bug#12430: Glitches caused by addition of psec to timers

[Paul Eggert <eggert@cs.ucla.edu>]

Tags: patch

A private correspondent pointed out that the higher-resolution time
stamps patch (see Bug#9000) changed the format of timers but some
Lisp code that accesses timer-list wasn't updated.  The patch
below fixes the instances I found.  This
patch should be applied anyway, for clarity, but this raises
a compatibility point.  The old timer format (through 24.2) was:

  [high-seconds low-seconds usecs repeat-delay function args idle-delay]

The new (24.3) format, introduced to the trunk on 2012-06-22, adds a
PSECS component after USECS, like this:

  [high-seconds low-seconds usecs psecs repeat-delay function args idle-delay]

which means that old code like (aref timer 5) to get the function, no
longer has the intended meaning.  Code is supposed to use
(timer--function timer) instead of (aref timer 5), but not everyone
got the memo apparently.  Clearly this stuff should be documented in
NEWS so the patch below does that too.

My correspondent suggests that the new format be changed to put PSECS
at the end:

  [high-seconds low-seconds usecs repeat-delay function args idle-delay psecs]

to support older code that uses aref or elt.  Does this sound like a
good idea?  It would cater to backward compatiblity better, but would
make the new code a bit weirder.

Here's the patch to fix the bugs mentioned above, which I plan to
install shortly:

=== modified file 'etc/ChangeLog'
--- etc/ChangeLog	2012-09-11 02:28:27 +0000
+++ etc/ChangeLog	2012-09-13 05:56:38 +0000
@@ -1,3 +1,7 @@
+2012-09-13  Paul Eggert  <eggert@cs.ucla.edu>
+
+	* NEWS: Document timer format change.
+
 2012-09-11  Paul Eggert  <eggert@cs.ucla.edu>
 
 	Simplify, document, and port floating-point (Bug#12381).

=== modified file 'etc/NEWS'
--- etc/NEWS	2012-09-12 19:16:36 +0000
+++ etc/NEWS	2012-09-13 05:56:38 +0000
@@ -101,6 +101,11 @@
 file-attributes and format-time-string, have been changed accordingly.
 Old-format time stamps are still accepted.
 
+** The format of timers in timer-list and timer-idle-list is now
+[HIGH-SECONDS LOW-SECONDS USECS PSECS REPEAT-DELAY FUNCTION ARGS IDLE-DELAY].
+The PSECS slot is new, and uses picosecond resolution.  It can be
+accessed via the new timer--psecs accessor.
+
 ** Emacs now generates backtraces on fatal errors.
 On encountering a fatal error, Emacs now outputs a textual description
 of the fatal signal, and a short backtrace on platforms like glibc

=== modified file 'lisp/ChangeLog'
--- lisp/ChangeLog	2012-09-13 02:41:46 +0000
+++ lisp/ChangeLog	2012-09-13 05:00:33 +0000
@@ -1,3 +1,11 @@
+2012-09-13  Paul Eggert  <eggert@cs.ucla.edu>
+
+	Fix glitches caused by addition of psec to timers.
+	* image.el (image-animate-timer):
+	* time.el (display-time-world-timer):
+	Use timer--function and timer--args rather than raw access to
+	timer vector.
+
 2012-09-13  Glenn Morris  <rgm@gnu.org>
 
 	* emacs-lisp/bytecomp.el (byte-compile-warning-prefix):

=== modified file 'lisp/gnus/ChangeLog'
--- lisp/gnus/ChangeLog	2012-09-11 10:08:59 +0000
+++ lisp/gnus/ChangeLog	2012-09-13 05:00:33 +0000
@@ -1,3 +1,9 @@
+2012-09-13  Paul Eggert  <eggert@cs.ucla.edu>
+
+	Fix glitches caused by addition of psec to timers.
+	* gnus-art.el (gnus-article-stop-animations): Use timer--function
+	rather than raw access to timer vector.
+
 2012-09-11  Julien Danjou  <julien@danjou.info>
 
 	* gnus-notifications.el (gnus-notifications): Check for nil values in

=== modified file 'lisp/gnus/gnus-art.el'
--- lisp/gnus/gnus-art.el	2012-08-14 05:34:20 +0000
+++ lisp/gnus/gnus-art.el	2012-09-13 05:00:33 +0000
@@ -4554,7 +4554,7 @@
 (defun gnus-article-stop-animations ()
   (dolist (timer (and (boundp 'timer-list)
 		      timer-list))
-    (when (eq (elt timer 5) 'image-animate-timeout)
+    (when (eq (timer--function timer) 'image-animate-timeout)
       (cancel-timer timer))))
 
 (defun gnus-stop-downloads ()

=== modified file 'lisp/image.el'
--- lisp/image.el	2012-08-15 16:29:11 +0000
+++ lisp/image.el	2012-09-13 05:00:33 +0000
@@ -645,8 +645,8 @@
     (while tail
       (setq timer (car tail)
 	    tail (cdr tail))
-      (if (and (eq (aref timer 5) 'image-animate-timeout)
-	       (eq (car-safe (aref timer 6)) image))
+      (if (and (eq (timer--function timer) 'image-animate-timeout)
+	       (eq (car-safe (timer--args timer)) image))
 	  (setq tail nil)
 	(setq timer nil)))
     timer))

=== modified file 'lisp/time.el'
--- lisp/time.el	2012-05-04 06:13:18 +0000
+++ lisp/time.el	2012-09-13 05:00:33 +0000
@@ -575,7 +575,8 @@
     (let ((list timer-list))
       (while list
         (let ((elt (pop list)))
-          (when (equal (symbol-name (aref elt 5)) "display-time-world-timer")
+          (when (equal (symbol-name (timer--function elt))
+		       "display-time-world-timer")
             (cancel-timer elt)))))))
 
 ;;;###autoload