Subject: Re: bug#79275: 30.2.50; overlay line-prefix display property fighting with text display property

From: "J.D. Smith" <[email-masked]>
Date: Thu, 21 Aug 2025 15:46:03 -0400

Eli Zaretskii <[email-masked]> writes:

> Please try the patch below, I hope it fixes both of the situations you
> described.

Your latest patch indeed fixes this display conflict between overlays
and text properties at both the front of a fringe-displaying overlay and
in its middle.  The code I used to test:

   ;; Insert at least 4 blank lines above this and evaluate
   (progn
     (delete-all-overlays)
     (let ((ov (make-overlay 1 5)))
       (overlay-put ov 'line-prefix (propertize "SHOULDNOTSEETHIS" 'display
   				     '(left-fringe right-triangle success))))
     (put-text-property 1 2 'display ">testing front-fringe display\n")
     (put-text-property 3 4 'display ">testing mid-fringe display\n"))   

Thanks very much for your work on this.  I know how challenging it can
be to hunt down subtle bugs in the redisplay code.  I appreciate all the
time and energy you volunteer to continuously improve Emacs.