PI); // full circle
      cr->set_source_rgba(0.0, 0.0, 0.8, 0.6);    // partially translucent
      cr->fill_preserve();
      cr->restore();  // back to opaque black
      cr->stroke();

      // and finally an ellipse
      double ex, ey, ew, eh;
      // center of ellipse
      ex = xc;
      ey = 3.0 * height / 4.0;
      // ellipse dimensions
      ew = 3.0 * width / 4.0;
      eh = height / 3.0;

      cr->save();

      cr->translate(ex, ey);  // make (ex, ey) == (0, 0)
      cr->scale(ew / 2.0, eh / 2.0);  // for width: ew / 2.0 == 1.0
                                      // for height: eh / 2.0 == 1.0

      cr->arc(0.0, 0.0, 1.0, 0.0, 2 * M_PI);  // 'circle' centered at (0, 0)
                                              // with 'radius' of 1.0

      cr->set_source_rgba(0.8, 0.0, 0.0, 0.7);
      cr->fill_preserve();
      cr->restore();  // back to opaque black
      cr->stroke();

      return true;
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "myarea.h"
    #include <gtkmm/application.h>
    #include <gtkmm/window.h>

    int main(int argc, char** argv)
    {
       Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

       Gtk::Window win;
       win.set_title("DrawingArea");

       MyArea area;
       win.add(area);
       area.show();

       return app->run(win);
    }

There are a couple of things to note about this example code. Again, the only real difference between this example and the previous ones is the `on_draw()` function, so we'll limit our focus to that function. In addition, the first part of the function is nearly identical to the previous examples, so we'll skip that portion.

Note that in this case, we've expressed nearly everything in terms of the height and width of the window, including the width of the lines. Because of this, when you resize the window, everything scales with the window. Also note that there are three drawing sections in the function and each is wrapped with a `save()`/`restore()` pair so that we're back at a known state after each drawing.

The section for drawing an arc introduces one new function, `close_path()`. This function will in effect draw a straight line from the current point back to the first point in the path. There is a significant difference between calling `close_path()` and manually drawing a line back to the starting point, however. If you use `close_path()`, the lines will be nicely joined together. If you use `line_to()` instead, the lines will end at the same point, but Cairo won't do any special joining.

##### Dibujar en sentido anti-horario

The function `Cairo::Context::arc_negative()` is exactly the same as `Cairo::Context::arc()` but the angles go the opposite direction.

### Dibujar texto

#### Dibujar texto con Pango

Text is drawn via Pango Layouts. The easiest way to create a `Pango::Layout` is to use `Gtk::Widget::create_pango_layout()`. Once created, the layout can be manipulated in various ways, including changing the text, font, etc. Finally, the layout can be rendered using the `Pango::Layout::show_in_cairo_context()` method.

#### Ejemplo

Here is an example of a program that draws some text, some of it upside-down. The Printing chapter contains another example of drawing text.

##### Drawing Area - Text

Código fuente

File: `myarea.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLE_MYAREA_H
    #define GTKMM_EXAMPLE_MYAREA_H

    #include <gtkmm/drawingarea.h>

    class MyArea : public Gtk::DrawingArea
    {
    public:
      MyArea();
      virtual ~MyArea();

    protected:
      //Override default signal handler:
      virtual bool on_draw(const Cairo::RefPtr<Cairo::Context>& cr);

    private:
      void draw_rectangle(const Cairo::RefPtr<Cairo::Context>& cr, int width, int height);
      void draw_text(const Cairo::RefPtr<Cairo::Context>& cr, int rectangle_width, int rectangle_height);

    };

    #endif // GTKMM_EXAMPLE_MYAREA_H

File: `myarea.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "myarea.h"

    MyArea::MyArea()
    {
    }

    MyArea::~MyArea()
    {
    }

    bool MyArea::on_draw(const Cairo::RefPtr<Cairo::Context>& cr)
    {
      Gtk::Allocation allocation = get_allocation();
      const int width = allocation.get_width();
      const int height = allocation.get_height();

      const int rectangle_width = width;
      const int rectangle_height = height / 2;

      // Draw a black rectangle
      cr->set_source_rgb(0.0, 0.0, 0.0);
      draw_rectangle(cr, rectangle_width, rectangle_height);

      // and some white text
      cr->set_source_rgb(1.0, 1.0, 1.0);
      draw_text(cr, rectangle_width, rectangle_height);

      // flip the image vertically
      // see http://www.cairographics.org/documentation/cairomm/reference/classCairo_1_1Matrix.html
      // the -1 corresponds to the yy part (the flipping part)
      // the height part is a translation (we could have just called cr->translate(0, height) instead)
      // it's height and not height / 2, since we want this to be on the second part of our drawing
      // (otherwise, it would draw over the previous part)
      Cairo::Matrix matrix(1.0, 0.0, 0.0, -1.0, 0.0, height);

      // apply the matrix
      cr->transform(matrix);

      // white rectangle
      cr->set_source_rgb(1.0, 1.0, 1.0);
      draw_rectangle(cr, rectangle_width, rectangle_height);

      // black text
      cr->set_source_rgb(0.0, 0.0, 0.0);
      draw_text(cr, rectangle_width, rectangle_height);

      return true;
    }

    void MyArea::draw_rectangle(const Cairo::RefPtr<Cairo::Context>& cr,
                                int width, int height)
    {
      cr->rectangle(0, 0, width, height);
      cr->fill();
    }

    void MyArea::draw_text(const Cairo::RefPtr<Cairo::Context>& cr,
                           int rectangle_width, int rectangle_height)
    {
      // http://developer.gnome.org/pangomm/unstable/classPango_1_1FontDescription.html
      Pango::FontDescription font;

      font.set_family("Monospace");
      font.set_weight(Pango::WEIGHT_BOLD);

      // http://developer.gnome.org/pangomm/unstable/classPango_1_1Layout.html
      Glib::RefPtr<Pango::Layout> layout = create_pango_layout("Hi there!");

      layout->set_font_description(font);

      int text_width;
      int text_height;

      //get the text dimensions (it updates the variables -- by reference)
      layout->get_pixel_size(text_width, text_height);

      // Position the text in the middle
      cr->move_to((rectangle_width-text_width)/2, (rectangle_height-text_height)/2);

      layout->show_in_cairo_context(cr);
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "myarea.h"
    #include <gtkmm/application.h>
    #include <gtkmm/window.h>

    int main(int argc, char* argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      Gtk::Window window;
      window.set_title("Drawing text example");

      MyArea area;
      window.add(area);
      area.show();

      return app->run(window);
    }

### Dibujar imágenes

There is a method for drawing from a `Gdk::Pixbuf` to a `Cairo::Context`. A `Gdk::Pixbuf` buffer is a useful wrapper around a collection of pixels, which can be read from files, and manipulated in various ways.

Probably the most common way of creating `Gdk::Pixbuf`s is to use `Gdk::Pixbuf::create_from_file()`, which can read an image file, such as a png file into a pixbuf ready for rendering.

The `Gdk::Pixbuf` can be rendered by setting it as the source pattern of the Cairo context with `Gdk::Cairo::set_source_pixbuf()`. Then draw the image with either `Cairo::Context::paint()` (to draw the whole image), or `Cairo::Context::rectangle()` and `Cairo::Context::fill()` (to fill the specified rectangle). `set_source_pixbuf()` is not a member of `Cairo::Context`. It takes a `Cairo::Context` as its first parameter.

Here is a small bit of code to tie it all together: (Note that usually you wouldn't load the image every time in the draw signal handler! It's just shown here to keep it all together.)

    bool MyArea::on_draw(const Cairo::RefPtr<Cairo::Context>& cr)
    {
      Glib::RefPtr<Gdk::Pixbuf> image = Gdk::Pixbuf::create_from_file("myimage.png");
      // Draw the image at 110, 90, except for the outermost 10 pixels.
      Gdk::Cairo::set_source_pixbuf(cr, image, 100, 80);
      cr->rectangle(110, 90, image->get_width()-20, image->get_height()-20);
      cr->fill();
      return true;
    }

#### Ejemplo

Here is an example of a simple program that draws an image.

##### Dibujar área: imagen

Código fuente

File: `myarea.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLE_MYAREA_H
    #define GTKMM_EXAMPLE_MYAREA_H

    #include <gtkmm/drawingarea.h>
    #include <gdkmm/pixbuf.h>

    class MyArea : public Gtk::DrawingArea
    {
    public:
      MyArea();
      virtual ~MyArea();

    protected:
      //Override default signal handler:
      virtual bool on_draw(const Cairo::RefPtr<Cairo::Context>& cr);

      Glib::RefPtr<Gdk::Pixbuf> m_image;
    };

    #endif // GTKMM_EXAMPLE_MYAREA_H

File: `myarea.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "myarea.h"
    #include <cairomm/context.h>
    #include <gdkmm/general.h> // set_source_pixbuf()
    #include <glibmm/fileutils.h>
    #include <iostream>

    MyArea::MyArea()
    {
      try
      {
        // The fractal image has been created by the XaoS program.
        // http://xaos.sourceforge.net
        m_image = Gdk::Pixbuf::create_from_file("fractal_image.png");
      }
      catch(const Glib::FileError& ex)
      {
        std::cerr << "FileError: " << ex.what() << std::endl;
      }
      catch(const Gdk::PixbufError& ex)
      {
        std::cerr << "PixbufError: " << ex.what() << std::endl;
      }

      // Show at least a quarter of the image.
      if (m_image)
        set_size_request(m_image->get_width()/2, m_image->get_height()/2);
    }

    MyArea::~MyArea()
    {
    }

    bool MyArea::on_draw(const Cairo::RefPtr<Cairo::Context>& cr)
    {
      if (!m_image)
        return false;

      Gtk::Allocation allocation = get_allocation();
      const int width = allocation.get_width();
      const int height = allocation.get_height();

      // Draw the image in the middle of the drawing area, or (if the image is
      // larger than the drawing area) draw the middle part of the image.
      Gdk::Cairo::set_source_pixbuf(cr, m_image,
        (width - m_image->get_width())/2, (height - m_image->get_height())/2);
      cr->paint();

      return true;
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "myarea.h"
    #include <gtkmm/application.h>
    #include <gtkmm/window.h>

    int main(int argc, char** argv)
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      Gtk::Window win;
      win.set_title("DrawingArea");
      win.set_default_size(300, 200);

      MyArea area;
      win.add(area);
      area.show();

      return app->run(win);
    }

### Ejemplo de aplicación: crear un reloj con Cairo

Now that we've covered the basics of drawing with Cairo, let's try to put it all together and create a simple application that actually does something. The following example uses Cairo to create a custom `Clock` widget. The clock has a second hand, a minute hand, and an hour hand, and updates itself every second.

Código fuente

File: `clock.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLE_CLOCK_H
    #define GTKMM_EXAMPLE_CLOCK_H

    #include <gtkmm/drawingarea.h>

    class Clock : public Gtk::DrawingArea
    {
    public:
      Clock();
      virtual ~Clock();

    protected:
      //Override default signal handler:
      virtual bool on_draw(const Cairo::RefPtr<Cairo::Context>& cr);

      bool on_timeout();

      double m_radius;
      double m_line_width;

    };

    #endif // GTKMM_EXAMPLE_CLOCK_H

File: `clock.cc` (For use with gtkmm 3, not gtkmm 2)

    #include <ctime>
    #include <cmath>
    #include <cairomm/context.h>
    #include <glibmm/main.h>
    #include "clock.h"

    Clock::Clock()
    : m_radius(0.42), m_line_width(0.05)
    {
      Glib::signal_timeout().connect( sigc::mem_fun(*this, &Clock::on_timeout), 1000 );

      #ifndef GLIBMM_DEFAULT_SIGNAL_HANDLERS_ENABLED
      //Connect the signal handler if it isn't already a virtual method override:
      signal_draw().connect(sigc::mem_fun(*this, &Clock::on_draw), false);
      #endif //GLIBMM_DEFAULT_SIGNAL_HANDLERS_ENABLED
    }

    Clock::~Clock()
    {
    }

    bool Clock::on_draw(const Cairo::RefPtr<Cairo::Context>& cr)
    {
      Gtk::Allocation allocation = get_allocation();
      const int width = allocation.get_width();
      const int height = allocation.get_height();

      // scale to unit square and translate (0, 0) to be (0.5, 0.5), i.e.
      // the center of the window
      cr->scale(width, height);
      cr->translate(0.5, 0.5);
      cr->set_line_width(m_line_width);

      cr->save();
      cr->set_source_rgba(0.337, 0.612, 0.117, 0.9);   // green
      cr->paint();
      cr->restore();
      cr->arc(0, 0, m_radius, 0, 2 * M_PI);
      cr->save();
      cr->set_source_rgba(1.0, 1.0, 1.0, 0.8);
      cr->fill_preserve();
      cr->restore();
      cr->stroke_preserve();
      cr->clip();

      //clock ticks
      for (int i = 0; i < 12; i++)
      {
        double inset = 0.05;

        cr->save();
        cr->set_line_cap(Cairo::LINE_CAP_ROUND);

        if(i % 3 != 0)
        {
          inset *= 0.8;
          cr->set_line_width(0.03);
        }

        cr->move_to(
          (m_radius - inset) * cos (i * M_PI / 6),
          (m_radius - inset) * sin (i * M_PI / 6));
        cr->line_to (
          m_radius * cos (i * M_PI / 6),
          m_radius * sin (i * M_PI / 6));
        cr->stroke();
        cr->restore(); /* stack-pen-size */
      }

      // store the current time
      time_t rawtime;
      time(&rawtime);
      struct tm * timeinfo = localtime (&rawtime);

      // compute the angles of the indicators of our clock
      double minutes = timeinfo->tm_min * M_PI / 30;
      double hours = timeinfo->tm_hour * M_PI / 6;
      double seconds= timeinfo->tm_sec * M_PI / 30;

      cr->save();
      cr->set_line_cap(Cairo::LINE_CAP_ROUND);

      // draw the seconds hand
      cr->save();
      cr->set_line_width(m_line_width / 3);
      cr->set_source_rgba(0.7, 0.7, 0.7, 0.8); // gray
      cr->move_to(0, 0);
      cr->line_to(sin(seconds) * (m_radius * 0.9),
        -cos(seconds) * (m_radius * 0.9));
      cr->stroke();
      cr->restore();

      // draw the minutes hand
      cr->set_source_rgba(0.117, 0.337, 0.612, 0.9);   // blue
      cr->move_to(0, 0);
      cr->line_to(sin(minutes + seconds / 60) * (m_radius * 0.8),
        -cos(minutes + seconds / 60) * (m_radius * 0.8));
      cr->stroke();

      // draw the hours hand
      cr->set_source_rgba(0.337, 0.612, 0.117, 0.9);   // green
      cr->move_to(0, 0);
      cr->line_to(sin(hours + minutes / 12.0) * (m_radius * 0.5),
        -cos(hours + minutes / 12.0) * (m_radius * 0.5));
      cr->stroke();
      cr->restore();

      // draw a little dot in the middle
      cr->arc(0, 0, m_line_width / 3.0, 0, 2 * M_PI);
      cr->fill();

      return true;
    }

    bool Clock::on_timeout()
    {
        // force our program to redraw the entire clock.
        Glib::RefPtr<Gdk::Window> win = get_window();
        if (win)
        {
            Gdk::Rectangle r(0, 0, get_allocation().get_width(),
                    get_allocation().get_height());
            win->invalidate_rect(r, false);
        }
        return true;
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "clock.h"
    #include <gtkmm/application.h>
    #include <gtkmm/window.h>

    int main(int argc, char** argv)
    {
       Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

       Gtk::Window win;
       win.set_title("Cairomm Clock");

       Clock c;
       win.add(c);
       c.show();

       return app->run(win);
    }

As before, almost all of the interesting stuff is done in the draw signal handler `on_draw()`. Before we dig into the draw signal handler, notice that the constructor for the `Clock` widget connects a handler function `on_timeout()` to a timer with a timeout period of 1000 milliseconds (1 second). This means that `on_timeout()` will get called once per second. The sole responsibility of this function is to invalidate the window so that gtkmm will be forced to redraw it.

Now let's take a look at the code that performs the actual drawing. The first section of `on_draw()` should be pretty familiar by now. This example again scales the coordinate system to be a unit square so that it's easier to draw the clock as a percentage of window size so that it will automatically scale when the window size is adjusted. Furthermore, the coordinate system is scaled over and down so that the (0, 0) coordinate is in the very center of the window.

The function `Cairo::Context::paint()` is used here to set the background color of the window. This function takes no arguments and fills the current surface (or the clipped portion of the surface) with the source color currently active. After setting the background color of the window, we draw a circle for the clock outline, fill it with white, and then stroke the outline in black. Notice that both of these actions use the `_preserve` variant to preserve the current path, and then this same path is clipped to make sure than our next lines don't go outside the outline of the clock.

After drawing the outline, we go around the clock and draw ticks for every hour, with a larger tick at 12, 3, 6, and 9. Now we're finally ready to implement the time-keeping functionality of the clock, which simply involves getting the current values for hours, minutes and seconds, and drawing the hands at the correct angles.

## Arrastrar y soltar

`Gtk::Widget` has several methods and signals which are prefixed with "drag_". These are used for Drag and Drop.

### Sources and Destinations

Things are dragged from `sources` to be dropped on `destinations`. Each source and destination has infomation about the data formats that it can send or receive, provided by `Gtk::TargetEntry` items. A drop destination will only accept a dragged item if they both share a compatible `Gtk::TargetEntry` item. Appropriate signals will then be emitted, telling the signal handlers which `Gtk::TargetEntry` was used.

Los objetos `Gtk::TargetEntry` contienen esta información:

- target: A name, such as "STRING"

- info: An identifier which will be sent to your signals to tell you which TargetEntry was used.

- flags: Used only for drag and drop, this specifies whether the data may be dragged to other widgets and applications, or only to the same ones.

### Métodos

`Widgets` can be identified as sources or destinations using these `Gtk::Widget` methods:

    void drag_source_set(const ArrayHandle_TargetEntry& targets,
          GdkModifierType start_button_mask, GdkDragAction actions);

- `targets` es un contenedor de elementos `Gtk::TargetEntry` (`std::list<Gtk::TargetEntry>` or `std::vector<Gtk::TargetEntry>`, por ejemplo).

- `start_button_mask` is an ORed combination of values, which specify which modifier key or mouse button must be pressed to start the drag.

- `actions` is an ORed combination of values, which specified which Drag and Drop operations will be possible from this source - for instance, copy, move, or link. The user can choose between the actions by using modifier keys, such as Shift to change from `copy` to `move`, and this will be shown by a different cursor.

    void drag_dest_set(const ArrayHandle_TargetEntry& targets,
        GtkDestDefaults flags, GdkDragAction actions);

- `flags` is an ORed combination of values which indicates how the widget will respond visually to Drag and Drop items.

- `actions` indicates the Drag and Drop actions which this destination can receive - see the description above.

### Señales

When a drop destination has accepted a dragged item, certain signals will be emitted, depending on what action has been selected. For instance, the user might have held down the Shift key to specify a `move` rather than a `copy`. Remember that the user can only select the actions which you have specified in your calls to `drag_dest_set()` and `drag_source_set()`.

#### Copiar

The source widget will emit these signals, in this order:

- `drag_begin`: proporciona DragContext.

- `drag_motion`: Provides DragContext and coordinates. You can call the drag_status() method of the DragContext to indicate which target will be accepted.

- `drag_get`: Provides `info` about the dragged data format, and a `GtkSelectionData` structure, in which you should put the requested data.

- `drag_drop`: Provides DragContext and coordinates.

- `drag_end`: proporciona DragContext.

The destination widget will emit this signal, after the source destination has emitted the `drag_get` signal:

- `drag_data_received`: Provides `info` about the dragged data format, and a `GtkSelectionData` structure which contains the dropped data. You should call the `drag_finish()` method of the `DragContext` to indicate whether the operation was successful.

#### Mover

Mientras se realice un `movimiento`, el widget origen también emitirá esta señal:

- `drag_delete`: Gives the source the opportunity to delete the original data if that's appropriate.

### DragContext

The drag and drop signals provide a DragContext, which contains some information about the drag and drop operation and can be used to influence the process. For instance, you can discover the source widget, or change the drag and drop icon, by using the `set_icon()` methods. More importantly, you should call the `drag_finish()` method from your `drag_data_received` signal handler to indicate whether the drop was successful.

### Ejemplo

Here is a very simple example, demonstrating a drag and drop `Copy` operation:

#### Arrastrar y soltar

Código fuente

File: `dndwindow.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLE_DNDWINDOW_H
    #define GTKMM_EXAMPLE_DNDWINDOW_H

    #include <gtkmm/box.h>
    #include <gtkmm/label.h>
    #include <gtkmm/window.h>
    #include <gtkmm/button.h>

    class DnDWindow : public Gtk::Window
    {

    public:
      DnDWindow();
      virtual ~DnDWindow();

    protected:
      //Signal handlers:
      void on_button_drag_data_get(
              const Glib::RefPtr<Gdk::DragContext>& context,
              Gtk::SelectionData& selection_data, guint info, guint time);
      void on_label_drop_drag_data_received(
              const Glib::RefPtr<Gdk::DragContext>& context, int x, int y,
              const Gtk::SelectionData& selection_data, guint info, guint time);

      //Member widgets:
      Gtk::Box m_HBox;
      Gtk::Button m_Button_Drag;
      Gtk::Label m_Label_Drop;
    };

    #endif // GTKMM_EXAMPLE_DNDWINDOW_H

File: `dndwindow.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "dndwindow.h"
    #include <iostream>

    DnDWindow::DnDWindow()
    : m_Button_Drag("Drag Here\n"),
      m_Label_Drop("Drop here\n")
    {
      set_title("DnD example");

      add(m_HBox);

      //Targets:
      std::vector<Gtk::TargetEntry> listTargets;
      listTargets.push_back( Gtk::TargetEntry("STRING") );
      listTargets.push_back( Gtk::TargetEntry("text/plain") );

      //Drag site:

      //Make m_Button_Drag a DnD drag source:
      m_Button_Drag.drag_source_set(listTargets);

      //Connect signals:
      m_Button_Drag.signal_drag_data_get().connect(sigc::mem_fun(*this,
                  &DnDWindow::on_button_drag_data_get));

      m_HBox.pack_start(m_Button_Drag);

      //Drop site:

      //Make m_Label_Drop a DnD drop destination:
      m_Label_Drop.drag_dest_set(listTargets);

      //Connect signals:
      m_Label_Drop.signal_drag_data_received().connect(sigc::mem_fun(*this,
                  &DnDWindow::on_label_drop_drag_data_received) );

      m_HBox.pack_start(m_Label_Drop);

      show_all();
    }

    DnDWindow::~DnDWindow()
    {
    }

    void DnDWindow::on_button_drag_data_get(
            const Glib::RefPtr<Gdk::DragContext>&,
            Gtk::SelectionData& selection_data, guint, guint)
    {
      selection_data.set(selection_data.get_target(), 8 /* 8 bits format */,
              (const guchar*)"I'm Data!",
              9 /* the length of I'm Data! in bytes */);
    }

    void DnDWindow::on_label_drop_drag_data_received(
            const Glib::RefPtr<Gdk::DragContext>& context, int, int,
            const Gtk::SelectionData& selection_data, guint, guint time)
    {
      const int length = selection_data.get_length();
      if((length >= 0) && (selection_data.get_format() == 8))
      {
        std::cout << "Received \"" << selection_data.get_data_as_string()
            << "\" in label " << std::endl;
      }

      context->drag_finish(false, false, time);
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "dndwindow.h"
    #include <gtkmm/application.h>

    int main (int argc, char *argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      DnDWindow dndWindow;

      //Shows the window and returns when it is closed.
      return app->run(dndWindow);
    }

There is a more complex example in examples/others/dnd.

## El portapapeles

Simple text copy-paste functionality is provided for free by widgets such as Gtk::Entry and Gtk::TextView, but you might need special code to deal with your own data formats. For instance, a drawing program would need special code to allow copy and paste within a view, or between documents.

`Gtk::Clipboard` is a singleton. You can get the one and only instance with `Gtk::Clipboard::get()`.

So your application doesn't need to wait for clipboard operations, particularly between the time when the user chooses Copy and then later chooses Paste, most `Gtk::Clipboard` methods take `sigc::slot`s which specify callback methods. When `Gtk::Clipboard` is ready, it will call these methods, either providing the requested data, or asking for data.

Referencia

### Objetivos

Different applications contain different types of data, and they might make that data available in a variety of formats. gtkmm calls these data types `target`s.

For instance, gedit can supply and receive the `"UTF8_STRING"` target, so you can paste data into gedit from any application that supplies that target. Or two different image editing applications might supply and receive a variety of image formats as targets. As long as one application can receive one of the targets that the other supplies then you will be able to copy data from one to the other.

A target can be in a variety of binary formats. This chapter, and the examples, assume that the data is 8-bit text. This would allow us to use an XML format for the clipboard data. However this would probably not be appropriate for binary data such as images. `Gtk::Clipboard` provides overloads that allow you to specify the format in more detail if necessary.

The Drag and Drop API uses the same mechanism. You should probably use the same data targets and formats for both Clipboard and Drag and Drap operations.

### Copiar

When the user asks to copy some data, you should tell the `Clipboard` what targets are available, and provide the callback methods that it can use to get the data. At this point you should store a copy of the data, to be provided when the clipboard calls your callback method in repsonse to a paste.

Por ejemplo,

    Glib::RefPtr<Gtk::Clipboard> refClipboard = Gtk::Clipboard::get();

    //Targets:
    std::list<Gtk::TargetEntry> listTargets;
    listTargets.push_back( Gtk::TargetEntry("example_custom_target") );
    listTargets.push_back( Gtk::TargetEntry("UTF8_STRING") );

    refClipboard->set( listTargets,
        sigc::mem_fun(*this, &ExampleWindow::on_clipboard_get),
        sigc::mem_fun(*this, &ExampleWindow::on_clipboard_clear) );

Your callback will then provide the store data when the user chooses to paste the data. For instance:

    void ExampleWindow::on_clipboard_get(
        Gtk::SelectionData& selection_data, guint info)
    {
      const Glib::ustring target = selection_data.get_target();

      if(target == "example_custom_target")
        selection_data.set("example_custom_target", m_ClipboardStore);
    }

The `ideal` example below can supply more than one clipboard target.

The clear callback allows you to free the memory used by your stored data when the clipboard replaces its data with something else.

