GdkGLContext: GDK 4 Reference Manual

## GdkGLContext GdkGLContext — OpenGL context |

## Functions

GdkDisplay * | gdk_gl_context_get_display ()
GdkWindow * | gdk_gl_context_get_window ()
GdkGLContext * | gdk_gl_context_get_shared_context ()
void | gdk_gl_context_get_version ()
void | gdk_gl_context_set_required_version ()
void | gdk_gl_context_get_required_version ()
void | gdk_gl_context_set_debug_enabled ()
gboolean | gdk_gl_context_get_debug_enabled ()
void | gdk_gl_context_set_forward_compatible ()
gboolean | gdk_gl_context_get_forward_compatible ()
void | gdk_gl_context_set_use_es ()
gboolean | gdk_gl_context_get_use_es ()
gboolean | gdk_gl_context_is_legacy ()
gboolean | gdk_gl_context_realize ()
cairo_region_t * | gdk_gl_context_get_damage ()
void | gdk_gl_context_make_current ()
GdkGLContext * | gdk_gl_context_get_current ()
void | gdk_gl_context_clear_current ()

## Properties

GdkGLContext * | shared-context | Read / Write / Construct Only

## Types and Values

| GdkGLContext
enum | GdkGLError

## Object Hierarchy

        GObject
        ╰── GdkDrawContext
            ╰── GdkGLContext

## Includes

    #include <gdk/gdk.h>

## Description

GdkGLContext is an object representing the platform-specific OpenGL drawing context.

GdkGLContexts are created for a GdkWindow using `gdk_window_create_gl_context()`, and the context will match the GdkVisual of the window.

A GdkGLContext is not tied to any particular normal framebuffer. For instance, it cannot draw to the GdkWindow back buffer. The GDK repaint system is in full control of the painting to that. Instead, you can create render buffers or textures and use `gdk_cairo_draw_from_gl()` in the draw function of your widget to draw them. Then GDK will handle the integration of your rendering with that of other widgets.

Support for GdkGLContext is platform-specific, context creation can fail, returning `NULL` context.

A GdkGLContext has to be made "current" in order to start using it, otherwise any OpenGL call will be ignored.

#### Creating a new OpenGL context

In order to create a new GdkGLContext instance you need a GdkWindow, which you typically get during the realize call of a widget.

A GdkGLContext is not realized until either `gdk_gl_context_make_current()`, or until it is realized using `gdk_gl_context_realize()`. It is possible to specify details of the GL context like the OpenGL version to be used, or whether the GL context should have extra state validation enabled after calling `gdk_window_create_gl_context()` by calling `gdk_gl_context_realize()`. If the realization fails you have the option to change the settings of the GdkGLContext and try again.

#### Using a GdkGLContext

You will need to make the GdkGLContext the current context before issuing OpenGL calls; the system sends OpenGL commands to whichever context is current. It is possible to have multiple contexts, so you always need to ensure that the one which you want to draw with is the current one before issuing commands:

    1
    gdk_gl_context_make_current (context);

You can now perform your drawing using OpenGL commands.

You can check which GdkGLContext is the current one by using `gdk_gl_context_get_current()`; you can also unset any GdkGLContext that is currently set by calling `gdk_gl_context_clear_current()`.

## Functions

### gdk_gl_context_get_display ()

    GdkDisplay *
    gdk_gl_context_get_display (GdkGLContext *context);

Retrieves the GdkDisplay the `context` is created for

#### Parameters

context | a GdkGLContext |

#### Returns

a GdkDisplay or `NULL`.

[nullable][transfer none]

Since: 3.16

### gdk_gl_context_get_window ()

    GdkWindow *
    gdk_gl_context_get_window (GdkGLContext *context);

Retrieves the GdkWindow used by the `context` .

#### Parameters

context | a GdkGLContext |

#### Returns

a GdkWindow or `NULL`.

[nullable][transfer none]

Since: 3.16

### gdk_gl_context_get_shared_context ()

    GdkGLContext *
    gdk_gl_context_get_shared_context (GdkGLContext *context);

Retrieves the GdkGLContext that this `context` share data with.

#### Parameters

context | a GdkGLContext |

#### Returns

a GdkGLContext or `NULL`.

[nullable][transfer none]

Since: 3.16

### gdk_gl_context_get_version ()

    void
    gdk_gl_context_get_version (GdkGLContext *context,
                                int *major,
                                int *minor);

Retrieves the OpenGL version of the `context` .

The `context` must be realized prior to calling this function.

#### Parameters

context | a GdkGLContext |
major | return location for the major version. | [out]
minor | return location for the minor version. | [out]

Since: 3.16

### gdk_gl_context_set_required_version ()

    void
    gdk_gl_context_set_required_version (GdkGLContext *context,
                                         int major,
                                         int minor);

Sets the major and minor version of OpenGL to request.

Setting `major` and `minor` to zero will use the default values.

The GdkGLContext must not be realized or made current prior to calling this function.

#### Parameters

context | a GdkGLContext |
major | the major version to request |
minor | the minor version to request |

Since: 3.16

### gdk_gl_context_get_required_version ()

    void
    gdk_gl_context_get_required_version (GdkGLContext *context,
                                         int *major,
                                         int *minor);

Retrieves the major and minor version requested by calling `gdk_gl_context_set_required_version()`.

#### Parameters

context | a GdkGLContext |
major | return location for the major version to request. | [out][nullable]
minor | return location for the minor version to request. | [out][nullable]

Since: 3.16

### gdk_gl_context_set_debug_enabled ()

    void
    gdk_gl_context_set_debug_enabled (GdkGLContext *context,
                                      gboolean enabled);

Sets whether the GdkGLContext should perform extra validations and run time checking. This is useful during development, but has additional overhead.

