bug#65432: 30.0.50; jerky image movements when zoomed

[Eli Zaretskii]

> Date: Mon, 21 Aug 2023 16:45:31 +0200
> From:  Manuel Giraud via "Bug reports for GNU Emacs,
>  the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
> 
> When opening a rather big image into a quite big Emacs window, movements
> (C-n, C-p, C-f, C-b) are smooth at original image size but are jerky
> whenever there is some zooming (in or out) involved.
> 
> Recipe:
>         - emacs -Q
>         - 'C-x C-f' "a big image.jpg"
>         - 's o' (image-transform-reset-to-original)
>         - keep 'C-n' pressed, keep 'C-f' pressed -> movements are smooth
>         - 'i -' (image-decrease-size)
>         - keep 'C-n' pressed, keep 'C-f' pressed -> movements are jerky

I cannot reproduce this, on MS-Windows.  I see no difference between
"jerkyness" of motion commands before and after 'i -'.