Re: [matplotlib-devel] navbar mod: zoom/pan constrained to X or Y

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

Hi Eric,

On Sunday 13 April 2008 7:39:14 pm Eric Firing wrote:
> The present NavigationToolbar2 is very nice, but I am thinking about an
> improvement: adding a button that would rotate a constraint among three
> possibilities, so that pan/zoom and rectangle select could be set to
> affect only X, only Y, or be left unconstrained as at present.
[...]
> Although there might be more elegant ways to do it, I think the simplest
> way to get this functionality across backends would be to add a single
> button that rotates a variable among values of 'X', 'Y', and 'XY', and
> then let that variable constrain the effects of pan/zoom and
> rectangle-select.

I would prefer to not add a button to change the behavior of other buttons, 
but rather stack three buttons (XY,X,Y) for pan and zoom, perhaps selectable 
from a drop-down widget of some kind, so you can select which version of 
pan/zoom you want.

> It would be nicer, but more work, to have the 
> variable change the rubberband to a span-select in the latter case; I am
> inclined to start with the easiest implementation I can come up with.  I
> think the simple approach can be done with only a little bit of change
> in the backends.

That would be nice, maybe for a future addition.

> Comments?  Objections?
>
> This could also be done by making a NavigationToolbar3, but I think that
> even with inheritance from NavigationToolbar2, this would require more
> work.

I recently subclassed NavigationToolbar2 to add a crosshairs button. I have 
multi-dimensional data and I wanted to click on a point in an image to create 
an associated projection. I had to reimplement several of the toolbar2 
methods with minor changes to support an additional button. I wonder if we 
could come up with a toolbar that was easier to subclass without 
reimplementing so much of the machinery. I won't have time to pursue this 
until summer, just throwing it out there.

Darren