Hi again,
Ole Streicher <[email protected]> writes:
> could anyone reproduce this problem and/or has a solution for it? Is
> there anything wrong with my code?
after some discussion on the PyQt mailing list, I found the cause of the
problem:
In matplotlib.FigureCanvasQTAgg, the following piece of code is called
on a resizeEvent:
def draw( self ):
# ... some internal code
# Added following line to improve realtime pan/zoom on windows:
QtGui.qApp.processEvents()
This makes the problem clear:
- if we resize the window quickly, several resizeEvents are created and
are in the event queue of Qt
- the first one gets processed by the QVBoxLayout which starts the
processing in its first (matplotlib) widget.
- the matplotlib widget does what it should and at some point calls
matplotlib.FigureCanvasQTAgg.draw(self).
- this starts the processing of the next event in the queue which is
the next (2nd) resize event. BUT: we are still in the processing of
the first event!!!
- the 2nd event goes to the QVBoxLayout, from there to the matlotlib
widget (eventually starting some recursive behaviour here)
- if the 2nd event is finished, QVBoxLayout sends it to its other widget
(the scrollbar). The scrollbar is resized according to the *2nd event*.
- if the processing of the 2nd event was finished and no more events are
in the queue, the matplotlib.FigureCanvasQTAgg.draw() finishes
- at the end, this will finish the processing of the first resize event
in the matplotlib widget and start the *first resize event* for the
scrollbar
This is exactly the behaviour that I observed. It is caused by the
QtGui.qApp.processEvents() call in the draw() function.
So, I think this is clearly a bug in matplotlib:
QtGui.qApp.processEvents() should not be called while processing another
event.
Best regards
Ole
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