Something is bogus with idle timers

[Jorgen Schaefer <forcer@forcix.cx>]

Hi there!
I'm using "GNU Emacs 21.2.2 (i386-pc-linux-gnu, X toolkit, Xaw3d
scroll bars) of 2002-10-16 on raven, modified by Debian" and need
a pretty long-running idle timer (about 10 to 30 minutes). Adding
it using run-with-idle-timer, i found out it was never run.

It seems like emacs is resetting the idle timer sometimes (not
always) when it gets data for a process that has a filter. I don't
think this is wanted behaviour, right? From (elisp)Timers:

| Emacs becomes "idle" when it starts waiting for user input, and
| it remains idle until the user provides some input.
| [...]
| 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.

Can someone tell me what exactly besides user keyboard stuff
resets the idle timer? I couldn't find that much from the sources.

I used the following code to check wether Emacs got out of the
idle state:

(setq fc-idle-timer nil)
(defun fc-idle-test ()
  (interactive)
  (when fc-idle-timer
    (cancel-timer fc-idle-timer))
  (setq fc-idle-num 0)
  (setq fc-idle-timer (run-with-idle-timer 1 t 'fc-idle-meep)))
(defun fc-idle-meep ()
  (message "meep %i." fc-idle-num)
  (setq fc-idle-num (+ fc-idle-num 1)))

Since emacs runs a function only once for becoming idle, this will
message "meep" with an increasing number everytime emacs becomes
non-idle.

The following code will make emacs drop out of idleness
*sometimes* when receiving data from nc (I usually have to wait
for half a minute or so, after which sending data through the
process will reset the idle-timer each time i send). You should do
nc -lp 2000 before running this code to send data to emacs.

(setq process (start-process "nc" "*nc*" "nc" "localhost" "2000"))
(set-process-filter process 'fc-filter)
(defun fc-filter (proc data)
  t)

Any idea what is happening?

Greetings,
        -- Jorgen

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