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Setting display gamma in Wayland doesn't affect the cursor on some hardware

Steps to reproduce:

  • login into Gnome Wayland session,
  • enable Night Light,
  • the cursor remains unaffected by the changed gamma (and is a jarring cold-white on otherwise warm-colored display).

Expected result:

  • the cursor should have the same gamma as the display.

This happens only in Wayland; X11 session works fine.

Software used:

  • amdgpu kernel driver as shipped with 4.15rc9 kernel (from fedora's vanilla kernel mainline repository),
  • for X11 session, amdgpu xorg driver 1.4.0

Mutter controls the display gamma using the Monitor Manager and implements backends for KMS and X11.

The KMS backend calls drmModeCrtsSetGamma() inside meta_monitor_manager_kms_set_crtc_gamma() and that's it.

The X11 backend calls XRRSetCrtcGamma() in meta_monitor_manager_xrandr_set_crtc_gamma(), which bubbles into the xorg server and into the amdgpu driver, which, after also calling drmModeCrtsSetGamma() (in drmmode_crtc_gamma_do_set()) also calls xf86CursorResetCursor() (in drmmode_crtc_gamma_set()). This call has the consequence of forcing the cursor to have the same gamma as the surface behind.

Suggested resolution:

  • Mutter should ensure, that the cursor has the same gamma as the surface behind it, just like the amdgpu xorg driver does.