Hints for debugging a weird sw-cursor issue ?

[Hans de Goede]

Hi All,

I've noticed a weird sw-cursor issue when a slave-output is active
(I believe this is a sw-cursor issue because show_cursor never
  gets called when a slave-output is active at server start).

I'm seeing this with both 1.18 and master and with both the
intel and the modesetting drivers (running gnome3 / gnome-shell).

Everything is fine until I start glxgears (*) then the cursor becomes
invisible (flickering on the intel driver) when it is near the
top of the screen. Basically there is a horizontal bar where
the cursor does not show. Note this goes for the entire monitor,
not just where glxgears is running. This bar is near the top of
the screen, but not completely at the top, there is a small area
near the top where the cursor still shows.

Interestingly enough if I disable vblank for glxgears the problem
remains, but the bar becomes smaller (less high).

So anyone got any clues for debugging this ?

Regards,

Hans


*) It does not matter how I start it, with DRI2 or DRI3, with
DRI_PRIME=1 or without