#GdkGLContext is an object representing the platform-specific
OpenGL drawing context.
#GdkGLContexts are created for a #GdkWindow using
gdk.window.Window.createGlContext, 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.global.cairoDrawFromGl
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.
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:
gdk_gl_context_make_current (context);
You can now perform your drawing using OpenGL commands.
#GdkGLContext is an object representing the platform-specific OpenGL drawing context.
#GdkGLContexts are created for a #GdkWindow using gdk.window.Window.createGlContext, 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.global.cairoDrawFromGl 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.glcontext.GLContext.makeCurrent, or until it is realized using gdk.glcontext.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.Window.createGlContext by calling gdk.glcontext.GLContext.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:
You can now perform your drawing using OpenGL commands.
You can check which #GdkGLContext is the current one by using gdk.glcontext.GLContext.getCurrent; you can also unset any #GdkGLContext that is currently set by calling gdk.glcontext.GLContext.clearCurrent.