On Sun, Nov 21, 2010 at 11:58:42AM -0500, Darren Dale wrote: > > Apparently, to make it work with the Qt4 backend, one simply has to add: > > QtGui.QApplication.processEvents() > > to the method 'FigureCanvasQt.draw_idle' > > (matplotlib/backends/backend_qt4.py).
> , discussion of why processEvents was originally removed from draw(): > "that line can not be added back in. When that line > is in place, the backend attempts to process queued events before it > is finished processing the current event. It was leading to segfaults > in some cases. processEvents should not be called in the middle of > processing an event." Yes, I can confirm that adding processEvents in places to facilitate redraws is a good way to lead to segfaults. I have seen this in many places other than matplotlib. The reason Tk does not have this problem is that it deals with event loops in a fundementally different way that Wx or Qt. I am not sure what the difference is exactly, but I seem to remember that the Tk event loop is more or less hard-wired in Python, and (maybe ?) lives in a different C-level thread. The problem with animations in the example linked by Pierre is that there is no redraw triggered, because the redraw needs to be done in the event loop. The question that needs to be answered to make it easier for people doing animations outside of the mainloop is rather: is there a way to force a redraw without returning in the mainloop. Chances are that there isn't, because the toolkit (Qt) is not thread safe. But the problem really boils down to the fact that the example is not the right way to write animations in GUI programming. However people do not want to learn event loop programming (I can understand them) and want to write for loops. In Mayavi, we provide a helper function that enables to put such a for loop in a generator and pass the generator to the event loop framework without having to worry about timer: http://code.enthought.com/projects/mayavi/docs/development/html/mayavi/auto/mlab_other_functions.html#animate While this function should work out of the box in Spyder, if the ETS_TOOLKIT variable is well set for Mayavi/Traits to use the Qt backend, it would also be fairly easy to port the main idea out of Mayavi and Traits, in matplotlib or spyder: https://svn.enthought.com/enthought/browser/Mayavi/trunk/enthought/mayavi/tools/animator.py My 2 cents, Gaël ------------------------------------------------------------------------------ Beautiful is writing same markup. Internet Explorer 9 supports standards for HTML5, CSS3, SVG 1.1, ECMAScript5, and DOM L2 & L3. Spend less time writing and rewriting code and more time creating great experiences on the web. Be a part of the beta today http://p.sf.net/sfu/msIE9-sfdev2dev _______________________________________________ Matplotlib-users mailing list Matplotlib-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/matplotlib-users
