Stress testing KWin's screen handling

[Daniel Vrátil]

On Wednesday 26 of November 2014 08:19:26 Martin Gräßlin wrote:
> On Tuesday 25 November 2014 16:28:16 Daniel Vrátil wrote:
> > On Tuesday 25 of November 2014 13:17:28 Martin Gräßlin wrote:
> > > Hi all,
> > > 
> > > I spent some time on screen management in KWin today and got it to the
> > > point where it doesn't fail any more no matter what I try. So please
> > > everyone using multiple screens and especially dynamically plug in and
> > > out, please give a try to the patch set in [1]. Please ensure to have
> > > latest master as it contains a crash fix for a crash triggered by the
> > > patch set.
> > > 
> > > Short summary of the changes in the patch set:
> > > * uses XRandR instead of QDesktopWidget
> > > * uses KWin internal information about overall screen geometry instead
> > > of
> > > relying on the information in the X11 screen structure.
> > > 
> > > The second part is the code I added today. My testing showed that
> > > unplugging a screen gives us proper XRandR events so KWin's internal is
> > > up to date, but the X11 screen information is wrong. So when we
> > > partially
> > > used the one and partially the other the rendering was just horribly
> > > broken. Now it's all based on the KWin internal information and I
> > > couldn't get the rendering broken any more.
> > > 
> > > When changing screens please be patient. It takes time to settle the
> > > changes. Especially plasmashell takes quite some time on my system to
> > > render correctly again.
> > 
> > Coincidentally, I just merged my KScreen redesign, which should make this
> > faster.
> 
> sounds like I need to trigger kdesrc-build ;-)
> 
> > > I hope that it doesn't fail for others and we can get the changes in to
> > > improve the situation.
> > 
> > So far it's much better than before, but still it sometimes happens, that
> > after screen reshuffle, window decorations get detached from the windows
> > and moved elsewhere. It just happened to me, after plugging in the 3rd
> > screen: http://pub.dvratil.cz/kwin-bug.ogv, but I'm not able to reliably
> > reproduce this.
> 
> ok, that still sounds like a rendering error. A few questions:
> * does qdus.org.kde.KWin /KWin supportInformation report correct screen
> information?

Yes

> * does xrandr report correct screen information?

Yes

> * does restarting compositing fix it?

Yes

> 
> For three screens I'm completely out of testing possibilities. I don't have
> three screens and even if I had I would not be able to connect them.

I managed to reproduce this when I unplugged the 3rd screen, so I don't think 
this is strictly related to having ridiculous amount of screens, but should be 
reproducible with two screens too.

If there's any debug info I can provide, just let me know. I really want this 
fixed, but KWin internals are beyond my understanding :-)

> A kingdom, a kingdom for unit testing xrandr.

Amen to that


Dan

> 
> Cheers
> Martin

-- 
Daniel Vrátil | dvratil at redhat.com | dvratil on #kde-devel, #kontact, #akonadi
Software Engineer - KDE Desktop Team, Red Hat Inc.

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