/*

 * Copyright 1997-2006 Sun Microsystems, Inc.  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.  Sun designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

 * CA 95054 USA or visit www.sun.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);

    }

}