Runaway QSlider

Guillaume Laurent glaurent at
Wed Mar 3 21:49:49 GMT 2004

We have a strange bug in Rosegarden : a QSlider, when clicked on the ruler
part to move its cursor one notch, goes mad and suddenly slides all the way
to the last notch. It's just like instead of a single click you had a bunch of
quick repeated ones.

At first I suspected some sort of signal feedback, but that's apparently not
the case. For a start, it doesn't happen all the time. Then I managed to get
a stack trace of slot connected to the valueChanged() signal so as to see
where the "ghost clicks" come from. Here it is :

#6  0x0823a570 in NotationView::slotChangeFontSizeFromIndex(int) (this=0x8b40c80, n=6) at notationviewslots.cpp:302
#7  0x083b5988 in NotationView::qt_invoke(int, QUObject*) (this=0x8b40c80, _id=240, _o=0xbfffeb80) at notationview.moc.cpp:777
#8  0x40c19307 in QObject::activate_signal(QConnectionList*, QUObject*) () from /home/opt/qt-x11-free-3.2.2/lib/
#9  0x40c19448 in QObject::activate_signal(int, int) () from /home/opt/qt-x11-free-3.2.2/lib/
#10 0x40f0d298 in QSlider::valueChanged(int) () from /home/opt/qt-x11-free-3.2.2/lib/
#11 0x40d1ab89 in QSlider::valueChange() () from /home/opt/qt-x11-free-3.2.2/lib/
#12 0x40d11be4 in QRangeControl::setValue(int) () from /home/opt/qt-x11-free-3.2.2/lib/
#13 0x40d11c55 in QRangeControl::addPage() () from /home/opt/qt-x11-free-3.2.2/lib/
#14 0x40d1b9ef in QSlider::addStep() () from /home/opt/qt-x11-free-3.2.2/lib/
#15 0x40f0d3cb in QSlider::qt_invoke(int, QUObject*) () from /home/opt/qt-x11-free-3.2.2/lib/
#16 0x40c19307 in QObject::activate_signal(QConnectionList*, QUObject*) () from /home/opt/qt-x11-free-3.2.2/lib/
#17 0x40c1914c in QObject::activate_signal(int) () from /home/opt/qt-x11-free-3.2.2/lib/
#18 0x40ef9f25 in QTimer::timeout() () from /home/opt/qt-x11-free-3.2.2/lib/
#19 0x40c37979 in QTimer::event(QEvent*) () from /home/opt/qt-x11-free-3.2.2/lib/
#20 0x40bc29e4 in QApplication::internalNotify(QObject*, QEvent*) () from /home/opt/qt-x11-free-3.2.2/lib/
#21 0x40bc20c9 in QApplication::notify(QObject*, QEvent*) () from /home/opt/qt-x11-free-3.2.2/lib/
#22 0x407eb64d in KApplication::notify(QObject*, QEvent*) () from /opt/kde3.2/lib/
#23 0x40bb2c9e in QEventLoop::activateTimers() () from /home/opt/qt-x11-free-3.2.2/lib/
#24 0x40b74597 in QEventLoop::processEvents(unsigned) () from /home/opt/qt-x11-free-3.2.2/lib/
#25 0x40bd461f in QEventLoop::enterLoop() () from /home/opt/qt-x11-free-3.2.2/lib/
#26 0x40bd44d4 in QEventLoop::exec() () from /home/opt/qt-x11-free-3.2.2/lib/
#27 0x40bc2c20 in QApplication::exec() () from /home/opt/qt-x11-free-3.2.2/lib/
#28 0x08182f68 in main (argc=3, argv=0xbffff484) at main.cpp:611
#29 0x41380c57 in __libc_start_main () from /lib/i686/

and I have no frickin' clue of what happens :-). Is the signal caused by 
some internal timers or something ? Apparently that would be a KApplication
or Qt bug but I find this unlikely.


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