1.171 class timer

A timer is an object that -when the system is dispatching messages- generates an event at regular intervals. Timers are used to implement simulation, blinking (caret) or to wake-up the user under some (time-based) conditions.

The interval of a timer is specified as a real-number. The actual accuracy depends on the timing capabilities offered by the X-implementation on which PCE has been build.

When executing the message, no arguments are forwarded. @receiver is bound to the timer itself. See timer->execute.

NOTE: When multiple objects are animated at a similar speed performance will be much better if a single timer is used. The code below provides a skeleton:

:- pce_global(@stepping, chain).

start_stepping :-
        send(new(@stepper,
                         timer(1, message(@stepper, for_all,
                                                          step))),
             start).

step(Obj) :-
        send(@stepping, append, Obj).

See also

class date

1.171.1 Instance variables

timer <- interval: real

Interval in seconds. Note that

• The timer is only executing if PCE is in its idle loop (see display->dispatch).
• Granularity depends on the underlying implementation. For the X11 version, consult the manual page for select().

  The interval may be changed when the timer is running. In this case it will first fire timer<-interval seconds from the time is was changed.

timer <-> message: code*

Code executed each time. See timer->execute for details.

timer <-> service: bool

If @on, execution cannot be debugged. See also application->kind.

timer <- status: {idle,repeat,once}

Status of the timer. Its values:

idle	Timer is not running
once	After timer->execute’ing once it will stop
repeat	Timer will repeat timer->execute’ing

1.171.2 Send methods

timer ->delay:

Delay for timer<-interval. XPCE processes events while execution is suspended.

timer ->execute:

Execute the timers timer<-message with the following arguments:

@receiver		The timer itself.

timer ->initialise: interval=real, message=[code]*

Create a timer object from its interval and the message to execute. After creation, the timer is idle. Use timer->start or timer->status to start the timer.

timer ->start: how=[{repeat,once}]

Equivalent to timer->status: [repeat].

timer ->stop:

Equivalent to timer->status: idle.

timer ->running: running=bool

Start/stop the timer in repeat mode.

@on, timer->start	is equivalent to timer->status: repeat
@off, timer->stop	is equivalent to timer->status: idle.