[Bug 106935] [CHV] Mouse cursor flicker on external display, rendering artifacts under cursor

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=106935

--- Comment #8 from Ville Syrjala <ville.syrjala at linux.intel.com> ---
The problem happens because of that CHV bug where we can't show the cursor when
it's straddling the left screen edge. At that point we switch to using the
software cursor.

The flickering is pretty much unavoidable for the front buffer rendering cases.
But with page flipping/tearfree it should be possible to implement a flicker
free software cursor. Presumably no one has bothered since most hardware has a
working hardware cursor.

The trails being left behind by the software cursor I think is some kind of
damage tracking bug. It only seems to happen with tearfree here. Maybe it could
happen with a page flipping compositor as well, not sure.

I sent a patch [1] that causes us to at least switch back to using the hardware
cursor when then cursor is next updated. That tends to happen quite often so
should mitigate some of the problem. You may still see some ugly cursor trails
though. Fixing those could be a lot trickier.

[1] https://patchwork.freedesktop.org/series/51265/

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