bug#46320: 27.1; bugs about scrolling buffer with images

[Eli Zaretskii <eliz@gnu.org>]

> From: ynyaaa@gmail.com
> Date: Fri, 05 Feb 2021 14:45:34 +0900
> 
> (2)unable to scroll up
> Evaluate the form below and type C-v repeatedly, the buffer never scroll
> up to the end of the buffer. Once in three times, the buffer scrolls
> down and the line 2 is displayed at the top of the window.
> 
> (let* ((buf (generate-new-buffer "tmp"))
>        (width 80)
>        (height 250)
>        (svg (format "\
> <svg width=\"%d\" height=\"%d\" version=\"1.1\"
>  xmlns=\"http://www.w3.org/2000/svg\">
> <rect x=\"0\" y=\"0\" width=\"%d\" height=\"%d\" fill=\"blue\"/>
> </svg>
> " width height width height))
>        (img (create-image svg 'svg t :scale 1 :ascent 100)))
>   (switch-to-buffer buf)
>   (setq header-line-format "with header line")
>   (insert "1\n2\n3\n4\n5\n")
>   (insert-image img "6")
>   (insert "\n7\n8\n9\n10\n11\n")
>   (set-frame-height nil 18)
>   (delete-other-windows)
>   (goto-char (point-min))
>   )

Thanks, this is now fixed on the master branch.