bug#44284: 27.1; with some Unicode font, scrolling upward with the mouse wheel actually scrolls downward when the cursor needs repositioning

[Eli Zaretskii]

> Date: Sat, 31 Oct 2020 23:43:24 +0100
> From: Vincent Lefevre <vincent@vinc17.net>
> Cc: 44284@debbugs.gnu.org
> 
> window_scroll_pixel_based is not called at all, neither window_scroll
> is.

Are you sure?  That's very strange; it does get invoked on my system.
This happens because turning the mouse wheel invokes mwheel-scroll,
which calls the value of mwheel-scroll-up/down-function, whose default
value is scroll-up/down, and those functions call scroll_command, which
calls window_scroll, which on GUI frames calls
window_scroll_pixel_based.  Which part of this chain doesn't happen on
your system?