Take a look on the wiki :

This Robot example has some Java stuff to find the actual canvas coordinates. Also just noticed on my Windows 7 system it sets the mouse speed when running this for some reason.

http://www.openprocessing.org/sketch/20675

Okay, so I've used that sketch and put it into my own, it looks like it should be correct, but I'm getting an issue with the way the cursor draws on the screen.

The cursor is constantly moving up and to the right, and I can't see where the issue is. Movement related to where the mouse moves seems to work, but while the mouse is stationary, the cursor continues to move up to the top right of the screen. At the very least, it seems the screen limiter is working, the cursor does indeed stop at the top right of the screen and remain locked to the window.

I've commented out unnecessary code, related to the next thing I want to put in (the class that will control where units are positioned on the screen, class Actor). The program works the same regardless of these lines being commented out, so it isn't an issue regarding these lines.

RTStest

1. import java.awt.Robot;
2. Cursor cursor;
3. //ArrayList<Actor> actors;
4. void setup()
5. {
6.   size(800, 800);
7.   noCursor();
8.   cursor = new Cursor();
9.  
10.   //actors = new ArrayList<Actor>();
11. }
12. void draw()
13. {
14.   // Refresh the screen
15.   background(0);
16.  
17.   //Display the cursor
18.   cursor.update(frame.getX(), this.getX(), frame.getY(), this.getY());
19.   cursor.display();
20.   if (cursor.selecting == true)
21.   {
22.     cursor.selectionBox();
23.   }
24.  
25.   //Display the 'actors'
26.   /*for (int i = 0; i < actors.size(); i++)
27.   {
28.    
29.   }*/
30. }
31. void mousePressed()
32. {
33.   if (mouseButton == LEFT)
34.   {
35.     cursor.selecting = true;
36.     cursor.xStart = mouseX;
37.     cursor.yStart = mouseY;
38.   }
39. }
40. void mouseReleased()
41. {
42.   cursor.selecting = false;
43. }

You have the parameters to update(...) named xScreen, yScreen, xFrame, yFrame, but you're passing them in this order: xScreen, xFrame, yScreen, yFrame.

Sorry to bother you guys again, but I'm now confused as to why the cursor cannot move correctly while the mouse is held down... Mostly it just halts all movement, though sometimes it'll jerk around vaguely in the direction of the movement.

I didn't figure out why this was happening, but I don't think this kind of stuff is exactly the intended use of Robot. I had it working flawlessly by triggering the selection rectangle on keyPressed instead of mouse.

The Java game toolkit LWJGL has raw input stuff that wraps native code I believe. I guess you could use that just for its input handling. Just drop the jar in a folder called code inside your sketch folder.

Turns out you need to setup LWJGL's Display to get mouse input, but you can use the same library that LWJGL uses for input directly. Download JInput from its build management thing here: http://ci.newdawnsoftware.com/job/JInput/lastBuild/artifact/dist/ (click jinput_nightly_20130705.zip). Make a folder inside your sketch folder called code and drop every file from the zip in it. Here is some example code:

Controller mouse;
Component mx, my;
float ax, ay;

void setup() {
  size(400,400);
  ControllerEnvironment ce = 
    ControllerEnvironment.getDefaultEnvironment();
  for(Controller cur : ce.getControllers()) {
    if(cur.getType() == Controller.Type.MOUSE) {
      mouse = cur;
      break;
    }
  }
  Component[] mcomp = mouse.getComponents();
  mx = mcomp[0];
  my = mcomp[1];
  
  new Thread(new Runnable() {
    public void run() {
      while(true) {
        mouse.poll();
        if(!mousePressed) {
          ax += mx.getPollData();
          ay += my.getPollData();          
        }
        ax = max(0, ax);
        ax = min(width, ax);
        ay = max(0, ay);
        ay = min(height, ay);
        
        try {
          Thread.sleep(5);
        } catch(Throwable ex) {}
      }
    }
  }).start();
}

void draw() { 
  background(204);
  ellipse(ax, ay, 10, 10);
}