Linux: missing OpenGL functionality

[fzwoch]

I tried to port some OpenGL software to use the wrap system and encountered some trouble with the SDL2 wrap. It seems like not all OpenGL functionality gets enabled.

For example, SDL_GL_GetAttribute() would return SDL_Unsupported().

Glancing at the meson.build I discovered that cdata.set('SDL_VIDEO_RENDER_OGL', 1) and cdata.set('SDL_VIDEO_OPENGL_GLX', 1) are being set. But it seems it also needs some more defines to properly support SDL2 OpenGL functions.

I'm not sure what exactly is required, or how and when things to enable - but as a quick shot I tried adding cdata.set('SDL_VIDEO_OPENGL', 1) (what about OpenGL ES, etc?) and at least for me it got me a bit further (no thorough testing done though).

|Executing subproject sdl2 method meson 
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|Project name: sdl2
|Project version: 2.0.12
|C compiler for the host machine: cc (gcc 10.2.1 "cc (Debian 10.2.1-6) 10.2.1 20210110")
|C linker for the host machine: cc ld.bfd 2.35.1
|Library m found: YES
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|Configuring SDL_config.h using configuration
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|Subproject sdl2 finished.