/*
 *  Timer
 *  -----
 *  Every program can have a timer. This program demonstrates the
 *  use of the timer function.
 *
 *  Use settimerfn to set the call-back function which is called by
 *  the timer. The call-back takes one parameter, a void pointer,
 *  and returns nothing.
 *
 *  Use settimer to start or stop the timer. The number passed to
 *  this function is the number of milliseconds between timeouts.
 *  In the example, the function draw_something will occur every
 *  2 seconds (2000 milliseconds).
 *
 *  Because the timer call-back is passed a void pointer, that
 *  pointer must be cast back to a window, then the drawto function
 *  is called to explicitly allow drawing to that window.
 *  (Ordinarily a call-back which belongs to a window is set up to
 *  draw to the window when it is called, but not with timers.)
 */

#include <graphapp.h>

rect r;

void draw_something(void * w)
{
	drawto((window) w);
	drawellipse(r);
	r.x += 10;
	r.y += 10;
}

void main(void)
{
	window w;

	w = newwindow("Timer", rect(20,20,400,300), StandardWindow);
	show(w);

	r = rect(10,10,30,15);

	settimerfn(draw_something, w);
	settimer(2000);
	draw_something(w);
	mainloop();
}