### Pegar

When the user asks to paste data from the `Clipboard`, you should request a specific format and provide a callback method which will be called with the actual data. For instance:

    refClipboard->request_contents("example_custom_target",
        sigc::mem_fun(*this, &ExampleWindow::on_clipboard_received) );

Here is an example callback method:

    void ExampleWindow::on_clipboard_received(
        const Gtk::SelectionData& selection_data)
    {
      Glib::ustring clipboard_data = selection_data.get_data_as_string();
      //Do something with the pasted data.
    }

#### Descubrir los objetivos disponibles

To find out what targets are currently available on the `Clipboard` for pasting, call the `request_targets()` method, specifying a method to be called with the information. For instance:

    refClipboard->request_targets( sigc::mem_fun(*this,
        &ExampleWindow::on_clipboard_received_targets) );

In your callback, compare the list of available targets with those that your application supports for pasting. You could enable or disable a Paste menu item, depending on whether pasting is currently possible. For instance:

    void ExampleWindow::on_clipboard_received_targets(
      const Glib::StringArrayHandle& targets_array)
    {
      // Get the list of available clipboard targets:
      std::list<std::string> targets = targets_array;

      const bool bPasteIsPossible =
        std::find(targets.begin(), targets.end(),
          example_target_custom) != targets.end();

      // Enable/Disable the Paste button appropriately:
      m_Button_Paste.set_sensitive(bPasteIsPossible);
    }

### Ejemplos

#### Simple

This example allows copy and pasting of application-specific data, using the standard text target. Although this is simple, it's not ideal because it does not identify the `Clipboard` data as being of a particular type.

##### Clipboard - Simple

Código fuente

File: `examplewindow.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      void on_button_copy();
      void on_button_paste();
      void on_clipboard_text_received(const Glib::ustring& text);

      //Child widgets:
      Gtk::Box m_VBox;

      Gtk::Label m_Label;

      Gtk::Grid m_Grid;
      Gtk::ToggleButton m_ButtonA1, m_ButtonA2, m_ButtonB1, m_ButtonB2;

      Gtk::ButtonBox m_ButtonBox;
      Gtk::Button m_Button_Copy, m_Button_Paste;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"

    ExampleWindow::ExampleWindow()
    : m_VBox(Gtk::ORIENTATION_VERTICAL),
      m_Label("Select cells in the grid, click Copy, then open a second "
            "instance of this example to try pasting the copied data."),
      m_ButtonA1("A1"), m_ButtonA2("A2"), m_ButtonB1("B1"), m_ButtonB2("B2"),
      m_Button_Copy(Gtk::Stock::COPY), m_Button_Paste(Gtk::Stock::PASTE)
    {
      set_title("Gtk::Clipboard example");
      set_border_width(12);

      add(m_VBox);

      m_VBox.pack_start(m_Label, Gtk::PACK_SHRINK);

      //Fill Grid:
      m_VBox.pack_start(m_Grid);
      m_Grid.set_row_homogeneous(true);
      m_Grid.set_column_homogeneous(true);
      m_Grid.attach(m_ButtonA1, 0, 0, 1, 1);
      m_Grid.attach(m_ButtonA2, 1, 0, 1, 1);
      m_Grid.attach(m_ButtonB1, 0, 1, 1, 1);
      m_Grid.attach(m_ButtonB2, 1, 1, 1, 1);

      //Add ButtonBox to bottom:
      m_VBox.pack_start(m_ButtonBox, Gtk::PACK_SHRINK);
      m_VBox.set_spacing(6);

      //Fill ButtonBox:
      m_ButtonBox.set_layout(Gtk::BUTTONBOX_END);
      m_ButtonBox.pack_start(m_Button_Copy, Gtk::PACK_SHRINK);
      m_Button_Copy.signal_clicked().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_button_copy) );
      m_ButtonBox.pack_start(m_Button_Paste, Gtk::PACK_SHRINK);
      m_Button_Paste.signal_clicked().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_button_paste) );

      show_all_children();
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_button_copy()
    {
      //Build a string representation of the stuff to be copied:
      //Ideally you would use XML, with an XML parser here:
      Glib::ustring strData;
      strData += m_ButtonA1.get_active() ? "1" : "0";
      strData += m_ButtonA2.get_active() ? "1" : "0";
      strData += m_ButtonB1.get_active() ? "1" : "0";
      strData += m_ButtonB2.get_active() ? "1" : "0";

      Glib::RefPtr<Gtk::Clipboard> refClipboard = Gtk::Clipboard::get();
      refClipboard->set_text(strData);
    }

    void ExampleWindow::on_button_paste()
    {
      //Tell the clipboard to call our method when it is ready:
      Glib::RefPtr<Gtk::Clipboard> refClipboard = Gtk::Clipboard::get();
      refClipboard->request_text(sigc::mem_fun(*this,
                  &ExampleWindow::on_clipboard_text_received) );
    }

    void ExampleWindow::on_clipboard_text_received(const Glib::ustring& text)
    {
      //See comment in on_button_copy() about this silly clipboard format.
      if(text.size() >= 4)
      {
        m_ButtonA1.set_active( text[0] == '1' );
        m_ButtonA2.set_active( text[1] == '1' );
        m_ButtonB1.set_active( text[2] == '1' );
        m_ButtonB2.set_active( text[3] == '1' );
      }
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      ExampleWindow window;

      //Shows the window and returns when it is closed.
      return app->run(window);
    }

#### Ideal

This is like the simple example, but it

1. Defines a custom clipboard target, though the format of that target is still text.

2. It supports pasting of 2 targets - both the custom one and a text one that creates an arbitrary text representation of the custom data.

3. It uses `request_targets()` and the `owner_change` signal and disables the Paste button if it can't use anything on the clipboard.

##### Clipboard - Ideal

Código fuente

File: `examplewindow.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      void on_button_copy();
      void on_button_paste();

      void on_clipboard_owner_change(GdkEventOwnerChange* event);
      void on_clipboard_get(Gtk::SelectionData& selection_data, guint info);
      void on_clipboard_clear();

      void on_clipboard_received(const Gtk::SelectionData& selection_data);
      void on_clipboard_received_targets(const Glib::StringArrayHandle& targets_array);

      virtual void update_paste_status(); //Disable the paste button if there is nothing to paste.

      //Child widgets:
      Gtk::Box m_VBox;

      Gtk::Label m_Label;

      Gtk::Grid m_Grid;
      Gtk::ToggleButton m_ButtonA1, m_ButtonA2, m_ButtonB1, m_ButtonB2;

      Gtk::ButtonBox m_ButtonBox;
      Gtk::Button m_Button_Copy, m_Button_Paste;

      Glib::ustring m_ClipboardStore; //Keep copied stuff here, until it is pasted. This could be a big complex data structure.
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <algorithm>

    namespace
    {

    //These should usually be MIME types.
    const char example_target_custom[] = "gtkmmclipboardexample";
    const char example_target_text[]   = "UTF8_STRING";

    } // anonymous namespace

    ExampleWindow::ExampleWindow()
    : m_VBox(Gtk::ORIENTATION_VERTICAL),
      m_Label("Select cells in the grid, click Copy, then open a second instance "
              "of this example to try pasting the copied data.\nOr try pasting the "
              "text representation into gedit."),
      m_ButtonA1("A1"), m_ButtonA2("A2"), m_ButtonB1("B1"), m_ButtonB2("B2"),
      m_Button_Copy(Gtk::Stock::COPY), m_Button_Paste(Gtk::Stock::PASTE)
    {
      set_title("Gtk::Clipboard example");
      set_border_width(12);

      add(m_VBox);

      m_VBox.pack_start(m_Label, Gtk::PACK_SHRINK);

      //Fill Grid:
      m_VBox.pack_start(m_Grid);
      m_Grid.set_row_homogeneous(true);
      m_Grid.set_column_homogeneous(true);
      m_Grid.attach(m_ButtonA1, 0, 0, 1, 1);
      m_Grid.attach(m_ButtonA2, 1, 0, 1, 1);
      m_Grid.attach(m_ButtonB1, 0, 1, 1, 1);
      m_Grid.attach(m_ButtonB2, 1, 1, 1, 1);

      //Add ButtonBox to bottom:
      m_VBox.pack_start(m_ButtonBox, Gtk::PACK_SHRINK);
      m_VBox.set_spacing(6);

      //Fill ButtonBox:
      m_ButtonBox.set_layout(Gtk::BUTTONBOX_END);
      m_ButtonBox.pack_start(m_Button_Copy, Gtk::PACK_SHRINK);
      m_Button_Copy.signal_clicked().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_button_copy) );
      m_ButtonBox.pack_start(m_Button_Paste, Gtk::PACK_SHRINK);
      m_Button_Paste.signal_clicked().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_button_paste) );

      //Connect a signal handler that will be called when the contents of
      //the clipboard change.
      Gtk::Clipboard::get()->signal_owner_change().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_clipboard_owner_change) );

      show_all_children();

      update_paste_status();
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_button_copy()
    {
      //Build a string representation of the stuff to be copied:
      //Ideally you would use XML, with an XML parser here:
      Glib::ustring strData;
      strData += m_ButtonA1.get_active() ? "1" : "0";
      strData += m_ButtonA2.get_active() ? "1" : "0";
      strData += m_ButtonB1.get_active() ? "1" : "0";
      strData += m_ButtonB2.get_active() ? "1" : "0";

      Glib::RefPtr<Gtk::Clipboard> refClipboard = Gtk::Clipboard::get();

      //Targets:
      std::vector<Gtk::TargetEntry> listTargets;

      listTargets.push_back( Gtk::TargetEntry(example_target_custom) );
      listTargets.push_back( Gtk::TargetEntry(example_target_text) );

      refClipboard->set(listTargets, sigc::mem_fun(*this,
                  &ExampleWindow::on_clipboard_get), sigc::mem_fun(*this,
                      &ExampleWindow::on_clipboard_clear) );

      //Store the copied data until it is pasted:
      //(Must be done after the call to refClipboard->set, because that call
      //may trigger a call to on_clipboard_clear.)
      m_ClipboardStore = strData;

      update_paste_status();
    }

    void ExampleWindow::on_button_paste()
    {
      //Tell the clipboard to call our method when it is ready:
      Glib::RefPtr<Gtk::Clipboard> refClipboard = Gtk::Clipboard::get();

      refClipboard->request_contents(example_target_custom,
        sigc::mem_fun(*this, &ExampleWindow::on_clipboard_received) );

      update_paste_status();
    }

    void ExampleWindow::on_clipboard_owner_change(GdkEventOwnerChange*)
    {
      update_paste_status();
    }

    void ExampleWindow::on_clipboard_get(Gtk::SelectionData& selection_data, guint)
    {
      //info is meant to indicate the target, but it seems to be always 0,
      //so we use the selection_data's target instead.

      const std::string target = selection_data.get_target();

      if(target == example_target_custom)
      {
        // This set() override uses an 8-bit text format for the data.
        selection_data.set(example_target_custom, m_ClipboardStore);
      }
      else if(target == example_target_text)
      {
        //Build some arbitrary text representation of the data,
        //so that people see something when they paste into a text editor:
        Glib::ustring text_representation;

        text_representation += m_ButtonA1.get_active() ? "A1, " : "";
        text_representation += m_ButtonA2.get_active() ? "A2, " : "";
        text_representation += m_ButtonB1.get_active() ? "B1, " : "";
        text_representation += m_ButtonB2.get_active() ? "B2, " : "";

        selection_data.set_text(text_representation);
      }
      else
      {
        g_warning("ExampleWindow::on_clipboard_get(): "
                "Unexpected clipboard target format.");
      }
    }

    void ExampleWindow::on_clipboard_clear()
    {
      //This isn't really necessary. I guess it might save memory.
      m_ClipboardStore.clear();
    }

    void ExampleWindow::on_clipboard_received(
            const Gtk::SelectionData& selection_data)
    {
      const std::string target = selection_data.get_target();

      //It should always be this, because that' what we asked for when calling
      //request_contents().
      if(target == example_target_custom)
      {
        Glib::ustring clipboard_data = selection_data.get_data_as_string();

        //See comment in on_button_copy() about this silly clipboard format.
        if(clipboard_data.size() >= 4)
        {
          m_ButtonA1.set_active( clipboard_data[0] == '1' );
          m_ButtonA2.set_active( clipboard_data[1] == '1' );
          m_ButtonB1.set_active( clipboard_data[2] == '1' );
          m_ButtonB2.set_active( clipboard_data[3] == '1' );
        }
      }
    }

    void ExampleWindow::update_paste_status()
    {
      //Disable the paste button if there is nothing to paste.

      Glib::RefPtr<Gtk::Clipboard> refClipboard = Gtk::Clipboard::get();

      //Discover what targets are available:
      refClipboard->request_targets(sigc::mem_fun(*this,
                  &ExampleWindow::on_clipboard_received_targets) );
    }

    void ExampleWindow::on_clipboard_received_targets(
      const Glib::StringArrayHandle& targets_array)
    {
      // Get the list of available clipboard targets:
      std::vector<std::string> targets = targets_array;

      const bool bPasteIsPossible =
        std::find(targets.begin(), targets.end(),
          example_target_custom) != targets.end();

      // Enable/Disable the Paste button appropriately:
      m_Button_Paste.set_sensitive(bPasteIsPossible);
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      ExampleWindow window;

      //Shows the window and returns when it is closed.
      return app->run(window);
    }

## Impresión

At the application development level, gtkmm's printing API provides dialogs that are consistent across applications and allows us of Cairo's common drawing API, with Pango-driven text rendering. In the implementation of this common API, platform-specific backends and printer-specific drivers are used.

### PrintOperation

The primary object is `Gtk::PrintOperation`, allocated for each print operation. To handle page drawing connect to its signals, or inherit from it and override the default virtual signal handlers. `PrintOperation` automatically handles all the settings affecting the print loop.

#### Señales

The `PrintOperation::run()` method starts the print loop, during which various signals are emitted:

- `begin_print`: You must handle this signal, because this is where you create and set up a `Pango::Layout` using the provided `Gtk::PrintContext`, and break up your printing output into pages.

- `paginate`: Pagination is potentially slow so if you need to monitor it you can call the `PrintOperation::set_show_progress()` method and handle this signal.

- For each page that needs to be rendered, the following signals are emitted:

  - `request_page_setup`: Provides a `PrintContext`, page number and `Gtk::PageSetup`. Handle this signal if you need to modify page setup on a per-page basis.

  - `draw_page`: You must handle this signal, which provides a `PrintContext` and a page number. The `PrintContext` should be used to create a `Cairo::Context` into which the provided page should be drawn. To render text, iterate over the `Pango::Layout` you created in the `begin_print` handler.

- `end_print`: A handler for it is a safe place to free any resources related to a `PrintOperation`. If you have your custom class that inherits from `PrintOperation`, it is naturally simpler to do it in the destructor.

- `done`: This signal is emitted when printing is finished, meaning when the print data is spooled. Note that the provided `Gtk::PrintOperationResult` may indicate that an error occurred. In any case you probably want to notify the user about the final status.

- `status_changed`: Emitted whenever a print job's status changes, until it is finished. Call the `PrintOperation::set_track_print_status()` method to monitor the job status after spooling. To see the status, use `get_status()` or `get_status_string()`.

Referencia

### Configuración de página

The `PrintOperation` class has a method called `set_default_page_setup()` which selects the default paper size, orientation and margins. To show a page setup dialog from your application, use the `Gtk::run_page_setup_dialog()` method, which returns a `Gtk::PageSetup` object with the chosen settings. Use this object to update a `PrintOperation` and to access the selected `Gtk::PaperSize`, `Gtk::PageOrientation` and printer-specific margins.

You should save the chosen `Gtk::PageSetup` so you can use it again if the page setup dialog is shown again.

Por ejemplo,

    //Within a class that inherits from Gtk::Window and keeps m_refPageSetup and m_refSettings as members...
    Glib::RefPtr<Gtk::PageSetup> new_page_setup = Gtk::run_page_setup_dialog(*this, m_refPageSetup, m_refSettings);
    m_refPageSetup = new_page_setup;

Referencia

The Cairo coordinate system, in the `draw_page` handler, is automatically rotated to the current page orientation. It is normally within the printer margins, but you can change that via the `PrintOperation::set_use_full_page()` method. The default measurement unit is device pixels. To select other units, use the `PrintOperation::set_unit()` method.

### Renderizar texto

Text rendering is done using Pango. The `Pango::Layout` object for printing should be created by calling the `PrintContext::create_pango_layout()` method. The `PrintContext` object also provides the page metrics, via `get_width()` and `get_height()`. The number of pages can be set with `PrintOperation::set_n_pages()`. To actually render the Pango text in `on_draw_page`, get a `Cairo::Context` with `PrintContext::get_cairo_context()` and show the `Pango::LayoutLine`s that appear within the requested page number.

See an example of exactly how this can be done.

### Operaciones asíncronas

By default, `PrintOperation::run()` returns when a print operation is completed. If you need to run a non-blocking print operation, call `PrintOperation::set_allow_async()`. Note that `set_allow_async()` is not supported on all platforms, however the `done` signal will still be emitted.

`run()` may return `PRINT_OPERATION_RESULT_IN_PROGRESS`. To track status and handle the result or error you need to implement signal handlers for the `done` and `status_changed` signals:

Por ejemplo,

    // in class ExampleWindow's method...
    Glib::RefPtr<PrintOperation> op = PrintOperation::create();
    // ...set up op...
    op->signal_done().connect(sigc::bind(sigc::mem_fun(*this, &ExampleWindow::on_printoperation_done), op));
    // run the op

Segundo, comprobar si hay errores y conectar la señal `status_changed`. Por ejemplo:

    void ExampleWindow::on_printoperation_done(Gtk::PrintOperationResult result, const Glib::RefPtr<PrintOperation>& op)
    {
      if (result == Gtk::PRINT_OPERATION_RESULT_ERROR)
        //notify user
      else if (result == Gtk::PRINT_OPERATION_RESULT_APPLY)
        //Update PrintSettings with the ones used in this PrintOperation

      if (! op->is_finished())
        op->signal_status_changed().connect(sigc::bind(sigc::mem_fun(*this, &ExampleWindow::on_printoperation_status_changed), op));
    }

Por último, comprobar el estado. Por ejemplo,

    void ExampleWindow::on_printoperation_status_changed(const Glib::RefPtr<PrintFormOperation>& op)
    {
      if (op->is_finished())
        //the print job is finished
      else
        //get the status with get_status() or get_status_string()

      //update UI
    }

### Exportar a PDF

The 'Print to file' option is available in the print dialog, without the need for extra implementation. However, it is sometimes useful to generate a pdf file directly from code. For instance,

    Glib::RefPtr<Gtk::PrintOperation> op = Gtk::PrintOperation::create();
    // ...set up op...
    op->set_export_filename("test.pdf");
    Gtk::PrintOperationResult res = op->run(Gtk::PRINT_OPERATION_ACTION_EXPORT);

### Extending the print dialog

You may add a custom tab to the print dialog:

- Set the title of the tab via `PrintOperation::set_custom_tab_label()`, create a new widget and return it from the `create_custom_widget` signal handler. You'll probably want this to be a container widget, packed with some others.

- Get the data from the widgets in the `custom_widget_apply` signal handler.

Although the `custom_widget_apply` signal provides the widget you previously created, to simplify things you can keep the widgets you expect to contain some user input as class members. For example, let's say you have a `Gtk::Entry` called `m_Entry` as a member of your `CustomPrintOperation` class:

    Gtk::Widget* CustomPrintOperation::on_create_custom_widget()
    {
      set_custom_tab_label("My custom tab");

      Gtk::Box* hbox = new Gtk::Box(Gtk::ORIENTATION_HORIZONTAL, 8);
      hbox->set_border_width(6);

      Gtk::Label* label = Gtk::manage(new Gtk::Label("Enter some text: "));
      hbox->pack_start(*label, false, false);
      label->show();

      hbox->pack_start(m_Entry, false, false);
      m_Entry.show();

      return hbox;
    }

    void CustomPrintOperation::on_custom_widget_apply(Gtk::Widget* /* widget */)
    {
      Glib::ustring user_input = m_Entry.get_text();
      //...
    }

The example in examples/book/printing/advanced demonstrates this.

### Vista previa

The native GTK+ print dialog has a preview button, but you may also start a preview directly from an application:

    // in a class that inherits from Gtk::Window...
    Glib::RefPtr<PrintOperation> op = PrintOperation::create();
    // ...set up op...
    op->run(Gtk::PRINT_OPERATION_ACTION_PREVIEW, *this);

On Unix, the default preview handler uses an external viewer program. On Windows, the native preview dialog will be shown. If necessary you may override this behaviour and provide a custom preview dialog. See the example located in /examples/book/printing/advanced.

### Ejemplo

#### Simple

The following example demonstrates how to print some input from a user interface. It shows how to implement `on_begin_print` and `on_draw_page`, as well as how to track print status and update the print settings.

##### Printing - Simple

Código fuente

File: `printformoperation.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_PRINT_FORM_OPERATION_H
    #define GTKMM_PRINT_FORM_OPERATION_H

    #include <pangomm.h>
    #include <gtkmm.h>
    #include <vector>

    //We derive our own class from PrintOperation,
    //so we can put the actual print implementation here.
    class PrintFormOperation : public Gtk::PrintOperation
    {
     public:
      static Glib::RefPtr<PrintFormOperation> create();
      virtual ~PrintFormOperation();

      void set_name(const Glib::ustring& name) { m_Name = name; }
      void set_comments(const Glib::ustring& comments) { m_Comments = comments; }

     protected:
      PrintFormOperation();

      //PrintOperation default signal handler overrides:
      virtual void on_begin_print(const Glib::RefPtr<Gtk::PrintContext>& context);
      virtual void on_draw_page(const Glib::RefPtr<Gtk::PrintContext>& context, int page_nr);

      Glib::ustring m_Name;
      Glib::ustring m_Comments;
      Glib::RefPtr<Pango::Layout> m_refLayout;
      std::vector<int> m_PageBreaks; // line numbers where a page break occurs
    };

    #endif // GTKMM_PRINT_FORM_OPERATION_H

File: `examplewindow.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class PrintFormOperation;

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:

      void build_main_menu();

      void print_or_preview(Gtk::PrintOperationAction print_action);

      //PrintOperation signal handlers.
      //We handle these so can get necessary information to update the UI or print settings.
      //Our derived PrintOperation class also overrides some default signal handlers.
      void on_printoperation_status_changed(const Glib::RefPtr<PrintFormOperation>& operation);

      void on_printoperation_done(Gtk::PrintOperationResult result, const Glib::RefPtr<PrintFormOperation>& operation);

      //Action signal handlers:
      void on_menu_file_new();
      void on_menu_file_page_setup();
      void on_menu_file_print_preview();
      void on_menu_file_print();
      void on_menu_file_quit();

      //Printing-related objects:
      Glib::RefPtr<Gtk::PageSetup> m_refPageSetup;
      Glib::RefPtr<Gtk::PrintSettings> m_refSettings;

      //Child widgets:
      Gtk::Box m_VBox;
      Gtk::Grid m_Grid;

      Gtk::Label m_NameLabel;
      Gtk::Entry m_NameEntry;

      Gtk::Label m_SurnameLabel;
      Gtk::Entry m_SurnameEntry;

      Gtk::Label m_CommentsLabel;
      Gtk::ScrolledWindow m_ScrolledWindow;
      Gtk::TextView m_TextView;

      Glib::RefPtr<Gtk::TextBuffer> m_refTextBuffer;

      unsigned m_ContextId;
      Gtk::Statusbar m_Statusbar;

      Glib::RefPtr<Gtk::UIManager> m_refUIManager;
      Glib::RefPtr<Gtk::ActionGroup> m_refActionGroup;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `printformoperation.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "printformoperation.h"

    PrintFormOperation::PrintFormOperation()
    {
    }

    PrintFormOperation::~PrintFormOperation()
    {
    }

    Glib::RefPtr<PrintFormOperation> PrintFormOperation::create()
    {
      return Glib::RefPtr<PrintFormOperation>(new PrintFormOperation());
    }

    void PrintFormOperation::on_begin_print(
            const Glib::RefPtr<Gtk::PrintContext>& print_context)
    {
      //Create and set up a Pango layout for PrintData based on the passed
      //PrintContext: We then use this to calculate the number of pages needed, and
      //the lines that are on each page.
      m_refLayout = print_context->create_pango_layout();

      Pango::FontDescription font_desc("sans 12");
      m_refLayout->set_font_description(font_desc);

      const double width = print_context->get_width();
      const double height = print_context->get_height();

      m_refLayout->set_width(static_cast<int>(width * Pango::SCALE));

      //Set and mark up the text to print:
      Glib::ustring marked_up_form_text;
      marked_up_form_text += "<b>Name</b>: " + m_Name + "\n\n";
      marked_up_form_text += "<b>Comments</b>: " + m_Comments;

      m_refLayout->set_markup(marked_up_form_text);

      //Set the number of pages to print by determining the line numbers
      //where page breaks occur:
      const int line_count = m_refLayout->get_line_count();

      Glib::RefPtr<Pango::LayoutLine> layout_line;
      double page_height = 0;

      for (int line = 0; line < line_count; ++line)
      {
        Pango::Rectangle ink_rect, logical_rect;

        layout_line = m_refLayout->get_line(line);
        layout_line->get_extents(ink_rect, logical_rect);

        const double line_height = logical_rect.get_height() / 1024.0;

        if (page_height + line_height > height)
        {
          m_PageBreaks.push_back(line);
          page_height = 0;
        }

        page_height += line_height;
      }

      set_n_pages(m_PageBreaks.size() + 1);
    }

    void PrintFormOperation::on_draw_page(
            const Glib::RefPtr<Gtk::PrintContext>& print_context, int page_nr)
    {
      //Decide which lines we need to print in order to print the specified page:
      int start_page_line = 0;
      int end_page_line = 0;

      if(page_nr == 0)
      {
        start_page_line = 0;
      }
      else
      {
        start_page_line = m_PageBreaks[page_nr - 1];
      }

      if(page_nr < static_cast<int>(m_PageBreaks.size()))
      {
        end_page_line = m_PageBreaks[page_nr];
      }
      else
      {
        end_page_line = m_refLayout->get_line_count();
      }

      //Get a Cairo Context, which is used as a drawing board:
      Cairo::RefPtr<Cairo::Context> cairo_ctx = print_context->get_cairo_context();

      //We'll use black letters:
      cairo_ctx->set_source_rgb(0, 0, 0);

      //Render Pango LayoutLines over the Cairo context:
      Pango::LayoutIter iter = m_refLayout->get_iter();

      double start_pos = 0;
      int line_index = 0;

      do
      {
        if(line_index >= start_page_line)
        {
          Glib::RefPtr<Pango::LayoutLine> layout_line = iter.get_line();
          Pango::Rectangle logical_rect = iter.get_line_logical_extents();
          int baseline = iter.get_baseline();

          if (line_index == start_page_line)
          {
            start_pos = logical_rect.get_y() / 1024.0;
          }

          cairo_ctx->move_to(logical_rect.get_x() / 1024.0,
            baseline / 1024.0 - start_pos);

          layout_line->show_in_cairo_context(cairo_ctx);
        }

        line_index++;
      }
      while(line_index < end_page_line && iter.next_line());
    }

