FLTK 1.3.8: Designing a Simple Text Editor

FLTK 1.3.8

Designing a Simple Text Editor

This chapter takes you through the design of a simple FLTK-based text editor.

# Determining the Goals of the Text Editor

Since this will be the first big project you'll be doing with FLTK, lets define what we want our text editor to do:

1. Provide a menubar/menus for all functions.
2. Edit a single text file, possibly with multiple views.
3. Load from a file.
4. Save to a file.
5. Cut/copy/delete/paste functions.
6. Search and replace functions.
7. Keep track of when the file has been changed.

# Designing the Main Window

Now that we've outlined the goals for our editor, we can begin with the design of our GUI. Obviously the first thing that we need is a window, which we'll place inside a class called `EditorWindow:`

class EditorWindow : public Fl_Double_Window {
public:
EditorWindow(int w, int h, const char* t);
~EditorWindow();
Fl_Window *replace_dlg;
Fl_Input *replace_find;
Fl_Input *replace_with;
Fl_Button *replace_all;
Fl_Return_Button *replace_next;
Fl_Button *replace_cancel;
Fl_Text_Editor *editor;
char search[256];
};
Fl_Button
Buttons generate callbacks when they are clicked by the user.
Definition: Fl_Button.H:76
Fl_Double_Window
The Fl_Double_Window provides a double-buffered window.
Definition: Fl_Double_Window.H:40
Fl_Input
This is the FLTK text input widget.
Definition: Fl_Input.H:222
Fl_Return_Button
The Fl_Return_Button is a subclass of Fl_Button that generates a callback when it is pressed or when ...
Definition: Fl_Return_Button.H:33
Fl_Text_Editor
This is the FLTK text editor widget.
Definition: Fl_Text_Editor.H:40
Fl_Window
This widget produces an actual window.
Definition: Fl_Window.H:57

# Variables

Our text editor will need some global variables to keep track of things:

int changed = 0;
char filename[256] = "";
Fl_Text_Buffer *textbuf;
Fl_Text_Buffer
This class manages Unicode text displayed in one or more Fl_Text_Display widgets.
Definition: Fl_Text_Buffer.H:158

The `textbuf` variable is the text editor buffer for our window class described previously. We'll cover the other variables as we build the application.

# Menubars and Menus

The first goal requires us to use a menubar and menus that define each function the editor needs to perform. The Fl_Menu_Item structure is used to define the menus and items in a menubar:

Fl_Menu_Item menuitems[] = {
{ "&File", 0, 0, 0, FL_SUBMENU },
{ "&New File", 0, (Fl_Callback *)new_cb },
{ "&Open File...", FL_COMMAND + 'o', (Fl_Callback *)open_cb },
{ "&Insert File...", FL_COMMAND + 'i', (Fl_Callback *)insert_cb, 0, FL_MENU_DIVIDER },
{ "&Save File", FL_COMMAND + 's', (Fl_Callback *)save_cb },
{ "Save File &As...", FL_COMMAND + FL_SHIFT + 's', (Fl_Callback *)saveas_cb, 0, FL_MENU_DIVIDER },
{ "New &View", FL_ALT + 'v', (Fl_Callback *)view_cb, 0 },
{ "&Close View", FL_COMMAND + 'w', (Fl_Callback *)close_cb, 0, FL_MENU_DIVIDER },
{ "E&xit", FL_COMMAND + 'q', (Fl_Callback *)quit_cb, 0 },
{ 0 },
{ "&Edit", 0, 0, 0, FL_SUBMENU },
{ "&Undo", FL_COMMAND + 'z', (Fl_Callback *)undo_cb, 0, FL_MENU_DIVIDER },
{ "Cu&t", FL_COMMAND + 'x', (Fl_Callback *)cut_cb },
{ "&Copy", FL_COMMAND + 'c', (Fl_Callback *)copy_cb },
{ "&Paste", FL_COMMAND + 'v', (Fl_Callback *)paste_cb },
{ "&Delete", 0, (Fl_Callback *)delete_cb },
{ 0 },
{ "&Search", 0, 0, 0, FL_SUBMENU },
{ "&Find...", FL_COMMAND + 'f', (Fl_Callback *)find_cb },
{ "F&ind Again", FL_COMMAND + 'g', find2_cb },
{ "&Replace...", FL_COMMAND + 'r', replace_cb },
{ "Re&place Again", FL_COMMAND + 't', replace2_cb },
{ 0 },
{ 0 }
};
FL_ALT
#define FL_ALT
One of the alt keys is down.
Definition: Enumerations.H:558
FL_COMMAND
#define FL_COMMAND
An alias for FL_CTRL on WIN32 and X11, or FL_META on MacOS X.
Definition: Enumerations.H:578
FL_SHIFT
#define FL_SHIFT
One of the shift keys is down.
Definition: Enumerations.H:555
Fl_Callback
void() Fl_Callback(Fl_Widget *, void *)
Default callback type definition for all fltk widgets (by far the most used)
Definition: Fl_Widget.H:49

