OpenGL support

[TheKruger]

Is your feature request related to a problem? Please describe.
Currently Im working on a game and I will want to publish it on steam, so I will use SteamworksPy, to get steamid and steam overlay. The problem is when I add the pygame.OPENGL flag the UIs will not draw.

Describe the solution you'd like
Adding an option to use pygame_gui with/without the OpenGL flag.

Describe alternatives you've considered
I tried this solution which worked, but the performance was worse.
Edit: Rendering UI besides the game and then converting the surface for OpenGL requires more time. Maybe my game rendering code still lacks of optimalizations, but I will try to improve it more.

[pichenka007]

same problem
I'd like to put a shader on the background :(