File: `examplewindow.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include "printformoperation.h"

    #include <iostream>

    #include <pangomm.h>

    const Glib::ustring app_title = "gtkmm Printing Example";

    ExampleWindow::ExampleWindow()
    : m_VBox(Gtk::ORIENTATION_VERTICAL),
      m_NameLabel("Name"),
      m_SurnameLabel("Surname"),
      m_CommentsLabel("Comments")
    {
      m_refPageSetup = Gtk::PageSetup::create();
      m_refSettings = Gtk::PrintSettings::create();

      m_ContextId = m_Statusbar.get_context_id(app_title);

      set_title(app_title);
      set_default_size(400, 300);

      add(m_VBox);

      build_main_menu();

      m_VBox.pack_start(m_Grid);

      //Arrange the widgets inside the grid:
      m_Grid.set_row_spacing(5);
      m_Grid.set_column_spacing(5);
      m_Grid.attach(m_NameLabel, 0, 0, 1, 1);
      m_Grid.attach(m_NameEntry, 1, 0, 1, 1);

      m_Grid.attach(m_SurnameLabel, 0, 1, 1, 1);
      m_Grid.attach(m_SurnameEntry, 1, 1, 1, 1);

      //Add the TextView, inside a ScrolledWindow:
      m_ScrolledWindow.add(m_TextView);

      //Only show the scrollbars when they are necessary:
      m_ScrolledWindow.set_policy(Gtk::POLICY_AUTOMATIC, Gtk::POLICY_AUTOMATIC);

      m_Grid.attach(m_CommentsLabel, 0, 2, 1, 1);
      m_Grid.attach(m_ScrolledWindow, 1, 2, 1, 1);
      m_ScrolledWindow.set_hexpand(true);
      m_ScrolledWindow.set_vexpand(true);

      m_refTextBuffer = Gtk::TextBuffer::create();
      m_TextView.set_buffer(m_refTextBuffer);

      m_VBox.pack_start(m_Statusbar);

      show_all_children();
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::build_main_menu()
    {
      //Create actions for menus and toolbars:
      m_refActionGroup = Gtk::ActionGroup::create();

      //File menu:
      m_refActionGroup->add(
        Gtk::Action::create("FileMenu", "_File"));

      m_refActionGroup->add(
        Gtk::Action::create("New", Gtk::Stock::NEW),
        sigc::mem_fun(*this, &ExampleWindow::on_menu_file_new));

      m_refActionGroup->add(
        Gtk::Action::create("PageSetup", "Page _Setup"),
        sigc::mem_fun(*this, &ExampleWindow::on_menu_file_page_setup));

      m_refActionGroup->add(
        Gtk::Action::create("PrintPreview", "Print Preview"),
        sigc::mem_fun(*this, &ExampleWindow::on_menu_file_print_preview));

      m_refActionGroup->add(
        Gtk::Action::create("Print", Gtk::Stock::PRINT),
        sigc::mem_fun(*this, &ExampleWindow::on_menu_file_print));

      m_refActionGroup->add(
        Gtk::Action::create("Quit", Gtk::Stock::QUIT),
        sigc::mem_fun(*this, &ExampleWindow::on_menu_file_quit));

      m_refUIManager = Gtk::UIManager::create();
      m_refUIManager->insert_action_group(m_refActionGroup);

      add_accel_group(m_refUIManager->get_accel_group());

      //Layout the actions in a menubar and toolbar:

      Glib::ustring ui_info =
            "<ui>"
            "  <menubar name='MenuBar'>"
            "    <menu action='FileMenu'>"
            "      <menuitem action='New'/>"
            "      <menuitem action='PageSetup'/>"
            "      <menuitem action='PrintPreview'/>"
            "      <menuitem action='Print'/>"
            "      <separator/>"
            "      <menuitem action='Quit'/>"
            "    </menu>"
            "  </menubar>"
            "  <toolbar  name='ToolBar'>"
            "    <toolitem action='New'/>"
            "    <toolitem action='Print'/>"
            "      <separator/>"
            "    <toolitem action='Quit'/>"
            "  </toolbar>"
            "</ui>";

      try
      {
        m_refUIManager->add_ui_from_string(ui_info);
      }
      catch(const Glib::Error& ex)
      {
        std::cerr << "building menus failed: " << ex.what();
      }

      //Get the menubar and toolbar widgets, and add them to a container widget:
      Gtk::Widget* pMenubar = m_refUIManager->get_widget("/MenuBar");
      if(pMenubar)
        m_VBox.pack_start(*pMenubar, Gtk::PACK_SHRINK);

      Gtk::Widget* pToolbar = m_refUIManager->get_widget("/ToolBar") ;
      if(pToolbar)
        m_VBox.pack_start(*pToolbar, Gtk::PACK_SHRINK);
    }

    void ExampleWindow::on_printoperation_status_changed(
            const Glib::RefPtr<PrintFormOperation>& operation)
    {
      Glib::ustring status_msg;

      if (operation->is_finished())
      {
        status_msg = "Print job completed.";
      }
      else
      {
        //You could also use get_status().
        status_msg = operation->get_status_string();
      }

      m_Statusbar.push(status_msg, m_ContextId);
    }

    void ExampleWindow::on_printoperation_done(Gtk::PrintOperationResult result,
            const Glib::RefPtr<PrintFormOperation>& operation)
    {
      //Printing is "done" when the print data is spooled.

      if (result == Gtk::PRINT_OPERATION_RESULT_ERROR)
      {
        Gtk::MessageDialog err_dialog(*this, "Error printing form", false,
                Gtk::MESSAGE_ERROR, Gtk::BUTTONS_OK, true);
        err_dialog.run();
      }
      else if (result == Gtk::PRINT_OPERATION_RESULT_APPLY)
      {
        //Update PrintSettings with the ones used in this PrintOperation:
        m_refSettings = operation->get_print_settings();
      }

      if (! operation->is_finished())
      {
        //We will connect to the status-changed signal to track status
        //and update a status bar. In addition, you can, for example,
        //keep a list of active print operations, or provide a progress dialog.
        operation->signal_status_changed().connect(sigc::bind(sigc::mem_fun(*this,
                        &ExampleWindow::on_printoperation_status_changed),
                    operation));
      }
    }

    void ExampleWindow::print_or_preview(Gtk::PrintOperationAction print_action)
    {
      //Create a new PrintOperation with our PageSetup and PrintSettings:
      //(We use our derived PrintOperation class)
      Glib::RefPtr<PrintFormOperation> print = PrintFormOperation::create();

      print->set_name(m_NameEntry.get_text() + " " + m_SurnameEntry.get_text());
      print->set_comments(m_refTextBuffer->get_text(false /*Don't include hidden*/));

      print->set_track_print_status();
      print->set_default_page_setup(m_refPageSetup);
      print->set_print_settings(m_refSettings);

      print->signal_done().connect(sigc::bind(sigc::mem_fun(*this,
                      &ExampleWindow::on_printoperation_done), print));
      try
      {
        print->run(print_action /* print or preview */, *this);
      }
      catch (const Gtk::PrintError& ex)
      {
        //See documentation for exact Gtk::PrintError error codes.
        std::cerr << "An error occurred while trying to run a print operation:"
            << ex.what() << std::endl;
      }
    }

    void ExampleWindow::on_menu_file_new()
    {
      //Clear entries and textview:
      m_NameEntry.set_text("");
      m_SurnameEntry.set_text("");
      m_refTextBuffer->set_text("");
      m_TextView.set_buffer(m_refTextBuffer);
    }

    void ExampleWindow::on_menu_file_page_setup()
    {
      //Show the page setup dialog, asking it to start with the existing settings:
      Glib::RefPtr<Gtk::PageSetup> new_page_setup =
          Gtk::run_page_setup_dialog(*this, m_refPageSetup, m_refSettings);

      //Save the chosen page setup dialog for use when printing, previewing, or
      //showing the page setup dialog again:
      m_refPageSetup = new_page_setup;
    }

    void ExampleWindow::on_menu_file_print_preview()
    {
      print_or_preview(Gtk::PRINT_OPERATION_ACTION_PREVIEW);
    }

    void ExampleWindow::on_menu_file_print()
    {
      print_or_preview(Gtk::PRINT_OPERATION_ACTION_PRINT_DIALOG);
    }

    void ExampleWindow::on_menu_file_quit()
    {
      hide();
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      ExampleWindow window;

      //Shows the window and returns when it is closed.
      return app->run(window);
    }

## Documentos usados recientemente

gtkmm provides an easy way to manage recently used documents. The classes involved in implementing this functionality are `RecentManager`, `RecentChooserDialog`, `RecentChooserMenu`, `RecentChooserWidget`, `RecentAction`, and `RecentFilter`.

Each item in the list of recently used files is identified by its URI, and can have associated metadata. The metadata can be used to specify how the file should be displayed, a description of the file, its mime type, which application registered it, whether it's private to the registering application, and several other things.

### RecentManager

`RecentManager` acts as a database of recently used files. You use this class to register new files, remove files from the list, or look up recently used files. There is one list of recently used files per user.

You can create a new `RecentManager`, but you'll most likely just want to use the default one. You can get a reference to the default `RecentManager` with `get_default()`.

`RecentManager` is the model of a model-view pattern, where the view is a class that implements the `RecentChooser` interface.

#### Agregar elementos a la lista de archivos recientes

To add a new file to the list of recent documents, in the simplest case, you only need to provide the URI. For example:

    Glib::RefPtr<Gtk::RecentManager> recent_manager = Gtk::RecentManager::get_default();
    recent_manager->add_item(uri);

If you want to register a file with metadata, you can pass a `RecentManager::Data` parameter to `add_item()`. The metadata that can be set on a particular file item is as follows:

- `app_exec`: The command line to be used to launch this resource. This string may contain the "f" and "u" escape characters which will be expanded to the resource file path and URI respectively

- `app_name`: The name of the application that registered the resource

- `description`: A short description of the resource as a UTF-8 encoded string

- `display_name`: The name of the resource to be used for display as a UTF-8 encoded string

- `groups`: A list of groups associated with this item. Groups are essentially arbitrary strings associated with a particular resource. They can be thought of as 'categories' (such as "email", "graphics", etc) or tags for the resource.

- `is_private`: Whether this resource should be visible only to applications that have registered it or not

- `mime_type`: The MIME type of the resource

In addition to adding items to the list, you can also look up items from the list and modify or remove items.

#### Looking up Items in the List of Recent Files

To look up recently used files, `RecentManager` provides several functions. To look up a specific item by its URI, you can use the `lookup_item()` function, which will return a `RecentInfo` class. If the specified URI did not exist in the list of recent files, `lookup_item()` throws a `RecentManagerError` exception. For example:

    Glib::RefPtr<Gtk::RecentInfo> info;
    try
    {
      info = recent_manager->lookup_item(uri);
    }
    catch(const Gtk::RecentManagerError& ex)
    {
      std::cerr << "RecentManagerError: " << ex.what() << std::endl;
    }
    if (info)
    {
      // item was found
    }

Un objeto `RecentInfo` es esencialmente un objeto que contiene todos los metadatos de un solo archivo utilizado recientemente. Puede utilizar este objeto para buscar cualquiera de las propiedades enumeradas anteriormente.

If you don't want to look for a specific URI, but instead want to get a list of all recently used items, `RecentManager` provides the `get_items()` function. The return value of this function is a `std::vector` of all recently used files. The following code demonstrates how you might get a list of recently used files:

    std::vector< Glib::RefPtr<Gtk::RecentInfo> > info_list = recent_manager->get_items();

The maximum age of items in the recently used files list can be set with `Gtk::Settings::property_gtk_recent_files_max_age()`. Default value: 30 days.

#### Modificar la lista de archivos recientes

There may be times when you need to modify the list of recent files. For instance, if a file is moved or renamed, you may need to update the file's location in the recent files list so that it doesn't point to an incorrect location. You can update an item's location by using `move_item()`.

In addition to changing a file's URI, you can also remove items from the list, either one at a time or by clearing them all at once. The former is accomplished with `remove_item()`, the latter with `purge_items()`.

The functions `move_item()`, `remove_item()` and `purge_items()` have no effect on the actual files that are referred to by the URIs, they only modify the list of recent files.

### RecentChooser

`RecentChooser` is an interface that can be implemented by widgets displaying the list of recently used files. gtkmm provides four built-in implementations for choosing recent files: `RecentChooserWidget`, `RecentChooserDialog`, `RecentChooserMenu`, and `RecentAction`.

`RecentChooserWidget` is a simple widget for displaying a list of recently used files. `RecentChooserWidget` is the basic building block for `RecentChooserDialog`, but you can embed it into your user interface if you want to.

`RecentChooserMenu` and `RecentAction` allow you to list recently used files as a menu.

#### Ejemplo de RecentChooserDialog

Shown below is a simple example of how to use the `RecentChooserDialog` and the `RecentAction` classes in a program. This simple program has a menubar with a Recent Files Dialog menu item. When you select this menu item, a dialog pops up showing the list of recently used files.

If this is the first time you're using a program that uses the Recent Files framework, the dialog may be empty at first. Otherwise it should show the list of recently used documents registered by other applications.

After selecting the Recent Files Dialog menu item, you should see something similar to the following window.

Código fuente

File: `examplewindow.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      void on_menu_file_recent_files_item();
      void on_menu_file_recent_files_dialog();
      void on_menu_file_quit();
      void on_menu_file_new();

      //Child widgets:
      Gtk::Box m_Box;

      Glib::RefPtr<Gtk::UIManager> m_refUIManager;
      Glib::RefPtr<Gtk::ActionGroup> m_refActionGroup;
      Glib::RefPtr<Gtk::RecentAction> m_refRecentAction;

      Glib::RefPtr<Gtk::RecentManager> m_refRecentManager;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/stock.h>
    #include <iostream>

    ExampleWindow::ExampleWindow()
    : m_Box(Gtk::ORIENTATION_VERTICAL),
      m_refRecentManager(Gtk::RecentManager::get_default())
    {
      set_title("recent files example");
      set_default_size(200, 200);

      //We can put a MenuBar at the top of the box and other stuff below it.
      add(m_Box);

      //Create actions for menus and toolbars:
      m_refActionGroup = Gtk::ActionGroup::create();

      //File menu:
      m_refActionGroup->add( Gtk::Action::create("FileMenu", "_File") );
      m_refActionGroup->add( Gtk::Action::create("FileNew", Gtk::Stock::NEW),
        sigc::mem_fun(*this, &ExampleWindow::on_menu_file_new));

      //A recent-files submenu:
      m_refRecentAction = Gtk::RecentAction::create("FileRecentFiles", "_Recent Files");
      m_refActionGroup->add(m_refRecentAction);
      //Connect to RecentChooser's item_activated signal
      //instead of Action's activate signal:
      m_refRecentAction->signal_item_activated().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_menu_file_recent_files_item) );

      //A menu item to open the recent-files dialog:
      m_refActionGroup->add( Gtk::Action::create("FileRecentDialog", "Recent Files _Dialog"),
        sigc::mem_fun(*this, &ExampleWindow::on_menu_file_recent_files_dialog) );

      m_refActionGroup->add( Gtk::Action::create("FileQuit", Gtk::Stock::QUIT),
        sigc::mem_fun(*this, &ExampleWindow::on_menu_file_quit) );

      m_refUIManager = Gtk::UIManager::create();
      m_refUIManager->insert_action_group(m_refActionGroup);

      add_accel_group(m_refUIManager->get_accel_group());

      //Layout the actions in a menubar and toolbar:
      Glib::ustring ui_info =
            "<ui>"
            "  <menubar name='MenuBar'>"
            "    <menu action='FileMenu'>"
            "      <menuitem action='FileNew'/>"
            "      <menuitem action='FileRecentFiles'/>"
            "      <menuitem action='FileRecentDialog'/>"
            "      <separator/>"
            "      <menuitem action='FileQuit'/>"
            "    </menu>"
            "  </menubar>"
            "  <toolbar  name='ToolBar'>"
            "    <toolitem action='FileNew'/>"
            "    <toolitem action='FileQuit'/>"
            "  </toolbar>"
            "</ui>";

      try
      {
        m_refUIManager->add_ui_from_string(ui_info);
      }
      catch(const Glib::Error& ex)
      {
        std::cerr << "building menus failed: " <<  ex.what();
      }

      //Get the menubar and toolbar widgets, and add them to a container widget:
      Gtk::Widget* pMenubar = m_refUIManager->get_widget("/MenuBar");
      if(pMenubar)
        m_Box.pack_start(*pMenubar, Gtk::PACK_SHRINK);

      Gtk::Widget* pToolbar = m_refUIManager->get_widget("/ToolBar");
      if(pToolbar)
        m_Box.pack_start(*pToolbar, Gtk::PACK_SHRINK);

      show_all_children();
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_menu_file_new()
    {
      std::cout << " New File" << std::endl;
    }

    void ExampleWindow::on_menu_file_quit()
    {
      hide(); //Closes the main window to stop the app->run().
    }

    void ExampleWindow::on_menu_file_recent_files_item()
    {
      std::cout << "URI selected = " << m_refRecentAction->get_current_uri() << std::endl;
    }

    void ExampleWindow::on_menu_file_recent_files_dialog()
    {
      Gtk::RecentChooserDialog dialog(*this, "Recent Files", m_refRecentManager);
      dialog.add_button("Select File", Gtk::RESPONSE_OK);
      dialog.add_button(Gtk::Stock::CANCEL, Gtk::RESPONSE_CANCEL);

      const int response = dialog.run();
      dialog.hide();
      if(response == Gtk::RESPONSE_OK)
      {
        std::cout << "URI selected = " << dialog.get_current_uri() << std::endl;
      }
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      ExampleWindow window;

      //Shows the window and returns when it is closed.
      return app->run(window);
    }

The constructor for `ExampleWindow` creates the menu using `UIManager` (see chapter-menus-and-toolbars for more information). It then adds the menu and the toolbar to the window.

#### Filtrar los archivos recientes

For any of the `RecentChooser` classes, if you don't wish to display all of the items in the list of recent files, you can filter the list to show only those that you want. You can filter the list with the help of the `RecentFilter` class. This class allows you to filter recent files by their name (`add_pattern()`), their mime type (`add_mime_type()`), the application that registered them (`add_application()`), or by a custom filter function (`add_custom()`). It also provides the ability to filter based on how long ago the file was modified and which groups it belongs to.

After you've created and set up the filter to match only the items you want, you can apply a filter to a chooser widget with the `RecentChooser::add_filter()` function.

## Plugs and Sockets

### Vista general

From time to time, it may be useful to be able to embed a widget from another application within your application. gtkmm allows you to do this with the `Gtk::Socket` and `Gtk::Plug` classes. It is not anticipated that very many applications will need this functionality, but in the rare case that you need to display a widget that is running in a completely different process, these classes can be very helpful.

The communication between a `Socket` and a `Plug` follows the XEmbed protocol. This protocol has also been implemented in other toolkits (e.g. Qt), which allows the same level of integration when embedding a Qt widget in GTK+ or vice versa.

The way that `Sockets` and `Plugs` work together is through their window ids. Both a `Socket` and a `Plug` have IDs that can be retrieved with their `get_id()` member functions. The use of these IDs will be explained below in sec-connecting-plugs-sockets.

#### Sockets

Un `Socket` es un tipo especial de widget contenedor que ofrece la posibilidad de incorporar widgets de un proceso en otro proceso de manera que sea transparente para el usuario.

#### Plugs

Un `Plug` es un tipo especial de ventana que se puede conectar a un `Socket`. Además de las propiedades y los métodos normales de `Gtk::Window`, un `Plug` proporciona un constructor que toma el ID de un `Socket`, lo que automáticamente incrusta el `Plug` en el `Socket` que coincide con el ID.

Since a `Plug` is just a special type of `Gtk::Window` class, you can add containers or widgets to it like you would to any other window.

#### Connecting Plugs and Sockets

After a `Socket` or `Plug` object is realized, you can obtain its ID with its `get_id()` function. This ID can then be shared with other processes so that other processes know how to connect to eachother.

There are two basic strategies that can be used:

- Create a `Socket` object in one process and pass the ID of that `Socket` to another process so that it can create a `Plug` object by specifying the given `Socket` ID in its constructor. There is no way to assign a `Plug` to a particular `Socket` after creation, so you must pass the `Socket` ID to the `Plug`'s constructor.

- Create a `Plug` independantly from any particular `Socket` and pass the ID of the `Plug` to other processes that need to use it. The ID of the `Plug` can be associated with a particular `Socket` object using the `Socket::add_id()` function. This is the approach used in the example below.

### Plugs and Sockets Example

The following is a simple example of using sockets and plugs. The method of communication between processes is deliberately kept very simple: The `Plug` writes its ID out to a text file named `plug.id` and the process with the socket reads the ID from this files. In a real program, you may want to use a more sophisticated method of inter-process communication.

Código fuente

File: `socket.cc` (For use with gtkmm 3, not gtkmm 2)

    #include <iostream>
    #include <fstream>
    #include <gtkmm.h>
    #include <gtkmm/socket.h>

    using namespace std;

    const char* id_filename = "plug.id";

    void plug_added()
    {
      cout << "A plug was added" << endl;
    }

    bool plug_removed()
    {
      cout << "A Plug was removed" << endl;
      return true;
    }

    class MySocketWindow : public Gtk::Window
    {
      public:
        MySocketWindow()
        {
          ifstream infile(id_filename);
          if (infile)
          {
            Gtk::Socket* socket = Gtk::manage(new Gtk::Socket());
            add(*socket);
            socket->signal_plug_added().connect(sigc::ptr_fun(plug_added));
            socket->signal_plug_removed().connect(sigc::ptr_fun(plug_removed));
            ::Window plug_id = 0;
            infile >> plug_id;
            infile.close();
            socket->add_id(plug_id);
          }
          else
          {
            Gtk::Label* label = Gtk::manage(
                new Gtk::Label(
                  "Plug id file not found.\n Make sure plug is running."));
            add(*label);
            set_size_request(150, 50);
          }
          show_all();
        }
    };

    int main(int argc, char** argv)
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");
      MySocketWindow win;
      app->run(win);
      return 0;
    }

File: `plug.cc` (For use with gtkmm 3, not gtkmm 2)

    #include <iostream>
    #include <fstream>
    #include <gtkmm.h>
    #include <gtkmm/plug.h>
    #include <glib/gstdio.h>

    using namespace std;

    const char* id_filename = "plug.id";

    void on_embed()
    {
      cout << "I've been embedded." << endl;
    }

    class MyPlug : public Gtk::Plug
    {
      public:
        MyPlug() :
          m_label("I am the plug")
      {
        set_size_request(150, 100);
        add(m_label);
        signal_embedded().connect(sigc::ptr_fun(on_embed));
        show_all_children();
      }

      private:
        Gtk::Label m_label;
    };

    int main(int argc, char** argv)
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");
      MyPlug plug;
      plug.show();

      ofstream out(id_filename);
      out << plug.get_id();
      out.close();
      cout << "The window ID is: " << plug.get_id() << endl;

      app->run(plug);

      // remove the ID file when the program exits
      g_remove(id_filename);
      return 0;
    }

This example creates two executable programs: `socket` and `plug`. The idea is that `socket` has an application window that will embed a widget from the `plug` program. The way this example is designed, `plug` must be running first before starting `socket`. To see the example in action, execute the following commands in order from within the example directory:

Start the `plug` program and send it to the background (or just use a different terminal).

    $ ./plug &

After which you should see something like the following:

    El ID de la ventana es: 69206019

Then start the `socket` program:

    $ ./socket

After starting `socket`, you should see the following output in the terminal:

    I've been embedded.
    A plug was added

The first line of output is from `plug`, after it has been notified that it has been embedded inside of a `Socket`. The second line was emitted by `socket` in response to its `plug_added` signal. If everything was done as described above, the `socket` window should look roughly like the following:

If for some reason the `Socket` couldn't attach the `Plug`, the window would look something like this:

## Eventos de teclado

X events differ in some ways from other signals. These differences are described in the X Event signals section in the appendix. Here we will use keyboard events to show how X events can be used in a program.

### Vista general

Whenever you press or release a key, an event is emitted. You can connect a signal handler to handle such events.

To receive the keyboard events, you must first call the `Gtk::Widget::add_events()` function with a bit mask of the events you're interested in. The event signal handler will receive an argument that depends on the type of event. For keyboard events it's a `GdkEventKey*`. As discribed in the appendix, the event signal handler returns a `bool` value, to indicate that the signal is fully handled (`true`) or allow event propagation (`false`).

To determine which key was pressed or released, you read the value of `GdkEventKey::keyval` and compare it with a constant in the `<gdk/gdkkeysyms.h>` header file. The states of modifier keys (shift, ctrl, etc.) are available as bit-flags in `GdkEventKey::state`.

Un ejemplo sencillo:

    bool on_key_press_or_release_event(GdkEventKey* event)
    {
      if (event->type == GDK_KEY_PRESS &&
        event->keyval == GDK_KEY_1 &&
        (event->state & (GDK_SHIFT_MASK | GDK_CONTROL_MASK | GDK_MOD1_MASK)) == GDK_MOD1_MASK)
      {
        handle_alt_1_press(); // GDK_MOD1_MASK is normally the Alt key
        return true;
      }
      return false;
    }

    Gtk::Entry m_entry; // in a class definition

    // in the class constructor
    m_entry.signal_key_press_event().connect( sigc::ptr_fun(&on_key_press_or_release_event) );
    m_entry.signal_key_release_event().connect( sigc::ptr_fun(&on_key_press_or_release_event) );
    m_entry.add_events(Gdk::KEY_PRESS_MASK | Gdk::KEY_RELEASE_MASK);

#### Ejemplo

In this example there are three keyboard shortcuts: Alt+1 selects the first radio button, Alt+2 selects the second one, and the Esc key hides (closes) the window. The default event signal handler is overridden, as described in the Overriding default signal handlers section in the appendix.

