bug#69534: Scrolling up causes all text to shift drastically when cursor hits bottom of viewable area.

[Eli Zaretskii]

> Date: Sun, 03 Mar 2024 15:56:36 +0000
> From:  Arkdae via "Bug reports for GNU Emacs,
>  the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
> 
> Start 'emacs -Q'. Open a long document which is longer than can fit in
> the window all at once. C-x 2 to split into two windows. Drag with the
> mouse on the information bar with button one to shrink the bottom
> window a bit. Then grab the scroll bar in the top window and drag up.
> 
> The cursor reaches the bottom. Then I slowly scroll one more pixel up
> and all of the text contents are repositioned with the cursor at the
> middle. The next pixel scrolled up keeps the cursor in the middle and
> corrects the text to where it should have been.

I cannot reproduce this, but then I don't think I understand what you
mean by "scroll one more pixel up".  AFAIK, scrolling text in Emacs
works by lines, not by pixels.  Maybe a GTK3 build allows pixelwise
scrolling via the scroll-bar?  If so, this could be specific to GTK3
builds or something.

Are you sure you don't have some local changes wrt stock Emacs 29.2,
or maybe activated some non-default feature that affects scrolling?