python3 opengl client

[Antoine Martin]

Split from #640. For general python3 issues, see #1568.

See ticket:640#comment:41.

If this can be made to work, maybe it will be more stable than the GTK2 version?

See also: #921 native win32 opengl client

[Antoine Martin]

poc using GLX to wrap the X11 window

[Antoine Martin]

Just because GTK3 decided to break every existing GTK opengl application out there does not mean that it should be that way.

Preparatory work removing unneeded dependencies on GTK from the pure opengl code: r16915, r16916, r16917, r16919, r16920, r16921, r16925, r16926, r16927.

The patch above almost works - it paints the screen OK but then the next update comes and messes it up.. It works fine with mmap.
It probably needs xsync to prevent crashes too.
It should be moved to platform code, and the client init code will need to be re-worked.
The code could be made generic enough to be used with both GTK2 and GTK3: the context code only needs a window XID.
Support for win32 and macos should also be possible.
We may then also be able to query the real pixel depth supported on those platforms.