The Timer

#include <stdio.h>
#include "graphapp.h"
 
Rect r;
Window *w;
 
void draw_something(Timer *t)
{
  Graphics *g = get_window_graphics(w);
  draw_ellipse(g, r);
  r.x += 10;
  r.y += 10;
  del_graphics(g);
}
 
int main(int argc, char *argv[])
{
  App *app;
  Timer *t;

  app = new_app(argc, argv);
  w = new_window(app, rect(20,20,400,300), "Timer", STANDARD_WINDOW);
  show_window(w);
 
  r = rect(10,10,30,15);
 
  t = new_timer(app, draw_something, 2000);
  draw_something(t);
  main_loop(app);
  return 0;
}

Notes:

• Use new_timer to create a timer.
• The last parameter is a time interval in milliseconds. In the example, the timer will activate every 2 seconds (2000 milliseconds).
• The timer's call-back function is passed a pointer to the timer.
• To draw to a window or control, you must first obtain a Graphics object. In the example, the get_window_graphics function is used, and the object is later destroyed by del_graphics. Normally this is not necessary, since a window or control's redraw call-back is passed a Graphics object.