Re: Smoother macOS touchpad scrolling

[Alan Third <alan@idiocy.org>]

On Mon, Sep 18, 2017 at 10:19:30PM +0200, Charles A. Roelli wrote:
> Yes, it returns nil.  I think this check (or maybe a function that
> returns the appkit version as an integer) could be added to ns-win.el.

I’m leaving it as an inline check at the moment as we only have a
single use of it just now. If you’re aware of other places it could be
useful, please let me know.

> > (let ((appkit-version (progn
> >                         (string-match "^appkit-\\([^\s-]*\\)" ns-version-string)
> >                         (match-string 1 ns-version-string))))
> >   (when (and (featurep 'cocoa) (>= (string-to-number appkit-version) 1138))
> >     (setq mouse-wheel-scroll-amount '(1 ((shift) . 5) ((control))))
> >     (put 'mouse-wheel-scroll-amount 'customized-value
> >          (list (custom-quote (symbol-value 'mouse-wheel-scroll-amount))))
> >     
> >     (setq mouse-wheel-progressive-speed nil)
> >     (put 'mouse-wheel-progressive-speed 'customized-value
> >          (list (custom-quote (symbol-value 'mouse-wheel-progressive-speed))))))

I’ve pushed (roughly) this to Emacs 26. See below.

> We could also make the defcustoms in mwheel.el look something like
> this:
> 
> (defcustom mouse-wheel-scroll-amount
>   (cond
>    ((and (featurep 'cocoa) (>= (ns-appkit-version) 1138))
>      '(1 ((shift) . 5) ((control) . nil)))
>    (t '(5 ((shift) . 1) ((control) . nil)))) ...
> 
> instead of:
> 
> (defcustom mouse-wheel-scroll-amount '(5 ((shift) . 1) ((control) . nil)) ...
> 
> Then in ns-win.el we could do:
> 
> (custom-reevaluate-setting 'mouse-wheel-scroll-amount)

I tried this but it just set mouse-wheel-scroll-amount to nil. It
seems that custom-reevaluate-setting uses the :set function, which is
already in use for mouse-wheel-scroll-amount.

Since I want this in Emacs 26 I figured it’s better to go with an ugly
method that works for now, and figure out a neater solution later.

>      Then it sets the user option to that value (using the option’s
>      ‘:set’ property if that is defined).
        ^^^^

> I /think/ this is the right thing to do, but if any Customize experts
> can weigh in, that would be great.

Please do.
-- 
Alan Third