Re: [matplotlib-devel] Bug when embedding Matplotlib 0.91.2 in PyQt 4.4.2

[Darren D. <dar...@co...>]

On Sunday 01 June 2008 04:10:45 am Pierre Raybaut wrote:
> > Hi Pierre,
> >
> > On Friday 30 May 2008 5:21:01 pm Pierre Raybaut wrote:
> >> > First, I would like to congratulate you for your work on Matplotlib. I
> >> > am using Matplotlib widgets in all my current projects, embedded in
> >> > PyQt graphical user interfaces.
> >> >
> >> > As you may know, PyQt 4.4.2 has been released a few days ago.
> >> > And I found out a performance bug when embedding a Matplotlib 0.91.2
> >> > canvas in a PyQt 4.4.2 object: the pan/zoom feature is very slow (with
> >> > PyQt 4.3.3, and the exact same scripts, pan/zoom is real-time).
> >
> > Would it be possible to post some benchmarks, something a little more
> > concrete, like specifically what calls are taking the most time, and how
> > they compare for the different versions of PyQt?
>
> Yes of course, I will send the requested informations as soon as I can.
>
> >> > I am posting this in PyQt mailing-list too, but I guess that you could
> >> > have more ideas on that matter (Matplotlib widgets may not be used
> >> > very often in PyQt).
> >
> > Please don't do that. Its not fair to the people who volunteer their time
> > on open source projects to try to draw so many people into the problem
> > before the problem is understood.
>
> Wow... I did not expect this reaction! :) The only reason that I posted
> on the two mailing-list was to be sure to inform everyone who was
> potentially interested by the topic. Otherwise, if I was really trying
> outrageously to draw many people into the problem, I wouldn't have
> mentioned the post on the other mailing-list, would I? Thanks for the
> warm welcome though ;)

Sorry, I didn't mean to seem brusque. If there is a problem with matplotlib's 
qt4 support, I would prefer to have a chance to look into it before the 
problem is announced to the pyqt community.

I tried putting some print statements in backend_qt4agg to see how long it was 
taking to draw the canvas:

    def draw( self ):
        """
        Draw the figure when xwindows is ready for the update
        """

        if DEBUG: print "FigureCanvasQtAgg.draw", self
        self.replot = True
        d0 = time.time()
        FigureCanvasAgg.draw(self)
        d = time.time()
        print d-d0, 'agg:draw'
        d0=d
        self.update()
        print time.time()-d0, 'qt4:update'

FigureCanvasAgg.draw(self) takes about .02 seconds, and self.update() takes 
less than .0004 seconds. FigureCanvasAgg.draw is independent of qt/pyqt, so 
it look like panning/zooming is limited only by how fast matplotlib/agg can 
draw the canvas on my machine, which has qt-4.4.0 and PyQt4-4.4.2.

Darren