Re: [Matplotlib-users] Cursor corruption with pyqt4 and a work-around.

[Darren D. <dsd...@gm...>]

On Thu, Jun 17, 2010 at 11:04 PM, David Smith <dav...@gm...> wrote:
> I have been developing an application using PyQt ant Matplotlib and encountered
> a problem with the mouse cursor shape being incorrect.  I found a work-around
> that seems to work, but I think this is a bug and the fix needs to go into the
> Matplotlib code base. Here are details.
>
> My application has a central widget used fo r a Matplotlib Figure.
>  Additionally there is a menu bar, button bar and two dock panels with
>  controls for the plot.  I see the following behavior for the cursor:
>
> * On start up, the cursor acts normally on startup provided
>  the mouse cursor is not inside the figure widget on start-up.
>
> * Mouse pointer shapes are set by Windows (in this case VISTA)
>  and change shape according to location.  For example, touching
>  the application window's border results in the arrow pointer
>  changing shape to a double-headed arrow indicating the border
>  can be dragged to adjust the size of the window.
>
> * Once the mouse pointer touches the Matplotlib figure widget
>  in any way, the mouse pointer will cease to show the double-arrow
>  shape on the window borders - the pointer remains an arrowhead.
>  You can still resize the window and the cursor does change to
>  a double-arrow when you press the left button.
>
> My workaround for this was to add the following lines of code in my
> application:
>
>        def onleave(self):
>           QtGui.QApplication.restoreOverrideCursor()
>
>        self.fig.canvas.mpl_connect('figure_leave_event',  onleave)
>
> I guessed these lines by studying the matplotlib code.  Probably they
> need to go somewhere inside the Matplotlib class definitions.
>
> I hope this helps developers to correct this problem.  My application
> code is medium-large and I didn't try to build a smaller example.  The
> mysterious 3-line workaround solves my problem for the moment.
> Perhaps it will help another PyQt and Matplotlib user and perhaps
> urge developers to fix the problem in the Matplotlib core.

Now that you mention it, I have seen similar behavior. Thanks for the
report, I'll look into it.

Darren