Gdk.GLContext.Gdk_GLContext is an object representing the platform-specific OpenGL drawing context.
Gdk_GLContexts are created for a Gdk.Gdk_Window using Gdk.Window.Create_Gl_Context, and the context will match the Gdk.Visual.Gdk_Visual of the window.
A Gdk.GLContext.Gdk_GLContext is not tied to any particular normal framebuffer. For instance, it cannot draw to the Gdk.Gdk_Window 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 Gdk.GLContext.Gdk_GLContext is platform-specific, context creation can fail, returning null context.
A Gdk.GLContext.Gdk_GLContext 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 Gdk.GLContext.Gdk_GLContext instance you need a Gdk.Gdk_Window, which you typically get during the realize call of a widget.
A Gdk.GLContext.Gdk_GLContext is not realized until either Gdk.GLContext.Make_Current, or until it is realized using Gdk.GLContext.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.GLContext.Realize. If the realization fails you have the option to change the settings of the Gdk.GLContext.Gdk_GLContext and try again.
## Using a GdkGLContext ##
You will need to make the Gdk.GLContext.Gdk_GLContext 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:
gdk_gl_context_make_current (context);
You can now perform your drawing using OpenGL commands.
You can check which Gdk.GLContext.Gdk_GLContext is the current one by using Gdk.GLContext.Get_Current; you can also unset any Gdk.GLContext.Gdk_GLContext that is currently set by calling Gdk.GLContext.Clear_Current.
procedure Clear_Current
Clears the current Gdk.GLContext.Gdk_GLContext. Any OpenGL call after this function returns will be ignored until Gdk.GLContext.Make_Current is called. Since: gtk+ 3.16
Display_Property : constant Glib.Properties.Property_Boxed;
Type: Display The Gdk.Display.Gdk_Display used to create the Gdk.GLContext.Gdk_GLContext.
type Gdk_GLContext is access all Gdk_GLContext_Record'Class;
type Gdk_GLContext_Record is new GObject_Record with null record;
function Get_Current return Gdk_GLContext
Retrieves the current Gdk.GLContext.Gdk_GLContext. Since: gtk+ 3.16
the current Gdk.GLContext.Gdk_GLContext, or null
function Get_Debug_Enabled
(Self : not null access Gdk_GLContext_Record) return Boolean
Retrieves the value set using Gdk.GLContext.Set_Debug_Enabled. Since: gtk+ 3.16
True if debugging is enabled
function Get_Display
(Self : not null access Gdk_GLContext_Record)
return Gdk.Display.Gdk_Display
Retrieves the Gdk.Display.Gdk_Display the Context is created for Since: gtk+ 3.16
a Gdk.Display.Gdk_Display or null
function Get_Forward_Compatible
(Self : not null access Gdk_GLContext_Record) return Boolean
Retrieves the value set using Gdk.GLContext.Set_Forward_Compatible. Since: gtk+ 3.16
True if the context should be forward compatible
procedure Get_Required_Version
(Self : not null access Gdk_GLContext_Record;
Major : out Glib.Gint;
Minor : out Glib.Gint)
Retrieves the major and minor version requested by calling Gdk.GLContext.Set_Required_Version. Since: gtk+ 3.16
return location for the major version to request
return location for the minor version to request
function Get_Shared_Context
(Self : not null access Gdk_GLContext_Record) return Gdk_GLContext
Retrieves the Gdk.GLContext.Gdk_GLContext that this Context share data with. Since: gtk+ 3.16
a Gdk.GLContext.Gdk_GLContext or null
function Get_Type return Glib.GType
function Get_Use_Es
(Self : not null access Gdk_GLContext_Record) return Boolean
Checks whether the Context is using an OpenGL or OpenGL ES profile. Since: gtk+ 3.22
True if the Gdk.GLContext.Gdk_GLContext is using an OpenGL ES profile
procedure Get_Version
(Self : not null access Gdk_GLContext_Record;
Major : out Glib.Gint;
Minor : out Glib.Gint)
Retrieves the OpenGL version of the Context. The Context must be realized prior to calling this function. Since: gtk+ 3.16
return location for the major version
return location for the minor version
function Get_Window
(Self : not null access Gdk_GLContext_Record) return Gdk.Gdk_Window
Retrieves the Gdk.Gdk_Window used by the Context. Since: gtk+ 3.16
a Gdk.Gdk_Window or null
function Is_Legacy
(Self : not null access Gdk_GLContext_Record) return Boolean
Whether the Gdk.GLContext.Gdk_GLContext is in legacy mode or not. The Gdk.GLContext.Gdk_GLContext 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. Since: gtk+ 3.20
True if the GL context is in legacy mode
procedure Make_Current (Self : not null access Gdk_GLContext_Record)
Makes the Context the current one. Since: gtk+ 3.16
function Realize
(Self : not null access Gdk_GLContext_Record) return Boolean
Realizes the given Gdk.GLContext.Gdk_GLContext. It is safe to call this function on a realized Gdk.GLContext.Gdk_GLContext. Since: gtk+ 3.16
True if the context is realized
procedure Set_Debug_Enabled
(Self : not null access Gdk_GLContext_Record;
Enabled : Boolean)
Sets whether the Gdk.GLContext.Gdk_GLContext should perform extra validations and run time checking. This is useful during development, but has additional overhead. The Gdk.GLContext.Gdk_GLContext must not be realized or made current prior to calling this function. Since: gtk+ 3.16
whether to enable debugging in the context
procedure Set_Forward_Compatible
(Self : not null access Gdk_GLContext_Record;
Compatible : Boolean)
Sets whether the Gdk.GLContext.Gdk_GLContext 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 Gdk.GLContext.Gdk_GLContext must not be realized or made current prior to calling this function. Since: gtk+ 3.16
whether the context should be forward compatible
procedure Set_Required_Version
(Self : not null access Gdk_GLContext_Record;
Major : Glib.Gint;
Minor : Glib.Gint)
Sets the major and minor version of OpenGL to request. Setting Major and Minor to zero will use the default values. The Gdk.GLContext.Gdk_GLContext must not be realized or made current prior to calling this function. Since: gtk+ 3.16
the major version to request
the minor version to request
procedure Set_Use_Es
(Self : not null access Gdk_GLContext_Record;
Use_Es : Glib.Gint)
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.GLContext.Get_Use_Es after calling Gdk.GLContext.Realize to decide whether to use the OpenGL or OpenGL ES API, extensions, or shaders. Since: gtk+ 3.22
whether the context should use OpenGL ES instead of OpenGL, or -1 to allow auto-detection
Shared_Context_Property : constant Glib.Properties.Property_Boxed;
Type: GLContext The Gdk.GLContext.Gdk_GLContext that this context is sharing data with, or null
Window_Property : constant Glib.Properties.Property_Object;
Type: Gtk.Window.Gtk_Window The Gdk.Gdk_Window the gl context is bound to.