[PATCH weston] xwm: fix intermittent half-drawn decorations problem

[Daniel Stone]

Hi,

On 17 January 2017 at 15:33, Pekka Paalanen <ppaalanen at gmail.com> wrote:
> To reproduce the problem:
> - start weston (x11 backend worked, glamor in Xwayland makes no
>   difference)
> - start xterm
> - very very slowly move the pointer in the xterm decorations onto or
>   away from a button
> - the moment the decorations are updated, they will appear incomplete,
>   e.g. completely without buttons and title text
> - if you cause just one more pointer motion event, the decorations will
>   update to completely drawn appearance
>
> Another way to reproduce the problem is to have an xterm and change its
> window title. This is easy if you use a shell prompt that updates the
> terminal window title. When the title updates, decorations will be
> half-drawn until something happens in XWM.
>
> The fix: flush.
>
> Apparently the drawing commands did not get flushed to the X server
> until any other X11 action pushed them through.
>
> xcb_flush() is the real fix here. cairo_surface_flush() is added just
> for good measure, because documentation indicates it would be better
> used, however it was not strictly necessary to fix the problem in my
> experiments.
>
> Signed-off-by: Pekka Paalanen <pekka.paalanen at collabora.co.uk>

Oh dear.

Reviewed-by: Daniel Stone <daniels at collabora.com>

Cheers,
Daniel