Mouse position based movement - unnecessary offset

Question

I'm making Pong game, I can't get the player and AI paddles to move correctly. This explanation may be a little chaotic.

First, the player's paddle. I will make a separate question for AI to keep the length of this post within reason.

HEIGHT and WIDTH defines paddle size, image is texture for the paddle

double mouseY = MouseInfo.getPointerInfo().getLocation().getY();
        if (mouseY < getHeight() - HEIGHT) {
            paddleLeft.setLocation(2 * WIDTH, mouseY);
            image.setLocation(2 * WIDTH, mouseY);
            image.sendToFront();
        } else {     

                   // stop paddle from sliding off screen

            paddleLeft.setLocation(2 * WIDTH, getHeight() - HEIGHT);
            image.setLocation(2 * WIDTH, getHeight() - HEIGHT);
            image.sendToFront();

Player's paddle is being controlled by mouse. Right now, when i move my cursor to the top of my screen, my paddle (top border) touches the top of the window. This could be considered correct but I don't like it. If i move the window to the center of my screen, i need to move my mouse off the screen to steer. It works like this: mouse controll range

and I want the paddle's top border to be parallel with cursor Y coordinate. I tried using different code to get mouse position with:

addMouseListeners();

and

public void mouseMoved(MouseEvent e) {
     mouseY=e.getYOnScreen();
}

but then my cursor still is not aligned with the paddle and I can only move my paddle within range shown on screenshot 2: (with cursor on top window border)

paddle range

possible duplicate of [Finding Mouse Position relative to a panel](http://stackoverflow.com/questions/12866205/finding-mouse-position-relative-to-a-panel) — Jason C, Apr 03 '14 at 19:50
You should **NOT** abuse `MouseInfo` for something like this. As already mentioned in the answer: Use a proper `MouseListener`, and the problem will vanish anyhow. — Marco13, Apr 03 '14 at 20:02

score 1 · Accepted Answer · answered Apr 03 '14 at 19:48

1

Subtract the frame's X and Y screen positions from the screen mouse coordinate to get the offset in the frame, or add a proper MouseListener to the frame itself, which will provide mouse position in window client coordinates.

The listener approach is generally better anyways, as it means you can also, e.g., add other components to your window without affecting mouse code; it keeps everything self-contained in the game frame.

answered Apr 03 '14 at 19:48

Jason C

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I thought `getYOnScreen();` meant inside game window, while `getY();` whole computer sreen, so I swapped it and it works. – Asalas77 Apr 03 '14 at 20:09

Mouse position based movement - unnecessary offset

1 Answers1