4e02acf2ba
This main thread check was introduced in 4536a4c610. At the time OpenGL
only ever worked in the main thread, but that limitation was lifted in
Blender 2.80.
With this operator being converted to use the jobs system, it now needs
to work in non-main threads. Note that this code does not run in parallel
with main thread drawing anyway, because of WM_job_main_thread_lock_acquire
and draw manager locks. What changed is that we can now activate OpenGL
contexts on other threads.
Pull Request: https://projects.blender.org/blender/blender/pulls/134696