[PyKDE] PyQt Qthreads

Krzysztof Lichota krzysiek at lichota.net
Tue Oct 31 17:26:26 GMT 2006

Gregor Kling napisał(a):
> I can see that the printouts are as intended, but
> the presentation in the WidgetTable ist presented when
> the thread is complete instead of an iterative update.
> Anyone has an idea ?

As far as I understand your code, in GUI you are running in loop,
processing incoming pieces of data. This will not work, GUI updating is
event-driven, so you should process one piece of data at the time and
return control to GUI event processing loop to update GUI.
In my apps I solve this problem by sending data to widgets in
QCustomEvent. Something like that (note that this is for Qt3, not Qt4, I
don't know if it has been changed):

Background thread does:
class FrontendCustomEvent(qt.QCustomEvent):
    def __init__(self, data, *args):
        apply(qt.QCustomEvent.__init__, (self,) + args)
        self.pythonData = data
def sendEvent(object, data):
    import qt
    event = FrontendCustomEvent(data, qt.QEvent.User + 100)
    qt.QApplication.postEvent(object, event)

while True:
	sendEvent(mainWidget, "some data")

In main widget I have:
class MyWidget(qt.QWidget):
    def customEvent(self, event):
        if event.type() == qt.QEvent.User + 100:
            itemData = event.pythonData
            qt.QListViewItem(self.listView, itemData)

BTW. In your code you have race condition - if background thread does
not send data fast enough, you would stop processing prematurely. You
should use some other way of detecting if this is end of results, for
example a flag saying that all results were sent.


	Krzysztof Lichota

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