This make the workbench draw everything in the background routine just like
eevee. This is because the workbench uses floating point buffers too and
rendering background to this buffer makes it incorrect without proper
color management.
This could be improved because in xray the background is not blended but
dithered as it's drawn after the main pass.
OpenGL rendering only implemented the deferred renderer. This commit
will add the forward renderer. The forward renderer is used when XRay
mode is enabled
When playing animations the anti-aliasing was not reset, resulting in
ghosts from previous frames to be drawn. Also when playing animations
and switching to X-Ray mode for the first time would most likely
result in a write to uninitialized memory.
