[Matplotlib-users] capturing arrow key events

[Tim L. <ti...@cs...>]

Hi all,

I'm developing an app where i'd like the user to be able to navigate using
the up/down/left/right keys. Currently the mpl event handlers just return
None for these, but I figured it'd be easy enough to add the code myself.

in lib/matplotlib/backends/backend_gtk.py I added the following diff,
which adds in some new code -> string mappings and also notifies me when a
key press or key release is made (for debugging).

109,112d108
<                65361 : 'left',
<                65362 : 'up',
<                65363 : 'right',
<                65364 : 'down',
176c172
<
---
>
184d179
<         print "hit", key
189d183
<         print "release", key

This all works fine except that the down key doesn't register as released.
After registering the down key press, no other key events register until
you hit the up key, at which point the key release triggers for the up.

If i hit the following sequence: [up, left, right, down, <any sequence not
including up or down>, up, up] I get the following events registering.

hit up
release up
hit left
release left
hit right
release right
hit down    <== we never get the matching "release down" or anything else
release up  <== until we hit the up key and get this release event for it
hit up
release up

I really don't know a lot about Gtk or the matplotlib internals so I
couldn't trace this bug deeper into the libraries. Can anyone shed some
light on what's going on? If we can get the arrow keys working is there a
chance of getting them into the standard distribution (assuming we had all
backends working)?

Cheers,

Tim Leslie