bug#49803: 27.2; Mouse wheel on MacOS is reported as mouse-4 and mouse-5, but Emacs mwheel seems to use wheel-up/wheel-down instead

[Eli Zaretskii]

> From: Didier <didibus@gmail.com>
> Date: Sun, 1 Aug 2021 23:44:05 -0700
> Cc: 49803@debbugs.gnu.org
> 
> In macOS, when running Emacs in GUI, the wheel is received as <wheel-up> and 
> <wheel-down> and it all
> works.
> 
> But in macOS, when running inside a terminal such as Terminal.app or iTerm2, 
> the wheel is received as
> <mouse-4> and <mouse-5> and it no longer works, because the defcustom is not 
> smart enough to check if
> we are running in GUI or not.
> 
> So I think it should be modified to something like:
> 
> (if (or (featurep 'w32-win) (and (display-graphic-p) (featurep 'ns-win)))
>         'wheel-down
>       'mouse-5)

Did you try that?

The problem here is that the initial frame is not a GUI frame even in
a GUI session, so the defcustom could pick up the wrong value.