bug#72681: 31.0.50; visual-wrap-prefix-mode interacts badly with plain lists in org-mode

[Jim Porter <jporterbugs@gmail.com>]

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On 8/17/2024 12:19 AM, Eli Zaretskii wrote:
> Jim, could you please look into this?  Is visual-wrap-prefix-mode at
> all supposed to be used in Org buffers?

Yes, I think 'visual-wrap-prefix-mode' should support Org buffers. It's 
probably one of the more useful text-based modes where 
'visual-wrap-prefix-mode' would be convenient.

It looks like this was just a small corner case in the visual-wrap code 
for aligning prefix lines that didn't account for Org-Mode's custom 
'adaptive-fill-function'. I've fixed this by being more careful to only 
apply the 'min-width' display property to a single logical line.

Mark, does the attached patch fix things for you? It looks like it works 
in my tests, but maybe you have some more complicated test cases you'd 
like to try to verify this.

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From fe116a69a79653041817c7de9306bbc5040c9652 Mon Sep 17 00:00:00 2001
From: Jim Porter <jporterbugs@gmail.com>
Date: Sat, 17 Aug 2024 13:21:00 -0700
Subject: [PATCH] Be more careful about aligning prefix lines in
 'visual-wrap-prefix-mode'

* lisp/visual-wrap.el (visual-wrap--apply-to-line): Ensure we don't
apply the 'min-width' property across multiple lines (bug#72681).
---
 lisp/visual-wrap.el | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/lisp/visual-wrap.el b/lisp/visual-wrap.el
index cac3bc767b8..eb5daa89222 100644
--- a/lisp/visual-wrap.el
+++ b/lisp/visual-wrap.el
@@ -121,9 +121,15 @@ visual-wrap--apply-to-line
                (next-line-prefix (visual-wrap--content-prefix
                                   first-line-prefix position)))
       (when (numberp next-line-prefix)
+        ;; Set a minimum width for the prefix so it lines up correctly
+        ;; with subsequent lines.  Make sure not to do this past the end
+        ;; of the line though!  (`fill-match-adaptive-prefix' could
+        ;; potentially return a number larger the length of the current
+        ;; line in the buffer.)
         (put-text-property
-         position (+ position (length first-line-prefix)) 'display
-         `(min-width ((,next-line-prefix . width)))))
+         position (min (+ position (length first-line-prefix))
+                       (line-end-position))
+         'display `(min-width ((,next-line-prefix . width)))))
       (setq next-line-prefix (visual-wrap--adjust-prefix next-line-prefix))
       (put-text-property
        position (line-end-position) 'wrap-prefix
-- 
2.25.1