Once we have the menus defined we can create the Fl_Menu_Bar widget and assign the menus to it with:

Fl_Menu_Bar *m = new Fl_Menu_Bar(0, 0, 640, 30);
m->copy(menuitems);

We'll define the callback functions later.

# Editing the Text

To keep things simple our text editor will use the Fl_Text_Editor widget to edit the text:

w->editor = new Fl_Text_Editor(0, 30, 640, 370);
w->editor->buffer(textbuf);

So that we can keep track of changes to the file, we also want to add a "modify" callback:

textbuf->add_modify_callback(changed_cb, w);
textbuf->call_modify_callbacks();
Fl_Text_Buffer::call_modify_callbacks
void call_modify_callbacks()
Calls all modify callbacks that have been registered using the add_modify_callback() method.
Definition: Fl_Text_Buffer.H:485
Fl_Text_Buffer::add_modify_callback
void add_modify_callback(Fl_Text_Modify_Cb bufModifiedCB, void *cbArg)
Adds a callback function that is called whenever the text buffer is modified.
Definition: Fl_Text_Buffer.cxx:652

Finally, we want to use a mono-spaced font like `FL_COURIER:`

w->editor->textfont(FL_COURIER);
FL_COURIER
const Fl_Font FL_COURIER
Courier normal.
Definition: Enumerations.H:881

# The Replace Dialog

We can use the FLTK convenience functions for many of the editor's dialogs, however the replace dialog needs its own custom window. To keep things simple we will have a "find" string, a "replace" string, and "replace all", "replace next", and "cancel" buttons. The strings are just Fl_Input widgets, the "replace all" and "cancel" buttons are Fl_Button widgets, and the "replace next " button is a Fl_Return_Button widget:

Figure 4-1: The search and replace dialog
Fl_Window *replace_dlg = new Fl_Window(300, 105, "Replace");
Fl_Input *replace_find = new Fl_Input(70, 10, 200, 25, "Find:");
Fl_Input *replace_with = new Fl_Input(70, 40, 200, 25, "Replace:");
Fl_Button *replace_all = new Fl_Button(10, 70, 90, 25, "Replace All");
Fl_Button *replace_next = new Fl_Button(105, 70, 120, 25, "Replace Next");
Fl_Button *replace_cancel = new Fl_Button(230, 70, 60, 25, "Cancel");

# Callbacks

Now that we've defined the GUI components of our editor, we need to define our callback functions.

## changed_cb()

This function will be called whenever the user changes any text in the `editor` widget:

void changed_cb(int, int nInserted, int nDeleted,int, const char*, void* v) {
if ((nInserted || nDeleted) && !loading) changed = 1;
EditorWindow *w = (EditorWindow *)v;
set_title(w);
if (loading) w->editor->show_insert_position();
}

The `set_title()` function is one that we will write to set the changed status on the current file. We're doing it this way because we want to show the changed status in the window's title bar.

## copy_cb()

This callback function will call Fl_Text_Editor::kf_copy() to copy the currently selected text to the clipboard:

void copy_cb(Fl_Widget*, void* v) {
EditorWindow* e = (EditorWindow*)v;
Fl_Text_Editor::kf_copy(0, e->editor);
}
Fl_Text_Editor::kf_copy
static int kf_copy(int c, Fl_Text_Editor *e)
Does a copy of selected text or the current character in the current buffer of editor 'e'.
Definition: Fl_Text_Editor.cxx:566
Fl_Widget
Fl_Widget is the base class for all widgets in FLTK.
Definition: Fl_Widget.H:101

