[LaganYT]

Fixes #3

Problem

Selecting D3DMetal on the FEX build of CrossOver silently runs the game on a different backend. The FEX build's cxcompatdb.so only treats D3DMetal as usable when CX_ENABLE_ARM_D3DM=1, and logs d3dmetal was set as the graphics backend but it is unusable otherwise. Setting that flag wouldn't help: every D3DMetal file in the runner (D3DMetal.framework, libd3dshared.dylib, the x86_64-unix .so files and PE DLLs) is x86_64-only, and the FEX build's Wine is a native arm64 process. Nothing tells the user, so the game just looks wrong (see #3).

Change

• compat_run.sh: new warn_d3dmetal_on_fex, run right after refuse_foreign_prefix. When the runner is the FEX build and CX_GRAPHICS_BACKEND=d3dmetal:
  • logs a line to notproton-run.log on every launch
  • shows a one-time alert per prefix (marker file notproton-d3dmetal-fex-warned) pointing at the Rosetta build, or DXMT/DXVK
  • skips the alert for the run verb, matching refuse_foreign_prefix
• README: notes that D3DMetal is Rosetta-only.

Testing

• sh -n, make compatcheck and make all pass (shellcheck isn't installed locally, so make runcheck skipped the lint)
• Ran the function with osascript stubbed: it alerts once for FEX with D3DMetal, stays quiet for DXMT, Automatic, the Rosetta build and the run verb, and logs every FEX + D3DMetal launch
• Not yet exercised in a live Steam launch

[NotProtonNot]

Thank you! I will review this and merge it in today, along with the other outstanding PR.

[LaganYT]

You're welcome, thanks.