opengl: Allow SDL_GL_MakeCurrent() to accept a NULL window (thanks, Martin!).
This allows you to bind surfaceless contexts on a background thread to, for
example, load assets in a separate context, for platforms that have different
requirements about sharing surfaces, etc.
Martin's notes on the matter:
"Here's a patch that enables passing NULL windows to SDL_GL_MakeCurrent, if
the involved APIs allow it. Currently, this is only the case for EGL, and
even then only if some specific extensions are present (which they usually
are).
If "surfaceless" contexts are not supported, SDL_GL_MakeCurrent continues to
generate an error (albeit with a more specific error message than it used to),
so this should not break anything that wasn't broken before."
(Please see https://bugzilla.libsdl.org/show_bug.cgi?id=3695 for more
discussion.)
Fixes Bugzilla #3695.
4 files changed
