on-timer

Arguments: timer

This function returns the value of the on-timer event property of the argument timer. The value should be a function object or a function name (a symbol naming a function). The function is invoked after timer's interval has elapsed (assuming that the default timer method has not been overridden). The function should take a single argument, which is the timer itself. Its returned values are not used. The default value is nil, and so a timer will not do anything when its interval has elapsed unless it is given a custom on-timer function (or a timer method is added for it).

An on-timer function can be specified with the :on-timer initarg when creating a timer instance with make-instance and setf can be used with on-timer to set or change the on-timer function of a timer.

See cg-timers.htm for more information on timers. See cg-events.htm for information about event handling in Common Graphics.

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Created 2019.8.20.