bug#28732: flymake mouse-wheel portability fix

[Eli Zaretskii]

> Date: Tue, 27 Feb 2018 20:28:42 +0100
> From: charles@aurox.ch (Charles A. Roelli)
> Cc: 28732@debbugs.gnu.org
> 
> Thanks.  Is the following change (ignoring whitespace differences)
> good for emacs-26?
> 
> diff --git a/lisp/progmodes/flymake.el b/lisp/progmodes/flymake.el
> index 58bad8f..d58c5943 100644
> --- a/lisp/progmodes/flymake.el
> +++ b/lisp/progmodes/flymake.el
> @@ -1078,7 +1078,9 @@
>                       face ,face
>                       mouse-face mode-line-highlight
>                       keymap
> -                     ,(let ((map (make-sparse-keymap))
> +                     ,(when (and (boundp 'mouse-wheel-down-event)
> +                                 (boundp 'mouse-wheel-up-event))
> +                        (let ((map (make-sparse-keymap))

Is there any reason you cannot simply require mwheel in flymake?  Or
does loading mwheel in a --without-x build fail?