Ergonomics: mouse clicking with scroll-margin

Ergonomics: mouse clicking with scroll-margin

[Yuri D'Elia]

The combined behavior of the mouse and "scroll-margin" is a bit odd
currently and I wonder if there's something that can be done to improve
it.

If you have a buffer which has "scroll-margin" enabled, and you click
anywhere in the scroll-margin region, the point is moved and the buffer
is immediately scrolled.

This in turn often results in the click becoming a "drag" instead,
selecting parts of the buffer.

I rarely use the mouse, but when I do (usually in customize groups, or
when using eww), it trips me all the time since I use a rather large
scroll-margin.

Can this be improved _without_ disabling scroll-margin?

If feels like that moving the point when using the mouse shouldn't
trigger scroll-margin ever, since any action that causes a scroll would
immediately move the current target away and result in unintended
behavior. I can see the same effect when performing a selection by
dragging: once you reach the scroll-margin area every single motion
events selects half the visible buffer, which is also broken.

Is there a better approach?

Re: Ergonomics: mouse clicking with scroll-margin

[Eli Zaretskii]

> From: Yuri D'Elia <wavexx@thregr.org>
> Date: Sun, 14 Jun 2020 19:09:20 +0200
> 
> Can this be improved _without_ disabling scroll-margin?

Can you propose a more useful behavior in that case?

> If feels like that moving the point when using the mouse shouldn't
> trigger scroll-margin ever

If you are saying that Emacs should put point inside the scroll-margin
and leave it there in this case, then I don't recommend such a
solution: any subsequent command will scroll the window anyway,
because Emacs is programmed to keep point outside of the scroll
margin.

We need to come up with a more clever approach.

Re: Ergonomics: mouse clicking with scroll-margin

[Yuri D'Elia]

On Sun, Jun 14 2020, Eli Zaretskii wrote:
>> Can this be improved _without_ disabling scroll-margin?
>
> Can you propose a more useful behavior in that case?

Another solution would be to move the pointer along with the scrolling
buffer (as done occasionally in cad software when moving the viewport),
so that the pointer doesn't move from the POV of the buffer.

Kind of odd for an editor though.

> If you are saying that Emacs should put point inside the scroll-margin
> and leave it there in this case, then I don't recommend such a
> solution: any subsequent command will scroll the window anyway,
> because Emacs is programmed to keep point outside of the scroll
> margin.

Would that happen for _any_ command or just for commands that already
move the point?

If that happens only with a command that already moves the point up or
down, such as next-line, I'd actually say that's OK and I would find
that expected.

It's definitely an edge scenario, but less unorthodox than moving the
pointer IMHO.

> We need to come up with a more clever approach.

Fully open to any idea here.
This is just the first thing that came to mind.

Re: Ergonomics: mouse clicking with scroll-margin

[Eli Zaretskii]

> From: Yuri D'Elia <wavexx@thregr.org>
> Cc: emacs-devel@gnu.org
> Date: Sun, 14 Jun 2020 19:58:56 +0200
> 
> > If you are saying that Emacs should put point inside the scroll-margin
> > and leave it there in this case, then I don't recommend such a
> > solution: any subsequent command will scroll the window anyway,
> > because Emacs is programmed to keep point outside of the scroll
> > margin.
> 
> Would that happen for _any_ command or just for commands that already
> move the point?

Any command that causes a non-trivial redisplay.  Which in practice
means quite a few (not only those which move point).

Re: Ergonomics: mouse clicking with scroll-margin

[Stefan Monnier]

> The combined behavior of the mouse and "scroll-margin" is a bit odd
> currently and I wonder if there's something that can be done to
> improve it.
>
> If you have a buffer which has "scroll-margin" enabled, and you click
> anywhere in the scroll-margin region, the point is moved and the buffer
> is immediately scrolled.
>
> This in turn often results in the click becoming a "drag" instead,
> selecting parts of the buffer.

I think this is a bug.  It's not immediately clear how we could/should
fix it, but I think it deserves a bug number (and ideally a slightly
more precise recipe).


        Stefan

Re: Ergonomics: mouse clicking with scroll-margin

[Yuri D'Elia]

On Sun, Jun 14 2020, Stefan Monnier wrote:
>> This in turn often results in the click becoming a "drag" instead,
>> selecting parts of the buffer.
>
> I think this is a bug.  It's not immediately clear how we could/should
> fix it, but I think it deserves a bug number (and ideally a slightly
> more precise recipe).

I don't have anything to add at the moment, but I filed it as bug
report: bug#42150