Restart blink cursor timers on interval changes

This prevents surprising behavior when timer interval customizations are
only applied whenever the timers happen to be restarted (see Bug#24372).

* lisp/frame.el (blink-cursor--start-idle-timer)
(blink-cursor--start-timer): New functions.
(blink-cursor-start, blink-cursor-check, blink-cursor-mode): Use
the new helper functions.
(blink-cursor-delay, blink-cursor-interval): Restart timers when
the value is changed.

1 files changed, 30 insertions, 19 deletions

diff --git a/lisp/frame.el b/lisp/frame.el
index d3b6353d2a2..ab3b722d993 100644
--- a/lisp/frame.el
+++ b/lisp/frame.el
@@ -2029,12 +2029,18 @@ widths."
 (defcustom blink-cursor-delay 0.5
   "Seconds of idle time after which cursor starts to blink."
   :type 'number
-  :group 'cursor)
+  :group 'cursor
+  :set (lambda (symbol value)
+         (set-default symbol value)
+         (when blink-cursor-idle-timer (blink-cursor--start-idle-timer))))
 
 (defcustom blink-cursor-interval 0.5
   "Length of cursor blink interval in seconds."
   :type 'number
-  :group 'cursor)
+  :group 'cursor
+  :set (lambda (symbol value)
+         (set-default symbol value)
+         (when blink-cursor-timer (blink-cursor--start-timer))))
 
 (defcustom blink-cursor-blinks 10
   "How many times to blink before using a solid cursor on NS, X, and MS-Windows.
@@ -2055,6 +2061,24 @@ The function `blink-cursor-start' is called when the timer fires.")
 This timer calls `blink-cursor-timer-function' every
 `blink-cursor-interval' seconds.")
 
+(defun blink-cursor--start-idle-timer ()
+  "Start the `blink-cursor-idle-timer'."
+  (when blink-cursor-idle-timer (cancel-timer blink-cursor-idle-timer))
+  (setq blink-cursor-idle-timer
+        ;; The 0.2 sec limitation from below is to avoid erratic
+        ;; behavior (or downright failure to display the cursor
+        ;; during command execution) if they set blink-cursor-delay
+        ;; to a very small or even zero value.
+        (run-with-idle-timer (max 0.2 blink-cursor-delay)
+                             :repeat #'blink-cursor-start)))
+
+(defun blink-cursor--start-timer ()
+  "Start the `blink-cursor-timer'."
+  (when blink-cursor-timer (cancel-timer blink-cursor-timer))
+  (setq blink-cursor-timer
+        (run-with-timer blink-cursor-interval blink-cursor-interval
+                        #'blink-cursor-timer-function)))
+
 (defun blink-cursor-start ()
   "Timer function called from the timer `blink-cursor-idle-timer'.
 This starts the timer `blink-cursor-timer', which makes the cursor blink
@@ -2064,9 +2088,7 @@ command starts, by installing a pre-command hook."
     ;; Set up the timer first, so that if this signals an error,
     ;; blink-cursor-end is not added to pre-command-hook.
     (setq blink-cursor-blinks-done 1)
-    (setq blink-cursor-timer
-          (run-with-timer blink-cursor-interval blink-cursor-interval
-                          'blink-cursor-timer-function))
+    (blink-cursor--start-timer)
     (add-hook 'pre-command-hook 'blink-cursor-end)
     (internal-show-cursor nil nil)))
 
@@ -2113,13 +2135,7 @@ This is done when a frame gets focus.  Blink timers may be stopped by
   (when (and blink-cursor-mode
              (not blink-cursor-idle-timer))
     (remove-hook 'post-command-hook 'blink-cursor-check)
-    (setq blink-cursor-idle-timer
-          ;; The 0.2 sec limitation from below is to avoid erratic
-          ;; behavior (or downright failure to display the cursor
-          ;; during command execution) if they set blink-cursor-delay
-          ;; to a very small or even zero value.
-          (run-with-idle-timer (max 0.2 blink-cursor-delay)
-                               :repeat #'blink-cursor-start))))
+    (blink-cursor--start-idle-timer)))
 
 (define-obsolete-variable-alias 'blink-cursor 'blink-cursor-mode "22.1")
 
@@ -2150,13 +2166,8 @@ terminals, cursor blinking is controlled by the terminal."
   (when blink-cursor-mode
     (add-hook 'focus-in-hook #'blink-cursor-check)
     (add-hook 'focus-out-hook #'blink-cursor-suspend)
-    (setq blink-cursor-idle-timer
-          ;; The 0.2 sec limitation from below is to avoid erratic
-          ;; behavior (or downright failure to display the cursor
-          ;; during command execution) if they set blink-cursor-delay
-          ;; to a very small or even zero value.
-          (run-with-idle-timer (max 0.2 blink-cursor-delay)
-                               :repeat #'blink-cursor-start))))
+    (blink-cursor--start-idle-timer)))
+
 
 
 ;; Frame maximization/fullscreen