Improve cursor-face-highlight-mode a bit more.

Add the hook locally to the buffer only when needed to avoid even
calling the function redisplay--update-cursor-face-highlight when the
mode is enabled.

* lisp/simple.el (redisplay--update-cursor-face-highlight) : Remove
unneeded condition.
(cursor-face-highlight-mode) : Conditionally add or remove
redisplay--update-cursor-face-highlight to pre-redisplay-functions with
buffer local flag.

diff --git a/lisp/simple.el b/lisp/simple.el
index 02f05ccb04122fdffda0f1aee82a79d6474dc10e..cada2e5571ab5e474e06d5dc858f7428a1ffa676 100644 (file)
--- a/lisp/simple.el
+++ b/lisp/simple.el
@@ -6540,37 +6540,41 @@ The overlay is returned by the function.")
         (unless (equal new rol)
           (set-window-parameter window 'internal-region-overlay new))))))
 
-(define-minor-mode cursor-face-highlight-mode
-  "When enabled the cursor-face property is respected.")
-
 (defun redisplay--update-cursor-face-highlight (window)
   "Highlights the overlay used to highlight text with cursor-face."
-  (when cursor-face-highlight-mode
-    (let ((rol (window-parameter window 'internal-cursor-face-overlay)))
-      (if-let (((or (eq window (selected-window))
-                    (and (window-minibuffer-p)
-                         (eq window (minibuffer-selected-window)))))
-               (pt (window-point window))
-               (value (get-text-property pt 'cursor-face))
-               ;; Extra code needed here for when passing plists.
-               (cursor-face (if (facep value) value)))
-          (let* ((start (previous-single-property-change
-                         (1+ pt) 'cursor-face nil (point-min)))
-                 (end (next-single-property-change
-                       pt 'cursor-face nil (point-max)))
-                 (new (redisplay--highlight-overlay-function
-                       start end window rol cursor-face)))
-            (unless (equal new rol)
-              (set-window-parameter window 'internal-cursor-face-overlay new)))
-        (redisplay--unhighlight-overlay-function rol)))))
-
-(defvar pre-redisplay-functions (list #'redisplay--update-cursor-face-highlight
-                                      #'redisplay--update-region-highlight)
+  (let ((rol (window-parameter window 'internal-cursor-face-overlay)))
+    (if-let (((or (eq window (selected-window))
+                  (and (window-minibuffer-p)
+                       (eq window (minibuffer-selected-window)))))
+             (pt (window-point window))
+             (value (get-text-property pt 'cursor-face))
+             ;; Extra code needed here for when passing plists.
+             (cursor-face (if (facep value) value)))
+        (let* ((start (previous-single-property-change
+                       (1+ pt) 'cursor-face nil (point-min)))
+               (end (next-single-property-change
+                     pt 'cursor-face nil (point-max)))
+               (new (redisplay--highlight-overlay-function
+                     start end window rol cursor-face)))
+          (unless (equal new rol)
+            (set-window-parameter window 'internal-cursor-face-overlay new)))
+      (redisplay--unhighlight-overlay-function rol))))
+
+(defvar pre-redisplay-functions (list #'redisplay--update-region-highlight)
   "Hook run just before redisplay.
 It is called in each window that is to be redisplayed.  It takes one argument,
 which is the window that will be redisplayed.  When run, the `current-buffer'
 is set to the buffer displayed in that window.")
 
+(define-minor-mode cursor-face-highlight-mode
+  "When enabled the cursor-face property is respected."
+  :global nil
+  (if cursor-face-highlight-mode
+      (add-hook 'pre-redisplay-functions
+                #'redisplay--update-cursor-face-highlight nil t)
+    (add-hook 'pre-redisplay-functions
+              #'redisplay--update-cursor-face-highlight)))
+
 (defun redisplay--pre-redisplay-functions (windows)
   (with-demoted-errors "redisplay--pre-redisplay-functions: %S"
     (if (null windows)