Remove all the old 2.x and 3.x version annotations.
GTK+ 4 is a new start, and from the perspective of a
GTK+ 4 developer all these APIs have been around since
the beginning.
The existence of OpenGL implementations that do not provide the full
core profile compatibility because of reasons beyond the technical, like
llvmpipe not implementing floating point buffers, makes the existence of
GdkGLProfile and documenting the fact that we use core profiles a bit
harder.
Since we do not have any existing profile except the default, we can
remove the GdkGLProfile and its related API from GDK and GTK+, and sweep
the whole thing under the carpet, while we wait for an extension that
lets us ask for the most compatible profile possible.
https://bugzilla.gnome.org/show_bug.cgi?id=744407
This restructures the way buffers are allocated and bound in a way
that is more flexible.
Buffer operation happens in three phases:
create_buffer() - Creates the gl objects
allocate_buffers() - Allocates space for the buffers at a given size
attach_buffers() - Attaches the buffers to the framebuffer and makes
the framebuffer the default drawing target
And destroy via
delete_buffers()
We call all these the first draw, and after that we allocate buffers
each time the widget changes size until the buffers are deleted.
We delete the buffers at unrealize.
However, anyone that wants to manually control buffer allocation strategies
can manually call allocate/delete_buffers().
There are also some other changes:
* Support for stencil buffers.
* A manual render mode where ::draw doesn't render unless you manually
invalidated the previous rendering.
Its not really reasonable to handle failures to make_current, it
basically only happens if you pass invalid arguments to it, and
thats not something we trap on similar things on the X drawing side.
If GL is not supported that should be handled by the context creation
failing, and anything going wrong after that is essentially a critical
(or an async X error).