##### Keyboard Events - Simple

Código fuente

File: `examplewindow.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:

      ExampleWindow();
      virtual ~ExampleWindow();

    private:
      //Override default signal handler:
      virtual bool on_key_press_event(GdkEventKey* event);

      Gtk::Grid m_container;
      Gtk::RadioButton m_first;
      Gtk::RadioButton m_second;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"

    ExampleWindow::ExampleWindow()
    {
      set_title("Keyboard Events");
      set_border_width(10);
      add(m_container);

      // Radio buttons:
      m_first.set_label("First");
      m_second.set_label("Second");

      Gtk::RadioButton::Group group = m_first.get_group();
      m_second.set_group(group);
      m_first.set_active();

      // Main Container:
      m_container.add(m_first);
      m_container.add(m_second);

      // Events.
      // We override the default event signal handler.
      add_events(Gdk::KEY_PRESS_MASK);

      show_all_children();
    }

    bool ExampleWindow::on_key_press_event(GdkEventKey* event)
    {
      //GDK_MOD1_MASK -> the 'alt' key(mask)
      //GDK_KEY_1 -> the '1' key
      //GDK_KEY_2 -> the '2' key

      //select the first radio button, when we press alt + 1
      if((event->keyval == GDK_KEY_1) &&
        (event->state &(GDK_SHIFT_MASK | GDK_CONTROL_MASK | GDK_MOD1_MASK)) == GDK_MOD1_MASK)
      {
        m_first.set_active();
        //returning true, cancels the propagation of the event
        return true;
      }
      else if((event->keyval == GDK_KEY_2) &&
        (event->state & (GDK_SHIFT_MASK | GDK_CONTROL_MASK | GDK_MOD1_MASK)) == GDK_MOD1_MASK)
      {
        //and the second radio button, when we press alt + 2
        m_second.set_active();
        return true;
      }
      else if(event->keyval == GDK_KEY_Escape)
      {
        //close the window, when the 'esc' key is pressed
        hide();
        return true;
      }

      //if the event has not been handled, call the base class
      return Gtk::Window::on_key_press_event(event);
    }

    ExampleWindow::~ExampleWindow()
    {
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      ExampleWindow window;

      //Shows the window and returns when it is closed.
      return app->run(window);
    }

### Propagación de eventos

Event propagation means that, when an event is emitted on a particular widget, it can be passed to its parent widget (and that widget can pass it to its parent, and so on) and, if the parent has an event handler, that handler will be called.

Contrary to other events, keyboard events are first sent to the toplevel window (`Gtk::Window`), where it will be checked for any keyboard shortcuts that may be set (accelerator keys and mnemonics, used for selecting menu items from the keyboard). After this (and assuming the event wasn't handled), it is sent to the widget which has focus, and the propagation begins from there.

The event will propagate until it reaches the top-level widget, or until you stop the propagation by returning `true` from an event handler.

Notice, that after canceling an event, no other function will be called (even if it is from the same widget).

#### Ejemplo

In this example there are three event handlers that are called after `Gtk::Window`'s default event handler, one in the `Gtk::Entry`, one in the `Gtk::Grid` and one in the `Gtk::Window`.

In the `Gtk::Window`, we have also the default handler overridden (`on_key_release_event()`), and another handler being called before the default handler (`windowKeyReleaseBefore()`).

The purpose of this example is to show the steps the event takes when it is emitted.

When you write in the entry, a key release event will be emitted, which will go first to the toplevel window (`Gtk::Window`), since we have one event handler set to be called before, that's what is called first (`windowKeyReleaseBefore()`). Then the default handler is called (which we have overridden), and after that the event is sent to the widget that has focus, the `Entry` in our example and, depending on whether we let it propagate, it can reach the `Grid`'s and the `Window`'s event handlers. If it propagates, the text you're writing will appear in the `Label` above the `Entry`.

##### Eventos de teclado: propagación de eventos

Código fuente

File: `examplewindow.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EVENT_PROPAGATION_H
    #define GTKMM_EVENT_PROPAGATION_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:

      ExampleWindow();
      virtual ~ExampleWindow();

    private:
      //Override default signal handler:
      virtual bool on_key_release_event(GdkEventKey* event);

      bool entryKeyRelease(GdkEventKey* event);
      bool gridKeyRelease(GdkEventKey* event);
      bool windowKeyReleaseBefore(GdkEventKey* event);
      bool windowKeyRelease(GdkEventKey* event);

      Gtk::Grid m_container;

      Gtk::Label m_label;
      Gtk::Entry m_entry;
      Gtk::CheckButton m_checkbutton_can_propagate;
    };

    #endif //GTKMM_EVENT_PROPAGATION_H

File: `examplewindow.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <iostream>

    ExampleWindow::ExampleWindow()
    {
      add(m_container);
      set_title("Event Propagation");
      set_border_width(10);

      m_label.set_label("A label");
      m_checkbutton_can_propagate.set_label("Can Propagate");
      m_checkbutton_can_propagate.set_active();

      // Main Container
      m_container.set_orientation(Gtk::ORIENTATION_VERTICAL);
      m_container.add(m_label);
      m_container.add(m_entry);
      m_container.add(m_checkbutton_can_propagate);

      // Events
      add_events(Gdk::KEY_RELEASE_MASK);

      m_entry.signal_key_release_event().connect(
        sigc::mem_fun(*this, &ExampleWindow::entryKeyRelease));

      m_container.signal_key_release_event().connect(
        sigc::mem_fun(*this, &ExampleWindow::gridKeyRelease));

      // Called before the default event signal handler.
      signal_key_release_event().connect(
        sigc::mem_fun(*this, &ExampleWindow::windowKeyReleaseBefore), false);

      // Called after the default event signal handler.
      signal_key_release_event().connect(
        sigc::mem_fun(*this, &ExampleWindow::windowKeyRelease));

      show_all_children();
    }

    //By changing the return value we allow, or don't allow, the event to propagate to other elements.
    bool ExampleWindow::entryKeyRelease(GdkEventKey* /* event */ )
    {
      std::cout << "Entry" << std::endl;

      if(m_checkbutton_can_propagate.get_active())
      {
        return false;
      }

      return true;
    }

    bool ExampleWindow::gridKeyRelease(GdkEventKey* /* event */ )
    {
      std::cout << "Grid" << std::endl;

      //Let it propagate:
      return false;
    }

    bool ExampleWindow::windowKeyReleaseBefore(GdkEventKey* /* event */ )
    {
      std::cout << "Window before" << std::endl;
      return false;
    }

    bool ExampleWindow::on_key_release_event(GdkEventKey* event)
    {
      std::cout << "Window overridden" << std::endl;

      // call base class function (to get the normal behaviour)
      return Gtk::Window::on_key_release_event(event);
    }

    // This will set the entry's text in the label, every time a key is pressed.
    bool ExampleWindow::windowKeyRelease(GdkEventKey* /* event */ )
    {
      std::cout << "Window after";

      //checking if the entry is on focus, otherwise the label would get changed by pressing keys
      //on the window (when the entry is not on focus), even if m_checkbutton_can_propagate wasn't active
      if(m_entry.has_focus())
      {
        m_label.set_text(m_entry.get_text());
        std::cout << ", " << m_entry.get_text();
      }
      std::cout << std::endl;

      return true;
    }

    ExampleWindow::~ExampleWindow()
    {
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      ExampleWindow window;

      //Shows the window and returns when it is closed.
      return app->run(window);
    }

## Timeouts, I/O and Idle Functions

### Timeouts

You may be wondering how to make gtkmm do useful work while it's idling along. Happily, you have several options. Using the following methods you can create a timeout method that will be called every few milliseconds.

    sigc::connection Glib::SignalTimeout::connect(const sigc::slot<bool>& slot, unsigned int interval, int priority = Glib::PRIORITY_DEFAULT);

The first argument is a `slot` you wish to have called when the timeout occurs. The second argument is the number of milliseconds between calls to that method. You receive a `sigc::connection` object that can be used to deactivate the connection using its `disconnect()` method:

    my_connection.disconnect();

Another way of destroying the connection is your signal handler. It has to be of the type `sigc::slot<bool>`. As you see from the definition your signal handler has to return a value of the type `bool`. A definition of a sample method might look like this:

    bool MyCallback() { std::cout << "Hello World!\n" << std::endl; return true; }

You can stop the timeout method by returning `false` from your signal handler. Therefore, if you want your method to be called repeatedly, it should return `true`.

Un ejemplo de esta técnica:

Código fuente

File: `timerexample.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLE_TIMEREXAMPLE_H
    #define GTKMM_EXAMPLE_TIMEREXAMPLE_H

    #include <gtkmm.h>
    #include <iostream>
    #include <map>

    class TimerExample : public Gtk::Window
    {
    public:
      TimerExample();

    protected:
      // signal handlers
      void on_button_add_timer();
      void on_button_delete_timer();
      void on_button_quit();

      // This is the callback function the timeout will call
      bool on_timeout(int timer_number);

      // Member data:

      Gtk::Box m_Box;
      Gtk::Button m_ButtonAddTimer, m_ButtonDeleteTimer, m_ButtonQuit;

      // Keep track of the timers being added:
      int m_timer_number;

      // These two constants are initialized in the constructor's member initializer:
      const int count_value;
      const int timeout_value;

      // STL map for storing our connections
      std::map<int, sigc::connection> m_timers;

      // STL map for storing our timer values.
      // Each timer counts back from COUNT_VALUE to 0 and is removed when it reaches 0
      std::map<int, int> m_counters;
    };

    #endif // GTKMM_EXAMPLE_TIMEREXAMPLE_H

File: `timerexample.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "timerexample.h"

    TimerExample::TimerExample() :
      m_Box(Gtk::ORIENTATION_HORIZONTAL, 10),
        // use Gtk::Stock wherever possible for buttons, etc.
      m_ButtonAddTimer(Gtk::Stock::ADD),
      m_ButtonDeleteTimer(Gtk::Stock::REMOVE),
      m_ButtonQuit(Gtk::Stock::QUIT),
      m_timer_number(0), // start numbering the timers at 0
      count_value(5), // each timer will count down 5 times before disconnecting
      timeout_value(1500) // 1500 ms = 1.5 seconds
    {
      set_border_width(10);

      add(m_Box);
      m_Box.pack_start(m_ButtonAddTimer);
      m_Box.pack_start(m_ButtonDeleteTimer);
      m_Box.pack_start(m_ButtonQuit);

      // Connect the three buttons:
      m_ButtonQuit.signal_clicked().connect(sigc::mem_fun(*this,
                  &TimerExample::on_button_quit));
      m_ButtonAddTimer.signal_clicked().connect(sigc::mem_fun(*this,
                  &TimerExample::on_button_add_timer));
      m_ButtonDeleteTimer.signal_clicked().connect(sigc::mem_fun(*this,
                  &TimerExample::on_button_delete_timer));

      show_all_children();
    }

    void TimerExample::on_button_quit()
    {
      hide();
    }

    void TimerExample::on_button_add_timer()
    {
      // Creation of a new object prevents long lines and shows us a little
      // how slots work.  We have 0 parameters and bool as a return value
      // after calling sigc::bind.
      sigc::slot<bool> my_slot = sigc::bind(sigc::mem_fun(*this,
                  &TimerExample::on_timeout), m_timer_number);

      // This is where we connect the slot to the Glib::signal_timeout()
      sigc::connection conn = Glib::signal_timeout().connect(my_slot,
              timeout_value);

      // Remember the connection:
      m_timers[m_timer_number] = conn;

      // Initialize timer count:
      m_counters[m_timer_number] = count_value + 1;

      // Print some info to the console for the user:
      std::cout << "added timeout " << m_timer_number++ << std::endl;
    }

    void TimerExample::on_button_delete_timer()
    {
      // any timers?
      if(m_timers.empty())
      {
        // no timers left
        std::cout << "Sorry, there are no timers left." << std::endl;
      }
      else
      {
        // get the number of the first timer
        int timer_number = m_timers.begin()->first;

        // Give some info to the user:
        std::cout << "manually disconnecting timer " << timer_number
            << std::endl;

        // Remove the entry in the counter values
        m_counters.erase(timer_number);

        // Diconnect the signal handler:
        m_timers[timer_number].disconnect();

        // Forget the connection:
        m_timers.erase(timer_number);
      }
    }

    bool TimerExample::on_timeout(int timer_number)
    {
      // Print the timer:
      std::cout << "This is timer " << timer_number;

      // decrement and check counter value
      if (--m_counters[timer_number] == 0)
      {
        std::cout << " being disconnected" <<  std::endl;

        // delete the counter entry in the STL MAP
        m_counters.erase(timer_number);

        // delete the connection entry in the STL MAP
        m_timers.erase(timer_number);

        // Note that we do not have to explicitly call disconnect() on the
        // connection since Gtk::Main does this for us when we return false.
        return false;
      }

      // Print the timer value
      std::cout << " - " << m_counters[timer_number] << "/"
          << count_value << std::endl;

     // Keep going (do not disconnect yet):
      return true;
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "timerexample.h"
    #include <gtkmm/application.h>

    int main (int argc, char *argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      TimerExample example;
      return app->run(example);
    }

### Monitoring I/O

A nifty feature of Glib (one of the libraries underlying gtkmm) is the ability to have it check for data on a file descriptor for you. This is especially useful for networking applications. The following method is used to do this:

    sigc::connection Glib::SignalInput::connect(const sigc::slot<bool,Glib::IOCondition>& slot,
                                        int fd, Glib::IOCondition condition,
                                        int priority = Glib::PRIORITY_DEFAULT);

The first argument is a slot you wish to have called when then the specified event (see argument 3) occurs on the file descriptor you specify using argument two. Argument three may be one or more (using `|`) of:

- Glib::IO_IN - Call your method when there is data ready for reading on your file descriptor.

- Glib::IO_OUT - Call your method when the file descriptor is ready for writing.

- Glib::IO_PRI - Call your method when the file descriptor has urgent data to be read.

- Glib::IO_ERR - Call your method when an error has occurred on the file descriptor.

- Glib::IO_HUP - Call your method when hung up (the connection has been broken usually for pipes and sockets).

The return value is a `sigc::connection` that may be used to stop monitoring this file descriptor using its `disconnect()` method. The `slot` signal handler should be declared as follows:

    bool input_callback(Glib::IOCondition condition);

where `condition` is as specified above. As usual the slot is created with `sigc::mem_fun()` (for a member method of an object.), or `sigc::ptr_fun()` (for a function).

A little example follows. To use the example just execute it from a terminal; it doesn't create a window. It will create a pipe named `testfifo` in the current directory. Then start another shell and execute `echo "Hello" > testfifo`. The example will print each line you enter until you execute `echo "Q" > testfifo`.

Código fuente

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include <build/config.h>
    #include <gtkmm/application.h>
    #include <glibmm/main.h>
    #include <glibmm/iochannel.h>
    #include <fcntl.h>
    #include <iostream>

    #include <unistd.h> //The SUN Forte compiler puts F_OK here.

    //The SUN Forte compiler needs these for mkfifo:
    #include <sys/types.h>
    #include <sys/stat.h>

    Glib::RefPtr<Gtk::Application> app;

    int read_fd;
    Glib::RefPtr<Glib::IOChannel> iochannel;

    /*
      send to the fifo with:
      echo "Hello" > testfifo

      quit the program with:
      echo "Q" > testfifo
    */

    // this will be our signal handler for read operations
    // it will print out the message sent to the fifo
    // and quit the program if the message was 'Q'.
    bool MyCallback(Glib::IOCondition io_condition)
    {

      if ((io_condition & Glib::IO_IN) == 0) {
        std::cerr << "Invalid fifo response" << std::endl;
      }
      else {
       Glib::ustring buf;

       iochannel->read_line(buf);
       std::cout << buf;
       if (buf == "Q\n")
         app->quit();

      }
      return true;
    }

    int main(int argc, char *argv[])
    {
      app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      if (access("testfifo", F_OK) == -1) {
        // fifo doesn't exit - create it
        #ifdef HAVE_MKFIFO
        if (mkfifo("testfifo", 0666) != 0) {
          std::cerr << "error creating fifo" << std::endl;
          return -1;
        }
        #else
          std::cerr << "error creating fifo: This platform does not have mkfifo()"
              << std::endl;
        #endif //HAVE_MKFIFO
      }

      read_fd = open("testfifo", O_RDONLY);
      if (read_fd == -1)
      {
        std::cerr << "error opening fifo" << std::endl;
        return -1;
      }

      // connect the signal handler
      Glib::signal_io().connect(sigc::ptr_fun(MyCallback), read_fd, Glib::IO_IN);

      // Creates a iochannel from the file descriptor
      iochannel = Glib::IOChannel::create_from_fd(read_fd);

      // and last but not least - run the application main loop
      app->run();

      // now remove the temporary fifo
      if(unlink("testfifo"))
        std::cerr << "error removing fifo" << std::endl;

      return 0;
    }

### Idle Functions

If you want to specify a method that gets called when nothing else is happening, use the following:

    sigc::connection  Glib::SignalIdle::connect(const sigc::slot<bool>& slot, int priority = Glib::PRIORITY_DEFAULT_IDLE);

This causes gtkmm to call the specified method whenever nothing else is happening. You can add a priority (lower numbers are higher priorities). There are two ways to remove the signal handler: calling `disconnect()` on the `sigc::connection` object, or returning `false` in the signal handler, which should be declared as follows:

    bool idleFunc();

Since this is very similar to the methods above this explanation should be sufficient to understand what's going on. However, here's a little example:

Código fuente

File: `idleexample.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLE_IDLEEXAMPLE_H
    #define GTKMM_EXAMPLE_IDLEEXAMPLE_H

    #include <gtkmm.h>
    #include <iostream>

    class IdleExample : public Gtk::Window
    {
    public:
      IdleExample();

    protected:
      // Signal Handlers:
      bool on_timer();
      bool on_idle();
      void on_button_clicked();

      // Member data:
      Gtk::Box m_Box;
      Gtk::Button m_ButtonQuit;
      Gtk::ProgressBar m_ProgressBar_c;
      Gtk::ProgressBar m_ProgressBar_d;
    };

    #endif // GTKMM_EXAMPLE_IDLEEXAMPLE_H

File: `idleexample.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "idleexample.h"

    IdleExample::IdleExample() :
      m_Box(Gtk::ORIENTATION_VERTICAL, 5),
      m_ButtonQuit(Gtk::Stock::QUIT)
    {
      set_border_width(5);

      // Put buttons into container

      // Adding a few widgets:
      add(m_Box);
      m_Box.pack_start( *Gtk::manage(new Gtk::Label("Formatting Windows drive C:")));
      m_Box.pack_start( *Gtk::manage(new Gtk::Label("100 MB")) );
      m_Box.pack_start(m_ProgressBar_c);

      m_Box.pack_start( *Gtk::manage(new Gtk::Label("")) );

      m_Box.pack_start( *Gtk::manage(new Gtk::Label("Formatting Windows drive D:")));
      m_Box.pack_start( *Gtk::manage(new Gtk::Label("5000 MB")) );
      m_Box.pack_start(m_ProgressBar_d);

      Gtk::Box* hbox = Gtk::manage( new Gtk::Box(Gtk::ORIENTATION_HORIZONTAL,10));
      m_Box.pack_start(*hbox);
      hbox->pack_start(m_ButtonQuit, Gtk::PACK_EXPAND_PADDING);

      // Connect the signal handlers:
      m_ButtonQuit.signal_clicked().connect( sigc::mem_fun(*this,
                  &IdleExample::on_button_clicked) );

      // formatting drive c in timeout signal handler - called once every 50ms
      Glib::signal_timeout().connect( sigc::mem_fun(*this, &IdleExample::on_timer),
              50 );

      // formatting drive d in idle signal handler - called as quickly as possible
      Glib::signal_idle().connect( sigc::mem_fun(*this, &IdleExample::on_idle) );

      show_all_children();
    }

    void IdleExample::on_button_clicked()
    {
      hide();
    }

    // this timer callback function is executed once every 50ms (set in connection
    // above).  Use timeouts when speed is not critical. (ie periodically updating
    // something).
    bool IdleExample::on_timer()
    {
      double value = m_ProgressBar_c.get_fraction();

      // Update progressbar 1/500th each time:
      m_ProgressBar_c.set_fraction(value + 0.002);

      return value < 0.99;  // return false when done
    }

    // This idle callback function is executed as often as possible, hence it is
    // ideal for processing intensive tasks.
    bool IdleExample::on_idle()
    {
      double value = m_ProgressBar_d.get_fraction();

      // Update progressbar 1/5000th each time:
      m_ProgressBar_d.set_fraction(value + 0.0002);

      return value < 0.99;  // return false when done
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "idleexample.h"
    #include <gtkmm/application.h>

    int main (int argc, char *argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      IdleExample example;
      return app->run(example);
    }

This example points out the difference of idle and timeout methods a little. If you need methods that are called periodically, and speed is not very important, then you want timeout methods. If you want methods that are called as often as possible (like calculating a fractal in background), then use idle methods.

Try executing the example and increasing the system load. The upper progress bar will increase steadily; the lower one will slow down.

## Gestión de la memoria

### Widgets

#### Gestión normal de la memoria en C++

gtkmm allows the programmer to control the lifetime (that is, the construction and destruction) of any widget in the same manner as any other C++ object. This flexibility allows you to use `new` and `delete` to create and destroy objects dynamically or to use regular class members (that are destroyed automatically when the class is destroyed) or to use local instances (that are destroyed when the instance goes out of scope). This flexibility is not present in some C++ GUI toolkits, which restrict the programmer to only a subset of C++'s memory management features.

Algunos ejemplos de gestión normal de la memoria en C++:

##### Class Scope widgets

If a programmer does not need dynamic memory allocation, automatic widgets in class scope may be used. One advantage of automatic widgets in class scope is that memory management is grouped in one place. The programmer does not risk memory leaks from failing to `delete` a widget.

The primary disadvantages of using class scope widgets are revealing the class implementation rather than the class interface in the class header. Class scope widgets also require Automatic widgets in class scope suffer the same disadvantages as any other class scope automatic variable.

    #include <gtkmm/button.h>
    class Foo
    {
    private:
      Gtk::Button theButton;
      // will be destroyed when the Foo object is destroyed
    };

##### Function scope widgets

If a programmer does not need a class scope widget, a function scope widget may also be used. The advantages to function scope over class scope are the increased data hiding and reduced dependencies.

    {
      Gtk::Button aButton;
      aButton.show();
      ...
      kit.run();
    }

##### Dynamic allocation with new and delete

Although, in most cases, the programmer will prefer to allow containers to automatically destroy their children using `manage()` (see below), the programmer is not required to use `manage()`. The traditional `new` and `delete` operators may also be used.

    Gtk::Button* pButton = new Gtk::Button("Test");

    // do something useful with pButton

    delete pButton;

Here, the programmer deletes pButton to prevent a memory leak.

#### Managed Widgets

Alternatively, you can let a widget's container control when the widget is destroyed. In most cases, you want a widget to last only as long as the container it is in. To delegate the management of a widget's lifetime to its container, first create it with `manage()` and pack it into its container with `add()`. Now, the widget will be destroyed whenever its container is destroyed.

##### Asignación dinamica mediante el uso de manage() y add()

gtkmm provides the `manage()` function and `add()` methods to create and destroy widgets. Every widget except a top-level window must be added or packed into a container in order to be displayed. The `manage()` function marks a packed widget so that when the widget is added to a container, the container becomes responsible for deleting the widget.

    MyWidget::MyWidget()
    {
      Gtk::Button* pButton = manage(new Gtk::Button("Test"));
      add(*pButton); //add aButton to MyWidget
    }

Now, when objects of type `MyWidget` are destroyed, the button will also be deleted. It is no longer necessary to delete pButton to free the button's memory; its deletion has been delegated to the `MyWidget` object.

gtkmm also provides the `set_manage()` method for all widgets. This can be used to generate the same result as `manage()`, but is more tedious:

foo.add( (w=new Gtk::Label("Hello"), w->set_manage(), &w) );

es lo mismo que

foo.add( manage(new Gtk::Label("Hello")) );

Of course, a top level container will not be added to another container. The programmer is responsible for destroying the top level container using one of the traditional C++ techniques. For instance, your top-level Window might just be an instance in your `main()` function..

### Recursos compartidos

Some objects, such as `Gdk::Pixbuf`s and `Pango::Font`s, are obtained from a shared store. Therefore you cannot instantiate your own instances. These classes typically inherit from `Glib::Object`. Rather than requiring you to reference and unreference these objects, gtkmm uses the `Glib::RefPtr<>` smartpointer. Cairomm has its own smartpointer, `Cairo::RefPtr<>`.

Objects such as `Gdk::Pixbuf` can only be instantiated with a `create()` function. For instance,

    Glib::RefPtr<Gdk::Pixbuf> pixbuf = Gdk::Pixbuf::create_from_file(filename);

You have no way of getting a bare `Gdk::Pixbuf`. In the example, `pixbuf` is a smart pointer, so you can do this, much like a normal pointer:

    int width = 0;
    if(pixbuf)
    {
      width = pixbuf->get_width();
    }

When `pixbuf` goes out of scope an `unref()` will happen in the background and you don't need to worry about it anymore. There's no `new` so there's no `delete`.

If you copy a `RefPtr`, for instance

    Glib::RefPtr<Gdk::Pixbuf> pixbuf2 = pixbuf;

, or if you pass it as a method argument or a return type, then `RefPtr` will do any necessary referencing to ensure that the instance will not be destroyed until the last `RefPtr` has gone out of scope.

See the appendix for detailed information about RefPtr.

If you wish to learn more about smartpointers, you might look in these books:

- Bjarne Stroustrup, «The C++ Programming Language»: sección 14.4.2

- Nicolai M. Josuttis, «The C++ Standard Library» - sección 4.2

## Glade y Gtk::Builder

Although you can use C++ code to instantiate and arrange widgets, this can soon become tedious and repetitive. And it requires a recompilation to show changes. The Glade application allows you to layout widgets on screen and then save an XML description of the arrangement. Your application can then use the Gtk::Builder API to load that XML file at runtime and obtain a pointer to specifically named widget instances.

This has the following advantages:

1. Se requiere menos código en C++

2. UI changes can be seen more quickly, so UIs are able to improve.

3. Designers without programming skills can create and edit UIs.

You still need C++ code to deal with User Interface changes triggered by user actions, but using Gtk::Builder for the widget layout allows you to focus on implementing that functionality.

### Cargar el archivo .glade

`Gtk::Builder` must be used via a `Glib::RefPtr`. Like all such classes, you need to use a `create()` method to instantiate it. For instance,

    Glib::RefPtr<Gtk::Builder> builder = Gtk::Builder::create_from_file("basic.glade");

This will instantiate the windows defined in the .glade file, though they will not be shown immediately unless you have specified that via the Properties window in Glade.

To instantiate just one window, or just one of the child widgets, you can specify the name of a widget as the second parameter. For instance,

    Glib::RefPtr<Gtk::Builder> builder = Gtk::Builder::create_from_file("basic.glade", "treeview_products");

### Acceso a widgets

To access a widget, for instance to `show()` a dialog, use the `get_widget()` method, providing the widget's name. This name should be specified in the Glade Properties window. If the widget could not be found, or is of the wrong type, then the pointer will be set to 0.

    Gtk::Dialog* pDialog = 0;
    builder->get_widget("DialogBasic", pDialog);

Gtk::Builder checks for a null pointer, and checks that the widget is of the expected type, and will show warnings on the command line about these.

