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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * This code is free software; you can redistribute it and/or modify it
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 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
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 * 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).
 *
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 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
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package javax.swing;

import java.awt.*;
import java.awt.event.*;

import sun.awt.AWTAccessor;
import sun.awt.AWTAccessor.MouseEventAccessor;

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, Scott Violet/**
 * 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.
/**
     * 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.
/**
     * 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.
/**
     * 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.
/**
     * 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.
/**
     * Starts the timer targeting the passed in component.
     */
    @SuppressWarnings("deprecation")
    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);
        MouseEventAccessor meAccessor = AWTAccessor.getMouseEventAccessor();
        meAccessor.setCausedByTouchEvent(event,
            meAccessor.isCausedByTouchEvent(e));

        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.
/**
     * 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.
/**
     * 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.
/**
     * 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.
/**
     * ActionListener method. Invoked when the Timer fires. This will scroll
     * if necessary.
     */
    @SuppressWarnings("deprecation")
    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);
        MouseEventAccessor meAccessor = AWTAccessor.getMouseEventAccessor();
        meAccessor.setCausedByTouchEvent(e,
            meAccessor.isCausedByTouchEvent(event));
        component.superProcessMouseMotionEvent(e);
    }

}