[Help]: Question about compositing with xfwm4

[Olivier Fourdan]

On Thu, Oct 22, 2009 at 5:22 PM, andy wang <wandy817 at gmail.com> wrote:
> Hi all,
> I have one question about 'compositing' with xfwm4.
> In one shell, I start a new x server with Xephyr on 1.0 display:
> Xephyr -ac :1.0
> In another shell,
> export DISPLAY=:1.0
> I start xfwm4 and enable 'Enable display compositing' with
> xfwm4-tweaks-settings.
> then set background image with xli:
> xli -onroot /usr/share/pixmaps/xx.png
> Then drag any window , however, the background is coverd, looks like the
> background was not re-painted yet(grey).
> But if I use xfdesktop or disable compositing option, there is no problem.
> I don't know why? and how to solve this problem with xli.
> Thanks!

Simply because a compositor draws on the root win, so if another
application draws on the root win you end up with problems.

If "xli" sets the root pixmap property XROOTPMAP, xfwm4 can be built
to "listen" to the XROOTPMAP property and repaint the background
accordingly, you just need to built xfwm4 from sources with
MONITOR_ROOT_PIXMAP defined.

But as this is not needed in the default configuration (ie you have
xfdesktop or another desktop that uses a separate window on top of the
root win), that define is not set in the default build (read, you're
on your own).

Cheers,
Olivier.