bug#53275: 29.0.50; Cursor shows up at the middle of the screen after window start is forced when vscroll is set

[Po Lu]

Eli Zaretskii <eliz@gnu.org> writes:

>> From: Po Lu <luangruo@yahoo.com>
>> Cc: 53275@debbugs.gnu.org
>> Date: Sat, 15 Jan 2022 15:52:50 +0800
>> 
>> Eli Zaretskii <eliz@gnu.org> writes:
>> 
>> >>   (progn
>> >>     (set-window-vscroll nil 30 t)
>> >>     (redisplay)
>> >>     (set-window-start nil (point-max)))
>> 
>> > Sorry, I missed the "M-<" part.  With it, the behavior is
>> > reproducible, but I'm not sure I understand what is "the correct
>> > position" of the cursor in this case
>> 
>> It should show up where point is, which in this case is at the window
>> start.
>> 
>> > or why does it matter what Emacs does in that case (except that it
>> > should not crash).
>> 
>> Precision scrolling relies on this: when the buffer cannot be scrolled
>> downwards sufficiently, it sets the window start to point-max and
>> redisplays, which right now results in the cursor being displayed in the
>> middle of the screen until the next redisplay.
>
> Should be fixed now on the master branch.

Indeed, I'm closing this bug.  Many thanks!