[Emacs-diffs] Changes to emacs/lispref/os.texi

[Richard M . Stallman]

Index: emacs/lispref/os.texi
diff -c emacs/lispref/os.texi:1.66 emacs/lispref/os.texi:1.67
*** emacs/lispref/os.texi:1.66  Sat Nov  6 17:03:18 2004
--- emacs/lispref/os.texi       Wed Dec 29 20:10:57 2004
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*** 1368,1373 ****
--- 1368,1378 ----
  timer to call a function that takes substantial time to run is likely
  to be annoying.
  
+   Timer functions should normally not alter the current buffer
+ contents, but it may be ok to alter some other buffer that exists for
+ special purposes.  A general guideline is that if a buffer has undo
+ enabled, timers should not write in it.
+ 
  @deffn Command run-at-time time repeat function &rest args
  This sets up a timer that calls the function @var{function} with
  arguments @var{args} at time @var{time}.  If @var{repeat} is a number
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*** 1481,1486 ****
--- 1486,1496 ----
  input.  Then it becomes idle again, and all the idle timers that are
  set up to repeat will subsequently run another time, one by one.
  
+   It is legitimate for an idle timer to edit the current buffer.  If
+ it does, it should explicitly call @code{undo-boundary} once at the
+ beginning and once just before exiting, since Emacs won't do that
+ automatically for an idle timer.
+ 
  @defun cancel-timer timer
  Cancel the requested action for @var{timer}, which should be a value
  previously returned by @code{run-at-time} or @code{run-with-idle-timer}.