Remember that you are not instantiating a widget with `get_widget()`, you are just obtaining a pointer to one that already exists. You will always receive a pointer to the same instance when you call `get_widget()` on the same `Gtk::Builder`, with the same widget name. The widgets are instantiated during `Gtk::Builder::create_from_file()`.

`get_widget()` returns child widgets that are `manage()`ed (see the Memory Management chapter), so they will be deleted when their parent container is deleted. So, if you get only a child widget from Gtk::Builder, instead of a whole window, then you must either put it in a `Container` or delete it. `Windows` (such as `Dialogs`) cannot be managed because they have no parent container, so you must delete them at some point.

#### Ejemplo

This simple example shows how to load a Glade file at runtime and access the widgets with Gtk::Builder.

Código fuente

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include <gtkmm.h>
    #include <iostream>

    Gtk::Dialog* pDialog = 0;

    static
    void on_button_clicked()
    {
      if(pDialog)
        pDialog->hide(); //hide() will cause main::run() to end.
    }

    int main (int argc, char **argv)
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      //Load the GtkBuilder file and instantiate its widgets:
      Glib::RefPtr<Gtk::Builder> refBuilder = Gtk::Builder::create();
      try
      {
        refBuilder->add_from_file("basic.glade");
      }
      catch(const Glib::FileError& ex)
      {
        std::cerr << "FileError: " << ex.what() << std::endl;
        return 1;
      }
      catch(const Glib::MarkupError& ex)
      {
        std::cerr << "MarkupError: " << ex.what() << std::endl;
        return 1;
      }
      catch(const Gtk::BuilderError& ex)
      {
        std::cerr << "BuilderError: " << ex.what() << std::endl;
        return 1;
      }

      //Get the GtkBuilder-instantiated Dialog:
      refBuilder->get_widget("DialogBasic", pDialog);
      if(pDialog)
      {
        //Get the GtkBuilder-instantiated Button, and connect a signal handler:
        Gtk::Button* pButton = 0;
        refBuilder->get_widget("quit_button", pButton);
        if(pButton)
        {
          pButton->signal_clicked().connect( sigc::ptr_fun(on_button_clicked) );
        }

        app->run(*pDialog);
      }

      delete pDialog;

      return 0;
    }

### Usar widgets derivados

You can use Glade to layout your own custom widgets derived from gtkmm widget classes. This keeps your code organized and encapsulated. Of course you won't see the exact appearance and properties of your derived widget in Glade, but you can specify its location and child widgets and the properties of its gtkmm base class.

Use `Gtk::Builder::get_widget_derived()` like so:

    DerivedDialog* pDialog = 0;
    builder->get_widget_derived("DialogBasic", pDialog);

Your derived class must have a constructor that takes a pointer to the underlying C type, and the `Gtk::Builder` instance. All relevant classes of gtkmm typedef their underlying C type as `BaseObjectType` (`Gtk::Dialog` typedefs `BaseObjectType` as `GtkDialog`, for instance).

You must call the base class's constructor in the initialization list, providing the C pointer. For instance,

    DerivedDialog::DerivedDialog(BaseObjectType* cobject, const Glib::RefPtr<Gtk::Builder>& builder)
    : Gtk::Dialog(cobject)
    {
    }

You could then encapsulate the manipulation of the child widgets in the constructor of the derived class, maybe using `get_widget()` or `get_widget_derived()` again. For instance,

    DerivedDialog::DerivedDialog(BaseObjectType* cobject, const Glib::RefPtr<Gtk::Builder>& builder)
    : Gtk::Dialog(cobject),
      m_builder(builder),
      m_pButton(0)
    {
      //Get the Glade-instantiated Button, and connect a signal handler:
      m_builder->get_widget("quit_button", m_pButton);
      if(m_pButton)
      {
        m_pButton->signal_clicked().connect( sigc::mem_fun(*this, &DerivedDialog::on_button_quit) );
      }
    }

#### Ejemplo

This example shows how to load a Glade file at runtime and access the widgets via a derived class.

Código fuente

File: `deriveddialog.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLE_DERIVED_DIALOG_H
    #define GTKMM_EXAMPLE_DERIVED_DIALOG_H

    #include <gtkmm.h>

    class DerivedDialog : public Gtk::Dialog
    {
    public:
      DerivedDialog(BaseObjectType* cobject, const Glib::RefPtr<Gtk::Builder>& refGlade);
      virtual ~DerivedDialog();

    protected:
      //Signal handlers:
      void on_button_quit();

      Glib::RefPtr<Gtk::Builder> m_refGlade;
      Gtk::Button* m_pButton;
    };

    #endif //GTKMM_EXAMPLE_DERIVED_WINDOW_H

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "deriveddialog.h"
    #include <iostream>

    int main (int argc, char **argv)
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      //Load the Glade file and instiate its widgets:
      Glib::RefPtr<Gtk::Builder> refBuilder = Gtk::Builder::create();
      try
      {
        refBuilder->add_from_file("derived.glade");
      }
      catch(const Glib::FileError& ex)
      {
        std::cerr << "FileError: " << ex.what() << std::endl;
        return 1;
      }
      catch(const Glib::MarkupError& ex)
      {
        std::cerr << "MarkupError: " << ex.what() << std::endl;
        return 1;
      }
      catch(const Gtk::BuilderError& ex)
      {
        std::cerr << "BuilderError: " << ex.what() << std::endl;
        return 1;
      }

      //Get the GtkBuilder-instantiated dialog::
      DerivedDialog* pDialog = 0;
      refBuilder->get_widget_derived("DialogDerived", pDialog);
      if(pDialog)
      {
        //Start:
        app->run(*pDialog);
      }

      delete pDialog;

      return 0;
    }

File: `deriveddialog.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "deriveddialog.h"

    DerivedDialog::DerivedDialog(BaseObjectType* cobject, const Glib::RefPtr<Gtk::Builder>& refGlade)
    : Gtk::Dialog(cobject),
      m_refGlade(refGlade),
      m_pButton(0)
    {
      //Get the Glade-instantiated Button, and connect a signal handler:
      m_refGlade->get_widget("quit_button", m_pButton);
      if(m_pButton)
      {
        m_pButton->signal_clicked().connect( sigc::mem_fun(*this, &DerivedDialog::on_button_quit) );
      }
    }

    DerivedDialog::~DerivedDialog()
    {
    }

    void DerivedDialog::on_button_quit()
    {
      hide(); //hide() will cause main::run() to end.
    }

## Internacionalización y localización

gtkmm applications can easily support multiple languages, including non-European languages such as Chinese and right-to-left languages such as Arabic. An appropriately-written and translated gtkmm application will use the appropriate language at runtime based on the user's environment.

You might not anticipate the need to support additional languages, but you can never rule it out. And it's easier to develop the application properly in the first place rather than retrofitting later.

The process of writing source code that allows for translation is called `internationalization`, often abbreviated to `i18n`. The `Localization` process, sometimes abbreviated as `l10n`, provides translated text for other languages, based on that source code.

The main activity in the internationalization process is finding strings seen by users and marking them for translation. You do not need to do it all at once - if you set up the necessary project infrastructure correctly then your application will work normally regardless of how many strings you've covered.

String literals should be typed in the source code in English, but surrounded by a macro. The gettext (or intltool) utility can then extract the marked strings for tramslation, and substitute the translated text at runtime.

### Preparar su proyecto

In the instructions below we will assume that you will not be using gettext directly, but intltool, which was written specifically for `GNOME`. intltool uses `gettext()`, which extracts strings from source code, but intltool can also combine strings from other files, for example from desktop menu details, and GUI resource files such as Glade files, into standard gettext `.pot/.po` files.

We also assume that you are using autotools (e.g. automake and autoconf) to build your project, and that you are using `./autogen.sh` from gnome-common, which, among other things, takes care of some intltool initialization.

Create a sub-directory named `po` in your project's root directory. This directory will eventually contain all of your translations. Within it, create a file named `LINGUAS` and a file named `POTFILES.in`. It is common practice to also create a `ChangeLog` file in the `po` directory so that translators can keep track of translation changes.

`LINGUAS` contains an alphabetically sorted list of codes identifying the languages for which your program is translated (comment lines starting with a `#` are ignored). Each language code listed in the `LINGUAS` file must have a corresponding `.po` file. So, if your program has German and Japanese translations, your `LINGUAS` file would look like this:

    # keep this file sorted alphabetically, one language code per line
    de
    ja

(In addition, you'd have the files `ja.po` and `de.po` in your `po` directory which contain the German and Japanese translations, respectively.)

`POTFILES.in` is a list of paths to all files which contain strings marked up for translation, starting from the project root directory. So for example, if your project sources were located in a subdirectory named `src`, and you had two files that contained strings that should be translated, your `POTFILES.in` file might look like this:

    src/main.cc
    src/other.cc

If you are using gettext directly, you can only mark strings for translation if they are in source code file. However, if you use intltool, you can mark strings for translation in a variety of other file formats, including Glade UI files, xml, .desktop files and several more. So, if you have designed some of the application UI in Glade then also add your `.glade` files to the list in `POTFILES.in`.

Now that there is a place to put your translations, you need to initialize intltool and gettext. Add the following code to your `configure.ac`, substituting 'programname' with the name of your program:

    IT_PROG_INTLTOOL([0.35.0])

    GETTEXT_PACKAGE=programname
    AC_SUBST(GETTEXT_PACKAGE)
    AC_DEFINE_UNQUOTED([GETTEXT_PACKAGE], ["$GETTEXT_PACKAGE"],
                       [The domain to use with gettext])
    AM_GLIB_GNU_GETTEXT

    PROGRAMNAME_LOCALEDIR=[${datadir}/locale]
    AC_SUBST(PROGRAMNAME_LOCALEDIR)

This `PROGRAMNAME_LOCALEDIR` variable will be used later in the `Makefile.am` file, to define a macro that will be used when you initialize gettext in your source code.

In the top-level Makefile.am:

- Añada `po` a la variable `SUBDIRS`. Sin esto, las traducciones no se construirán al construir el programa.

- Define `INTLTOOL_FILES` as:

      INTLTOOL_FILES = intltool-extract.in \
                       intltool-merge.in \
                       intltool-update.in

- Añada `INTLTOOL_FILES` a la lista de archivos `EXTRA_DIST`. Esto asegura que cuando hace un `make dist`, este comando se incluya en el archivo fuente.

- Update your `DISTCLEANFILES`:

      DISTCLEANFILES = ... intltool-extract \
                       intltool-merge \
                       intltool-update \
                       po/.intltool-merge-cache

In your `src/Makefile.am`, update your `AM_CPPFLAGS` to add the following preprocessor macro definition:

    AM_CPPFLAGS = ... -DPROGRAMNAME_LOCALEDIR=\"${PROGRAMNAME_LOCALEDIR}\"

This macro will be used when you initialize `gettext` in your source code.

### Marcar cadenas para traducir

String literals should be typed in the source code in English, but they should be surrounded by a call to the `gettext()` function. These strings will be extracted for translation and the translations may be used at runtime instead of the original English strings.

The GNU gettext package allows you to mark strings in source code, extract those strings for translation, and use the translated strings in your application.

However, Glib defines `gettext()` support macros which are shorter wrappers in an easy-to-use form. To use these macros, include `<glibmm/i18n.h>`, and then, for example, substitute:

    display_message("Getting ready for i18n.");

with:

    display_message(_("Getting ready for i18n."));

For reference, it is possible to generate a file which contains all strings which appear in your code, even if they are not marked for translation, together with file name and line number references. To generate such a file named `my-strings`, execute the following command, within the source code directory:

    xgettext -a -o my-strings --omit-header *.cc *.h

Finally, to let you program use the translation for the current locale, add this code to the beginning of your `main.cc` file, to initialize gettext.

    bindtextdomain(GETTEXT_PACKAGE, PROGRAMNAME_LOCALEDIR);
    bind_textdomain_codeset(GETTEXT_PACKAGE, "UTF-8");
    textdomain(GETTEXT_PACKAGE);

#### Cómo funciona gettext

intltool / xgettext script extracts the strings and puts them in a `mypackage.pot` file. The translators of your application create their translations by first copying this `.pot` file to a `localename.po` file. A locale identifies a language and an encoding for that language, including date and numerical formats. Later, when the text in your source code has changed, the `msmerge` script is used to update the `localename.po` files from the regenerated `.pot` file.

At install time, the `.po` files are converted to a binary format (with the extension `.mo`) and placed in a system-wide directory for locale files, for example `/usr/share/locale/`.

When the application runs, the gettext library checks the system-wide directory to see if there is a `.mo` file for the user's locale environment (you can set the locale with, for instance, "export LANG=de_DE.UTF-8" from a bash console). Later, when the program reaches a `gettext` call, it looks for a translation of a particular string. If none is found, the original string is used.

#### Comprobar y añadir las traducciones

To convince yourself that you've done well, you may wish to add a translation for a new locale. In order to do that, go to the `po` subdirectory of your project and execute the following command:

    intltool-update --pot

That will create a file named `programname.pot`. Now copy that file to `languagecode.po`, such as `de.po` or `hu.po`. Also add that language code to `LINGUAS`. The `.po` file contains a header and a list of English strings, with space for the translated strings to be entered. Make sure you set the encoding of the `.po` file (specified in the header, but also as content) to `UTF-8`.

It's possible that certain strings will be marked as `fuzzy` in the `.po` file. These translations will not substitute the original string. To make them appear, simply remove the `fuzzy` tag.

#### Recursos

More information about what lies behind the internationalization and localization process is presented and demonstrated in:

- Internacionalizar aplicaciones de GNOME

- README de intltool

- How to use GNOME CVS as a Translator

- manual de gettext

- `gtkmm_hello` paquete de ejemplo

- `gnomemm_hello` paquete de ejemplo

### Expecting UTF8

A properly internationalized application will not make assumptions about the number of bytes in a character. That means that you shouldn't use pointer arithmetic to step through the characters in a string, and it means you shouldn't use `std::string` or standard C functions such as `strlen()` because they make the same assumption.

However, you probably already avoid bare char* arrays and pointer arithmetic by using `std::string`, so you just need to start using `Glib::ustring` instead. See the Basics chapter about `Glib::ustring`.

#### Glib::ustring y std::iostreams

Unfortunately, the integration with the standard iostreams is not completely foolproof. gtkmm converts `Glib::ustring`s to a locale-specific encoding (which usually is not UTF-8) if you output them to an `ostream` with `operator<<`. Likewise, retrieving `Glib::ustrings` from `istream` with `operator>>` causes a conversion in the opposite direction. But this scheme breaks down if you go through a `std::string`, e.g. by inputting text from a stream to a `std::string` and then implicitly converting it to a `Glib::ustring`. If the string contained non-ASCII characters and the current locale is not UTF-8 encoded, the result is a corrupted `Glib::ustring`. You can work around this with a manual conversion. For instance, to retrieve the `std::string` from a `ostringstream`:

    std::ostringstream output;
    output.imbue(std::locale("")); // use the user's locale for this stream
    output << percentage << " % done";
    label->set_text(Glib::locale_to_utf8(output.str()));

### Pitfalls

There are a few common mistakes that you would discover eventually yourself. But this section might help you to avoid them.

#### Same strings, different semantics

Sometimes two english strings are identical but have different meanings in different contexts, so they would probably not be identical when translated. Since the English strings are used as look-up keys, this causes problems.

In these cases, you should add extra characters to the strings. For instance, use `"jumps[noun]"` and `"jumps[verb]"` instead of just `"jumps"`) and strip them again outside the `gettext` call. If you add extra characters you should also add a comment for the translators before the `gettext` call. Such comments will be shown in the `.po` files. For instance:

    // note to translators: don't translate the "[noun]" part - it is
    // just here to distinguish the string from another "jumps" string
    text = strip(gettext("jumps[noun]"), "[noun]");

#### Composición de cadenas

C programmers use `sprintf()` to compose and concatenate strings. C++ favours streams, but unfortunately, this approach makes translation difficult, because each fragment of text is translated separately, without allowing the translators to rearrange them according to the grammar of the language.

Por ejemplo, este código podría ser problemático:

    std::cout << _("Current amount: ") << amount
              << _(" Future: ") << future << std::endl;

    label.set_text(_("Really delete ") + filename + _(" now?"));

So you should either avoid this situation or revert to the C-style `sprintf()`. One possible solution is the compose library which supports syntax such as:

    label.set_text(compose(_("Really delete %1 now?"), filename));

#### Assuming the displayed size of strings

You never know how much space a string will take on screen when translated. It might very possibly be twice the size of the original English string. Luckily, most gtkmm widgets will expand at runtime to the required size.

#### Palabras poco frecuentes

You should avoid cryptic abbreviations, slang, or jargon. They are usually difficult to translate, and are often difficult for even native speakers to understand. For instance, prefer "application" to "app"

#### Using non-ASCII characters in strings

Currently, gettext does not support non-ASCII characters (i.e. any characters with a code above 127) in source code. For instance, you cannot use the copyright sign (©).

To work around this, you could write a comment in the source code just before the string, telling the translators to use the special character if it is available in their languages. For english, you could then make an American English `en_US.po` translation which used that special charactger.

### Obtener ayuda con las traducciones

If your program is free software, there is a whole `GNOME` subproject devoted to helping you make translations, the `GNOME` Translation Project.

The way it works is that you contact the gnome-i18n mailing list to find out how the translators can access your `po/` subdirectory, and to add your project to the big status tables.

Then you make sure you update the file `POTFILES.in` in the `po/` subdirectory (`intltool-update -M` can help with this) so that the translators always access updated `myprogram.pot` files, and simply freeze the strings at least a couple of days before you make a new release, announcing it on gnome-i18n. Depending on the number of strings your program contains and how popular it is, the translations will then start to tick in as `languagename.po` files.

Note that most language teams only consist of 1-3 persons, so if your program contains a lot of strings, it might last a while before anyone has the time to look at it. Also, most translators do not want to waste their time (translating is a very time-consuming task) so if they do not assess your project as being really serious (in the sense that it is polished and being maintained) they may decide to spend their time on some other project.

## Widgets personalizados

gtkmm makes it very easy to derive new widgets by inheriting from an existing widget class, either by deriving from a container and adding child widgets, or by deriving from a single-item widget, and changing its behaviour. But you might occasionally find that no suitable starting point already exists. In this case, you can implement a widget from scratch.

### Contenedores personalizados

When deriving from `Gtk::Container`, you should override the following virtual methods:

- `get_request_mode_vfunc()`: Return what `Gtk::SizeRequestMode` is preferred by the container.

- `get_preferred_width_vfunc()`: Calculate the minimum and natural width of the container.

- `get_preferred_height_vfunc()`: Calculate the minimum and natural height of the container.

- `get_preferred_width_for_height_vfunc()`: Calculate the minimum and natural width of the container, if it would be given the specified height.

- `get_preferred_height_for_width_vfunc()`: Calculate the minimum and natural height of the container, if it would be given the specified width.

- `on_size_allocate()`: Position the child widgets, given the height and width that the container has actually been given.

- `forall_vfunc()`: Call the same callback for each of the children.

- `on_add()`: Add a child widget to the container.

- `on_remove()`: Remove a child widget from the container.

- `child_type_vfunc()`: Return what type of child can be added.

The `get_request_mode_vfunc()`, `get_preferred_width_vfunc()`, `get_preferred_height_vfunc()`, `get_preferred_width_for_height_vfunc()`, `get_preferred_height_for_width_vfunc()`, and `on_size_allocate()` virtual methods control the layout of the child widgets. For instance, if your container has 2 child widgets, with one below the other, your `get_request_mode_vfunc()` might request height-for-width layout. Then your `get_preferred_width_vfunc()` might report the maximum of the widths of the child widgets, and `get_preferred_height_for_width_vfunc()` might report the sum of their heights. If you want padding between the child widgets then you would add that to the width and height too. Your widget's container will use this result to ensure that your widget gets enough space, and not less. By examining each widget's parent, and its parent, this logic will eventually decide the size of the top-level window.

You are not guaranteed to get the `Gtk::SizeRequestMode` that you request. Therefore all four of the `get_preferred_xxx_vfunc()` methods must return sensible values.

`on_size_allocate()` receives the actual height and width that the parent container has decided to give to your widget. This might be more than the minimum, or even more than the natural size, for instance if the top-level window has been expanded. You might choose to ignore the extra space and leave a blank area, or you might choose to expand your child widgets to fill the space, or you might choose to expand the padding between your widgets. It's your container, so you decide. Don't forget to call `set_allocation()` inside your `on_size_allocate()` implementation to actually use the allocated space that has been offered by the parent container.

Unless your container is a top-level window that derives from `Gtk::Window`, you should probably also call `Gtk::Widget::set_has_window(false)` in your constructor. This means that your container does not create its own `Gdk::Window`, but uses its parent's window. (Note the difference between `Gtk::Window` and `Gdk::Window`.) If your container does need its own `Gdk::Window`, and does not derive from `Gtk::Window`, you must also override the `on_realize()` method as described in the Custom Widgets section. And unless your container draws directly onto the underlying `Gdk::Window`, you should probably call `set_redraw_on_allocate(false)` to improve performance.

By overriding `forall_vfunc()` you can allow applications to operate on all of the container's child widgets. For instance, `show_all_children()` uses this to find all the child widgets and show them.

Although your container might have its own method to set the child widgets, you should still provide an implementation for the virtual `on_add()` and `on_remove()` methods from the base class, so that the add() and remove() methods will do something appropriate if they are called.

Your implementation of the `child_type_vfunc()` method should report the type of widget that may be added to your container, if it is not yet full. This is usually `Gtk::Widget::get_type()` to indicate that the container may contain any class derived from `Gtk::Widget`. If the container may not contain any more widgets, then this method should return `G_TYPE_NONE`.

#### Ejemplo

This example implements a container with two child widgets, one above the other. Of course, in this case it would be far simpler just to use a vertical `Gtk::Box`.

##### Contenedor personalizado

Código fuente

File: `mycontainer.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_CUSTOM_CONTAINER_MYCONTAINER_H
    #define GTKMM_CUSTOM_CONTAINER_MYCONTAINER_H

    #include <gtkmm/container.h>

    class MyContainer : public Gtk::Container
    {
    public:
      MyContainer();
      virtual ~MyContainer();

      void set_child_widgets(Gtk::Widget& child_one, Gtk::Widget& child_two);

    protected:

      //Overrides:
      virtual Gtk::SizeRequestMode get_request_mode_vfunc() const;
      virtual void get_preferred_width_vfunc(int& minimum_width, int& natural_width) const;
      virtual void get_preferred_height_for_width_vfunc(int width, int& minimum_height, int& natural_height) const;
      virtual void get_preferred_height_vfunc(int& minimum_height, int& natural_height) const;
      virtual void get_preferred_width_for_height_vfunc(int height, int& minimum_width, int& natural_width) const;
      virtual void on_size_allocate(Gtk::Allocation& allocation);

      virtual void forall_vfunc(gboolean include_internals, GtkCallback callback, gpointer callback_data);

      virtual void on_add(Gtk::Widget* child);
      virtual void on_remove(Gtk::Widget* child);
      virtual GType child_type_vfunc() const;

      Gtk::Widget* m_child_one;
      Gtk::Widget* m_child_two;
    };

    #endif //GTKMM_CUSTOM_CONTAINER_MYCONTAINER_H

File: `examplewindow.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>
    #include "mycontainer.h"

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      void on_button_quit();

      //Child widgets:
      Gtk::Box m_VBox;
      MyContainer m_MyContainer;
      Gtk::Button m_Button_One;
      Gtk::Label m_Label_Two;
      Gtk::ButtonBox m_ButtonBox;
      Gtk::Button m_Button_Quit;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 3, not gtkmm 2)

    #include <iostream>
    #include "examplewindow.h"

    ExampleWindow::ExampleWindow()
    : m_VBox(Gtk::ORIENTATION_VERTICAL),
      m_Button_One("Child One"),
      m_Label_Two("Child 2"),
      m_Button_Quit("Quit")
    {
      set_title("Custom Container example");
      set_border_width(6);
      set_default_size(400, 200);

      add(m_VBox);

      //Add the child widgets to the custom container:
      m_MyContainer.set_child_widgets(m_Button_One, m_Label_Two);

      m_Label_Two.set_alignment(1.0, 0.5);

      m_VBox.pack_start(m_MyContainer, Gtk::PACK_EXPAND_WIDGET);
      m_VBox.pack_start(m_ButtonBox, Gtk::PACK_SHRINK);

      m_ButtonBox.pack_start(m_Button_Quit, Gtk::PACK_SHRINK);
      m_ButtonBox.set_border_width(6);
      m_ButtonBox.set_layout(Gtk::BUTTONBOX_END);
      m_Button_Quit.signal_clicked().connect( sigc::mem_fun(*this,
                  &ExampleWindow::on_button_quit) );

      show_all_children();
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_button_quit()
    {
      hide();
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      ExampleWindow window;

      //Shows the window and returns when it is closed.
      return app->run(window);
    }

File: `mycontainer.cc` (For use with gtkmm 3, not gtkmm 2)

    #include <iostream>
    #include <algorithm> // std::max
    #include "mycontainer.h"

    MyContainer::MyContainer()
    : m_child_one(0), m_child_two(0)
    {
      set_has_window(false);
      set_redraw_on_allocate(false);
    }

    MyContainer::~MyContainer()
    {
    }

    void MyContainer::set_child_widgets(Gtk::Widget& child_one,
            Gtk::Widget& child_two)
    {
      m_child_one = &child_one;
      m_child_two = &child_two;

      m_child_one->set_parent(*this);
      m_child_two->set_parent(*this);
    }

    //This example container is a simplified VBox with at most two children.
    Gtk::SizeRequestMode MyContainer::get_request_mode_vfunc() const
    {
      return Gtk::SIZE_REQUEST_HEIGHT_FOR_WIDTH;
    }

    //Discover the total amount of minimum space and natural space needed by
    //this container and its children.
    void MyContainer::get_preferred_width_vfunc(int& minimum_width, int& natural_width) const
    {
      int child_minimum_width[2] = {0, 0};
      int child_natural_width[2] = {0, 0};

      if(m_child_one && m_child_one->get_visible())
        m_child_one->get_preferred_width(child_minimum_width[0], child_natural_width[0]);

      if(m_child_two && m_child_two->get_visible())
        m_child_two->get_preferred_width(child_minimum_width[1], child_natural_width[1]);

      //Request a width equal to the width of the widest visible child.
      minimum_width = std::max(child_minimum_width[0], child_minimum_width[1]);
      natural_width = std::max(child_natural_width[0], child_natural_width[1]);
    }

    void MyContainer::get_preferred_height_for_width_vfunc(int width,
       int& minimum_height, int& natural_height) const
    {
      int child_minimum_height[2] = {0, 0};
      int child_natural_height[2] = {0, 0};
      int nvis_children = 0;

      if(m_child_one && m_child_one->get_visible())
      {
        ++nvis_children;
        m_child_one->get_preferred_height_for_width(width, child_minimum_height[0],
                                                    child_natural_height[0]);
      }

      if(m_child_two && m_child_two->get_visible())
      {
        ++nvis_children;
        m_child_two->get_preferred_height_for_width(width, child_minimum_height[1],
                                                    child_natural_height[1]);
      }

      //The allocated height will be divided equally among the visible children.
      //Request a height equal to the number of visible children times the height
      //of the highest child.
      minimum_height = nvis_children * std::max(child_minimum_height[0],
                                                child_minimum_height[1]);
      natural_height = nvis_children * std::max(child_natural_height[0],
                                                child_natural_height[1]);
    }

    void MyContainer::get_preferred_height_vfunc(int& minimum_height, int& natural_height) const
    {
      int child_minimum_height[2] = {0, 0};
      int child_natural_height[2] = {0, 0};
      int nvis_children = 0;

      if(m_child_one && m_child_one->get_visible())
      {
        ++nvis_children;
        m_child_one->get_preferred_height(child_minimum_height[0], child_natural_height[0]);
      }

      if(m_child_two && m_child_two->get_visible())
      {
        ++nvis_children;
        m_child_two->get_preferred_height(child_minimum_height[1], child_natural_height[1]);
      }

      //The allocated height will be divided equally among the visible children.
      //Request a height equal to the number of visible children times the height
      //of the highest child.
      minimum_height = nvis_children * std::max(child_minimum_height[0],
                                                child_minimum_height[1]);
      natural_height = nvis_children * std::max(child_natural_height[0],
                                                child_natural_height[1]);
    }

    void MyContainer::get_preferred_width_for_height_vfunc(int height,
       int& minimum_width, int& natural_width) const
    {
      int child_minimum_width[2] = {0, 0};
      int child_natural_width[2] = {0, 0};
      int nvis_children = 0;

      //Get number of visible children.
      if(m_child_one && m_child_one->get_visible())
        ++nvis_children;
      if(m_child_two && m_child_two->get_visible())
        ++nvis_children;

      if(nvis_children > 0)
      {
        //Divide the height equally among the visible children.
        const int height_per_child = height / nvis_children;

        if(m_child_one && m_child_one->get_visible())
          m_child_one->get_preferred_width_for_height(height_per_child,
                       child_minimum_width[0], child_natural_width[0]);

        if(m_child_two && m_child_two->get_visible())
          m_child_two->get_preferred_width_for_height(height_per_child,
                       child_minimum_width[1], child_natural_width[1]);
      }

      //Request a width equal to the width of the widest child.
      minimum_width = std::max(child_minimum_width[0], child_minimum_width[1]);
      natural_width = std::max(child_natural_width[0], child_natural_width[1]);
    }

    void MyContainer::on_size_allocate(Gtk::Allocation& allocation)
    {
      //Do something with the space that we have actually been given:
      //(We will not be given heights or widths less than we have requested, though
      //we might get more.)

