…) matplotlibrc, it will be copied into "savefig.format", where "auto" is not a supported choice. This will fix it so it becomes "png" if it's currently set to "auto". This bug discovered as part of #1530, though it doesn't fix it.
Hiding the FileChooserDialog was pointless, because a
new one is created each time the Save Figure button is
clicked in the Toolbar. Hiding seems to have prevented
the widget from being destroyed based on refcount, and this
led to heavy access to the recently-used.xbel file with
every subsequent keystroke.