Subject: Simple example to reproduce.

From: Felix <[email-masked]>
Date: Thu, 03 Aug 2023 19:20:06 +0200

The following code should visualize the problem.

(font-lock-mode -1)
(set-frame-parameter (selected-frame) 'alpha-background 50)
(let* ((w (window-font-width))
       (stipple `(,w 1 ,(apply #'unibyte-string
			       (append (make-list (1- (/ (+ w 7) 8)) ?\0)
				       '(1))))))
  (insert "\n" (propertize (concat  (make-string 15 ?\s)
				    "THIS IS A TEST"
				    (make-string 15 ?\s))
                           'face `(:foreground "blue" :stipple ,stipple))))