      //Use the offered allocation for this container:
      set_allocation(allocation);

      //Get number of visible children.
      int nvis_children = 0;
      if(m_child_one && m_child_one->get_visible())
        ++nvis_children;
      if(m_child_two && m_child_two->get_visible())
        ++nvis_children;

      if(nvis_children <= 0)
        return;

      //Assign space to the children:
      Gtk::Allocation child_allocation_one;
      Gtk::Allocation child_allocation_two;

      //Place the first child at the top-left:
      child_allocation_one.set_x( allocation.get_x() );
      child_allocation_one.set_y( allocation.get_y() );

      //Make it take up the full width available:
      child_allocation_one.set_width( allocation.get_width() );

      if(m_child_one && m_child_one->get_visible())
      {
        //Divide the height equally among the visible children.
        child_allocation_one.set_height( allocation.get_height() / nvis_children);
        m_child_one->size_allocate(child_allocation_one);
      }
      else
        child_allocation_one.set_height(0);

      //Place the second child below the first child:
      child_allocation_two.set_x( allocation.get_x() );
      child_allocation_two.set_y( allocation.get_y() +
              child_allocation_one.get_height());

      //Make it take up the full width available:
      child_allocation_two.set_width( allocation.get_width() );

      //Make it take up the remaining height:
      child_allocation_two.set_height( allocation.get_height() -
              child_allocation_one.get_height());

      if(m_child_two && m_child_two->get_visible())
        m_child_two->size_allocate(child_allocation_two);
    }

    void MyContainer::forall_vfunc(gboolean, GtkCallback callback, gpointer callback_data)
    {
      if(m_child_one)
        callback(m_child_one->gobj(), callback_data);

      if(m_child_two)
        callback(m_child_two->gobj(), callback_data);
    }

    void MyContainer::on_add(Gtk::Widget* child)
    {
      if(!m_child_one)
      {
        m_child_one = child;
        m_child_one->set_parent(*this);
      }
      else if(!m_child_two)
      {
        m_child_two = child;
        m_child_two->set_parent(*this);
      }
    }

    void MyContainer::on_remove(Gtk::Widget* child)
    {
      if(child)
      {
        const bool visible = child->get_visible();
        bool found = false;

        if(child == m_child_one)
        {
          m_child_one = 0;
          found = true;
        }
        else if(child == m_child_two)
        {
          m_child_two = 0;
          found = true;
        }

        if(found)
        {
          child->unparent();

          if(visible)
            queue_resize();
        }
      }
    }

    GType MyContainer::child_type_vfunc() const
    {
      //If there is still space for one widget, then report the type of widget that
      //may be added.
      if(!m_child_one || !m_child_two)
        return Gtk::Widget::get_type();
      else
      {
        //No more widgets may be added.
        return G_TYPE_NONE;
      }
    }

### Widgets personalizados

By deriving directly from `Gtk::Widget` you can do all the drawing for your widget directly, instead of just arranging child widgets. For instance, a `Gtk::Label` draws the text of the label, but does not do this by using other widgets.

When deriving from `Gtk::Widget`, you should override the following virtual methods. The methods marked (optional) need not be overridden in all custom widgets. The base class's methods may be appropriate.

- `get_request_mode_vfunc()`: (optional) Return what `Gtk::SizeRequestMode` is preferred by the widget.

- `get_preferred_width_vfunc()`: Calculate the minimum and natural width of the widget.

- `get_preferred_height_vfunc()`: Calculate the minimum and natural height of the widget.

- `get_preferred_width_for_height_vfunc()`: Calculate the minimum and natural width of the widget, if it would be given the specified height.

- `get_preferred_height_for_width_vfunc()`: Calculate the minimum and natural height of the widget, if it would be given the specified width.

- `on_size_allocate()`: Position the widget, given the height and width that it has actually been given.

- `on_realize()`: Associate a `Gdk::Window` with the widget.

- `on_unrealize()`: (optional) Break the association with the `Gdk::Window`.

- `on_map()`: (opcional)

- `on_unmap()`: (opcional)

- `on_draw()`: Draw on the supplied `Cairo::Context`.

The first 6 methods in the previous table are also overridden in custom containers. They are briefly described in the Custom Containers section.

Most custom widgets need their own `Gdk::Window` to draw on. Then you can call `Gtk::Widget::set_has_window(true)` in your constructor. (This is the default value.) If you do not call `set_has_window(false)`, you must override `on_realize()` and call `Gtk::Widget::set_realized()` and `Gtk::Widget::set_window()` from there.

#### Ejemplo

This example implements a widget which draws a Penrose triangle.

##### Widget personalizado

Código fuente

File: `mywidget.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_CUSTOM_WIDGET_MYWIDGET_H
    #define GTKMM_CUSTOM_WIDGET_MYWIDGET_H

    #include <gtkmm/widget.h>
    #include <gtkmm/cssprovider.h>

    class MyWidget : public Gtk::Widget
    {
    public:
      MyWidget();
      virtual ~MyWidget();

    protected:

      //Overrides:
      virtual Gtk::SizeRequestMode get_request_mode_vfunc() const;
      virtual void get_preferred_width_vfunc(int& minimum_width, int& natural_width) const;
      virtual void get_preferred_height_for_width_vfunc(int width, int& minimum_height, int& natural_height) const;
      virtual void get_preferred_height_vfunc(int& minimum_height, int& natural_height) const;
      virtual void get_preferred_width_for_height_vfunc(int height, int& minimum_width, int& natural_width) const;
      virtual void on_size_allocate(Gtk::Allocation& allocation);
      virtual void on_map();
      virtual void on_unmap();
      virtual void on_realize();
      virtual void on_unrealize();
      virtual bool on_draw(const Cairo::RefPtr<Cairo::Context>& cr);

      Glib::RefPtr<Gdk::Window> m_refGdkWindow;
      Glib::RefPtr<Gtk::CssProvider> m_refStyleProvider;

      int m_scale;
    };

    #endif //GTKMM_CUSTOM_WIDGET_MYWIDGET_H

File: `examplewindow.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>
    #include "mywidget.h"

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      void on_button_quit();

      //Child widgets:
      Gtk::Box m_VBox;
      MyWidget m_MyWidget;
      Gtk::ButtonBox m_ButtonBox;
      Gtk::Button m_Button_Quit;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `mywidget.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "mywidget.h"
    #include <gdkmm/general.h>  // for cairo helper functions
    #include <iostream>
    //#include <gtk/gtkwidget.h> //For GTK_IS_WIDGET()
    #include <cstring>

    MyWidget::MyWidget() :
      //The GType name will actually be gtkmm__CustomObject_mywidget
      Glib::ObjectBase("mywidget"),
      Gtk::Widget(),
      m_scale(1000)
    {
      set_has_window(true);

      //This shows the GType name, which must be used in the CSS file.
      std::cout << "GType name: " << G_OBJECT_TYPE_NAME(gobj()) << std::endl;

      //This shows that the GType still derives from GtkWidget:
      //std::cout << "Gtype is a GtkWidget?:" << GTK_IS_WIDGET(gobj()) << std::endl;

      //Install a style so that an aspect of this widget may be themed via a CSS
      //style sheet file:
      gtk_widget_class_install_style_property(GTK_WIDGET_CLASS(
                  G_OBJECT_GET_CLASS(gobj())),
          g_param_spec_int("example_scale",
            "Scale of Example Drawing",
            "The scale to use when drawing. This is just a silly example.",
            G_MININT,
            G_MAXINT,
            500,
            G_PARAM_READABLE) );

      m_refStyleProvider = Gtk::CssProvider::create();
      Glib::RefPtr<Gtk::StyleContext> refStyleContext = get_style_context();
      refStyleContext->add_provider(m_refStyleProvider,
        GTK_STYLE_PROVIDER_PRIORITY_APPLICATION);

      try
      {
        m_refStyleProvider->load_from_path("custom_gtk.css");
      }
      catch(const Glib::Error& ex)
      {
        std::cerr << "Gtk::CssProvider::load_from_path() failed: " << ex.what() << std::endl;
      }
    }

    MyWidget::~MyWidget()
    {
    }

    Gtk::SizeRequestMode MyWidget::get_request_mode_vfunc() const
    {
      //Accept the default value supplied by the base class.
      return Gtk::Widget::get_request_mode_vfunc();
    }

    //Discover the total amount of minimum space and natural space needed by
    //this widget.
    //Let's make this simple example widget always need minimum 60 by 50 and
    //natural 100 by 70.
    void MyWidget::get_preferred_width_vfunc(int& minimum_width, int& natural_width) const
    {
      minimum_width = 60;
      natural_width = 100;
    }

    void MyWidget::get_preferred_height_for_width_vfunc(int /* width */,
       int& minimum_height, int& natural_height) const
    {
      minimum_height = 50;
      natural_height = 70;
    }

    void MyWidget::get_preferred_height_vfunc(int& minimum_height, int& natural_height) const
    {
      minimum_height = 50;
      natural_height = 70;
    }

    void MyWidget::get_preferred_width_for_height_vfunc(int /* height */,
       int& minimum_width, int& natural_width) const
    {
      minimum_width = 60;
      natural_width = 100;
    }

    void MyWidget::on_size_allocate(Gtk::Allocation& allocation)
    {
      //Do something with the space that we have actually been given:
      //(We will not be given heights or widths less than we have requested, though
      //we might get more)

      //Use the offered allocation for this container:
      set_allocation(allocation);

      if(m_refGdkWindow)
      {
        m_refGdkWindow->move_resize( allocation.get_x(), allocation.get_y(),
                allocation.get_width(), allocation.get_height() );
      }
    }

    void MyWidget::on_map()
    {
      //Call base class:
      Gtk::Widget::on_map();
    }

    void MyWidget::on_unmap()
    {
      //Call base class:
      Gtk::Widget::on_unmap();
    }

    void MyWidget::on_realize()
    {
      //Do not call base class Gtk::Widget::on_realize().
      //It's intended only for widgets that set_has_window(false).

      set_realized();

      //Get the themed style from the CSS file:
      get_style_property("example_scale", m_scale);
      std::cout << "m_scale (example_scale from the theme/css-file) is: "
          << m_scale << std::endl;

      if(!m_refGdkWindow)
      {
        //Create the GdkWindow:

        GdkWindowAttr attributes;
        memset(&attributes, 0, sizeof(attributes));

        Gtk::Allocation allocation = get_allocation();

        //Set initial position and size of the Gdk::Window:
        attributes.x = allocation.get_x();
        attributes.y = allocation.get_y();
        attributes.width = allocation.get_width();
        attributes.height = allocation.get_height();

        attributes.event_mask = get_events () | Gdk::EXPOSURE_MASK;
        attributes.window_type = GDK_WINDOW_CHILD;
        attributes.wclass = GDK_INPUT_OUTPUT;

        m_refGdkWindow = Gdk::Window::create(get_parent_window(), &attributes,
                GDK_WA_X | GDK_WA_Y);
        set_window(m_refGdkWindow);

        //set colors
        override_background_color(Gdk::RGBA("red"));
        override_color(Gdk::RGBA("blue"));

        //make the widget receive expose events
        m_refGdkWindow->set_user_data(gobj());
      }
    }

    void MyWidget::on_unrealize()
    {
      m_refGdkWindow.reset();

      //Call base class:
      Gtk::Widget::on_unrealize();
    }

    bool MyWidget::on_draw(const Cairo::RefPtr<Cairo::Context>& cr)
    {
      const double scale_x = (double)get_allocation().get_width() / m_scale;
      const double scale_y = (double)get_allocation().get_height() / m_scale;

      // paint the background
      Gdk::Cairo::set_source_rgba(cr, get_style_context()->get_background_color());
      cr->paint();

      // draw the foreground
      Gdk::Cairo::set_source_rgba(cr, get_style_context()->get_color());
      cr->move_to(155.*scale_x, 165.*scale_y);
      cr->line_to(155.*scale_x, 838.*scale_y);
      cr->line_to(265.*scale_x, 900.*scale_y);
      cr->line_to(849.*scale_x, 564.*scale_y);
      cr->line_to(849.*scale_x, 438.*scale_y);
      cr->line_to(265.*scale_x, 100.*scale_y);
      cr->line_to(155.*scale_x, 165.*scale_y);
      cr->move_to(265.*scale_x, 100.*scale_y);
      cr->line_to(265.*scale_x, 652.*scale_y);
      cr->line_to(526.*scale_x, 502.*scale_y);
      cr->move_to(369.*scale_x, 411.*scale_y);
      cr->line_to(633.*scale_x, 564.*scale_y);
      cr->move_to(369.*scale_x, 286.*scale_y);
      cr->line_to(369.*scale_x, 592.*scale_y);
      cr->move_to(369.*scale_x, 286.*scale_y);
      cr->line_to(849.*scale_x, 564.*scale_y);
      cr->move_to(633.*scale_x, 564.*scale_y);
      cr->line_to(155.*scale_x, 838.*scale_y);
      cr->stroke();

      return true;
    }

File: `examplewindow.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"

    ExampleWindow::ExampleWindow()
    : m_VBox(Gtk::ORIENTATION_VERTICAL),
      m_Button_Quit("Quit")
    {
      set_title("Custom Widget example");
      set_border_width(6);
      set_default_size(400, 200);

      add(m_VBox);
      m_VBox.pack_start(m_MyWidget, Gtk::PACK_EXPAND_WIDGET);
      m_MyWidget.show();

      m_VBox.pack_start(m_ButtonBox, Gtk::PACK_SHRINK);

      m_ButtonBox.pack_start(m_Button_Quit, Gtk::PACK_SHRINK);
      m_ButtonBox.set_border_width(6);
      m_ButtonBox.set_layout(Gtk::BUTTONBOX_END);
      m_Button_Quit.signal_clicked().connect( sigc::mem_fun(*this, &ExampleWindow::on_button_quit) );

      show_all_children();
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_button_quit()
    {
      hide();
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");

      ExampleWindow window;

      //Shows the window and returns when it is closed.
      return app->run(window);
    }

## Técnicas recomendadas

This section is simply a gathering of wisdom, general style guidelines and hints for creating gtkmm applications.

Use GNU autoconf and automake! They are your friends :) Automake examines C files, determines how they depend on each other, and generates a `Makefile` so the files can be compiled in the correct order. Autoconf permits automatic configuration of software installation, handling a large number of system quirks to increase portability..

Subclass Widgets to better organize your code. You should probably subclass your main `Window` at least. Then you can make your child Widgets and signal handlers members of that class.

Create your own signals instead of passing pointers around. Objects can communicate with each other via signals and signal handlers. This is much simpler than objects holding pointers to each other and calling each other's methods. gtkmm's classes uses special versions of `sigc::signal`, but you should use normal `sigc::signal`s, as described in the libsigc++ documentation.

### Tiempo de vida de la aplicación

Most applications will have only one `Window`, or only one main window. These applications can use the `Gtk::Application::run(Gtk::Window&)` overload. It shows the window and returns when the window has been hidden. This might happen when the user closes the window, or when your code decides to `hide()` the window. You can prevent the user from closing the window (for instance, if there are unsaved changes) by overriding `Gtk::Window::on_delete_event()`.

Most of our examples use this technique.

### Using a gtkmm widget

Our examples all tend to have the same structure. They follow these steps for using a `Widget`:

1. Declare a variable of the type of `Widget` you wish to use, generally as member variable of a derived container class. You could also declare a pointer to the widget type, and then create it with `new` in your code. Even when using the widget via a pointer, it's still probably best to make that pointer a member variable of a container class so that you can access it later.

2. Set the attributes of the widget. If the widget has no default constructor, then you will need to initialize the widget in the initalizer list of your container class's constructor.

3. Conecte las señales que quiere usar a los manejadores apropiados.

4. Pack the widget into a container using the appropriate call, e.g. `Gtk::Container::add()` or `pack_start()`.

5. Call `show()` to display the widget.

`Gtk::Widget::show()` lets gtkmm know that we have finished setting the attributes of the widget, and that it is ready to be displayed. You can use `Gtk::Widget::hide()` to make it disappear again. The order in which you show the widgets is not important, but we do suggest that you show the top-level window last; this way, the whole window will appear with its contents already drawn. Otherwise, the user will first see a blank window, into which the widgets will be gradually drawn.

## Contribuir

This document, like so much other great software out there, was created for free by volunteers. If you are at all knowledgeable about any aspect of gtkmm that does not already have documentation, please consider contributing to this document.

Ideally, we would like you to provide a patch to the `docs/tutorial/C/gtkmm-tutorial-in.xml` file. This file is currently in the `gtkmm-documentation` module in GNOME git.

If you do decide to contribute, please post your contribution to the gtkmm mailing list at <gtkmm-list@gnome.org>. Also, be aware that the entirety of this document is free, and any addition you provide must also be free. That is, people must be able to use any portion of your examples in their programs, and copies of this document (including your contribution) may be distributed freely.

## The RefPtr smartpointer

`Glib::RefPtr` is a smartpointer. Specifically, it is a reference-counting smartpointer. You might be familiar with `std::auto_ptr<>`, which is also a smartpointer, but `Glib::RefPtr<>` is much simpler, and more useful. We expect a future version of the C++ Standard Library to contain a reference-counting shared smartpointer, and a future version of gtkmm might possibly use that instead.

Referencia

Un puntero inteligente actúa como un puntero normal. Aquí hay algunos ejemplos.

### Copiado

You can copy `RefPtr`s, just like normal pointers. But unlike normal pointers, you don't need to worry about deleting the underlying instance.

    Glib::RefPtr<Gdk::Pixbuf> refPixbuf = Gdk::Pixbuf::create_from_file(filename);
    Glib::RefPtr<Gdk::Pixbuf> refPixbuf2 = refPixbuf;

Of course this means that you can store `RefPtr`s in standard containers, such as `std::vector` or `std::list`.

    std::list< Glib::RefPtr<Gdk::Pixbuf> > listPixbufs;
    Glib::RefPtr<Gdk::Pixbuf> refPixbuf = Gdk::Pixbuf::create_from_file(filename);
    listPixbufs.push_back(refPixbuf);

### Eliminar referencia

You can dereference a smartpointer with the -> operator, to call the methods of the underlying instance, just like a normal pointer.

    Glib::RefPtr<Gdk::Pixbuf> refPixbuf = Gdk::Pixbuf::create_from_file(filename);
    int width = refPixbuf->get_width();

Pero a diferencia de la mayoría de punteros inteligentes, no se puede utilizar el operador * para acceder a la instancia de base.

    Glib::RefPtr<Gdk::Pixbuf> refPixbuf = Gdk::Pixbuf::create_from_file(filename);
    Gdk::Pixbuf& underlying = *refPixbuf; //Syntax error - will not compile.

### Casting

You can cast `RefPtrs` to base types, just like normal pointers.

    Glib::RefPtr<Gtk::TreeStore> refStore = Gtk::TreeStore::create(columns);
    Glib::RefPtr<Gtk::TreeModel> refModel = refStore;

This means that any method which takes a `const Glib::RefPtr<BaseType>` argument can also take a `const Glib::RefPtr<DerivedType>`. The cast is implicit, just as it would be for a normal pointer.

You can also cast to a derived type, but the syntax is a little different than with a normal pointer.

    Glib::RefPtr<Gtk::TreeStore> refStore =
    Glib::RefPtr<Gtk::TreeStore>::cast_dynamic(refModel);
    Glib::RefPtr<Gtk::TreeStore> refStore2 =
    Glib::RefPtr<Gtk::TreeStore>::cast_static(refModel);

### Checking for null

Just like normal pointers, you can check whether a `RefPtr` points to anything.

    Glib::RefPtr<Gtk::TreeModel> refModel = m_TreeView.get_model();
    if(refModel)
    {
      int cols_count = refModel->get_n_columns();
      ...
    }

But unlike normal pointers, `RefPtr`s are automatically initialized to null so you don't need to remember to do that yourself.

### Constness

The use of the `const` keyword in C++ is not always clear. You might not realise that `const Something*` declares a pointer to a `const Something`, The pointer can be changed, but not the `Something` that it points to.

Therefore, the `RefPtr` equivalent of `Something*` for a method parameter is `const Glib::RefPtr<Something>&`, and the equivalent of `const Something*` is `const Glib::RefPtr<const Something>&`.

The `const ... &` around both is just for efficiency, like using `const std::string&` instead of `std::string` for a method parameter to avoid unnecessary copying.

## Señales

### Connecting signal handlers

gtkmm widget classes have signal accessor methods, such as `Gtk::Button::signal_clicked()`, which allow you to connect your signal handler. Thanks to the flexibility of libsigc++, the callback library used by gtkmm, the signal handler can be almost any kind of function, but you will probably want to use a class method. Among GTK+ C coders, these signal handlers are often named callbacks.

Here's an example of a signal handler being connected to a signal:

    #include <gtkmm/button.h>

    void on_button_clicked()
    {
        std::cout << "Hello World" << std::endl;
    }

    main()
    {
        Gtk::Button button("Hello World");
        button.signal_clicked().connect(sigc::ptr_fun(&on_button_clicked));
    }

There's rather a lot to think about in this (non-functional) code. First let's identify the parties involved:

- The signal handler is `on_button_clicked()`.

- We're hooking it up to the `Gtk::Button` object called `button`.

- When the Button emits its `clicked` signal, `on_button_clicked()` will be called.

Now let's look at the connection again:

        ...
        button.signal_clicked().connect(sigc::ptr_fun(&on_button_clicked));
        ...

Note that we don't pass a pointer to `on_button_clicked()` directly to the signal's `connect()` method. Instead, we call `sigc::ptr_fun()`, and pass the result to `connect()`.

`sigc::ptr_fun()` generates a `sigc::slot`. A slot is an object which looks and feels like a function, but is actually an object. These are also known as function objects, or functors. `sigc::ptr_fun()` generates a slot for a standalone function or static method. `sigc::mem_fun()` generates a slot for a member method of a particular instance.

Here's a slightly larger example of slots in action:

    void on_button_clicked();

    class some_class
    {
        void on_button_clicked();
    };

    some_class some_object;

    main()
    {
        Gtk::Button button;
        button.signal_clicked().connect( sigc::ptr_fun(&on_button_clicked) );
        button.signal_clicked().connect( sigc::mem_fun(some_object, &some_class::on_button_clicked) );
    }

The first call to `connect()` is just like the one we saw last time; nothing new here.

The next is more interesting. `sigc::mem_fun()` is called with two arguments. The first argument is `some_object`, which is the object that our new slot will be pointing at. The second argument is a pointer to one of its methods. This particular version of `sigc::mem_fun()` creates a slot which will, when "called", call the pointed-to method of the specified object, in this case `some_object.on_button_clicked()`.

Another thing to note about this example is that we made the call to `connect()` twice for the same signal object. This is perfectly fine - when the button is clicked, both signal handlers will be called.

We just told you that the button's `clicked` signal is expecting to call a method with no arguments. All signals have requirements like this - you can't hook a function with two arguments to a signal expecting none (unless you use an adapter, such as `sigc::bind()`, of course). Therefore, it's important to know what type of signal handler you'll be expected to connect to a given signal.

### Writing signal handlers

To find out what type of signal handler you can connect to a signal, you can look it up in the reference documentation or the header file. Here's an example of a signal declaration you might see in the gtkmm headers:

    Glib::SignalProxy1<bool, Gtk::DirectionType> signal_focus()

Other than the signal's name (`focus`), two things are important to note here: the number following the word `SignalProxy` at the beginning (1, in this case), and the types in the list (`bool` and `Gtk::DirectionType`). The number indicates how many arguments the signal handler should have; the first type, `bool`, is the type that the signal handler should return; and the next type, `Gtk::DirectionType`, is the type of this signal's first, and only, argument. By looking at the reference documentation, you can see the names of the arguments too.

