Calling PyEval_ReleaseLock() was crashing with Python 3.9
because it accessed the NULL pointer set by PyThreadState_Swap().
This happened when calling ViewLayer.update() for example.
While the existing logic could be fixed by swapping the thread-state
back before calling PyEval_ReleaseLock(), this depends on functions
which are tagged to be removed by v4.0.
Replace use of deprecated functions by calling PyEval_SaveThread(),
instead of inlining the logic, using _PyThreadState_UncheckedGet()
to prevent Python aborting.
The call to PyEval_ThreadsInitialized has been removed
as threads are now initialized with Python.
This could be replaced with Py_IsInitialized() however it doesn't look
like this is necessary.
This is compatible with Python 3.7 & 3.9.
BF-admins agree to remove header information that isn't useful,
to reduce noise.
- BEGIN/END license blocks
Developers should add non license comments as separate comment blocks.
No need for separator text.
- Contributors
This is often invalid, outdated or misleading
especially when splitting files.
It's more useful to git-blame to find out who has developed the code.
See P901 for script to perform these edits.
This way blender player can easily use BPY_thread_save/restore.
Not so much important for master branch, but crucial to solve
linking issues in threaded depsgraph branch.
