.. currentmodule:: mood.event
.. py:class:: Timer(after, repeat, loop, callback[, data=None, priority=0])
:param float after: configure the timer to trigger after *after*
seconds.
:param float repeat: if *repeat* is ``0.0``, then it will automatically
be stopped once the timeout is reached. If it is positive, then the
timer will automatically be configured to trigger again every
*repeat* seconds later, again and again, until stopped manually.
:type loop: :py:class:`Loop`
:param loop: loop object responsible for this watcher (accessible through
:py:attr:`~Watcher.loop`).
:param callable callback: see :py:attr:`~Watcher.callback`.
:param object data: any Python object you might want to attach to the
watcher (stored in :py:attr:`~Watcher.data`).
:param int priority: see :py:attr:`~Watcher.priority`.
:py:class:`Timer` watchers are simple relative timers that generate an event
after a given time, and optionally repeating in regular intervals after that.
The timers are based on real time, that is, if you register an event that
times out after an hour and you reset your system clock to January last
year, it will still time out after (roughly) one hour. "Roughly" because
detecting time jumps is hard, and some inaccuracies are unavoidable.
The callback is guaranteed to be invoked only **after** its timeout has
passed (**not** *at*, so on systems with very low-resolution clocks this
might introduce a small delay). If multiple timers become ready during the
same loop iteration then the ones with earlier time-out values are invoked
before ones of the same priority with later time-out values (but this is no
longer true when a callback calls :py:meth:`Loop.start` recursively).
The timer itself will do a best-effort at avoiding drift, that is, if you
configure a timer to trigger every 10 seconds, then it will normally trigger
at exactly 10 second intervals. If, however, your program cannot keep up
with the timer (because it takes longer than those 10 seconds to do stuff)
the timer will not fire more than once per event loop iteration.
.. seealso::
`ev_timer - relative and optionally repeating timeouts
<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#code_ev_timer_code_relative_and_opti>`_
* `Be smart about timeouts
<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#Be_smart_about_timeouts>`_
* `The special problem of being too early
<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#The_special_problem_of_being_too_ear>`_
* `The special problem of time updates
<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#The_special_problem_of_time_updates>`_
* `The special problem of unsynchronised clocks
<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#The_special_problem_of_unsynchronise>`_
* `The special problems of suspended animation
<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#The_special_problems_of_suspended_an>`_
.. py:method:: set(after, repeat)
:param float after: configure the timer to trigger after *after*
seconds.
:param float repeat: if *repeat* is ``0.0``, then it will automatically
be stopped once the timeout is reached. If it is positive, then the
timer will automatically be configured to trigger again every
*repeat* seconds later, again and again, until stopped manually.
Reconfigures the watcher.
.. py:method:: reset
This will act as if the timer timed out, and restarts it again if it is
repeating. It basically works like calling :py:meth:`~Watcher.stop`,
updating the timeout to the :py:attr:`repeat` value and calling
:py:meth:`~Watcher.start`. The exact semantics are:
* if the timer is pending, the pending status is always cleared.
* if the timer is started but non-repeating, stop it (as if it timed
out, without invoking it).
* if the timer is repeating, make the :py:attr:`repeat` value the new
timeout and start the timer, if necessary.
.. seealso::
`Be smart about timeouts
<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#Be_smart_about_timeouts>`_
for a usage example.
.. py:attribute:: repeat
The current *repeat* value. Will be used each time the watcher times out
or :py:meth:`reset` is called, and determines the next timeout (if any),
which is also when any modifications are taken into account.
.. py:attribute:: remaining
*Read only*
The remaining time until a timer fires. If the timer is active, then
this time is relative to the current event loop time, otherwise it's the
timeout value currently configured.
That is, after instanciating a :py:class:`Timer` with an *after* value
of ``5.0`` and a *repeat* value of ``7.0``, :py:attr:`remaining` is
``5.0``. When the timer is started and one second passes,
:py:attr:`remaining` will be ``4.0``. When the timer expires and is
restarted, it will be roughly ``7.0`` (likely slightly less as callback
invocation takes some time, too), and so on.