Fix "first-differente" face in completion-pcm--hilit-commonalityscratch/bug-42149-funny-pcm-completion-scores

Fixes: bug#42149

Depending on the position of point in the completion and the
completion style being used, it may or may not make sense for this
face to appear immediately after point.  This patch assumes that it
should appear in the first non-matched character after point, which
may likely be the next one to type to disambiguate between two or more
completions.

Suggested by Dario Gjorgjevski <dario.gjorgjevski@gmail.com>.

* lisp/minibuffer.el (completion-pcm--hilit-commonality): Fix
occasional misplacement of completions-first-differente.

1 files changed, 6 insertions, 5 deletions

diff --git a/lisp/minibuffer.el b/lisp/minibuffer.el
index dc37c5f4476..074d436b355 100644
--- a/lisp/minibuffer.el
+++ b/lisp/minibuffer.el
@@ -3332,11 +3332,12 @@ between 0 and 1, and with faces `completions-common-part',
            ;; for that extra bit of match (bug#42149).
            (unless (= from match-end)
              (funcall update-score-and-face from match-end))
-           (if (> (length str) pos)
-               (add-face-text-property
-                pos (1+ pos)
-                'completions-first-difference
-                nil str))
+           (cl-loop for p from pos below (length str)
+                    unless (eq (get-text-property p 'face str)
+                               'completions-common-part)
+                    return (add-face-text-property p (1+ p)
+                                                   'completions-first-difference
+                                                   nil str))
            (unless (zerop (length str))
              (put-text-property
               0 1 'completion-score