Picard freezes X when overlay scrollbars are enabled

[Lars Düsing]

after starting a wireframe shows up, and then a high I/O-load occurs, memory is consumed up to 90%, X-Windows gets completely unusable (freezes), but changing to console (ctrl-alt-f1) is possible - 20-40s after pressing the keys - and instantly I/O-load drops to zero as switching to console happens.
Therefore I think this may be a problem with QT or even X-Windows itself.
There are some errors printed by picard/QT/X-Windows on the running terminal:
(python:5103): Gtk-CRITICAL **: IA__gtk_widget_style_get: assertion `GTK_IS_WIDGET (widget)' failed
{Comment: dozens of that}
QWidget::setMinimumSize: (/MainWindow) The largest allowed size is (16777215,16777215)
{Comment: some of that}
QNativeImage: Unable to attach to shared memory segment.
X Error: BadDrawable (invalid Pixmap or Window parameter) 9
  Major opcode: 62 (X_CopyArea)
  Resource id: 0x0
X Error: BadDrawable (invalid Pixmap or Window parameter) 9
  Major opcode: 62 (X_CopyArea)
  Resource id: 0x0
{Comment: these are the last lines of the log - after that everything freezes}

ProblemType: Bug
DistroRelease: Ubuntu 12.10
Package: picard 1.0-1
ProcVersionSignature: Ubuntu 3.5.0-14.18-generic 3.5.3
Uname: Linux 3.5.0-14-generic i686
ApportVersion: 2.5.1-0ubuntu7
Architecture: i386
Date: Sat Sep 15 13:11:43 2012
ExecutablePath: /usr/lib/picard/run
InstallationMedia: Ubuntu 12.10 "Quantal Quetzal" - Alpha i386 (20120724.2)
InterpreterPath: /usr/bin/python2.7
ProcEnviron:
 TERM=xterm
 SHELL=/bin/bash
 PATH=(custom, no user)
 LANG=de_DE.UTF-8
SourcePackage: picard
UpgradeStatus: No upgrade log present (probably fresh install)

[Lars Düsing (lars.duesing)]

iotop-snapshot:

Total DISK READ: 13.58 M/s | Total DISK WRITE: 0.00 B/s
  TID PRIO USER DISK READ DISK WRITE SWAPIN IO COMMAND
 1190 be/4 root 10.86 M/s 0.00 B/s 82.75 % 0.00 % X :0 -core -auth /var/run/lightdm/root/:0 -nolisten tcp vt7 -novtswitch -background none

(Do I see right, X _reads_ all the time from swap?!? )

[Lars Düsing (lars.duesing)]

Problem exists in current git-version of upstream too... So I think pyqt, qt or xf86-server-intel is the problem.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Jan Simon (jan-simon)]

Same here, tested with Calibre and bzr-Explorer. Last time this two applications crashed with this kind of failure it was because of python-qt4, if i remember right.

[Ricardo Salveti (rsalveti)]

This bug is happening with any python-qt4 based applications, and I believe apport is publishing the bugs at the python-qt4 based applications instead of here.

[Michael Terry (mterry)]

This seems to be due to overlay-scrollbar. If you run it like:
LIBOVERLAY_SCROLLBAR=0 picard
it works fine.

[Lars Düsing (lars.duesing)]

Yes, then it works fine.
Any way how to debug it to give some hints?