Re: Disabling mouse input

[Daniel Radetsky <dradetsky@gmail.com>]

On Sat, Nov 02, 2024 at 09:38:20AM GMT, Eli Zaretskii wrote:
> (This should not surprise anyone, because input events are handled in
> C, not in Lisp, and so disabling this in Lisp is expected to be
> impossible.)

Well, everyone I talked to was sure it must be possible in
Lisp, so I figured somebody would ask eventually.

> Thanks, but this is not enough, and I also think it doesn't
> necessarily ignore the mouse events on the right level.  We should
> instead ignore these events where they are read, here:

It was clearly enough for you to tell me I was doing it the
Stupid Way, which was my objective, so I don't see the
problem. I mean, obviously you're not going to merge what I
sent. That wasn't the point.

> This loop should ignore and remove from the queue any events whose
> 'kind' (as declared in termhooks.h) is a mouse or touchpad event.  And
> perhaps we also should allow ignoring the latter, but not the former.

Sounds reasonable. I'll take another look soon.

> Otherwise, the "ignored" input events will act like ghosts: they do
> exist in the queue, and do trigger input-even related mechanisms we
> have, such as while-no-input, but cannot be accessed.

I can't tell if this issue is supposed to be a consequence
of not implementing ignore-touchpad-but-not-mouse, or of
ignoring the events the way I was doing it (via the goto in
read_key_sequence).

> In addition, we'd need to change display-mouse-p, so that it reflects
> the fact that mouse clicks are not available.  Otherwise, some
> features will present mouse-driven UI that cannot be used.

Good point. I'm thoroughly ignorant of emacs' mouse-driven UI.

> > +  DEFVAR_LISP ("ignore-mouse-input", ignore_mouse_input,
> > +	       doc: /* If non-nil, discard mouse input in the command loop */);
> > +  ignore_mouse_input = Qnil;
> 
> This should be DEFVAR_BOOL instead.

Okay, wasn't certain about that.

It was also suggested to me that other devs would want the
feature exposed via a global minor mode, not just a
variable. Do you? I looked into it and it was about 10 lines
of Lisp (most of which was to allow it to be set via
customize), so that's not a big deal if so. Or I mean
probably not; maybe I'll discover it's much worse in
practice once I know what's actually involved.

Thanks for the info.