Also declare the GL functions in tr_local.h so there is compile error
for non-core GL functions instead of SEGFAULT from dereferencing a NULL
pointer.
Disable the non-functional stencil shadow code that hasn't been updated
to use OpenGL 3.2 core compatible drawing.
If renderer is compiled into client (USE_RENDERER_DLOPEN=0) and after
start up set r_allowExtension to 0 and run vid_restart, some extension
were still used.
The values passed to SDL are just the minimum required. Get actually
values of colorbits, depthbits, and stencilbits from SDL instead of
assuming that the engine got exactly what it asked for.
- Parse OpenGL version in sdl_glimp.c to share with both renderers.
- Add GL_VERSION_ATLEAST(major, minor) macro.
- Get address of glGetStringi if using OpenGL 3.
- Fix glConfig.extensions_string when using GL3 core context in
opengl2 renderer.
- Make opengl1 renderer's gfxinfo support qglGetStringi too.
Get all OpenGL functions using SDL_GL_GetProcAddress(). This makes it
easier to cross-arch compile on Linux and add support for OpenGL ES
in the future.
Users still have to supply their own libSDL2 for cross-arch compiling
on Linux. But now the user does not have to re-install libgl1-mesa-dev
package for i386 or amd64 on Debian when switching between compiling
ioquake3 for x86 and x86_64.
When starting the game in windowed mode, the window buffer used whatever
was on the screen before running the game. Kind of like you could see
through the window, but it doesn't update what happens behind it.
It makes it look like something is broken or non-responsive.
So clear the window opengl buffer to black.
Credit to theinvsblman for the code.
Setting SDL_GL_ACCELERATED_VISUAL was disabled for ioq3 SDL 1.2
for other reasons. However, it causes creating GL context to fail
if multisampling is enabled on X11 for both SDL1.2 and SDL2.
Tested using nVidia proprietary driver on Debian 7.
