GNU bug report logs - #79275
30.2.50; overlay line-prefix display property fighting with text display property

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Package: emacs;

Reported by: JD Smith <jdtsmith <at> gmail.com>

Date: Wed, 20 Aug 2025 01:40:02 UTC

Severity: normal

Found in version 30.2.50

Done: Eli Zaretskii <eliz <at> gnu.org>

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From: JD Smith <jdtsmith <at> gmail.com>
To: 79275 <at> debbugs.gnu.org
Subject: bug#79275: 30.2.50; overlay line-prefix display property fighting with text display property
Date: Tue, 19 Aug 2025 21:39:38 -0400

An overlay which applies a line-prefix (e.g. to set the fringe) across several lines conflicts with underlying text which has a replacing display property set.  Evaluate the following in the *scratch* buffer, with at least 3 blank lines at the top of the buffer.

(progn
  (delete-all-overlays)
  (let ((ov (make-overlay 1 4)))
    (overlay-put ov 'line-prefix (propertize "SHOULDNOTSEETHIS" 'display
                                             '(left-fringe right-triangle success))))
  (put-text-property 2 3 'display ">testing fringe display"))

The result is very strange: the SHOULDNOTSEETHIS prefix string appears (sans fringe display), but then vanishes on the next redisplay.  Some (well-balanced) fight between overlay line-prefix display and normal display properties seems to be occurring.
This bug report was last modified 20 days ago.

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