Starting with Blender 4.0, Blender refuses to load a userpref.blend file
that had been generated on a macoOS machine, exiting immediately with an
unsupported GPU error. This is because when the userdef was written on
the macOS machine (assuming a recent version), it has gpu_backend set to
GPU_BACKEND_METAL (which is rejected). The same is true in reverse.
Prior to commit cdb8a8929c there was a runtime fallback such
that the setting for Metal backend would be ignored on non-Metal
platforms.
This adds a check in blo_do_versions_userdef() for if gpu_backend is set
to an unsupported backend; if so, it is set to a default supported value
for the current platform (Metal on macOS, OpenGL otherwise). This
replaces the current versioning check, as this isn't strictly related to
versioning. The new logic handles the narrower versioning case (a macOS
user upgrading to 4.0+ with a userprefs selecting OpenGL) as well.
This should be future-proof for other GPU backends, as it only overrides
in the case of an unsupported value. The logic could be generalized in
the future, perhaps.
Co-authored-by: Andrew Oates <andrew@andrewoates.com>
Pull Request: https://projects.blender.org/blender/blender/pulls/116861
2e48712508