## cut_cb()

This callback function will call Fl_Text_Editor::kf_cut() to cut the currently selected text to the clipboard:

void cut_cb(Fl_Widget*, void* v) {
EditorWindow* e = (EditorWindow*)v;
Fl_Text_Editor::kf_cut(0, e->editor);
}
Fl_Text_Editor::kf_cut
static int kf_cut(int c, Fl_Text_Editor *e)
Does a cut of selected text in the current buffer of editor 'e'.
Definition: Fl_Text_Editor.cxx:578

## delete_cb()

This callback function will call Fl_Text_Buffer::remove_selection() to delete the currently selected text to the clipboard:

void delete_cb(Fl_Widget*, void* v) {
textbuf->remove_selection();
}
Fl_Text_Buffer::remove_selection
void remove_selection()
Removes the text in the primary selection.
Definition: Fl_Text_Buffer.cxx:530

## find_cb()

This callback function asks for a search string using the fl_input() convenience function and then calls the `find2_cb()` function to find the string:

void find_cb(Fl_Widget* w, void* v) {
EditorWindow* e = (EditorWindow*)v;
const char *val;
val = fl_input("Search String:", e->search);
if (val != NULL) {
// User entered a string - go find it!
strcpy(e->search, val);
find2_cb(w, v);
}
fl_input
const char * fl_input(const char *fmt, const char *defstr,...)
Shows an input dialog displaying the fmt message.
Definition: fl_ask.cxx:561

## find2_cb()

This function will find the next occurrence of the search string. If the search string is blank then we want to pop up the search dialog:

void find2_cb(Fl_Widget* w, void* v) {
EditorWindow* e = (EditorWindow*)v;
if (e->search[0] == '\0') {
// Search string is blank; get a new one...
find_cb(w, v);
return;
}
int pos = e->editor->insert_position();
int found = textbuf->search_forward(pos, e->search, &pos);
if (found) {
// Found a match; select and update the position...
textbuf->select(pos, pos+strlen(e->search));
e->editor->insert_position(pos+strlen(e->search));
e->editor->show_insert_position();
}
else fl_alert("No occurrences of \'%s\' found!", e->search);
}
Fl_Text_Buffer::select
void select(int start, int end)
Selects a range of characters in the buffer.
Definition: Fl_Text_Buffer.cxx:485
Fl_Text_Buffer::search_forward
int search_forward(int startPos, const char *searchString, int *foundPos, int matchCase=0) const
Search forwards in buffer for string searchString, starting with the character startPos,...
Definition: Fl_Text_Buffer.cxx:1006
fl_alert
void fl_alert(const char *fmt,...)
Shows an alert message dialog box.
Definition: fl_ask.cxx:367

If the search string cannot be found we use the fl_alert() convenience function to display a message to that effect.

## new_cb()

This callback function will clear the editor widget and current filename. It also calls the `check_save()` function to give the user the opportunity to save the current file first as needed:

void new_cb(Fl_Widget*, void*) {
if (!check_save()) return;
filename[0] = '\0';
textbuf->select(0, textbuf->length());
textbuf->remove_selection();
changed = 0;
textbuf->call_modify_callbacks();
}
Fl_Text_Buffer::length
int length() const
Returns the number of bytes in the buffer.
Definition: Fl_Text_Buffer.H:180

## open_cb()

This callback function will ask the user for a filename and then load the specified file into the input widget and current filename. It also calls the `check_save()` function to give the user the opportunity to save the current file first as needed:

void open_cb(Fl_Widget*, void*) {
if (!check_save()) return;
char *newfile = fl_file_chooser("Open File?", "*", filename);
if (newfile != NULL) load_file(newfile, -1);
}
Fl_File_Chooser::fl_file_chooser
char * fl_file_chooser(const char *message, const char *pat, const char *fname, int relative)
Shows a file chooser dialog and gets a filename.
Definition: fl_file_dir.cxx:89

We call the `load_file()` function to actually load the file.

