Hello,
I'm using PyQt 4.1.1 compiled against Qt 4.2.2. on WinXP with Python
2.5. I have been having a strange issue that appears to be some sort of
deadlock when using QThreads.
Below is some sample code that reproduces the problem for me.
----- CODE -----
import PyQt4.Qt as qt
class CounterWidget(qt.QWidget):
def __init__(self):
qt.QWidget.__init__(self)
self.count = 0
self.layout = qt.QHBoxLayout(self)
self.label = qt.QLabel()
self.label.setText("COUNT: %d" % self.count)
self.layout.addWidget(self.label)
self.thread = CounterThread()
self.thread.connect(self, qt.SIGNAL('START'),
self.thread.work_loop)
self.connect(self.thread, qt.SIGNAL('INCR_COUNT'),
self.incr_count, qt.Qt.QueuedConnection)
self.connect(self.thread, qt.SIGNAL('finished()'),
self.thread, qt.SLOT('deleteLater()'))
self.thread.start()
def incr_count(self):
self.count += 1
self.label.setText("COUNT: %d" % self.count)
def thread_start_work(self):
self.emit(qt.SIGNAL('START'))
class CounterThread(qt.QThread):
def __init__(self):
qt.QThread.__init__(self)
def run(self):
qt.QTimer.singleShot(0, self.work_loop)
self.exec_()
def work_loop(self):
for x in xrange(500):
self.emit(qt.SIGNAL('INCR_COUNT'))
self.msleep(1)
if __name__ == "__main__":
app = qt.QApplication([])
w = CounterWidget()
w.show()
app.connect(app, qt.SIGNAL('lastWindowClosed()'),
app, qt.SLOT('quit()'))
app.exec_()
----- END CODE -----
The code above will make a simple textlabel widget and attempt to update
an integer counter via signals. This code usually locks up around count
#430-450 for me. The GUI window freezes and the app has to be killed
forcefully.
Any idea why this is happening?
Hugh "Trey" Stout
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