Repaint Issue

Pekka Paalanen ppaalanen at
Tue Sep 11 04:53:28 PDT 2012

On Tue, 11 Sep 2012 15:44:55 +0530
Abhijit Potnis <abhijitpotnis at> wrote:

> Hello,
> Last few days I have been debugging a repaint issue in Weston. No repaint is
> triggered until an input event occurs or a Wayland client like simple-shm
> triggers
> one.
> Digging down, I see that struct weston_output.repaint is pointing to my
> output repaint
> function implementation. When I run weston and follow thru the logs, the
> repaint in
> my back-end implementation gets called when my
> 1. mouse moves/or an input event is sensed.
> 2. when a new client is launched.
> 3. when a client like simple-shm forces a repaint in a loop
> The intermittent screen repaints are timed long apart. So the screen
> doesn't get
> repainted until any one of the above event happens, which force a repaint.
> Here is a video of the behaviour. I launch simple-shm and then kill it
> (time 0:05), the
> screen isn't updated until I move my mouse (time 0:11). When I move the
> mouse the
> screen is updated and the residual simple-shm disappears from the screen,
> which is
> actually a repaint.
> Does any body else happen to see such behaviour ?

Yeah, I've seen similar issues on the DRM and X11 backends. When I
launch an app by clicking a button in the panel, the new window does not
appear, until something else causes a repaint. Weston-terminal and
flower, at least.

Repaint is supposed to be as-needed only, not periodical, but clearly
some trigger is missing. Maybe a new surface is not assigned an output
until redraw, and redraw does not happen until there is damage, and
damage is not applied, if the window is not mapped? Or something like
that, chicken-and-egg problem with assigning an output. A wild guess...


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