GdkGLContext is in legacy mode or not.
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
If the underlying OpenGL implementation does not support core profiles,
GDK will fall back to a pre-3.2 compatibility profile, and this function
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.
Available since: 3.20