Guide > Windows and Panels > Events > Example Non-Blocking Events

Example Non-Blocking Events

The following program opens two windows W1 and W2. The main loop reads all events, determines for each event in which of the two windows it occurred and puts the event back to the event queue. If the event occurred in W1 a point is drawn, for W2 a segment. 
#include <LEDA/graphics/window.h>
#include <LEDA/geo/point.h>
#include <LEDA/geo/segment.h>

using namespace leda;

int main()
{
  window W1(500,500,"Window 1: points");
  W1.display(window::min,window::min);

  window W2(500,500,"Window 2: segments");
  W2.display(window::max,window::min);

  for (;;) {
    window* wp;    
    double x,y;
    int val;

    if (read_event(wp,val,x,y)!=button_press_event) continue;

    if (val==MOUSE_BUTTON(3)) break;

    put_back_event();

    if (wp==&W1) {point p; W1 >> p; W1 << p;}
    if (wp==&W2) {segment s; W2 >> s; W2 << s;}
  }
		
  return 0;
}

See also:

Events

Windows and Panels

Basic Data Types for 2D Geometry

Mouse Input

Manual Pages:

Manual Page Windows


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