## paste_cb()

This callback function will call Fl_Text_Editor::kf_paste() to paste the clipboard at the current position:

void paste_cb(Fl_Widget*, void* v) {
EditorWindow* e = (EditorWindow*)v;
Fl_Text_Editor::kf_paste(0, e->editor);
}
Fl_Text_Editor::kf_paste
static int kf_paste(int c, Fl_Text_Editor *e)
Does a paste of selected text in the current buffer of editor 'e'.
Definition: Fl_Text_Editor.cxx:590

## quit_cb()

The quit callback will first see if the current file has been modified, and if so give the user a chance to save it. It then exits from the program:

void quit_cb(Fl_Widget*, void*) {
if (changed && !check_save())
return;
exit(0);
}

## replace_cb()

The replace callback just shows the replace dialog:

void replace_cb(Fl_Widget*, void* v) {
EditorWindow* e = (EditorWindow*)v;
e->replace_dlg->show();
}

## replace2_cb()

This callback will replace the next occurrence of the replacement string. If nothing has been entered for the replacement string, then the replace dialog is displayed instead:

void replace2_cb(Fl_Widget*, void* v) {
EditorWindow* e = (EditorWindow*)v;
const char *find = e->replace_find->value();
const char *replace = e->replace_with->value();
if (find[0] == '\0') {
// Search string is blank; get a new one...
e->replace_dlg->show();
return;
}
e->replace_dlg->hide();
int pos = e->editor->insert_position();
int found = textbuf->search_forward(pos, find, &pos);
if (found) {
// Found a match; update the position and replace text...
textbuf->select(pos, pos+strlen(find));
textbuf->remove_selection();
textbuf->insert(pos, replace);
textbuf->select(pos, pos+strlen(replace));
e->editor->insert_position(pos+strlen(replace));
e->editor->show_insert_position();
}
else fl_alert("No occurrences of \'%s\' found!", find);
}
Fl_Text_Buffer::insert
void insert(int pos, const char *text)
Inserts null-terminated string text at position pos.
Definition: Fl_Text_Buffer.cxx:269

## replall_cb()

This callback will replace all occurrences of the search string in the file:

void replall_cb(Fl_Widget*, void* v) {
EditorWindow* e = (EditorWindow*)v;
const char *find = e->replace_find->value();
const char *replace = e->replace_with->value();
find = e->replace_find->value();
if (find[0] == '\0') {
// Search string is blank; get a new one...
e->replace_dlg->show();
return;
}
e->replace_dlg->hide();
e->editor->insert_position(0);
int times = 0;
// Loop through the whole string
for (int found = 1; found;) {
int pos = e->editor->insert_position();
found = textbuf->search_forward(pos, find, &pos);
if (found) {
// Found a match; update the position and replace text...
textbuf->select(pos, pos+strlen(find));
textbuf->remove_selection();
textbuf->insert(pos, replace);
e->editor->insert_position(pos+strlen(replace));
e->editor->show_insert_position();
times++;
}
}
if (times) fl_message("Replaced %d occurrences.", times);
else fl_alert("No occurrences of \'%s\' found!", find);
}
fl_message
void fl_message(const char *fmt,...)
Shows an information message dialog box.
Definition: fl_ask.cxx:344

## replcan_cb()

This callback just hides the replace dialog:

void replcan_cb(Fl_Widget*, void* v) {
EditorWindow* e = (EditorWindow*)v;
e->replace_dlg->hide();
}

## save_cb()

This callback saves the current file. If the current filename is blank it calls the "save as" callback:

void save_cb(void) {
if (filename[0] == '\0') {
// No filename - get one!
saveas_cb();
return;
}
else save_file(filename);
}

The `save_file()` function saves the current file to the specified filename.

## saveas_cb()

This callback asks the user for a filename and saves the current file:

void saveas_cb(void) {
char *newfile;
newfile = fl_file_chooser("Save File As?", "*", filename);
if (newfile != NULL) save_file(newfile);
}

The `save_file()` function saves the current file to the specified filename.

