master 005efce764: Fix face issues in show-paren context overlay (bug#59527)

[Tassilo Horn]

branch: master
commit 005efce764c50f5fc68be84a7fb52565b9a2d2bc
Author: Tassilo Horn <tsdh@gnu.org>
Commit: Tassilo Horn <tsdh@gnu.org>

    Fix face issues in show-paren context overlay (bug#59527)
    
    * lisp/paren.el (show-paren--show-context-in-overlay): Use
    show-paren-priority as overlay priority (fixes problem 2 of
    bug#59527).
    * lisp/simple.el (blink-paren-open-paren-line-string): Ensure the
    context lines are font-locked before taking the
    buffer-substring (fixes problem 1 of bug#59527).
---
 lisp/paren.el  |  4 ++++
 lisp/simple.el | 60 ++++++++++++++++++++++++++++++++--------------------------
 2 files changed, 37 insertions(+), 27 deletions(-)

diff --git a/lisp/paren.el b/lisp/paren.el
index e2c060ceb9..1d7fb1c462 100644
--- a/lisp/paren.el
+++ b/lisp/paren.el
@@ -410,6 +410,10 @@ It is the default value of `show-paren-data-function'."
                 (line-end-position))))
     (setq show-paren--context-overlay (make-overlay beg end)))
   (overlay-put show-paren--context-overlay 'display text)
+  ;; Use the (default very high) `show-paren-priority' ensuring that
+  ;; not other overlays shine through (bug#59527).
+  (overlay-put show-paren--context-overlay 'priority
+               show-paren-priority)
   (overlay-put show-paren--context-overlay
                'face `(:box
                        ( :line-width (1 . -1)
diff --git a/lisp/simple.el b/lisp/simple.el
index e868736614..893a43b03f 100644
--- a/lisp/simple.el
+++ b/lisp/simple.el
@@ -9184,33 +9184,39 @@ The function should return non-nil if the two tokens do 
not match.")
   "Return the line string that contains the openparen at POS."
   (save-excursion
     (goto-char pos)
-    ;; Show what precedes the open in its line, if anything.
-    (cond
-     ((save-excursion (skip-chars-backward " \t") (not (bolp)))
-      (buffer-substring (line-beginning-position)
-                        (1+ pos)))
-     ;; Show what follows the open in its line, if anything.
-     ((save-excursion
-        (forward-char 1)
-        (skip-chars-forward " \t")
-        (not (eolp)))
-      (buffer-substring pos
-                        (line-end-position)))
-     ;; Otherwise show the previous nonblank line,
-     ;; if there is one.
-     ((save-excursion (skip-chars-backward "\n \t") (not (bobp)))
-      (concat
-       (buffer-substring (progn
-                           (skip-chars-backward "\n \t")
-                           (line-beginning-position))
-                         (progn (end-of-line)
-                                (skip-chars-backward " \t")
-                                (point)))
-       ;; Replace the newline and other whitespace with `...'.
-       "..."
-       (buffer-substring pos (1+ pos))))
-     ;; There is nothing to show except the char itself.
-     (t (buffer-substring pos (1+ pos))))))
+    ;; Capture the regions in terms of (beg . end) conses whose
+    ;; buffer-substrings we want to show as a context string.  Ensure
+    ;; they are font-locked (bug#59527).
+    (let (regions)
+      ;; Show what precedes the open in its line, if anything.
+      (cond
+       ((save-excursion (skip-chars-backward " \t") (not (bolp)))
+        (setq regions (list (cons (line-beginning-position)
+                                  (1+ pos)))))
+       ;; Show what follows the open in its line, if anything.
+       ((save-excursion
+          (forward-char 1)
+          (skip-chars-forward " \t")
+          (not (eolp)))
+        (setq regions (list (cons pos (line-end-position)))))
+       ;; Otherwise show the previous nonblank line,
+       ;; if there is one.
+       ((save-excursion (skip-chars-backward "\n \t") (not (bobp)))
+        (setq regions (list (cons (progn
+                                    (skip-chars-backward "\n \t")
+                                    (line-beginning-position))
+                                  (progn (end-of-line)
+                                         (skip-chars-backward " \t")
+                                         (point)))
+                            (cons pos (1+ pos)))))
+       ;; There is nothing to show except the char itself.
+       (t (setq regions (list (cons pos (1+ pos))))))
+      ;; Ensure we've font-locked the context region.
+      (font-lock-ensure (caar regions) (cdar (last regions)))
+      (mapconcat (lambda (region)
+                   (buffer-substring (car region) (cdr region)))
+                 regions
+                 "..."))))
 
 (defvar blink-paren-function 'blink-matching-open
   "Function called, if non-nil, whenever a close parenthesis is inserted.