gl_example.py is not working on linux

[cmbruns]

It doesn't crash, but it's not displaying the colors in each eye. At least not for me with Ubuntu LTS and og HTC Vive.

[nlsdvl]

I don't have a Vive to try, but it works fine for me with the monado runtime on Ubuntu 20.04 LTS.
As a side note, I also get it to work with Quest2 on windows.

[el-dee]

The problem is this one ValveSoftware/SteamVR-for-Linux#421 (and as of SteamVR 1.21.8 not yet solved)

Christoph Haag made a layer to work around this problem, see https://github.com/ChristophHaag/gl_context_fix_layer

When using this layer with gl_example.py there is some improvement: I get the blue color for the right eye, but the left eye stays black, however now if I activate the mirror window I correctly have the left side of the window colored green and the right side colored blue.