[pygtk] gobject.timeout_add timeout recalculation

[Mitko Haralanov]

On Thu, 15 May 2008 18:48:22 -0500
skip at pobox.com wrote:

> I believe it works like this:
> 
>     set wakeup for X milliseconds from now
>     call your callback
>     if it returned true:
>         set wakeup for X milliseconds from now
>     call your callback
>     if it returned true:
>         set wakeup for X milliseconds from now
>     call your callback
>     if it returned true:
>         set wakeup for X milliseconds from now
>     ...
> 
> If X is 2500ms and your callback takes 2ms to execute, the interval between
> successive calls will actually be 2502ms.

Unfortunately, it is how it work. In fact, that how I would like it to
work. Here is what my testing shows:

t0: set wakeup for X milliseconds from now
t0+X: set wakeup for X milliseconds from now (t0+X+X)
	call callback
	if it returned true: noop
	else: delete the timer

Here is an example:

#!/usr/bin/python

import gtk
import gobject
import time

def callback (timeout):
  print "callback called at: %s"%time.time ()
  time.sleep (timeout)
  print "callback returning at: %s"%time.time ()
  return True


if __name__ == "__main__":
  gobject.timeout_add (20*1000, callback, 10)
  gtk.main ()


If you run this, you get:
callback called at: 1210897497.69
callback returning at: 1210897507.69
callback called at: 1210897517.69
callback returning at: 1210897527.69
callback called at: 1210897537.69
callback returning at: 1210897547.69
callback called at: 1210897557.69


Note that the time difference between the "callback returning at" and
"callback called at" is not 20 seconds but 10 seconds (20 second timeout
- 10 second callback runtime).

-- 
Mitko Haralanov
==========================================
A programming language is low level when its programs require attention
to the irrelevant.