timer

See cg-timers.htm.

The class of timer objects. A timer can be used to cause an arbitrary piece of application code to be asynchronously invoked after a specified amount of time has elapsed. A timer can then be stopped in order to run its code a single time only, or it can be allowed to continue running in order to run its code an indefinite number of times at a regular time interval.

A single timer can be started and stopped a number of times, using various time intervals, to time a number of different activities. If multiple activities need to be timed simultaneously, then multiple timers can be created and run alongside each other. It is also convenient to create a separate timer for each piece of code that is to be invoked by timers, even when they do not need to run simultaneously.

A timer has the following properties. All of these except for id may be set by an application.

name: an arbitrary symbol that is used to find a timer (by calling find-timer), or to distinguish an individual timer during development and debugging.

active: a boolean value indicating whether a timer is currently running: an active timer "fires" each time its interval passes, while an inactive timer does nothing. This property of a timer will be non-nil if start-timer has been called on the timer more recently than stop-timer has. If the active property is explicitly modified by an application from nil to non-nil, then start-timer is called internally, and if the active property is explicitly modified from non-nil to nil, then stop-timer is called internally. Therefore, in order to wrap all starting and stopping of timers, it is sufficient to add start-timer and stop-timer methods.

id: a positive integer that is assigned and used by the operating system to uniquely identify a particular timer. An application should never modify this property, but may want to check its value for debugging purposes (for example, to see which timer id is being passed to a win:WM_TIMER method). Any given timer object will always use the same id, and no other timer object will use that id.

interval: a positive integer indicating the number of milliseconds after a timer is started that it will "fire" by calling the generic function timer. The interval default-initarg for the timer class is 1000, which will fire the timer once a second.

on-timer: the name of a function that is invoked after the timer's interval has elapsed (assuming that the default timer method has not been overridden).

timer-count: a non-negative integer indicating the number of times that a timer's interval has elapsed since it was most recently started.

timer-info: a place for an application to store arbitrary information about its current use of a timer.

Copyright (c) 1998-2002, Franz Inc. Oakland, CA., USA. All rights reserved.
Documentation for Allegro CL version 6.2. This page was not revised from the 6.1 page.
Created 2002.2.26.