Re: Additional cleanup around xterm-mouse

[Stefan Monnier <monnier@iro.umontreal.ca>]

> I'm about 33% through analyzing read-key and have already found the
> following differences:
>
> * read-key resets this-command-keys, read-event appends to it.

I think this is a misfeature of `read-key`.  I believe the better fix is
to introduce a new function which is like `read-key-sequence` but with
fewer side effects and on top of which we would re-implement `read-key`
and `read-key-sequence`.

By "fewer side effects", I mean that it should return a set of data:
- the key-sequence read.
- the corresponding list of undecoded input-events (instead of
  modifying this-command-keys).
- the command that was found in the keymaps and which made the function
  decide that this key sequence was complete (instead of setting
  read_key_sequence_cmd).
- maybe more...

> * read-key does not return switch-frame events as they happen,
>   read-event does.

I think this is what we want.

BTW, related to that, there is `read-char` which I believe can (almost?)
always be replaced with `read-key`.


        Stefan