# Other Functions

Now that we've defined the callback functions, we need our support functions to make it all work:

## check_save()

This function checks to see if the current file needs to be saved. If so, it asks the user if they want to save it:

int check_save(void) {
if (!changed) return 1;
int r = fl_choice("The current file has not been saved.\n"
"Would you like to save it now?",
"Cancel", "Save", "Discard");
if (r == 1) {
save_cb(); // Save the file...
return !changed;
}
return (r == 2) ? 1 : 0;
}
fl_choice
int fl_choice(const char *fmt, const char *b0, const char *b1, const char *b2,...)
Shows a dialog displaying the printf style fmt message, this dialog features up to 3 customizable cho...
Definition: fl_ask.cxx:465

## load_file()

This function loads the specified file into the `textbuf` variable:

int loading = 0;
void load_file(char *newfile, int ipos) {
loading = 1;
int insert = (ipos != -1);
changed = insert;
if (!insert) strcpy(filename, "");
int r;
if (!insert) r = textbuf->loadfile(newfile);
else r = textbuf->insertfile(newfile, ipos);
if (r)
fl_alert("Error reading from file \'%s\':\n%s.", newfile, strerror(errno));
else
if (!insert) strcpy(filename, newfile);
loading = 0;
textbuf->call_modify_callbacks();
}
Fl_Text_Buffer::insertfile
int insertfile(const char *file, int pos, int buflen=128 *1024)
Inserts a file at the specified position.
Definition: Fl_Text_Buffer.cxx:1670
Fl_Text_Buffer::loadfile
int loadfile(const char *file, int buflen=128 *1024)
Loads a text file into the buffer.
Definition: Fl_Text_Buffer.H:315

When loading the file we use the Fl_Text_Buffer::loadfile() method to "replace" the text in the buffer, or the Fl_Text_Buffer::insertfile() method to insert text in the buffer from the named file.

## save_file()

This function saves the current buffer to the specified file:

void save_file(char *newfile) {
if (textbuf->savefile(newfile))
fl_alert("Error writing to file \'%s\':\n%s.", newfile, strerror(errno));
else
strcpy(filename, newfile);
changed = 0;
textbuf->call_modify_callbacks();
}
Fl_Text_Buffer::savefile
int savefile(const char *file, int buflen=128 *1024)
Saves a text file from the current buffer.
Definition: Fl_Text_Buffer.H:340

## set_title()

This function checks the `changed` variable and updates the window label accordingly:

void set_title(Fl_Window* w) {
if (filename[0] == '\0') strcpy(title, "Untitled");
else {
char *slash;
slash = strrchr(filename, '/');
#ifdef WIN32
if (slash == NULL) slash = strrchr(filename, '\\');
#endif
if (slash != NULL) strcpy(title, slash + 1);
else strcpy(title, filename);
}
if (changed) strcat(title, " (modified)");
w->label(title);
}

# The main() Function

Once we've created all of the support functions, the only thing left is to tie them all together with the `main()` function. The `main()` function creates a new text buffer, creates a new view (window) for the text, shows the window, loads the file on the command-line (if any), and then enters the FLTK event loop:

int main(int argc, char **argv) {
textbuf = new Fl_Text_Buffer;
Fl_Window* window = new_view();
window->show(1, argv);
if (argc > 1) load_file(argv[1], -1);
return Fl::run();
}
Fl_Window::show
virtual void show()
Puts the window on the screen.
Fl::run
static int run()
As long as any windows are displayed this calls Fl::wait() repeatedly.
Definition: Fl.cxx:641

# Compiling the Editor

The complete source for our text editor can be found in the `test/editor.cxx` source file. Both the Makefile and Visual C++ workspace include the necessary rules to build the editor. You can also compile it using a standard compiler with:

CC -o editor editor.cxx -lfltk -lXext -lX11 -lm

or by using the `fltk-config` script with:

fltk-config --compile editor.cxx

As noted in Compiling Programs with Standard Compilers, you may need to include compiler and linker options to tell them where to find the FLTK library. Also, the `CC` command may also be called `gcc` or `c++` on your system.

Congratulations, you've just built your own text editor!

# The Final Product

The final editor window should look like the image in Figure 4-2.

Figure 4-2: The completed editor window

# Advanced Features

Now that we've implemented the basic functionality, it is time to show off some of the advanced features of the Fl_Text_Editor widget.

## Syntax Highlighting

The Fl_Text_Editor widget supports highlighting of text with different fonts, colors, and sizes. The implementation is based on the excellent NEdit text editor core, from http://www.nedit.org/, which uses a parallel "style" buffer which tracks the font, color, and size of the text that is drawn.

