Re: [Matplotlib-users] Double Zoom in WXAgg backend

[Michael D. <md...@st...>]

In your example, you are adding the axes to the figure twice:

        axes = self.figure.add_subplot(1, 1, 1)
        self.figure.add_axes(axes)

add_subplot both creates and adds the axes to the figure, so it is 
unnecessary to later add it.  add_axes is intended for axes that have 
been created directly from the Axes constructor.  Unfortunately, special 
care needs to be taken for overlapping axes (something that matplotlib 
could maybe improve on), so as you saw, the zooming happens twice.  
Also, perhaps we should consider raising an exception when the same Axes 
is added to the Figure twice.  (First I'll have to ensure there's no 
legitimate reason to do so.) 

In any case, simply removing the second line above appears to be enough 
to get this to work correctly.

Cheers,
Mike

Jervis Whitley wrote:
> Hi,
>
> Could anyone help me with the following problem I am having.
>
> http://dpaste.com/64913/
>
> The code listed above should be enough to reproduce the problem.
>
> I on using the zoom function from the toolbar, I find that the figure limits
> are set to a smaller size than the zoom i selected - a kind of 'double zoom'.
>
>
> I was able to track down the problem to backend_bases.py in the matplotlib
> distribution (current release).
>
> Inside this file there is a member called 'release_zoom'
>
> there is a section of code that says..
>
> for cur_xypress in self._xypress:
>
>   lastx, lasty, a, ind, lim, trans = cur_xypress
>   # code
>   a.transData.inverted()
>   # code
>   a.set_xlim((x0, x1)) # etc..
>
>
> I am finding that there are two items in self._xypress, and that
> the 'a' in both of them (axes i think) are the same object
> i.e a1 is a2 == True
>
> this means that a.transData.inverted() is called twice on the same axes.
> The first time through the for loop it gets the limits correct, the
> second time, they are incorrect
> because of the second call to inverted.
>
> I have implemented a shoddy fix where i check that if the axes is the same
> as one that is seen before, I just continue.
>
> Is anyone else able to see this, or is it just something in the way
> i've set up my
> original pasted code?
>
> Cheers,
>
> Jervis
>
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-- 
Michael Droettboom
Science Software Branch
Operations and Engineering Division
Space Telescope Science Institute
Operated by AURA for NASA