With some fonts, changing focus (M-x other-window) from a buffer with images, makes the content in the buffer with images to shift up and down.

I am seeing this in Debian, with both the GTK and Lucid builds, under X11.

The code below reproduces the problem. This problem has been identified while debugging a change on focus issue with pdf-tools (https://github.com/vedang/pdf-tools/pull/224#issuecomment-2014151358 and ff.)


How to reproduce

- Copy the images to /tmp  (or place there three reasonably sized images, named image1.png, image2.png, image3.png)

- emacs -Q

- eval the following code

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; Place images in /tmp
(progn
  (defun pin-vscroll-down (win)
    (set-window-vscroll win 200 t))
  ;; Any of the following leads to the bug
  (set-frame-font "JuliaMono" nil t)
  ;; (set-frame-font "DM Mono" nil t)
  ;; (set-frame-font "Intel One Mono" nil t)
  (let* ((height (/ (* 2 (frame-pixel-height)) 15))
         (image1 (create-image "/tmp/image1.png" nil nil :height height))
         (image2 (create-image "/tmp/image2.png" nil nil :height height))
         (image3 (create-image "/tmp/image3.png" nil nil :height height)))
    (with-current-buffer (get-buffer-create "*image-scroll-test*")
      (insert " \n \n \n \n \n \n")
      (put-image image1 1)
      (put-image image2 5)
      (put-image image3 9)
      ;; With larger image sizes (goto-char 3)
      ;; also triggers the problem.
      (goto-char 11)
      (add-hook 'pre-redisplay-functions #'pin-vscroll-down nil t))
    (split-window-right)
    (other-window 1)
    (switch-to-buffer "*image-scroll-test*")))
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

- M-x other-window

- Notice how the images on the buffer on the right move up and down.