MultiCursor should be able to bind to axes in more than one figure... #23339

Multicursor only works if all the axes are in the same figure...

Each tab is its own Figure/Canvas. MultiCursor only binds itself to one Canvas so it only sees mouse events from axes on in the figure that canvas is associated with.

The fix here is to add a check that all Axes are in the same Figure on init and raise otherwise.

Originally posted by @tacaswell in #23328 (comment)

and possible solution:

While I haven't looked at the details, it should be possible (and hopefully easy) for MultiCursor to just loop over all canvases of all artists (both when connecting the callbacks, and in the callbacks implementations). mplcursors does something similar, e.g. registration over all canvases is at https://github.com/anntzer/mplcursors/blob/main/lib/mplcursors/_mplcursors.py#L256-L259.

Originally posted by @anntzer in #23328 (comment)