KWinModule for several "kwin" processes

Lubos Lunak l.lunak at
Thu Mar 9 10:04:47 GMT 2006

On Thursday 09 March 2006 05:56, Andriy Rysin wrote:
> Got a question which came from bug 107877
> <>
> There's switching policies "per window" and "per application" for kxkb.
> It's implemented in a way that kxkb registers itself as a listener with
> KWinModule and gets notified when active window is changed. Now there's
> a case when user have multiple screens and don't use Xinerama he'll have
> several instances of kwin process running. kxkb currently registers
> itself only with 1st one, so whenever user switches to other screens
> kxkb never gets notified when active window is changed and thus "per
> window" and "per application" do not work. When user switches back to
> screen 0 everything is fine.

 Short answer: Non-xinerama multihead is not supported by KDE and nobody works 
on it. The only "support" we have is a hack to start one instance per screen 
of some important apps like kwin/kdesktop/kicker. Given that Xinerama mostly 
works quite fine I don't see anybody spending the effort on providing a 
proper support or even just finding out what that'd require, but if there's a 
volunteer you're of course welcome.

> The question is whether there's a way to get hold of KWinModule for
> other screens to be able to listen to their messages?

 Fast&simple solution: Enqueue the bugreport next to the all other 
non-xinerama multihead bugreport that nobody cares about, recommend the user 
to use xinerama and wait for all such users to get bored with non-xinerama or 
for somebody to fix it.

 Extend-the-hack solution: Fork kxkb per screen just like kwin/kdesktop/kicker 
etc. do in their main.cpp .

 Fixing-KWinModule solution: All netwm.* classes seem to have proper support 
for multiple screens, so just extending KWinModule to use proper screen 
number and root window could fix your problem.

Lubos Lunak
KDE developer
SuSE CR, s.r.o.  e-mail: l.lunak at , l.lunak at
Drahobejlova 27  tel: +420 2 9654 2373
190 00 Praha 9   fax: +420 2 9654 2374
Czech Republic

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