touch-packages team mailing list archive

[Antonis Kanouras <antonis+launchpad@xxxxxxxxxxxx>]

I did a few tests:

On the first reboot after installing qtdeclarative from the Wily PPA on
Vivid, I probably got lucky and managed to plug/unplug the external
monitor 4 times before the first crash (nvidia-340's xrandr also stopped
detecting changes for the next 2 topology changes at that point,
although that's nothing new).

On subsequent reboots I'm getting Plasma/Kwin/Konsole crashes on almost every screen change. 
Some changes in behaviour that I noticed:

1. Dr. Konqi is started for kwin crashes, but no window appears (no mention of it in xlsclients either).
2. Dr. Konqi is not started for plasmashell crashes (crashes on almost every screen change).
3. Dr. Konqi is not started for Konsole crashes (crashes on every screen change).
4. krunner does not crash on screen change - it crashes instead when called with Alt+F2, with Dr. Konqi appearing. It doesn't allow me to report krunner crashes by the way, but that's another bug. The backtrace (which I'm attaching) is different this time, there's no physicalSize() in it. Luckily it's restarted right after usually, so there's a way to recover manually.
5. System Settings 5 also usually crashes around screen changes; that's caught by apport however, which gives me zero information.
6. Usually after a crash, the Plasma panel flickers, with only the spacer being displayed when not flickering, and can't be clicked. Disabling composition with the shortcut works around this.

All in all, I'd say the behaviour has improved a bit, as regards the
frequency of crashes; however, losing Dr. Konqi is mildly disappointing.

I have to apologise here for jumping on this patch without having tested
it myself first. I'll try pre-attaching gdb to kwin/plasmashell/konsole
to get backtraces out of them, and a Fedora install in the next days to
see if the crashes are really fixed, at least on my machine, and report
back.

** Attachment added: "New krunner backtrace"
   https://bugs.launchpad.net/ubuntu/+source/qtdeclarative-opensource-src/+bug/1450137/+attachment/4396120/+files/krunner-20150511-231019_xrandr%2Bqtdeclarative_ubuntu8.kcrash.txt

-- 
You received this bug notification because you are a member of Ubuntu
Touch seeded packages, which is subscribed to qtdeclarative-opensource-
src in Ubuntu.
https://bugs.launchpad.net/bugs/1450137

Title:
  Qt5 applications crash when switching screens

Status in qtdeclarative-opensource-src package in Ubuntu:
  Incomplete
Status in qtdeclarative-opensource-src source package in Vivid:
  Confirmed
Status in qtdeclarative-opensource-src source package in Wily:
  Incomplete

Bug description:
  # Impact
  When switching screens (e. g. when putting the laptop onto the docking station the notebook screen is turned off and the external one is turned on) Qt5 applications (including plasmashell) quite often crash.

  # Test Case
  * Have two screens. One plugged-in one not
  * Run plasma 5
  * Plug-in second screen and wait 10 seconds
  * Unplug and wait 10 seconds
  * Plug-in and wait 10 seconds
  * Unplug and wait 10 seconds
  * ...

  # Regression Potential
  Worst case scenario an application using qquickscreen would slow down because of erroneous screen change singals being emitted too often per second. This would however only reveal a lower level issue in the foundations that ultimately needs to be fixed anyway. 

  # Other Info
  The upstream code review [1] explains the issue and solution pretty well.

  https://codereview.qt-project.org/#/c/111100/

  
  --------- original report ---------------

  When switching screens (e. g. when putting the laptop onto the docking
  station the notebook screen is turned off and the external one is
  turned on) Qt5 applications (including plasmashell) quite often crash.
  This makes my laptop unusable, since I do that very frequently.

  The problem has already been described here: https://bugs.kde.org/show_bug.cgi?id=341497
  Apparently it is fixed in Qt 5.5

  I am running Kubuntu 15.04 64bit and libqt5gui5 5.4.1+dfsg-2ubuntu4.

To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/qtdeclarative-opensource-src/+bug/1450137/+subscriptions