Re: [Matplotlib-users] executing function when view interval changes

[Ryan M. <rm...@gm...>]

On Fri, Feb 13, 2009 at 6:24 AM, John Hunter <jd...@gm...> wrote:

> On Thu, Feb 12, 2009 at 2:13 PM, Ryan May <rm...@gm...> wrote:
> > On Wed, Feb 11, 2009 at 7:30 PM, John Hunter <jd...@gm...> wrote:
> >>
> >> On Wed, Feb 11, 2009 at 2:49 PM, Ryan May <rm...@gm...> wrote:
>
> > Well, I checked in an example that shows the functionality.  The problem
> is
> > that using these events doesn't follow the standard event API.  You don't
> > connect using figure.canvas.mpl_connect() (it doesn't like the names
> > 'xlim_changed' and 'ylim_changed'), but rather you use
> > Axes.callbacks.connect().  Also, the an event object is not passed into
> the
> > callback, but rather the originating axes instance.  Are these events
> relics
> > to the older version of event handling that haven't been moved to the
> > present?
> >
> > Otherwise, should I add a special section to the event handling docs to
> > handle these?
>
>
> Thanks for the example -- you are right that this is a 'legacy' event
> callback outside the regular event framework.  So it doesn't really
> belong in the event handling chapter but may merit a quick note there.
>  Alternatively, we could rather easily draft up a special event
> (NavigationEvent?)  that *does* work in the regular event handling
> framework.  The quirk is that the events are handled at the canvas
> level, so it would be difficult to register for a single axes, but one
> could get a NavigationEvent if the limits of any of the axes in the
> figure were updated, and use the inaxes attribute to process it.  If
> this, or some variant of it, seems like a good idea I'm happy to add
> it.
>

I'm +1 on your idea.  While it may be a little quirky that you can't
register for a single axes limit change, it's even weirder that you have
different ways to register for different types of events.  I think the
overall API for matplotlib is improved by bringing *all* event callbacks
under a single, unified, API.  Along those lines, I see these other 'events'
being processed in the code, but not formally recognized by the canvas level
event handler:

Aixs : 'units', 'units finalize'
Figure : 'dpi_changed'

Would it be good to try to move these to the canvas-level handler as well? I
don't have a good idea myself of how that would work right now.

Ryan

-- 
Ryan May
Graduate Research Assistant
School of Meteorology
University of Oklahoma