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    1   /*
    2    * Copyright (c) 1997, 2006, Oracle and/or its affiliates. All rights reserved.
    3    * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
    4    *
    5    * This code is free software; you can redistribute it and/or modify it
    6    * under the terms of the GNU General Public License version 2 only, as
    7    * published by the Free Software Foundation.  Oracle designates this
    8    * particular file as subject to the "Classpath" exception as provided
    9    * by Oracle in the LICENSE file that accompanied this code.
   10    *
   11    * This code is distributed in the hope that it will be useful, but WITHOUT
   12    * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   13    * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
   14    * version 2 for more details (a copy is included in the LICENSE file that
   15    * accompanied this code).
   16    *
   17    * You should have received a copy of the GNU General Public License version
   18    * 2 along with this work; if not, write to the Free Software Foundation,
   19    * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   20    *
   21    * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
   22    * or visit www.oracle.com if you need additional information or have any
   23    * questions.
   24    */
   25   
   26   package javax.swing;
   27   
   28   import java.awt;
   29   import java.awt.event;
   30   
   31   /**
   32    * Autoscroller is responsible for generating synthetic mouse dragged
   33    * events. It is the responsibility of the Component (or its MouseListeners)
   34    * that receive the events to do the actual scrolling in response to the
   35    * mouse dragged events.
   36    *
   37    * @author Dave Moore
   38    * @author Scott Violet
   39    */
   40   class Autoscroller implements ActionListener {
   41       /**
   42        * Global Autoscroller.
   43        */
   44       private static Autoscroller sharedInstance = new Autoscroller();
   45   
   46       // As there can only ever be one autoscroller active these fields are
   47       // static. The Timer is recreated as necessary to target the appropriate
   48       // Autoscroller instance.
   49       private static MouseEvent event;
   50       private static Timer timer;
   51       private static JComponent component;
   52   
   53       //
   54       // The public API, all methods are cover methods for an instance method
   55       //
   56       /**
   57        * Stops autoscroll events from happening on the specified component.
   58        */
   59       public static void stop(JComponent c) {
   60           sharedInstance._stop(c);
   61       }
   62   
   63       /**
   64        * Stops autoscroll events from happening on the specified component.
   65        */
   66       public static boolean isRunning(JComponent c) {
   67           return sharedInstance._isRunning(c);
   68       }
   69   
   70       /**
   71        * Invoked when a mouse dragged event occurs, will start the autoscroller
   72        * if necessary.
   73        */
   74       public static void processMouseDragged(MouseEvent e) {
   75           sharedInstance._processMouseDragged(e);
   76       }
   77   
   78   
   79       Autoscroller() {
   80       }
   81   
   82       /**
   83        * Starts the timer targeting the passed in component.
   84        */
   85       private void start(JComponent c, MouseEvent e) {
   86           Point screenLocation = c.getLocationOnScreen();
   87   
   88           if (component != c) {
   89               _stop(component);
   90           }
   91           component = c;
   92           event = new MouseEvent(component, e.getID(), e.getWhen(),
   93                                  e.getModifiers(), e.getX() + screenLocation.x,
   94                                  e.getY() + screenLocation.y,
   95                                  e.getXOnScreen(),
   96                                  e.getYOnScreen(),
   97                                  e.getClickCount(), e.isPopupTrigger(),
   98                                  MouseEvent.NOBUTTON);
   99   
  100           if (timer == null) {
  101               timer = new Timer(100, this);
  102           }
  103   
  104           if (!timer.isRunning()) {
  105               timer.start();
  106           }
  107       }
  108   
  109       //
  110       // Methods mirror the public static API
  111       //
  112   
  113       /**
  114        * Stops scrolling for the passed in widget.
  115        */
  116       private void _stop(JComponent c) {
  117           if (component == c) {
  118               if (timer != null) {
  119                   timer.stop();
  120               }
  121               timer = null;
  122               event = null;
  123               component = null;
  124           }
  125       }
  126   
  127       /**
  128        * Returns true if autoscrolling is currently running for the specified
  129        * widget.
  130        */
  131       private boolean _isRunning(JComponent c) {
  132           return (c == component && timer != null && timer.isRunning());
  133       }
  134   
  135       /**
  136        * MouseListener method, invokes start/stop as necessary.
  137        */
  138       private void _processMouseDragged(MouseEvent e) {
  139           JComponent component = (JComponent)e.getComponent();
  140           boolean stop = true;
  141           if (component.isShowing()) {
  142               Rectangle visibleRect = component.getVisibleRect();
  143               stop = visibleRect.contains(e.getX(), e.getY());
  144           }
  145           if (stop) {
  146               _stop(component);
  147           } else {
  148               start(component, e);
  149           }
  150       }
  151   
  152       //
  153       // ActionListener
  154       //
  155       /**
  156        * ActionListener method. Invoked when the Timer fires. This will scroll
  157        * if necessary.
  158        */
  159       public void actionPerformed(ActionEvent x) {
  160           JComponent component = Autoscroller.component;
  161   
  162           if (component == null || !component.isShowing() || (event == null)) {
  163               _stop(component);
  164               return;
  165           }
  166           Point screenLocation = component.getLocationOnScreen();
  167           MouseEvent e = new MouseEvent(component, event.getID(),
  168                                         event.getWhen(), event.getModifiers(),
  169                                         event.getX() - screenLocation.x,
  170                                         event.getY() - screenLocation.y,
  171                                         event.getXOnScreen(),
  172                                         event.getYOnScreen(),
  173                                         event.getClickCount(),
  174                                         event.isPopupTrigger(),
  175                                         MouseEvent.NOBUTTON);
  176           component.superProcessMouseMotionEvent(e);
  177       }
  178   
  179   }

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