Double Zoom in WXAgg backend

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

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

Mike,

Thanks for your help!

Cheers,
Jervis

···