MouseDisplacementTracker.java

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/*
 * Scilab ( http://www.scilab.org/ ) - This file is part of Scilab
 * Copyright (C) 2008 - INRIA - Jean-Baptiste Silvy
 * 
 * This file must be used under the terms of the CeCILL.
 * This source file is licensed as described in the file COPYING, which
 * you should have received as part of this distribution.  The terms
 * are also available at    
 * http://www.cecill.info/licences/Licence_CeCILL_V2-en.txt
 *
 */

package org.scilab.modules.gui.events;

import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionListener;

import org.scilab.modules.gui.bridge.canvas.SwingScilabCanvas;

public class MouseDisplacementTracker implements MouseMotionListener {

        private SwingScilabCanvas canvas;
        private Object lock;
        
        private boolean coordinatesUpdated;
        
        // coordinates of last call and the one fo current call
        private int previousX;
        private int previousY;
        private int currentX;
        private int currentY;
        
        
        public MouseDisplacementTracker(SwingScilabCanvas canvas) {
                this.canvas = canvas;
                this.lock = new Object();
                reinit();
        }
        
        protected SwingScilabCanvas getTrackedCanvas() {
                return canvas;
        }
        
        protected Object getLock() {
                return lock;
        }
        
        protected void reinit() {
                this.coordinatesUpdated = false;
                this.previousX = -1;
                this.previousY = -1;
                this.currentX = -1;
                this.currentY = -1;
        }
        
        protected void activateTracking(int initX, int initY) {
                previousX = initX;
                previousY = initY;
                canvas.addMouseMotionListener(this);
        }
        
        protected void desactivateTracking() {
                canvas.removeMouseMotionListener(this);
        }
        
        public void getMouseDisplacement(int[] displacement) {
                
                synchronized (lock) {
                        if (!coordinatesUpdated) {
                                // no new displacement, wait for one
                                try {
                                        lock.wait();
                                } catch (InterruptedException e) {
                                        e.printStackTrace();
                                }
                        }
                        
                        // get displacement
                        displacement[0] = currentX - previousX;
                        displacement[1] = currentY - previousY;
                        
                        // update previous coordinates
                        previousX = currentX;
                        previousY = currentY;
                        
                        coordinatesUpdated = false;
                }
        }
        
        protected void getImmediateMouseDisplacement(int[] displacement) {
                synchronized (lock) {
                        // get displacement
                        displacement[0] = currentX - previousX;
                        displacement[1] = currentY - previousY;
                }
        }
        
        public void mouseDragged(MouseEvent event) {
                // same as mouse moved
                mouseMoved(event);
        }
        

        public void mouseMoved(MouseEvent event) {
                updateDisplacement(event.getX(), event.getY());
        }
        
        protected void updateDisplacement(int xPos, int yPos) {
                synchronized (lock) {
                        // record new position
                        currentX = xPos;
                        currentY = yPos;
                        
                        coordinatesUpdated = true;
                        
                        // wake threads waiting for a displacement
                        // if some
                        lock.notifyAll();
                }
        }

}

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