Styles are defined using the Fl_Text_Display::Style_Table_Entry structure defined in `<FL/Fl_Text_Display.H>`:

struct Style_Table_Entry {
Fl_Color color;
Fl_Font font;
int size;
unsigned attr;
};
Fl_Font
int Fl_Font
A font number is an index into the internal font table.
Definition: Enumerations.H:875
Fl_Color
unsigned int Fl_Color
An FLTK color value; see also Colors
Definition: Enumerations.H:932

The `color` member sets the color for the text, the `font` member sets the FLTK font index to use, and the `size` member sets the pixel size of the text. The `attr` member is currently not used.

For our text editor we'll define 7 styles for plain code, comments, keywords, and preprocessor directives:

Fl_Text_Display::Style_Table_Entry styletable[] = { // Style table
{ FL_BLACK, FL_COURIER, FL_NORMAL_SIZE }, // A - Plain
{ FL_DARK_GREEN, FL_COURIER_ITALIC, FL_NORMAL_SIZE }, // B - Line comments
{ FL_DARK_GREEN, FL_COURIER_ITALIC, FL_NORMAL_SIZE }, // C - Block comments
{ FL_BLUE, FL_COURIER, FL_NORMAL_SIZE }, // D - Strings
{ FL_DARK_RED, FL_COURIER, FL_NORMAL_SIZE }, // E - Directives
{ FL_DARK_RED, FL_COURIER_BOLD, FL_NORMAL_SIZE }, // F - Types
{ FL_BLUE, FL_COURIER_BOLD, FL_NORMAL_SIZE } // G - Keywords
};
FL_NORMAL_SIZE
FL_EXPORT Fl_Fontsize FL_NORMAL_SIZE
normal font size
Definition: Fl_Widget.cxx:117
FL_COURIER_BOLD
const Fl_Font FL_COURIER_BOLD
Courier bold.
Definition: Enumerations.H:882
FL_COURIER_ITALIC
const Fl_Font FL_COURIER_ITALIC
Courier italic.
Definition: Enumerations.H:883
Fl_Text_Display::Style_Table_Entry
This structure associates the color, font, and font size of a string to draw with an attribute mask m...
Definition: Fl_Text_Display.H:148

You'll notice that the comments show a letter next to each style - each style in the style buffer is referenced using a character starting with the letter 'A'.

You call the `highlight_data()` method to associate the style data and buffer with the text editor widget:

Fl_Text_Buffer *stylebuf;
w->editor->highlight_data(stylebuf, styletable,
sizeof(styletable) / sizeof(styletable[0]),
'A', style_unfinished_cb, 0);

Finally, you need to add a callback to the main text buffer so that changes to the text buffer are mirrored in the style buffer:

textbuf->add_modify_callback(style_update, w->editor);

The `style_update()` function, like the `change_cb()` function described earlier, is called whenever text is added or removed from the text buffer. It mirrors the changes in the style buffer and then updates the style data as necessary:

//
// 'style_update()' - Update the style buffer...
//
void
style_update(int pos, // I - Position of update
int nInserted, // I - Number of inserted chars
int nDeleted, // I - Number of deleted chars
int nRestyled, // I - Number of restyled chars
const char *deletedText, // I - Text that was deleted
void *cbArg) { // I - Callback data
int start, // Start of text
end; // End of text
char last, // Last style on line
*style, // Style data
*text; // Text data
// If this is just a selection change, just unselect the style buffer...
if (nInserted == 0 && nDeleted == 0) {
stylebuf->unselect();
return;
}
// Track changes in the text buffer...
if (nInserted > 0) {
// Insert characters into the style buffer...
style = new char[nInserted + 1];
memset(style, 'A', nInserted);
style[nInserted] = '\0';
stylebuf->replace(pos, pos + nDeleted, style);
delete[] style;
} else {
// Just delete characters in the style buffer...
stylebuf->remove(pos, pos + nDeleted);
}
// Select the area that was just updated to avoid unnecessary
// callbacks...
stylebuf->select(pos, pos + nInserted - nDeleted);
// Re-parse the changed region; we do this by parsing from the
// beginning of the line of the changed region to the end of
// the line of the changed region... Then we check the last
// style character and keep updating if we have a multi-line
// comment character...
start = textbuf->line_start(pos);
end = textbuf->line_end(pos + nInserted - nDeleted);
text = textbuf->text_range(start, end);
style = stylebuf->text_range(start, end);
last = style[end - start - 1];
style_parse(text, style, end - start);
stylebuf->replace(start, end, style);
((Fl_Text_Editor *)cbArg)->redisplay_range(start, end);
if (last != style[end - start - 1]) {
// The last character on the line changed styles, so reparse the
// remainder of the buffer...
free(text);
free(style);
end = textbuf->length();
text = textbuf->text_range(start, end);
style = stylebuf->text_range(start, end);
style_parse(text, style, end - start);
stylebuf->replace(start, end, style);
((Fl_Text_Editor *)cbArg)->redisplay_range(start, end);
}
free(text);
free(style);
}
Fl_Text_Buffer::unselect
void unselect()
Cancels any previous selection on the primary text selection object.
Definition: Fl_Text_Buffer.cxx:500
Fl_Text_Buffer::text_range
char * text_range(int start, int end) const
Get a copy of a part of the text buffer.
Definition: Fl_Text_Buffer.cxx:200
Fl_Text_Buffer::remove
void remove(int start, int end)
Deletes a range of characters in the buffer.
Definition: Fl_Text_Buffer.cxx:327
Fl_Text_Buffer::line_end
int line_end(int pos) const
Finds and returns the position of the end of the line containing position pos (which is either a poin...
Definition: Fl_Text_Buffer.cxx:821
Fl_Text_Buffer::replace
void replace(int start, int end, const char *text)
Deletes the characters between start and end, and inserts the null-terminated string text in their pl...
Definition: Fl_Text_Buffer.cxx:299
Fl_Text_Buffer::line_start
int line_start(int pos) const
Returns the position of the start of the line containing position pos.
Definition: Fl_Text_Buffer.cxx:810