The same principles apply for signals which have more arguments. Here's one with three (taken from `<gtkmm/editable.h>`):

    Glib::SignalProxy3<void, const Glib::ustring&, int, int*> signal_insert_text()

It follows the same form. The number 3 at the end of the type's name indicates that our signal handler will need three arguments. The first type in the type list is `void`, so that should be our signal handler's return type. The following three types are the argument types, in order. Our signal handler's prototype could look like this:

    void on_insert_text(const Glib::ustring& text, int length, int* position);

### Disconnecting signal handlers

Let's take another look at a Signal's `connect` method:

    sigc::signal<void,int>::iterator signal<void,int>::connect( const sigc::slot<void,int>& );

Notice that the return value is of type `sigc::signal<void,int>::iterator`. This can be implicitely converted into a `sigc::connection` which in turn can be used to control the connection. By keeping a connection object you can disconnect its associated signal handler using the method `sigc::connection::disconnect()`.

### Overriding default signal handlers

So far we've told you to perform actions in response to button-presses and the like by handling signals. That's certainly a good way to do things, but it's not the only way.

Instead of laboriously connecting signal handlers to signals, you can simply make a new class which inherits from a widget - say, a Button - and then override the default signal handler, such as Button::on_clicked(). This can be a lot simpler than hooking up signal handlers for everything.

Subclassing isn't always the best way to accomplish things. It is only useful when you want the widget to handle its own signal by itself. If you want some other class to handle the signal then you'll need to connect a separate handler. This is even more true if you want several objects to handle the same signal, or if you want one signal handler to respond to the same signal from different objects.

gtkmm classes are designed with overriding in mind; they contain virtual member methods specifically intended to be overridden.

Let's look at an example of overriding:

    #include <gtkmm/button.h>

    class OverriddenButton : public Gtk::Button
    {
    protected:
        virtual void on_clicked();
    }

    void OverriddenButton::on_clicked()
    {
        std::cout << "Hello World" << std::endl;

        // call the base class's version of the method:
        Gtk::Button::on_clicked();
    }

Here we define a new class called `OverriddenButton`, which inherits from `Gtk::Button`. The only thing we change is the `on_clicked()` method, which is called whenever `Gtk::Button` emits the `clicked` signal. This method prints "Hello World" to `stdout`, and then calls the original, overridden method, to let `Gtk::Button` do what it would have done had we not overridden.

You don't always need to call the parent's method; there are times when you might not want to. Note that we called the parent method after writing "Hello World", but we could have called it before. In this simple example, it hardly matters much, but there are times when it will. With signals, it's not quite so easy to change details like this, and you can do something here which you can't do at all with connected signal handlers: you can call the parent method in the middle of your custom code.

### Binding extra arguments

If you use one signal handler to catch the same signal from several widgets, you might like that signal handler to receive some extra information. For instance, you might want to know which button was clicked. You can do this with `sigc::bind()`. Here's some code from the helloworld2 example, which you will encounter later.

    m_button1.signal_clicked().connect( sigc::bind<Glib::ustring>( sigc::mem_fun(*this, &HelloWorld::on_button_clicked), "button 1") );

This says that we want the signal to send an extra `Glib::ustring` argument to the signal handler, and that the value of that argument should be "button 1". Of course we will need to add that extra argument to the declaration of our signal handler:

    virtual void on_button_clicked(Glib::ustring data);

Of course, a normal "clicked" signal handler would have no arguments.

`sigc::bind()` is not commonly used, but you might find it helpful sometimes. If you are familiar with GTK+ programming then you have probably noticed that this is similar to the extra `gpointer data` arguments which all GTK+ callbacks have. This is generally overused in GTK+ to pass information that should be stored as member data in a derived widget, but widget derivation is very difficult in C. We have far less need of this hack in gtkmm.

### X Event signals

The `Widget` class has some special signals which correspond to the underlying X-Windows events. These are suffixed by `_event`; for instance, `Widget::signal_button_pressed_event()`.

You might occasionally find it useful to handle X events when there's something you can't accomplish with normal signals. `Gtk::Button`, for example, does not send mouse-pointer coordinates with its `clicked` signal, but you could handle `button_pressed_event` if you needed this information. X events are also often used to handle key-presses.

These signals behave slightly differently. The value returned from the signal handler indicates whether it has fully "handled" the event. If the value is `false` then gtkmm will pass the event on to the next signal handler. If the value is `true` then no other signal handlers will need to be called.

Handling an X event doesn't affect the Widget's other signals. If you handle `button_pressed_event` for `Gtk::Button`, you'll still be able to get the `clicked` signal. They are emitted at (nearly) the same time.

Note also that not all widgets receive all X events by default. To receive additional X events, you can use `Gtk::Widget::set_events()` before showing the widget, or `Gtk::Widget::add_events()` after showing the widget. However, some widgets must first be placed inside an `EventBox` widget. See the Widgets Without X-Windows chapter.

Un ejemplo sencillo:

    bool on_button_press(GdkEventButton* event);
    Gtk::Button button("label");
    button.signal_button_press_event().connect( sigc::ptr_fun(&on_button_press) );

When the mouse is over the button and a mouse button is pressed, `on_button_press()` will be called.

`GdkEventButton` is a structure containing the event's parameters, such as the coordinates of the mouse pointer at the time the button was pressed. There are several different types of `GdkEvent` structures for the various events.

#### Signal Handler sequence

By default, your signal handlers are called after any previously-connected signal handlers. However, this can be a problem with the X Event signals. For instance, the existing signal handlers, or the default signal handler, might return `true` to stop other signal handlers from being called. To specify that your signal handler should be called before the other signal handlers, so that it will always be called, you can specify `false` for the optional `after` parameter. For instance,

    button.signal_button_press_event().connect( sigc::ptr_fun(&on_mywindow_button_press), false );

The event is delivered first to the widget the event occurred in. If all signal handlers in that widget return `false` (indicating that the event has not been handled), then the signal will be propagated to the parent widget and emitted there. This continues all the way up to the top-level widget if no one handles the event.

## Creating your own signals

Now that you've seen signals and signal handlers in gtkmm, you might like to use the same technique to allow interaction between your own classes. That's actually very simple by using the libsigc++ library directly.

This isn't purely a gtkmm or GUI issue. gtkmm uses libsigc++ to implement its proxy wrappers for the GTK+ signal system, but for new, non-GTK+ signals, you can create pure C++ signals, using the `sigc::signal<>` template.

For instance, to create a signal that sends 2 parameters, a `bool` and an `int`, just declare a `sigc::signal`, like so:

    sigc::signal<void, bool, int> signal_something;

You could just declare that signal as a public member variable, but some people find that distasteful and prefer to make it available via an accessor method, like so:

    class Server
    {
    public:
      //signal accessor:
      typedef sigc::signal<void, bool, int> type_signal_something;
      type_signal_something signal_something();

    protected:
      type_signal_something m_signal_something;
    };

    Server::type_signal_something Server::signal_something()
    {
      return m_signal_something;
    }

You can then connect to the signal using the same syntax used when connecting to gtkmm signals. For instance,

    server.signal_something().connect(
      sigc::mem_fun(client, &Client::on_server_something) );

### Ejemplo

This is a full working example that defines and uses custom signal.

Código fuente

File: `client.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLE_CLIENT_H
    #define GTKMM_EXAMPLE_CLIENT_H

    #include <sigc++/sigc++.h>

    //Client must inherit from sigc::trackable.
    //because libsigc++ needs to keep track of the lifetime of signal handlers.
    class Client : public sigc::trackable
    {
    public:
      Client();
      virtual ~Client();

      //Signal handler:
      void on_server_something(bool a, int b);
    };

    #endif //GTKMM_EXAMPLE_CLIENT_H

File: `server.h` (For use with gtkmm 3, not gtkmm 2)

    #ifndef GTKMM_EXAMPLE_SERVER_H
    #define GTKMM_EXAMPLE_SERVER_H

    #include <sigc++/sigc++.h>

    class Server
    {
    public:
      Server();
      virtual ~Server();

      void do_something();

      //signal accessor:
      typedef sigc::signal<void, bool, int> type_signal_something;
      type_signal_something signal_something();

    protected:
      type_signal_something m_signal_something;
    };

    #endif //GTKMM_EXAMPLE_SERVER_H

File: `server.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "server.h"
    #include <iostream>

    Server::Server()
    {
    }

    Server::~Server()
    {
    }

    Server::type_signal_something Server::signal_something()
    {
      return m_signal_something;
    }

    void Server::do_something()
    {
      m_signal_something.emit(false, 5);
    }

File: `main.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "server.h"
    #include "client.h"
    #include <iostream>

    int main(int, char**)
    {
      Server server;
      Client client;

      //Connect a Server signal to the signal handler in Client.
      server.signal_something().connect(sigc::mem_fun(client,
                  &Client::on_server_something) );

      std::cout << "Before Server::do_something()" << std::endl;

      //Tell the server to do something that will eventually cause it to emit the
      //"something" signal.
      server.do_something();    // Client::on_server_something() will run before
                                // Server::do_something() has completed.

      std::cout << "After Server::do_something()" << std::endl;

      return 0;
    }

File: `client.cc` (For use with gtkmm 3, not gtkmm 2)

    #include "client.h"
    #include <iostream>

    Client::Client()
    {
    }

    Client::~Client()
    {
    }

    void Client::on_server_something(bool a, int b)
    {
      std::cout << "Client::on_server_something() called with these parameters: "
          << a << ", " << b << std::endl;
    }

## Comparison with other signalling systems

(An aside: GTK+ calls this scheme "signalling"; the sharp-eyed reader with GUI toolkit experience will note that this same design is often seen under the name of "broadcaster-listener" (e.g., in Metrowerks' PowerPlant framework for the Macintosh). It works in much the same way: one sets up `broadcasters`, and then connects `listeners` to them; the broadcaster keeps a list of the objects listening to it, and when someone gives the broadcaster a message, it calls all of its objects in its list with the message. In gtkmm, signal objects play the role of broadcasters, and slots play the role of listeners - sort of. More on this later.)

gtkmm signal handlers are strongly-typed, whereas GTK+ C code allows you to connect a callback with the wrong number and type of arguments, leading to a segfault at runtime. And, unlike Qt, gtkmm achieves this without modifying the C++ language.

Re. Overriding signal handlers: You can do this in the straight-C world of GTK+ too; that's what GTK's object system is for. But in GTK+, you have to go through some complicated procedures to get object-oriented features like inheritance and overloading. In C++, it's simple, since those features are supported in the language itself; you can let the compiler do the dirty work.

This is one of the places where the beauty of C++ really comes out. One wouldn't think of subclassing a GTK+ widget simply to override its action method; it's just too much trouble. In GTK+, you almost always use signals to get things done, unless you're writing a new widget. But because overriding methods is so easy in C++, it's entirely practical - and sensible - to subclass a button for that purpose.

## gtkmm y Win32

One of the major advantages of gtkmm is that it is crossplatform. gtkmm programs written on other platforms such as GNU/Linux can generally be transferred to Windows (and vice versa) with few modifications to the source.

gtkmm currently works with the MingW/GCC3.4 compiler and Microsoft Visual C++ 2005 or later (including the freely available express editions) on the Windows platform. There is an installer available for gtkmm on Microsoft Windows. Refer to http://live.gnome.org/gtkmm/MSWindows for instructions how to use it.

### Construir aplicaciones gtkmm en Win32

Consulte http://live.gnome.org/gtkmm/MSWindows/BuildingGtkmm para obtener instrucciones sobre cómo construir gtkmm en Windows.

## Trabajar con el código fuente de gtkmm

If you are interested in helping out with the development of gtkmm, or fixing a bug in gtkmm, you'll probably need to build the development version of gtkmm. However, you should not install a development version over your stable version. Instead, you should install it alongside your existing gtkmm installation, in a separate path.

The easiest way to do this is using jhbuild. jhbuild is a program that makes building GNOME software much easier by calculating dependencies and building things in the correct order. This section will give a brief explanation of how to set up jhbuild to build and install gtkmm from the source repository (git). For up-to-date information on jhbuild, please refer to the jhbuild manual. If you need assistance using jhbuild, you should ask for help on the gnome-love mailing list.

Note that to build gtkmm from git, you'll often need to build all of its dependencies from git as well. jhbuild makes this easier than it would normally be, but it will take quite a while to build and install them all. You will probably encounter build problems, though these will usually be corrected quickly if you report them.

### Configurar JHBuild

To set up jhbuild, follow the basic installation instructions from the jhbuild manual. After you have installed jhbuild, you should copy the sample jhbuild configuration file into your home directory by executing the following command from the jhbuild directory:

    $ cp examples/sample.jhbuildrc ~/.jhbuildrc

The gtkmm module is defined in the `gnome-suites-core-deps-3.x.modules` moduleset, so edit your `.jhbuildrc` file and set your moduleset setting to the latest version e.g. like so:

    moduleset = 'gnome-suites-core-deps-3.4'

After setting the correct moduleset, you need to tell jhbuild which module or modules to build. To build gtkmm and all of its dependencies, set `modules` like so:

    modules = [ 'gtkmm' ]

You can build several modules by setting the `modules` variable to a meta-package, e.g. `meta-gnome-core`, or listing more than one module name. The `modules` variable specifies which modules that will be built when you don't explicitly specify anything on the command line. You can always build a different moduleset later by specifying it on the commandline (e.g. `jhbuild build gtkmm`).

#### Establecer un prefijo

By default, jhbuild's configuration is configured to install all software built with jhbuild under the `/opt/gnome` prefix. You can choose a different prefix, but it is recommended that you keep this prefix different from other software that you've installed (don't set it to `/usr`!) If you've followed the jhbuild instructions then this prefix belongs to your user, so you don't need to run jhbuild as `root`.

When you downloaded jhbuild from the git repository, you got a number of `.modules` files, specifying dependencies between modules. By default jhbuild does not use the downloaded versions of these files, but reads the latest versions in the git repository. This is usually what you want. If you don't want it, use the `use_local_modulesets` variable in `.jhbuildrc`.

### Installing and Using the git version of gtkmm

Once you've configured jhbuild as described above, building gtkmm should be relatively straightforward. The first time you run jhbuild, you should run the following sequence of commands to ensure that jhbuild has the required tools and verify that it is set up correctly:

    $ jhbuild bootstrap
    $ jhbuild sanitycheck

#### Instalar gtkmm con jhbuild

If everything worked correctly, you should be able to build gtkmm and all of its dependencies from git by executing `jhbuild build` (or, if you didn't specify gtkmm in the `modules` variable, with the command `jhbuild build gtkmm`).

This command will build and install a series of modules and will probably take quite a long time the first time through. After the first time, however, it should go quite a bit faster since it only needs to rebuild files that changed since the last build. Alternatively, after you've built and installed gtkmm the first time, you can rebuild gtkmm by itself (without rebuilding all of its dependencies) with the command `jhbuild buildone gtkmm`.

#### Using the git version of gtkmm

After you've installed the git version of gtkmm, you're ready to start using and experimenting with it. In order to use the new version of gtkmm you've just installed, you need to set some environment variables so that your `configure` script knows where to find the new libraries. Fortunately, jhbuild offers an easy solution to this problem. Executing the command `jhbuild shell` will start a new shell with all of the correct environment variables set. Now if you re-configure and build your project just as you usually do, it should link against the newly installed libraries. To return to your previous environment, simply exit the jhbuild shell.

Once you've built your software, you'll need to run your program within the jhbuild environment as well. To do this, you can again use the `jhbuild shell` command to start a new shell with the jhbuild environment set up. Alternatively, you can execute a one-off command in the jhbuild environment using the following command: `jhbuild run command-name`. In this case, the command will be run with the correct environment variables set, but will return to your previous environment after the program exits.

## Envolver bibliotecas C con gmmproc

gtkmm uses the `gmmproc` tool to generate most of its source code, using .defs files that define the APIs of `GObject`-based libraries. So it's quite easy to create additional gtkmm-style wrappers of other glib/GObject-based libraries.

This involves a variety of tools, some of them crufty, but it does at least work, and has been used successfully by several projects.

### La estructura de construcción

Generation of the source code for a gtkmm-style wrapper API requires use of tools such as `gmmproc` and `generate_wrap_init.pl`. In theory you could write your own build files to use these appropriately, but a much better option is to make use of the build infrastructure provided by the mm-common module. To get started, it helps a lot to pick an existing binding module as an example to look at.

For instance, let's pretend that we are wrapping a C library called libexample. It provides a `GObject`-based API with types named, for instance, `ExampleThing` and `ExampleStuff`.

#### Copiar el esqueleto del proyecto

Typically our wrapper library would be called libsomethingmm. We can start by copying the skeleton source tree from the mm-common module.

      $ git clone git://git.gnome.org/mm-common
      $ cp -a mm-common/skeletonmm libsomethingmm

This provides a directory structure for the source .hg and .ccg files and the generated .h and .cc files, with `filelist.am` Automake include files that can specify the various files in use, in terms of generic Automake variables. The directory structure usually looks like this, after we have renamed the directories appropriately:

- `libsomethingmm`: The top-level directory.

  - `libsomething`: Contains the main include file and the pkg-config .pc file.

    - `src`: Contains .hg and .ccg source files.

    - `libsomethingmm`: Contains generated and hand-written .h and .cc files.

      - `private`: Contains generated `*_p.h` files.

As well as renaming the directories, we should rename some of the source files. For instance:

    $ for f in $(find libsomethingmm -depth -name '*skeleton*'); do \
        d="${f%/*}"; b="${f##*/}"; mv "$f" "$d/${b//skeleton/libsomething}"; \
      done

A number of the skeleton files must still be filled in with project-specific content later.

Tenga en cuenta que los archivos que terminan en `.in` se utilizan para generar archivos con el mismo nombre pero sin el sufijo `.in`, mediante la sustitución de algunas variables con valores reales durante la fase de configuración.

#### Modifying build files

Now we edit the files to adapt them to our needs. You might prefer to use a multiple-file search-replace utility for this, such as `regexxer`. Note that nearly all of the files provided with the skeleton source tree contain placeholder text. Thus, the substitutions should be performed globally, and not be limited to the Automake and Autoconf files.

All mentions of `skeleton` should be replaced by the correct name of the C library you are wrapping, such as "something" or "libsomething". In the same manner, all instances of `SKELETON` should be replaced by "SOMETHING" or "LIBSOMETHING", and all occurrences of `Skeleton` changed to "Something".

Likewise, replace all instances of `Joe Hacker` by the name of the intended copyright holder, which is probably you. Do the same for the `joe@example.com` email address.

##### configure.ac

In `configure.ac`,

- The `AC_CONFIG_SRCDIR()` line must mention a file in our source tree. We can edit this later if we don't yet know the names of any of the files that we will create.

- It is common for binding modules to track the version number of the library they are wrapping. So, for instance, if the C library is at version 1.23.4, then the initial version of the binding module would be 1.23.0. However, avoid starting with an even minor version number as that usually indicates a stable release.

- The `AC_CONFIG_HEADERS()` line is used to generate two or more configuration header files. The first header file in the list contains all configuration macros which are set during the configure run. The remaining headers in the list contain only a subset of configuration macros and their corresponding `configh.h.in` file will not be autogenerated. The reason for this separation is that the namespaced configuration headers are installed with your library and define publically visible macros.

- The `AC_SUBST([SOMETHINGMM_MODULES], ['...'])` line may need to be modified to check for the correct dependencies.

- The `AC_CONFIG_FILES()` block must mention the correct directory names, as described above.

##### Archivos Makefile.am

Next we must adapt the various `Makefile.am` files:

- In `skeleton/src/Makefile.am` we must mention the correct values for the generic variables that are used elsewhere in the build system:

  `binding_name`

- El nombre de la biblioteca, por ejemplo libalgomm.

`wrap_init_flags`

- Additional command-line flags passed to the `generate_wrap_init.pl` script, such as the C++ namespace and the parent directory prefix of include files.

- In `skeleton/skeletonmm/Makefile.am` we must mention the correct values for the generic variables that are used elsewhere in the build system:

  `lib_LTLIBRARIES`

- This variable must mention the correct library name, and this library name must be used to form the `_SOURCES`, `_LDFLAGS`, and `_LIBADD` variable names. It is permissible to use variables substituted by `configure` like `@SOMETHINGMM_API_VERSION@` as part of the variable names.

`AM_CPPFLAGS`

- The command line options passed to the C preprocessor.

`AM_CXXFLAGS`

- The command line options passed to the C++ compiler.

##### Crear archivos .hg y .ccg

We should now create our first `.hg` and `.ccg` files, to wrap one of the objects in the C library. One pair of example source files already exists: `skeleton.ccg` and `skeleton.hg`. Create copies of these files as necessary.

We must mention all of our `.hg` and `.ccg` files in the `skeleton/src/filelist.am` file, typically in the `files_hg` variable.

Any additional non-generated `.h` and `.cc` source files may be placed in `skeleton/skeletonmm/` and listed in `skeleton/skeletonmm/filelist.am`, typically in the `files_extra_h` and `files_extra_cc` variables.

In the .hg and .ccg files section you can learn about the syntax used in these files.

### Generar los archivos .defs.

The `.defs` files are text files, in a lisp format, that describe the API of a C library, including its

- objects (GObjects, widgets, interfaces, boxed-types and plain structs)

- funciones

- enums

- signals

- propiedades

- vfuncs

At the moment, we have separate tools for generating different parts of these `.defs`, so we split them up into separate files. For instance, in the `gtk/src` directory of the gtkmm sources, you will find these files:

`gtk.defs`

- Includes the other files.

`gtk_methods.defs`

- Objetos y funciones.

`gtk_enums.defs`

- Enumerations.

`gtk_signals.defs`

- Señales y propiedades.

`gtk_vfuncs.defs`

- vfuncs (function pointer member fields in structs), written by hand.

#### Generating the methods .defs

This `.defs` file describes objects and their functions. It is generated by the `h2def.py` script which you can find in glibmm's `tools/defs_gen` directory. For instance,

    $ ./h2def.py /usr/include/gtk-3.0/gtk/*.h > gtk_methods.defs

#### Generating the enums .defs

This `.defs` file describes enum types and their possible values. It is generated by the `enum.pl` script which you can find in glibmm's `tools` directory. For instance,

    $ ./enum.pl /usr/include/gtk-3.0/gtk/*.h > gtk_enums.defs

#### Generating the signals and properties .defs

This `.defs` file describes signals and properties. It is generated by the special `extra_defs` utility that is in every wrapping project, such as `gtkmm/tools/extra_defs_gen/`. For instance

    $ cd tools/extra_defs_gen
    $ ./generate_extra_defs > gtk_signals.defs

You must edit the source code of your own `generate_extra_defs` tool in order to generate the `.defs` for the GObject C types that you wish to wrap. In the skeleton source tree, the source file is named `codegen/extradefs/generate_extra_defs_skeleton.cc`. If not done so already, the file should be renamed, with the basename of your new binding substituted for the `skeleton` placeholder. The `codegen/Makefile.am` file should also mention the new source filename.

Then edit the `.cc` file to specify the correct types. For instance, your `main()` function might look like this:

    #include <libsomething.h>

    int main(int, char**)
    {
      something_init();

      std::cout << get_defs(EXAMPLE_TYPE_SOMETHING)
                << get_defs(EXAMPLE_TYPE_THING);
      return 0;
    }

#### Writing the vfuncs .defs

This `.defs` file describes virtual functions (vfuncs). It must be written by hand. There is no skeleton to start from. You can look at gtkmm's `gtk/src/gtk_vfuncs.defs` file.

### Los archivos .hg y .ccg

The .hg and .ccg source files are very much like .h and .cc C++ source files, but they contain extra macros, such as `_CLASS_GOBJECT()` and `_WRAP_METHOD()`, from which `gmmproc` generates appropriate C++ source code, usually at the same position in the header. Any additional C++ source code will be copied verbatim into the corresponding .h or .cc file.

A .hg file will typically include some headers and then declare a class, using some macros to add API or behaviour to this class. For instance, gtkmm's `button.hg` looks roughly like this:

    #include <gtkmm/bin.h>
    #include <gtkmm/activatable.h>
    #include <gtkmm/stockid.h>
    _DEFS(gtkmm,gtk)
    _PINCLUDE(gtkmm/private/bin_p.h)

    namespace Gtk
    {

    class Button
      : public Bin,
        public Activatable
    {
      _CLASS_GTKOBJECT(Button,GtkButton,GTK_BUTTON,Gtk::Bin,GtkBin)
      _IMPLEMENTS_INTERFACE(Activatable)
    public:

      _CTOR_DEFAULT
      explicit Button(const Glib::ustring& label, bool mnemonic = false);
      explicit Button(const StockID& stock_id);

      _WRAP_METHOD(void set_label(const Glib::ustring& label), gtk_button_set_label)

      ...

      _WRAP_SIGNAL(void clicked(), "clicked")

      ...

      _WRAP_PROPERTY("label", Glib::ustring)
    };

    } // namespace Gtk

The macros in this example do the following:

`_DEFS()`

- Specifies the destination directory for generated sources, and the name of the main .defs file that `gmmproc` should parse.

`_PINCLUDE()`

- Tells `gmmproc` to include a header from the generated private/button_p.h file.

`_CLASS_GTKOBJECT()`

- Tells `gmmproc` to add some typedefs, constructors, and standard methods to this class, as appropriate when wrapping a widget.

`_IMPLEMENTS_INTERFACE()`

- Tells `gmmproc` to add initialization code for the interface.

`_CTOR_DEFAULT`

- Añadir un constructor predeterminado.

`_WRAP_METHOD()`, `_WRAP_SIGNAL()`, and `_WRAP_PROPERTY()`

- Añadir métodos para envolver las partes de la API de C.

The .h and .cc files will be generated from the .hg and .ccg files by processing them with `gmmproc` like so, though this happens automatically when using the above build structure:

    $ cd gtk/src
    $ /usr/lib/glibmm-2.4/proc/gmmproc -I ../../tools/m4 --defs . button . ./../gtkmm

Notice that we provided `gmmproc` with the path to the .m4 convert files, the path to the .defs file, the name of a .hg file, the source directory, and the destination directory.

You should avoid including the C header from your C++ header, to avoid polluting the global namespace, and to avoid exporting unnecessary public API. But you will need to include the necessary C headers from your .ccg file.

The macros are explained in more detail in the following sections.

#### Conversiones m4

The macros that you use in the .hg and .ccg files often need to know how to convert a C++ type to a C type, or vice-versa. gmmproc takes this information from an .m4 file in your `tools/m4/` directory. This allows it to call a C function in the implementation of your C++ method, passing the appropriate parameters to that C functon. For instance, this tells gmmproc how to convert a GtkTreeView pointer to a Gtk::TreeView pointer:

    _CONVERSION(`GtkTreeView*',`TreeView*',`Glib::wrap($3)')

`$3` will be replaced by the parameter name when this conversion is used by gmmproc.

