<p>Does any one know how the event handler manages the posted events?</p>

<p>In my app i have two threads (<em>guiThread</em> and <em>computationThread</em>). After an exception is thrown I call <code>postEvent(..)</code> to an existing dialog. The Qt-Event-Handler holds this one back until the dialog is closed. </p>

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<p>Sorry my question is a bit cloudy. I will write it more exactly, if I have time left. I found a work around. But for me the problem is still interesting.</p>

As mentionned in the Qt documentation about
QCoreApplication::postEvent
:
When control returns to the main event loop, all events that are stored in the queue will be sent using the notify() function.
...which explains why the Qt Event Handler holds the event until the dialog is closed.
If I understand correctly what you want to do, I would try using
sendEvent
.