The `style_parse()` function scans a copy of the text in the buffer and generates the necessary style characters for display. It assumes that parsing begins at the start of a line:

//
// 'style_parse()' - Parse text and produce style data.
//
void
style_parse(const char *text,
char *style,
int length) {
char current;
int col;
int last;
char buf[255],
*bufptr;
const char *temp;
for (current = *style, col = 0, last = 0; length > 0; length --, text ++) {
if (current == 'A') {
// Check for directives, comments, strings, and keywords...
if (col == 0 && *text == '#') {
// Set style to directive
current = 'E';
} else if (strncmp(text, "//", 2) == 0) {
current = 'B';
} else if (strncmp(text, "/*", 2) == 0) {
current = 'C';
} else if (strncmp(text, "\\\"", 2) == 0) {
// Quoted quote...
*style++ = current;
*style++ = current;
text ++;
length --;
col += 2;
continue;
} else if (*text == '\"') {
current = 'D';
} else if (!last && islower(*text)) {
// Might be a keyword...
for (temp = text, bufptr = buf;
islower(*temp) && bufptr < (buf + sizeof(buf) - 1);
*bufptr++ = *temp++);
if (!islower(*temp)) {
*bufptr = '\0';
bufptr = buf;
if (bsearch(&bufptr, code_types,
sizeof(code_types) / sizeof(code_types[0]),
sizeof(code_types[0]), compare_keywords)) {
while (text < temp) {
*style++ = 'F';
text ++;
length --;
col ++;
}
text --;
length ++;
last = 1;
continue;
} else if (bsearch(&bufptr, code_keywords,
sizeof(code_keywords) / sizeof(code_keywords[0]),
sizeof(code_keywords[0]), compare_keywords)) {
while (text < temp) {
*style++ = 'G';
text ++;
length --;
col ++;
}
text --;
length ++;
last = 1;
continue;
}
}
}
} else if (current == 'C' && strncmp(text, "*/", 2) == 0) {
// Close a C comment...
*style++ = current;
*style++ = current;
text ++;
length --;
current = 'A';
col += 2;
continue;
} else if (current == 'D') {
// Continuing in string...
if (strncmp(text, "\\\"", 2) == 0) {
// Quoted end quote...
*style++ = current;
*style++ = current;
text ++;
length --;
col += 2;
continue;
} else if (*text == '\"') {
// End quote...
*style++ = current;
col ++;
current = 'A';
continue;
}
}
// Copy style info...
if (current == 'A' && (*text == '{' || *text == '}')) *style++ = 'G';
else *style++ = current;
col ++;
last = isalnum(*text) || *text == '.';
if (*text == '\n') {
// Reset column and possibly reset the style
col = 0;
if (current == 'B' || current == 'E') current = 'A';
}
}
}

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