Your system information

• Steam client version (build number or date): 1599691266 / Sep 9 2020, at 22:05:48
• Distribution (e.g. Ubuntu): Gentoo
• Opted into Steam client beta?: Yes
• Have you checked for system updates?: Yes
• System Information
• glxinfo

Please describe your issue in as much detail as possible:

The Steam overlay calls glMatrixMode() with the invalid enum GL_COLOR. Using this enum requires the ARB_imaging extension which Mesa/radeonsi does not support

With Arx Libertatis, which creates a a KHR_no_error context by default, this causes all textures to be rendered as a single color, see dreamer/luxtorpeda#27.

Describe what you expected should happen and what did happen. Please link any large code pastes as a Github Gist

Steps for reproducing this issue:

1. Configure Steam to use Arx Libertatis for Arx Fatalis but leave the overlay enabled.
2. Start the game.
3. Watch as all textures are gone as soon as the overlay starts up.

Arx Libertatis supports creating a debug context instead using the --debug-gl option, which will print errors while the overlay is open or a notification is shown:
[E] GLDebug:90 API error #2: GL_INVALID_ENUM in glMatrixMode

Stack trace:

#0  gldebug::callback (source=33350, type=33356, id=2, severity=37190, length=31, message=0x7ffd16465290 "GL_INVALID_ENUM in glMatrixMode", userParam=0x0)
    at /home/dscharrer/pro/arx/src/graphics/opengl/GLDebug.cpp:73
#1  0x00007f6aa826d15b in _mesa_error (ctx=0x56516419a810, error=error@entry=1280, fmtString=fmtString@entry=0x7f6aa89e51a0 "%s")
    at ../mesa-9999/src/mesa/main/errors.c:357
#2  0x00007f6aa82d6902 in get_named_matrix_stack (mode=<optimized out>, caller=<optimized out>, ctx=<optimized out>) at ../mesa-9999/src/mesa/main/matrix.c:97
#3  get_named_matrix_stack (ctx=<optimized out>, mode=<optimized out>, caller=<optimized out>) at ../mesa-9999/src/mesa/main/matrix.c:50
#4  0x00007f6aa82d6f91 in _mesa_MatrixMode (mode=6144) at ../mesa-9999/src/mesa/main/matrix.c:282
#5  0x00007f6aab5ef7ff in ?? () from /home/dscharrer/.local/share/Steam/ubuntu12_64/gameoverlayrenderer.so
#6  0x00007f6aab5fc480 in ?? () from /home/dscharrer/.local/share/Steam/ubuntu12_64/gameoverlayrenderer.so
#7  0x00007f6aab5fe0c8 in ?? () from /home/dscharrer/.local/share/Steam/ubuntu12_64/gameoverlayrenderer.so
#8  0x00007f6aab5edf2e in glXSwapBuffers () from /home/dscharrer/.local/share/Steam/ubuntu12_64/gameoverlayrenderer.so
#9  0x00007f6aab1f74b3 in X11_GL_SwapWindow (_this=<optimized out>, window=<optimized out>)
    at /var/tmp/portage/media-libs/libsdl2-2.0.12-r2/work/SDL2-2.0.12/src/video/x11/SDL_x11opengl.c:931
[#10](/issue/ValveSoftware/steam-for-linux/10) 0x00005651620d6700 in SDL2Window::showFrame (this=<optimized out>) at /home/dscharrer/pro/arx/src/window/SDL2Window.cpp:850
[#11](/issue/ValveSoftware/steam-for-linux/11) ArxGame::doFrame (this=<optimized out>) at /home/dscharrer/pro/arx/src/core/ArxGame.cpp:1267
[#12](/issue/ValveSoftware/steam-for-linux/12) 0x00005651620d9c58 in ArxGame::run (this=0x565163fd86b0) at /home/dscharrer/pro/arx/src/core/ArxGame.cpp:1132
[#13](/issue/ValveSoftware/steam-for-linux/13) 0x0000565161ea7747 in runGame () at /home/dscharrer/pro/arx/src/core/Core.cpp:246
[#14](/issue/ValveSoftware/steam-for-linux/14) main (argc=<optimized out>, argv=<optimized out>) at /home/dscharrer/pro/arx/src/core/Startup.cpp:164