Add rectangular selection and/or lasso selections

[mwcraig]

See jupyter-widgets/ipywidgets#1727 (comment) and following comments

[pbugnion]

How did you see this implemented? I think Jason's comment about pushing that interaction to JavaScript and just returning the selection makes sense.

Should this be a new widget -- at the same level as Event?

e.g.

class RectangleSelector(CoreWidget):
    
    _selection_style = # define the style of the rectangle selector?

    def _on_selection(self, callback):
        # register handlers

[mwcraig]

Yeah, that might make more sense. One of the things I like about the current structure is that the JavaScript code is fairly simple. I'd also imagine there is a js library for selections out there.

[mwcraig]

Closing, because I agree this is out of scope for ipyevents.