Re: Additional cleanup around xterm-mouse

[Eli Zaretskii <eliz@gnu.org>]

> Date: Thu, 19 Nov 2020 00:03:30 -0800
> From: Jared Finder <jared@finder.org>
> Cc: emacs-devel@gnu.org
> 
> > I don't think I follow.  All the places where you need changes are
> > related to handling mouse events, so why cannot it be specific to
> > xt-mouse?
> 
> There is a bug in widget-key-sequence-read-event's usage of keyboard 
> events specifically.
> 
> The function widget-key-sequence-read-event currently does not correctly 
> translate function keys for the terminal.  It has code that attempts to 
> apply function-key-map, but does not apply input-decode-map, so it can 
> not read function keys.  (Additionally, it should be using 
> local-function-key-map now.)

OK, but that means widget-key-sequence-read-event has a bug that needs
to be fixed regardless.

So I'm still asking why can't we do something like

  (if xterm-mouse-mode
      (read-key)
    (read-event))

in all the affected places that currently call read-event?

> Changing to read-key fixes this as read-key goes through 
> read-key-sequence which applies input-decode-map.  However, to get the 
> same intended functionality requires some new parameters, which I also 
> add in my patch.

The problem is that we get lots of unintended functionalities even
with the new parameters.  read-key-sequence consults many internal
variables that read-event doesn't.  So I'm still wary of making such a
significant change, even though we are talking about a small number of
relatively minor feature (with the sole exception of Ediff, perhaps).
If the above less-elegant change which will only affect usage under
xterm-mouse-mode is feasible, I'd prefer to go that way instead.

>    (let ((ev2 (and (memq 'down (event-modifiers ev))
> -		  (read-event)))
> -	(tr (and (keymapp function-key-map)
> -		 (lookup-key function-key-map (vector ev)))))
> +		  (read-key)))
> +        ;; This is actually a separate bug-fix.  `function-key-map'
> +        ;; does not contain any term-specific function key mappings
> +        ;; like f13 --> S-f1.
> +        (tr (and (keymapp local-function-key-map)
> +		 (lookup-key local-function-key-map (vector ev)))))

Let's fix this part separately.