Here is how to set up a timer that runs when Emacs is idle for a certain length of time. Aside from how to set them up, idle timers work just like ordinary timers.
Set up a timer which runs when Emacs has been idle for secs seconds. The value of secs may be an integer or a floating point number; a value of the type returned by
current-idle-timeis also allowed.
If repeat is
nil, the timer runs just once, the first time Emacs remains idle for a long enough time. More often repeat is non-
nil, which means to run the timer each time Emacs remains idle for secs seconds.
run-with-idle-timerreturns a timer value which you can use in calling
Emacs becomes “idle” when it starts waiting for user input, and it
remains idle until the user provides some input. If a timer is set for
five seconds of idleness, it runs approximately five seconds after Emacs
first becomes idle. Even if repeat is non-
nil, this timer
will not run again as long as Emacs remains idle, because the duration
of idleness will continue to increase and will not go down to five
Emacs can do various things while idle: garbage collect, autosave or handle data from a subprocess. But these interludes during idleness do not interfere with idle timers, because they do not reset the clock of idleness to zero. An idle timer set for 600 seconds will run when ten minutes have elapsed since the last user command was finished, even if subprocess output has been accepted thousands of times within those ten minutes, and even if there have been garbage collections and autosaves.
When the user supplies input, Emacs becomes non-idle while executing the 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.
If Emacs is idle, this function returns the length of time Emacs has been idle, as a list of three integers:
(high low microsec
). The integers high and low combine to give the number of seconds of idleness, which is high * 2**16 + low.
The third element, microsec, gives the microseconds since the start of the current second (or 0 for systems that return time with the resolution of only one second).
When Emacs is not idle,
nil. This is a convenient way to test whether Emacs is idle.
The main use of this function is when an idle timer function wants to “take a break” for a while. It can set up another idle timer to call the same function again, after a few seconds more idleness. Here's an example:(defvar resume-timer nil "Timer that `timer-function' used to reschedule itself, or nil.") (defun timer-function () ;; If the user types a command while
resume-timer;; is active, the next time this function is called from ;; its main idle timer, deactivate
resume-timer. (when resume-timer (cancel-timer resume-timer)) ...do the work for a while... (when taking-a-break (setq resume-timer (run-with-idle-timer ;; Compute an idle time break-length ;; more than the current value. (time-add (current-idle-time) (seconds-to-time break-length)) nil 'timer-function))))
Some idle timer functions in user Lisp packages have a loop that
does a certain amount of processing each time around, and exits when
(input-pending-p) is non-
nil. That approach seems very
natural but has two problems:
To avoid these problems, don't use that technique. Instead, write
such idle timers to reschedule themselves after a brief pause, using
the method in the
timer-function example above.