Hints for debugging a weird sw-cursor issue ?

[Dave Airlie]

On 31 August 2016 at 22:10, Hans de Goede <hdegoede at redhat.com> wrote:
> 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 ?

Sounds like some wierdass tearing,

since swcursor has to paint the cursor on the screen, so you might
be seeing frames where the cursor hasn't been painted yet.

Dave.