static int forwardClicks_windowSize = 11; // odd should look nice. Set to 1 for an invisible window
static int forwardClicks_clickDelay = 0; // Delay in ms between closing window and forwarding click. 0 seems to work fine.
static int forwardClicks_dragDelay = 100; // Delay in ms when dragging
static int forwardClicks_trackingSpeed = 10; // How often to move the window (ms)
static int forwardClicks_restartDelay = 1000; // How quickly to restart after click (e.g. to allow untraced drags [forwarding dragging doesn't always work])
sbool forwardClicks_verbose;

// onClick: voidfunc(Point, Point, int) - press location, release location, button (1 to 3)
static void forwardClicks(final O onClickAndRelease) {
  awtIfNecessary {
    final new JWindow window;
    final int windowSize = forwardClicks_windowSize;
    window.setSize(windowSize, windowSize);
    window.setVisible(true);
    window.setAlwaysOnTop(true);
    JPanel panel = singleColorPanel(Color.red);
    window.setContentPane(panel);
    revalidate(window);
    final new Robot robot;
    panel.addMouseListener(new MouseAdapter {
      Point pressed;
      
      public void mousePressed(final MouseEvent e) {
        pressed = getMouseLocation();
      }
      
      public void mouseReleased(final MouseEvent e) {
        window.setVisible(false);
        final Point released = getMouseLocation();
        final Point _pressed = or(pressed, released);
        final int b = e.getButton();
        final int mod =
          b == 1 ? InputEvent.BUTTON1_DOWN_MASK
          : b == 2 ? InputEvent.BUTTON2_DOWN_MASK
          : InputEvent.BUTTON3_DOWN_MASK;
        swingLater(forwardClicks_clickDelay, r {
          pcallF(onClickAndRelease, _pressed, released, b);
          robot.mouseMove(_pressed.x, _pressed.y);
          robot.mousePress(mod);
          swingLater(neq(_pressed, released) ? forwardClicks_dragDelay : 0, r {
            robot.mouseMove(released.x, released.y);
            robot.mouseRelease(mod);
          
            // Start tracking again - make new JWindow otherwise we get a crazy item on task bar in Linux
            swingLater(forwardClicks_restartDelay, r {
              forwardClicks(onClickAndRelease);
            });
          });
        });
      }
    });
    
    swingEvery(window, forwardClicks_trackingSpeed, r {
      final Point p = getMouseLocation();
      // Expand height if in task bar (crude fix for Peppermint Linux)
      int bottom = getScreenHeight()-(768-743);
      final Point loc = new Point(p.x-windowSize/2, min(bottom, p.y-windowSize/2));
      int h = max(windowSize, p.y-loc.y+windowSize/2);
      window.setBounds(loc.x, loc.y, windowSize, h);

      if (forwardClicks_verbose) {
        Point onScreen = window.getLocationOnScreen();
        print(loc + " " + onScreen);
      }
      /*if (neq(onScreen, loc))
        print("Location not honored");*/
    });
  }
}

Began life as a copy of #1005566