bug#50993: 29.0.50; Problems when dragging the mouse over the toolbar

[Stefan Monnier via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

> This is because of commit 2e595b3: we now report mouse gestures on
> tool bar and tab bar with the corresponding prefixes.  And
> keyboard.c+mouse.el evidently don't like to see [tool-bar mouse-movement].
>
> I have no idea how to fix this mess; I tried many things, but gave up
> eventually.  Perhaps Stefan knows what to do here.  As a kludge, maybe
> remove the prefix if the full even has no binding?  Anyway, we cannot
> revert that change because it was done to support mouse wheel on the
> tab bar.

I'm afraid I don't have a good idea either: this business of adding
prefix events like `mode-line` and `tool-bar` is quite fiddly and
I haven't managed to wrap my head around precisely how it's supposed
to work.

I think it would make sense to drop those prefixes when the resulting
key sequence has otherwise no binding, but at the same time it feels
a bit like adding a hack on top of another one.


        Stefan "wondering if using modifiers instead of prefixes would
                have made things better or made them worse"