/* * Copyright (c) 1997, 2006, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation.  Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package javax.swing; import java.awt.*;import java.awt.event.*; /** * Autoscroller is responsible for generating synthetic mouse dragged * events. It is the responsibility of the Component (or its MouseListeners) * that receive the events to do the actual scrolling in response to the * mouse dragged events. * * @author Dave Moore * @author Scott Violet */class Autoscroller implements ActionListener {    /**     * Global Autoscroller.     */    private static Autoscroller sharedInstance = new Autoscroller();     // As there can only ever be one autoscroller active these fields are    // static. The Timer is recreated as necessary to target the appropriate    // Autoscroller instance.    private static MouseEvent event;    private static Timer timer;    private static JComponent component;     //    // The public API, all methods are cover methods for an instance method    //    /**     * Stops autoscroll events from happening on the specified component.     */    public static void stop(JComponent c) {        sharedInstance._stop(c);    }     /**     * Stops autoscroll events from happening on the specified component.     */    public static boolean isRunning(JComponent c) {        return sharedInstance._isRunning(c);    }     /**     * Invoked when a mouse dragged event occurs, will start the autoscroller     * if necessary.     */    public static void processMouseDragged(MouseEvent e) {        sharedInstance._processMouseDragged(e);    }      Autoscroller() {    }     /**     * Starts the timer targeting the passed in component.     */    private void start(JComponent c, MouseEvent e) {        Point screenLocation = c.getLocationOnScreen();         if (component != c) {            _stop(component);        }        component = c;        event = new MouseEvent(component, e.getID(), e.getWhen(),                               e.getModifiers(), e.getX() + screenLocation.x,                               e.getY() + screenLocation.y,                               e.getXOnScreen(),                               e.getYOnScreen(),                               e.getClickCount(), e.isPopupTrigger(),                               MouseEvent.NOBUTTON);         if (timer == null) {            timer = new Timer(100, this);        }         if (!timer.isRunning()) {            timer.start();        }    }     //    // Methods mirror the public static API    //     /**     * Stops scrolling for the passed in widget.     */    private void _stop(JComponent c) {        if (component == c) {            if (timer != null) {                timer.stop();            }            timer = null;            event = null;            component = null;        }    }     /**     * Returns true if autoscrolling is currently running for the specified     * widget.     */    private boolean _isRunning(JComponent c) {        return (c == component && timer != null && timer.isRunning());    }     /**     * MouseListener method, invokes start/stop as necessary.     */    private void _processMouseDragged(MouseEvent e) {        JComponent component = (JComponent)e.getComponent();        boolean stop = true;        if (component.isShowing()) {            Rectangle visibleRect = component.getVisibleRect();            stop = visibleRect.contains(e.getX(), e.getY());        }        if (stop) {            _stop(component);        } else {            start(component, e);        }    }     //    // ActionListener    //    /**     * ActionListener method. Invoked when the Timer fires. This will scroll     * if necessary.     */    public void actionPerformed(ActionEvent x) {        JComponent component = Autoscroller.component;         if (component == null || !component.isShowing() || (event == null)) {            _stop(component);            return;        }        Point screenLocation = component.getLocationOnScreen();        MouseEvent e = new MouseEvent(component, event.getID(),                                      event.getWhen(), event.getModifiers(),                                      event.getX() - screenLocation.x,                                      event.getY() - screenLocation.y,                                      event.getXOnScreen(),                                      event.getYOnScreen(),                                      event.getClickCount(),                                      event.isPopupTrigger(),                                      MouseEvent.NOBUTTON);        component.superProcessMouseMotionEvent(e);    } }