bug#35389: 27.0.50; [PATCH] Emacs on macOS sets mouse-wheel variables directly

[Alan Third <alan@idiocy.org>]

On Fri, May 10, 2019 at 10:53:33PM +0300, Eli Zaretskii wrote:
> > From: Robert Pluim <rpluim@gmail.com>
> > Date: Fri, 10 May 2019 17:29:46 +0200
> > Cc: 35389@debbugs.gnu.org
> > 
> > Having thought about this some more, does it make more sense to put
> > the value for macOS in the defcustoms for mouse-wheel-scroll-amount
> > and mouse-wheel-progressive-speed instead? (and discarding the test for
> > macOS < 10.7 at the same time) i.e.
> 
> Why does that system configuration need a different default to begin
> with?  In general, having different defaults on different systems is
> not a good idea.

macOS 10.7+ handles wheel scrolling differently from how other systems
handle it. If we stick with the defaults then it becomes
uncontrollably fast, the current defaults make it feel similar to X,
Windows, etc.

IIRC, fixing it in C is probably possible, but not as straight forward
as just changing the defaults. There was discussion of it in Emacs
devel at the time and only one person objected, but later changed
their mind.

> Also, the original patch mentioned a specific version of appkit,
> whereas this one is more general, AFAIU.  Wouldn't that cause trouble
> or surprise elsewhere?

We still support macOS 10.6, which behaves similarly to X and Windows.
Changing the defaults for it would result in unexpected behaviour.
-- 
Alan Third