Here is example to show how sketches in separate windows can talk to each other...
The problem is how to d isables decorations for both frames and put them on black background (SoftFullScreen - Hansi's fullscreen library for Processing)..

Any help is much appreciated!

1. //multisketchExample1.pde
   
   import org.gicentre.utils.multisketch.*; 
   import java.awt.MouseInfo;
    
   // The embedded sketch. 
   RightSketch rightSketch;   
    
   int mX;
   int mY;
   
   void setup()
   {
     size(300,300);
    
     smooth();
     stroke(120,20,20);
     strokeWeight(4);
     
     rightSketch = new RightSketch();
     PopupWindow win = new PopupWindow(this,rightSketch);
     win.setVisible(true);
   }
    
   void draw()
   {
     background(255,200,200);
     
     float xOffset = width-mouseX + rightSketch.width/2.0;
     float yOffset = rightSketch.height/2-mouseY;
     line(mouseX,mouseY,mouseX+xOffset,mouseY+yOffset);
     float angle = atan(yOffset/xOffset);
    
     // Tell the other sketch to draw a line from one edge to its centre. 
     rightSketch.setLine(0,mouseY+(width-mouseX)*tan(angle));
   }
   
   void mousePressed(){
     mX = mouseX;
     mY = mouseY;
   }
   
   void mouseDragged(){
     frame.setLocation(
     MouseInfo.getPointerInfo().getLocation().x-mX,
     MouseInfo.getPointerInfo().getLocation().y-mY);
     println(MouseInfo.getPointerInfo().getLocation().x-mX);
     println(MouseInfo.getPointerInfo().getLocation().y-mY);
   }
   
   public void init(){
     frame.removeNotify();
     frame.setUndecorated(true);
     frame.addNotify();
     super.init();
   }