Some extra macros make this easier and consistent. Look in gtkmm's .m4 files for examples. For instance:

    _CONVERSION(`PrintSettings&',`GtkPrintSettings*',__FR2P)
    _CONVERSION(`const PrintSettings&',`GtkPrintSettings*',__FCR2P)
    _CONVERSION(`const Glib::RefPtr<Printer>&',`GtkPrinter*',__CONVERT_REFPTR_TO_P($3))

#### inicializaciones de m4

Often when wrapping methods, it is desirable to store the return of the C function in what is called an output parameter. In this case, the C++ method returns `void` but an output parameter in which to store the value of the C function is included in the argument list of the C++ method. gmmproc allows such functionality, but appropriate inizialization macros must be included to tell gmmproc how to initialize the C++ parameter from the return of the C function.

For example, if there was a C function that returned a `GtkWidget*` and for some reason, instead of having the C++ method also return the widget, it was desirable to have the C++ method place the widget in a specified output parameter, an initialization macro such as the following would be necessary:

    _INITIALIZATION(`Gtk::Widget&',`GtkWidget*',`$3 = Glib::wrap($4)')

`$3` will be replaced by the output parameter name of the C++ method and `$4` will be replaced by the return of the C function when this initialization is used by gmmproc. For convenience, `$1` will also be replaced by the C++ type without the ampersand (&) and `$2` will be replaced by the C type.

#### Class macros

The class macro declares the class itself and its relationship with the underlying C type. It generates some internal constructors, the member `gobject_`, typedefs, the `gobj()` accessors, type registration, and the `Glib::wrap()` method, among other things.

Other macros, such as `_WRAP_METHOD()` and `_WRAP_SIGNAL()` may only be used after a call to a `_CLASS_*` macro.

##### _CLASS_GOBJECT

This macro declares a wrapper for a type that is derived from `GObject`, but whose wrapper is not derived from `Gtk::Object`.

`_CLASS_GOBJECT( C++ class, C class, C casting macro, C++ base class, C base class )`

For instance, from `accelgroup.hg`:

    _CLASS_GOBJECT(AccelGroup, GtkAccelGroup, GTK_ACCEL_GROUP, Glib::Object, GObject)

##### _CLASS_GTKOBJECT

This macro declares a wrapper for a type whose wrapper is derived from `Gtk::Object`, such as a widget or dialog.

`_CLASS_GTKOBJECT( C++ class, C class, C casting macro, C++ base class, C base class )`

For instance, from `button.hg`:

    _CLASS_GTKOBJECT(Button, GtkButton, GTK_BUTTON, Gtk::Bin, GtkBin)

You will typically use this macro when the class already derives from Gtk::Object. For instance, you will use it when wrapping a GTK+ Widget, because Gtk::Widget derives from Gtk::Object.

You might also derive non-widget classes from Gtk::Object so they can be used without `Glib::RefPtr`. For isntance, they could then be instantiated with `Gtk::manage()` or on the stack as a member variable. This is convenient, but you should use this only when you are sure that true reference-counting is not needed. We consider it useful for widgets.

##### _CLASS_BOXEDTYPE

This macro declares a wrapper for a non-`GObject` struct, registered with `g_boxed_type_register_static()`.

`_CLASS_BOXEDTYPE( C++ class, C class, new function, copy function, free function )`

For instance, for `Gdk::Color`:

    _CLASS_BOXEDTYPE(Color, GdkColor, NONE, gdk_color_copy, gdk_color_free)

##### _CLASS_BOXEDTYPE_STATIC

This macro declares a wrapper for a simple assignable struct such as `GdkRectangle`. It is similar to `_CLASS_BOXEDTYPE`, but the C struct is not allocated dynamically.

`_CLASS_BOXEDTYPE_STATIC( C++ class, C class )`

For instance, for `Gdk::Rectangle`:

    _CLASS_BOXEDTYPE_STATIC(Rectangle, GdkRectangle)

##### _CLASS_OPAQUE_COPYABLE

This macro declares a wrapper for an opaque struct that has copy and free functions. The new, copy and free functions will be used to instantiate the default constructor, copy constructor and destructor.

`_CLASS_OPAQUE_COPYABLE( C++ class, C class, new function, copy function, free function )`

Por ejemplo, desde `stockitem.hg`:

    _CLASS_OPAQUE_COPYABLE(StockItem, GtkStockItem, NONE, gtk_stock_item_copy, gtk_stock_item_free)

##### _CLASS_OPAQUE_REFCOUNTED

This macro declares a wrapper for a reference-counted opaque struct. The C++ wrapper cannot be directly instantiated and can only be used with `Glib::RefPtr`.

`_CLASS_OPAQUE_REFCOUNTED( C++ class, C class, new function, ref function, unref function )`

For instance, for `Pango::Coverage`:

    _CLASS_OPAQUE_REFCOUNTED(Coverage, PangoCoverage, pango_coverage_new, pango_coverage_ref, pango_coverage_unref)

##### _CLASS_GENERIC

This macro can be used to wrap structs which don't fit into any specialized category.

`_CLASS_GENERIC( C++ class, C class )`

For instance, for `Pango::AttrIter`:

    _CLASS_GENERIC(AttrIter, PangoAttrIterator)

##### _CLASS_INTERFACE

This macro declares a wrapper for a type that is derived from `GTypeInterface`.

`_CLASS_INTERFACE( C++ class, C class, C casting macro, C interface struct, Base C++ class (optional), Base C class (optional) )`

For instance, from `celleditable.hg`:

    _CLASS_INTERFACE(CellEditable, GtkCellEditable, GTK_CELL_EDITABLE, GtkCellEditableIface)

Two extra parameters are optional, for the case that the interface derives from another interface, which should be the case when the GInterface has another GInterface as a prerequisitite. For instance, from `loadableicon.hg`:

    _CLASS_INTERFACE(LoadableIcon, GLoadableIcon, G_LOADABLE_ICON, GLoadableIconIface, Icon, GIcon)

#### Constructor macros

The `_CTOR_DEFAULT()` and `_WRAP_CTOR()` macros add constructors, wrapping the specified `*_new()` C functions. These macros assume that the C object has properties with the same names as the function parameters, as is usually the case, so that it can supply the parameters directly to a `g_object_new()` call. These constructors never actually call the `*_new()` C functions, because gtkmm must actually instantiate derived GTypes, and the `*_new()` C functions are meant only as convenience functions for C programmers.

When using `_CLASS_GOBJECT()`, the constructors should be protected (rather than public) and each constructor should have a corresponding `_WRAP_CREATE()` in the public section. This prevents the class from being instantiated without using a `RefPtr`. For instance:

    class ActionGroup : public Glib::Object
    {
      _CLASS_GOBJECT(ActionGroup, GtkActionGroup, GTK_ACTION_GROUP, Glib::Object, GObject)

    protected:
      _WRAP_CTOR(ActionGroup(const Glib::ustring& name = Glib::ustring()), gtk_action_group_new)

    public:
      _WRAP_CREATE(const Glib::ustring& name = Glib::ustring())

##### _CTOR_DEFAULT

This macro creates a default constructor with no arguments.

##### _WRAP_CTOR

This macro creates a constructor with arguments, equivalent to a `*_new()` C function. It won't actually call the `*_new()` function, but will simply create an equivalent constructor with the same argument types. It takes a C++ constructor signature, and a C function name.

When wrapping constructors, it is possible for gmmproc to generate convenience overloads of the wrapped constructors if the C function has parameters that are optional (ie. the C API allows null for those parameters). For instance, to specify if a parameter is optional, the `_WRAP_CTOR()` macro would look something like the following:

    _WRAP_CTOR(ToolButton(Widget& icon_widget, const Glib::ustring& label{?}), gtk_tool_button_new)

The `{?}` following the name of the `label` parameter means that that parameter is optional. In this case, gmmproc will generate an extra constructor without that parameter.

It is also possible to have the order of the parameters of the constructor different from that of the C function by using gmmproc's C++ to C parameter mapping functionality. Using this functionality, it is possible to map a C++ parameter to a C parameter by specifying the C parameter name. For instance, assuming that the declaration of the `gtk_tool_button_new()` function is the following:

    GtkToolItem* gtk_tool_button_new(GtkWidget* icon_widget, const gchar* label);

The parameters of the wrapped constructor could be reordered using the following:

    _WRAP_CTOR(ToolButton(const Glib::ustring& label{label}, Widget& icon_widget{icon_widget}), gtk_tool_button_new)

The `{param_name}` following each of the names of the parameters tells gmmproc to map those C++ parameters to the C parameters with the given names. Since the C++ parameter names correspond to the C ones, the above could be re-written as:

    _WRAP_CTOR(ToolButton(const Glib::ustring& label{.}, Widget& icon_widget{.}), gtk_tool_button_new)

This same optional parameter syntax and parameter reordering is available for `_WRAP_CREATE()`. Additional `create()` overloads would be generated by gmmproc without the specified optional parameters.

##### Hand-coding constructors

When a constructor must be partly hand written because, for instance, the `*_new()` C function's parameters do not correspond directly to object properties, or because the `*_new()` C function does more than call `g_object_new()`, the `_CONSTRUCT()` macro may be used in the .ccg file to save some work. The `_CONSTRUCT` macro takes a series of property names and values. For instance, from `button.ccg`:

    Button::Button(const Glib::ustring& label, bool mnemonic)
    :
      _CONSTRUCT("label", label.c_str(), "use_underline", gboolean(mnemonic))
    {}

#### Method macros

##### _WRAP_METHOD

This macro generates the C++ method to wrap a C function.

`_WRAP_METHOD( C++ method signature, C function name)`

For instance, from `entry.hg`:

    _WRAP_METHOD(void set_text(const Glib::ustring& text), gtk_entry_set_text)

The C function (e.g. `gtk_entry_set_text`) is described more fully in the .defs file, and the `convert*.m4` files contain the necessary conversion from the C++ parameter type to the C parameter type. This macro also generates doxygen documentation comments based on the `*_docs.xml` and `*_docs_override.xml` files.

There are some optional extra arguments:

refreturn

- Do an extra `reference()` on the return value, in case the C function does not provide a reference.

errthrow

- Use the last GError* parameter of the C function to throw an exception.

deprecated

- Puts the generated code in #ifdef blocks. Text about the deprecation can be specified as an optional parameter.

constversion

- Just call the non-const version of the same function, instead of generating almost duplicate code.

ifdef

- Puts the generated code in #ifdef blocks.

As with `_WRAP_CTOR()` it is possible to specify if there are any optional parameters. If that is the case, gmmproc will generate convenience overload methods without those parameters. For example:

    _WRAP_METHOD(void get_preferred_size(Requisition& minimum_size, Requisition& natural_size{?}) const, gtk_widget_get_preferred_size)

Would indicate that the `natural_size` parameter is optional because its name ends with `{?}`. In this case, gmmproc would generate a method overload without that parameter.

Also, as with `_WRAP_CTOR()`, it is possible to reorder the parameters of the C++ method by using gmmproc's C++ to C parameter mapping functionality. Using this functionality, it is possible to map a C++ parameter to a C parameter by specifying the C parameter name. For example, if the `gtk_widget_set_device_events()` declaration is the following:

    void gtk_widget_set_device_events(GtkWidget* widget, GdkDevice* device, GdkEventMask events);

Something like the following would change the order of the parameters in the C++ method:

    _WRAP_METHOD(void set_device_events(Gdk::EventMask events{events}, const Glib::RefPtr<const Gdk::Device>& device{device}), gtk_widget_set_device_events)

The `{param_name}` following each of the names of the parameters tells gmmproc to map those C++ parameters to the C parameters with the given names. Since the C++ parameter names correspond to the C ones, the above could be re-written as:

    _WRAP_METHOD(void set_device_events(Gdk::EventMask events{.}, const Glib::RefPtr<const Gdk::Device>& device{.}), gtk_widget_set_device_events)

With `_WRAP_METHOD()` it is also possible to include an output parameter in the C++ method declaration in which the return of the C function would be placed and to have the C++ method return `void`. To do that, simply include the output parameter declaration in the C++ method declaration appending a `{OUT}` to the output parameter name. For example, if `gtk_widget_get_request_mode()` is declared as the following:

    GtkSizeRequestMode gtk_widget_get_request_mode(GtkWidget* widget);

And having the C++ method set an output parameter is desired instead of returning a `SizeRequestMode`, something like the following could be used:

    _WRAP_METHOD(void get_request_mode(SizeRequestMode& mode{OUT}) const, gtk_widget_get_request_mode)

the `{OUT}` appended to the name of the `mode` output parameter tells gmmproc to place the return of the C function in that output parameter. In this case, however, a necessary initialization macro like the following would also have to be specified:

    _INITIALIZATION(`SizeRequestMode&',`GtkSizeRequestMode',`$3 = (SizeRequestMode)($4)')

Which could also be written as:

    _INITIALIZATION(`SizeRequestMode&',`GtkSizeRequestMode',`$3 = ($1)($4)')

Though it's usually obvious what C++ types should be used in the C++ method, here are some hints:

- Objects used via `RefPtr`: Pass the `RefPtr` as a const reference. For instance, `const Glib::RefPtr<Gtk::Action>& action`.

- Const Objects used via `RefPtr`: If the object should not be changed by the function, then make sure that the object is const, even if the `RefPtr` is already const. For instance, `const Glib::RefPtr<const Gtk::Action>& action`.

- Wrapping `GList*` and `GSList*` parameters: First, you need to discover what objects are contained in the list's data field for each item, usually by reading the documentation for the C function. The list can then be wrapped by a `std::vector` type. For instance, `std::vector< Glib::RefPtr<Action> >`. You may need to define a Traits type to specify how the C and C++ types should be converted.

- Wrapping `GList*` and `GSList*` return types: You must discover whether the caller should free the list and whether it should release the items in the list, again by reading the documentation of the C function. With this information you can choose the ownership (none, shallow or deep) for the m4 conversion rule, which you should probably put directly into the .hg file because the ownership depends on the function rather than the type. For instance:

      #m4 _CONVERSION(`GSList*',`std::vector<Widget*>',`Glib::SListHandler<Widget*>::slist_to_vector($3, Glib::OWNERSHIP_SHALLOW)')

##### _WRAP_METHOD_DOCS_ONLY

This macro is like `_WRAP_METHOD()`, but it generates only the documentation for a C++ method that wraps a C function. Use this when you must hand-code the method, but you want to use the documentation that would be generated if the method was generated.

`_WRAP_METHOD_DOCS_ONLY(C function name)`

For instance, from `container.hg`:

    _WRAP_METHOD_DOCS_ONLY(gtk_container_remove)

##### _IGNORE / _IGNORE_SIGNAL

`gmmproc` will warn you on stdout about functions and signals that you have forgotten to wrap, helping to ensure that you are wrapping the complete API. But if you don't want to wrap some functions or signals, or if you chose to hand-code some methods then you can use the _IGNORE() or _IGNORE_SIGNAL() macro to make `gmmproc` stop complaining.

`_IGNORE(C function name 1, C function name2, etc)`

`_IGNORE_SIGNAL(C signal name 1, C signal name2, etc)`

For instance, from `buttonbox.hg`:

    _IGNORE(gtk_button_box_set_spacing, gtk_button_box_get_spacing)

##### _WRAP_SIGNAL

This macro generates the C++ libsigc++-style signal to wrap a C GObject signal. It actually generates a public accessor method, such as `signal_clicked()`, which returns a proxy object. `gmmproc` uses the .defs file to discover the C parameter types and the .m4 convert files to discover appropriate type conversions.

`_WRAP_SIGNAL( C++ signal handler signature, C signal name)`

For instance, from `button.hg`:

    _WRAP_SIGNAL(void clicked(),"clicked")

Signals usually have function pointers in the GTK struct, with a corresponding enum value. and a `g_signal_new()` in the .c file.

There are some optional extra arguments:

no_default_handler

- Do not generate an `on_something()` virtual method to allow easy overriding of the default signal handler. Use this when adding a signal with a default signal handler would break the ABI by increasing the size of the class's virtual function table.

custom_default_handler

- Generate a declaration of the `on_something()` virtual method in the `.h` file, but do not generate a definition in the `.cc` file. Use this when you must generate the definition by hand.

custom_c_callback

- Do not generate a C callback function for the signal. Use this when you must generate the callback function by hand.

refreturn

- Do an extra `reference()` on the return value of the `on_something()` virtual method, in case the C function does not provide a reference.

ifdef

- Puts the generated code in #ifdef blocks.

##### _WRAP_PROPERTY

This macro generates the C++ method to wrap a C GObject property. You must specify the property name and the wanted C++ type for the property. `gmmproc` uses the .defs file to discover the C type and the .m4 convert files to discover appropriate type conversions.

`_WRAP_PROPERTY(C property name, C++ type)`

For instance, from `button.hg`:

    _WRAP_PROPERTY("label", Glib::ustring)

##### _WRAP_VFUNC

This macro generates the C++ method to wrap a virtual C function.

`_WRAP_VFUNC( C++ method signature, C function name)`

For instance, from `widget.hg`:

    _WRAP_VFUNC(SizeRequestMode get_request_mode() const, get_request_mode)

The C function (e.g. `get_request_mode`) is described more fully in the `*_vfuncs.defs` file, and the `convert*.m4` files contain the necessary conversion from the C++ parameter type to the C parameter type.

There are some optional extra arguments:

refreturn

- Do an extra `reference()` on the return value of the `something_vfunc()` function, in case the virtual C function does not provide a reference.

refreturn_ctype

- Do an extra `reference()` on the return value of an overridden `something_vfunc()` function in the C callback function, in case the calling C function expects it to provide a reference.

custom_vfunc

- Do not generate a definition of the vfunc in the `.cc` file. Use this when you must generate the vfunc by hand.

custom_vfunc_callback

- Do not generate a C callback function for the vfunc. Use this when you must generate the callback function by hand.

ifdef

- Puts the generated code in #ifdef blocks.

A rule to which there may be exceptions: If the virtual C function returns a pointer to an object derived from `GObject`, i.e. a reference-counted object, then the virtual C++ function shall return a `Glib::RefPtr<>` object. One of the extra arguments `refreturn` or `refreturn_ctype` is required.

#### Otras macros

##### _IMPLEMENTS_INTERFACE

This macro generates initialization code for the interface.

`_IMPLEMENTS_INTERFACE(C++ interface name)`

For instance, from `button.hg`:

    _IMPLEMENTS_INTERFACE(Activatable)

Hay un argumento opcional adicional:

ifdef

- Puts the generated code in #ifdef blocks.

##### _WRAP_ENUM

This macro generates a C++ enum to wrap a C enum. You must specify the desired C++ name and the name of the underlying C enum.

For instance, from `widget.hg`:

    _WRAP_ENUM(WindowType, GdkWindowType)

If the enum is not a `GType`, you must pass a third parameter NO_GTYPE. This is the case when there is no `*_get_type()` function for the C enum, but be careful that you don't just need to include an extra header for that function. You should also file a bug against the C API, because all enums should be registered as GTypes.

For example, from `icontheme.hg`:

    _WRAP_ENUM(IconLookupFlags, GtkIconLookupFlags, NO_GTYPE)

##### _WRAP_GERROR

This macro generates a C++ exception class, derived from Glib::Error, with a Code enum and a code() method. You must specify the desired C++ name, the name of the corresponding C enum, and the prefix for the C enum values.

This exception can then be thrown by methods which are generated from _WRAP_METHOD() with the errthrow option.

For instance, from `pixbuf.hg`:

    _WRAP_GERROR(PixbufError, GdkPixbufError, GDK_PIXBUF_ERROR)

##### _MEMBER_GET / _MEMBER_SET

Use these macros if you're wrapping a simple struct or boxed type that provides direct access to its data members, to create getters and setters for the data members.

`_MEMBER_GET(C++ name, C name, C++ type, C type)`

`_MEMBER_SET(C++ name, C name, C++ type, C type)`

For example, in `rectangle.hg`:

    _MEMBER_GET(x, x, int, int)

##### _MEMBER_GET_PTR / _MEMBER_SET_PTR

Use these macros to automatically provide getters and setters for a data member that is a pointer type. For the getter function, it will create two methods, one const and one non-const.

`_MEMBER_GET_PTR(C++ name, C name, C++ type, C type)`

`_MEMBER_SET_PTR(C++ name, C name, C++ type, C type)`

For example, for `Pango::Analysis` in `item.hg`:

    // _MEMBER_GET_PTR(engine_lang, lang_engine, EngineLang*, PangoEngineLang*)
    // It's just a comment. It's difficult to find a real-world example.

##### _MEMBER_GET_GOBJECT / _MEMBER_SET_GOBJECT

Use these macros to provide getters and setters for a data member that is a `GObject` type that must be referenced before being returned.

`_MEMBER_GET_GOBJECT(C++ name, C name, C++ type, C type)`

`_MEMBER_SET_GOBJECT(C++ name, C name, C++ type, C type)`

For example, in Pangomm, `layoutline.hg`:

    _MEMBER_GET_GOBJECT(layout, layout, Pango::Layout, PangoLayout*)

#### Tipos básicos

Some of the basic types that are used in C APIs have better alternatives in C++. For example, there's no need for a `gboolean` type since C++ has `bool`. The following list shows some commonly-used types in C APIs and what you might convert them to in a C++ wrapper library.

#### Tipos básicos equivalentes

Tipo C Tipo C++
- `gboolean` `bool`
- `gint` `int`
- `guint` `guint`
- `gdouble` `doble`
- `gunichar` `gunichar`
- `gchar*``Glib::ustring` (o `std::string` para nombres de archivos)

### Archivos de código fuente programados a mano

You might want to include additional source files that will not be generated by `gmmproc` from `.hg` and `.ccg` files. You can simply place these in your `libsomething/libsomethingmm` directory and mention them in the `Makefile.am` in the `files_extra_h` and `files_extra_cc` variables.

### Inicialización

Your library must be initialized before it can be used, to register the new types that it makes available. Also, the C library that you are wrapping might have its own initialization function that you should call. You can do this in an `init()` function that you can place in hand-coded `init.h` and `init.cc` files. This function should initialize your dependencies (such as the C function, and gtkmm) and call your generated `wrap_init()` function. For instance:

    void init()
    {
      Gtk::Main::init_gtkmm_internals(); //Sets up the g type system and the Glib::wrap() table.
      wrap_init(); //Tells the Glib::wrap() table about the libsomethingmm classes.
    }

The implementation of the `wrap_init()` method in `wrap_init.cc` is generated by `generate_wrap_init.pl`, but the declaration in `wrap_init.h` is hand-coded, so you will need to adjust `wrap_init.h` so that the `init()` function appears in the correct C++ namespace.

### Problemas en la API de C.

You are likely to encounter some problems in the library that you are wrapping, particularly if it is a new project. Here are some common problems, with solutions.

#### No se pueden predeclarar estructuras

Por convenio, las estructuras se declaran en los encabezados de Glib/GTK+ igual que en:

    typedef struct _ExampleWidget ExampleWidget;

    struct _ExampleWidget
    {
      ...
    };

The extra typedef allows the struct to be used in a header without including its full definition, simply by predeclaring it, by repeating that typedef. This means that you don't have to include the C library's header in your C++ header, thus keeping it out of your public API. `gmmproc` assumes that this technique was used, so you will see compiler errors if that is not the case.

Este error del compilador podría tener este aspecto:

    example-widget.h:56: error: using typedef-name 'ExampleWidget' after 'struct'
    ../../libexample/libexamplemm/example-widget.h:34: error: 'ExampleWidget' has a previous declaration here
    make[4]: *** [example-widget.lo] Error 1

o este:

    example-widget.h:60: error: '_ExampleWidget ExampleWidget' redeclared as different kind of symbol
    ../../libexample/libexamplemm/example-widget.h:34: error: previous declaration of 'typedef struct _ExampleWidget ExampleWidget'

Esto es fácil de corregir en la biblioteca de C, así que envíe un parche al mantenedor pertinentes.

#### Falta de propiedades

By convention, glib/GTK+-style objects have `*_new()` functions, such as `example_widget_new()` that do nothing more than call `g_object_new()` and return the result. The input parameters are supplied to `g_object_new()` along with the names of the properties for which they are values. For instance,

    GtkWidget* example_widget_new(int something, const char* thing)
    {
            return g_object_new (EXAMPLE_TYPE_WIDGET, "something", something, "thing", thing, NULL);
    }

This allows language bindings to implement their own equivalents (such as C++ constructors), without using the `*_new()` function. This is often necessary so that they can actually instantiate a derived GType, to add their own hooks for signal handlers and vfuncs.

At the least, the `_new()` function should not use any private API (functions that are only in a .c file). Even when there are no functions, we can sometimes reimplement 2 or 3 lines of code in a `_new()` function as long as those lines of code use API that is available to us.

Another workaround is to add a `*_construct()` function that the C++ constructor can call after instantiating its own type. For instance,

    GtkWidget* example_widget_new(int something, const char* thing)
    {
            ExampleWidget* widget;
            widget = g_object_new (EXAMPLE_TYPE_WIDGET, NULL);
            example_widget_construct(widget, "something", something, "thing", thing);
    }

    void example_widget_construct(ExampleWidget* widget, int something, const char* thing)
    {
            //Do stuff that uses private API:
            widget->priv->thing = thing;
            do_something(something);
    }

Incorporar propiedades, y asegurar que interactúan con otras propiedades correctamente, es relativamente difícil de corregir en la biblioteca de C, pero es posible, por lo que rellene un informe de error e intente enviar un parche al mantenedor correspondiente.

### Documentación

In general, gtkmm-style projects use Doxygen, which reads specially formatted C++ comments and generates HTML documentation. You may write these doxygen comments directly in the header files.

#### Reutilizar la documentación de C

You might wish to reuse documentation that exists for the C library that you are wrapping. GTK-style C libraries typically use gtk-doc and therefore have source code comments formatted for gtk-doc and some extra documentation in .sgml and .xml files. The docextract_to_xml.py script, from glibmm's `tools/defs_gen` directory, can read these files and generate an .xml file that `gmmproc` can use to generate doxygen comments. `gmmproc` will even try to transform the documentation to make it more appropriate for a C++ API.

Por ejemplo,

    ./docextract_to_xml.py -s ~/checkout/gnome/gtk+/gtk/ -s ~/checkout/gnome/gtk+/docs/reference/gtk/ > gtk_docs.xml

Because this automatic transformation is not always appropriate, you might want to provide hand-written text for a particular method. You can do this by copying the XML node for the function from your `something_docs.xml` file to the `something_docs_override.xml` file and changing the contents.

#### Estructura de construcción de la documentación

If you copied the skeleton source tree in mm-common and substituted the placeholder text, then you will already have suitable `Makefile.am` and `Doxyfile.in` files. With the mm-common build setup, the list of Doxygen input files is not defined in the Doxygen configuration file, but passed along from `make` to the standard input of `doxygen`. The input file list is defined by the `doc_input` variable in the `Makefile.am` file.