New function.

(timer-max-repeats): New variable.
(timer-event-handler): Avoid rerunning a timer many times
if real time has "jumped" forward.

1 files changed, 20 insertions, 0 deletions

diff --git a/lisp/timer.el b/lisp/timer.el
index 1a343755661..3b6382989cb 100644
--- a/lisp/timer.el
+++ b/lisp/timer.el
@@ -248,6 +248,17 @@ fire repeatedly that many seconds apart."
 (defvar timer-event-last-1 nil)
 (defvar timer-event-last nil)
 
+(defvar timer-max-repeats 10
+  "*Maximum number of times to repeat a timer, if real time jumps.")
+
+(defun timer-until (timer time)
+  "Calculate number of seconds from when TIMER will run, until TIME.
+TIMER is a timer, and stands for the time when its next repeat is scheduled.
+TIME is a time-list.
+  (let ((high (- (car time) (aref timer 1)))
+        (low (- (nth 1 time) (aref timer 2))))
+    (+ low (* high 65536))))
+  
 (defun timer-event-handler (event)
   "Call the handler for the timer in the event EVENT."
   (interactive "e")
@@ -269,6 +280,15 @@ fire repeatedly that many seconds apart."
               (if (aref timer 7)
                   (timer-activate-when-idle timer)
                 (timer-inc-time timer (aref timer 4) 0)
+                ;; If real time has jumped forward,
+                ;; perhaps because Emacs was suspended for a long time,
+                ;; limit how many times things get repeated.
+                (if (and (numberp timer-max-repeats)
+                         (< 0 (timer-until timer (current-time))))
+                    (let ((repeats (/ (timer-until timer (current-time))
+                                      (aref timer 4))))
+                      (if (> repeats timer-max-repeats)
+                          (timer-inc-time timer (* (aref timer 4) repeats)))))
                 (timer-activate timer))))
       (error "Bogus timer event"))))