/*
 * Copyright (c) 1997, 2006, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
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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
 * @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);
 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.
 */
 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);
 MouseEventAccessor meAccessor = AWTAccessor.getMouseEventAccessor();
 meAccessor.setCausedByTouchEvent(e,
 meAccessor.isCausedByTouchEvent(event));
 component.superProcessMouseMotionEvent(e);
 }

}