Re: Question about weird vscroll behavior

[Eli Zaretskii <eliz@gnu.org>]

> From: dalanicolai <dalanicolai@gmail.com>
> Date: Sun, 5 Nov 2023 16:49:04 +0100
> 
> It works when I simply load my Emacs configuration, but for some
> reason it does not work when I start from emacs -Q.
> 
> Although I guess vscroll should be working on lines smaller than the
> screen, just for testing I now display 3 'spaces' and then try to set
> vscroll as follows:
> 
>  (progn
>    (pop-to-buffer "example")
>    (dotimes (i 3)
>      (let ((o (make-overlay (point)
>                             (progn (insert " ")
>                                    (point)))))
>        (insert "\n")
>        (overlay-put o 'display `(space . (:width (600) :height (800))))
>        (overlay-put o 'face (list :background (pcase (% i 3)
>                                                 (0 "red")
>                                                 (1 "green")
>                                                 (2 "blue"))))))
>    (goto-char (point-min))
>      
>    (set-window-vscroll nil 300 t))
> 
> I have tested it on Emacs 29.1 and 28.3.
> 
> I wonder if this is a bug, or if I am missing something.  Could you
> please evaluate the above code starting from emacs -Q, and confirm
> this is a bug (or tell me what I am missing)?

Works for me in "emacs -Q".