The GdkGLContext must not be realized or made current prior to calling this function.

#### Parameters

context | a GdkGLContext |
enabled | whether to enable debugging in the context |

Since: 3.16

### gdk_gl_context_get_debug_enabled ()

    gboolean
    gdk_gl_context_get_debug_enabled (GdkGLContext *context);

Retrieves the value set using `gdk_gl_context_set_debug_enabled()`.

#### Parameters

context | a GdkGLContext |

#### Returns

`TRUE` if debugging is enabled

Since: 3.16

### gdk_gl_context_set_forward_compatible ()

    void
    gdk_gl_context_set_forward_compatible (GdkGLContext *context,
                                           gboolean compatible);

Sets whether the GdkGLContext should be forward compatible.

Forward compatibile contexts must not support OpenGL functionality that has been marked as deprecated in the requested version; non-forward compatible contexts, on the other hand, must support both deprecated and non deprecated functionality.

The GdkGLContext must not be realized or made current prior to calling this function.

#### Parameters

context | a GdkGLContext |
compatible | whether the context should be forward compatible |

Since: 3.16

### gdk_gl_context_get_forward_compatible ()

    gboolean
    gdk_gl_context_get_forward_compatible (GdkGLContext *context);

Retrieves the value set using `gdk_gl_context_set_forward_compatible()`.

#### Parameters

context | a GdkGLContext |

#### Returns

`TRUE` if the context should be forward compatible

Since: 3.16

### gdk_gl_context_set_use_es ()

    void
    gdk_gl_context_set_use_es (GdkGLContext *context,
                               int use_es);

Requests that GDK create a OpenGL ES context instead of an OpenGL one, if the platform and windowing system allows it.

The `context` must not have been realized.

By default, GDK will attempt to automatically detect whether the underlying GL implementation is OpenGL or OpenGL ES once the `context` is realized.

You should check the return value of `gdk_gl_context_get_use_es()` after calling `gdk_gl_context_realize()` to decide whether to use the OpenGL or OpenGL ES API, extensions, or shaders.

#### Parameters

context | a GdkGLContext: |
use_es | whether the context should use OpenGL ES instead of OpenGL, or -1 to allow auto-detection |

Since: 3.22

### gdk_gl_context_get_use_es ()

    gboolean
    gdk_gl_context_get_use_es (GdkGLContext *context);

Checks whether the `context` is using an OpenGL or OpenGL ES profile.

#### Parameters

context | a GdkGLContext |

#### Returns

`TRUE` if the GdkGLContext is using an OpenGL ES profile

Since: 3.22

### gdk_gl_context_is_legacy ()

    gboolean
    gdk_gl_context_is_legacy (GdkGLContext *context);

Whether the GdkGLContext is in legacy mode or not.

The GdkGLContext must be realized before calling this function.

When realizing a GL context, GDK will try to use the OpenGL 3.2 core profile; this profile removes all the OpenGL API that was deprecated prior to the 3.2 version of the specification. If the realization is successful, this function will return `FALSE`.

If the underlying OpenGL implementation does not support core profiles, GDK will fall back to a pre-3.2 compatibility profile, and this function will return `TRUE`.

You can use the value returned by this function to decide which kind of OpenGL API to use, or whether to do extension discovery, or what kind of shader programs to load.

#### Parameters

context | a GdkGLContext |

#### Returns

`TRUE` if the GL context is in legacy mode

Since: 3.20

### gdk_gl_context_realize ()

    gboolean
    gdk_gl_context_realize (GdkGLContext *context,
                            GError **error);

Realizes the given GdkGLContext.

It is safe to call this function on a realized GdkGLContext.

#### Parameters

context | a GdkGLContext |
error | return location for a GError |

#### Returns

`TRUE` if the context is realized

Since: 3.16

### gdk_gl_context_get_damage ()

    cairo_region_t *
    gdk_gl_context_get_damage (GdkGLContext *context);

Returns the part of the backbuffer that is known to be damaged and would need to be redrawn. This is the area that needs to be respected in addition to areas invalidated by GTK or the windowing system itself.

#### Parameters

context | a GdkGLContext |

#### Returns

The damage to the backbuffer

### gdk_gl_context_make_current ()

    void
    gdk_gl_context_make_current (GdkGLContext *context);

Makes the `context` the current one.

#### Parameters

context | a GdkGLContext |

Since: 3.16

### gdk_gl_context_get_current ()

    GdkGLContext *
    gdk_gl_context_get_current (void);

Retrieves the current GdkGLContext.

#### Returns

the current GdkGLContext, or `NULL`.

[nullable][transfer none]

Since: 3.16

### gdk_gl_context_clear_current ()

    void
    gdk_gl_context_clear_current (void);

Clears the current GdkGLContext.

Any OpenGL call after this function returns will be ignored until `gdk_gl_context_make_current()` is called.

Since: 3.16

## Types and Values

### GdkGLContext

    typedef struct _GdkGLContext GdkGLContext;

### enum GdkGLError

Error enumeration for GdkGLContext.

#### Members

GDK_GL_ERROR_NOT_AVAILABLE | OpenGL support is not available |
GDK_GL_ERROR_UNSUPPORTED_FORMAT | The requested visual format is not supported |
GDK_GL_ERROR_UNSUPPORTED_PROFILE | The requested profile is not supported |
GDK_GL_ERROR_COMPILATION_FAILED | The shader compilation failed (available since 3.22) |
GDK_GL_ERROR_LINK_FAILED | The shader linking failed (available since 3.22) |

Since: 3.16

## Property Details

### The `“shared-context”` property

      “shared-context”           GdkGLContext *

The GdkGLContext that this context is sharing data with, or NULL

Flags: Read / Write / Construct Only

Since: 3.16