001/*
002 * $Id$
003 *
004 * Copyright 2009 Sun Microsystems, Inc., 4150 Network Circle,
005 * Santa Clara, California 95054, U.S.A. All rights reserved.
006 *
007 * This library is free software; you can redistribute it and/or
008 * modify it under the terms of the GNU Lesser General Public
009 * License as published by the Free Software Foundation; either
010 * version 2.1 of the License, or (at your option) any later version.
011 * 
012 * This library is distributed in the hope that it will be useful,
013 * but WITHOUT ANY WARRANTY; without even the implied warranty of
014 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
015 * Lesser General Public License for more details.
016 * 
017 * You should have received a copy of the GNU Lesser General Public
018 * License along with this library; if not, write to the Free Software
019 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
020 *
021 */
022package org.jdesktop.swingx.plaf.basic.core;
023
024/*
025 * @(#)DragRecognitionSupport.java      1.2 05/11/17
026 *
027 * Copyright 2006 Sun Microsystems, Inc. All rights reserved.
028 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
029 */
030
031import java.awt.Toolkit;
032import java.awt.event.*;
033import java.awt.dnd.DragSource;
034import javax.swing.*;
035
036import org.jdesktop.swingx.SwingXUtilities;
037//import sun.awt.dnd.SunDragSourceContextPeer;
038//import sun.awt.AppContext;
039
040/**
041 * Drag gesture recognition support for classes that have a
042 * <code>TransferHandler</code>. The gesture for a drag in this class is a mouse
043 * press followed by movement by <code>DragSource.getDragThreshold()</code>
044 * pixels. An instance of this class is maintained per AppContext, and the
045 * public static methods call into the appropriate instance. <p>
046 * 
047 * This is a c&p of core (package private) needed for BasicXListUI. It differs from
048 * core in that references to sun packages have been replaced.
049 * <ul>
050 * <li> a static method of SunDragSourceContextPeer has been copied into SwingXUtilities
051 *    and is used here
052 * <li> the shared instance of this class is maintained in the UIManager instead of
053 *   per appContext.
054 * </ul>
055 * 
056 * @author Shannon Hickey
057 * @version 1.2 11/17/05
058 */
059public class DragRecognitionSupport {
060    private int motionThreshold;
061    private MouseEvent dndArmedEvent;
062    private JComponent component;
063
064    /**
065     * This interface allows us to pass in a handler to mouseDragged,
066     * so that we can be notified immediately before a drag begins.
067     */
068    public static interface BeforeDrag {
069        public void dragStarting(MouseEvent me);
070    }
071
072    /**
073     * Returns the DragRecognitionSupport for the caller's AppContext.
074     */
075    private static DragRecognitionSupport getDragRecognitionSupport() {
076//        DragRecognitionSupport support =
077//            (DragRecognitionSupport)AppContext.getAppContext().
078//                get(DragRecognitionSupport.class);
079//
080//        if (support == null) {
081//            support = new DragRecognitionSupport();
082//            AppContext.getAppContext().put(DragRecognitionSupport.class, support);
083//        }
084
085        DragRecognitionSupport support = (DragRecognitionSupport) 
086            UIManager.get("sharedInstance.dragRecognitionSupport");
087        if (support == null) {
088            support = new DragRecognitionSupport();
089            UIManager.put("sharedInstance.dragRecognitionSupport", support);
090        }
091        return support;
092    }
093
094    /**
095     * Returns whether or not the event is potentially part of a drag sequence.
096     */
097    public static boolean mousePressed(MouseEvent me) {
098        return ((DragRecognitionSupport)getDragRecognitionSupport()).
099            mousePressedImpl(me);
100    }
101
102    /**
103     * If a dnd recognition has been going on, return the MouseEvent
104     * that started the recognition. Otherwise, return null.
105     */
106    public static MouseEvent mouseReleased(MouseEvent me) {
107        return ((DragRecognitionSupport)getDragRecognitionSupport()).
108            mouseReleasedImpl(me);
109    }
110
111    /**
112     * Returns whether or not a drag gesture recognition is ongoing.
113     */
114    public static boolean mouseDragged(MouseEvent me, BeforeDrag bd) {
115        return ((DragRecognitionSupport)getDragRecognitionSupport()).
116            mouseDraggedImpl(me, bd);
117    }
118
119    private void clearState() {
120        dndArmedEvent = null;
121        component = null;
122    }
123
124    private int mapDragOperationFromModifiers(MouseEvent me,
125                                              TransferHandler th) {
126
127        if (th == null || !SwingUtilities.isLeftMouseButton(me)) {
128            return TransferHandler.NONE;
129        }
130        // PENDING JW: c'p from SunDragSourceContextPeer
131        return SwingXUtilities.
132            convertModifiersToDropAction(me.getModifiersEx(),
133                                         th.getSourceActions(component));
134    }
135
136    /**
137     * Returns whether or not the event is potentially part of a drag sequence.
138     */
139    private boolean mousePressedImpl(MouseEvent me) {
140        component = (JComponent)me.getSource();
141
142        if (mapDragOperationFromModifiers(me, component.getTransferHandler())
143                != TransferHandler.NONE) {
144
145            motionThreshold = DragSource.getDragThreshold();
146            dndArmedEvent = me;
147            return true;
148        }
149
150        clearState();
151        return false;
152    }
153
154    /**
155     * If a dnd recognition has been going on, return the MouseEvent
156     * that started the recognition. Otherwise, return null.
157     */
158    private MouseEvent mouseReleasedImpl(MouseEvent me) {
159        /* no recognition has been going on */
160        if (dndArmedEvent == null) {
161            return null;
162        }
163
164        MouseEvent retEvent = null;
165
166        if (me.getSource() == component) {
167            retEvent = dndArmedEvent;
168        } // else component has changed unexpectedly, so return null
169
170        clearState();
171        return retEvent;
172    }
173
174    /**
175     * Returns whether or not a drag gesture recognition is ongoing.
176     */
177    private boolean mouseDraggedImpl(MouseEvent me, BeforeDrag bd) {
178        /* no recognition is in progress */
179        if (dndArmedEvent == null) {
180            return false;
181        }
182
183        /* component has changed unexpectedly, so bail */
184        if (me.getSource() != component) {
185            clearState();
186            return false;
187        }
188
189        int dx = Math.abs(me.getX() - dndArmedEvent.getX());
190        int dy = Math.abs(me.getY() - dndArmedEvent.getY());
191        if ((dx > motionThreshold) || (dy > motionThreshold)) {
192            TransferHandler th = component.getTransferHandler();
193            int action = mapDragOperationFromModifiers(me, th);
194            if (action != TransferHandler.NONE) {
195                /* notify the BeforeDrag instance */
196                if (bd != null) {
197                    bd.dragStarting(dndArmedEvent);
198                }
199                th.exportAsDrag(component, dndArmedEvent, action);
200                clearState();
201            }
202        }
203
204        return true;
205    }
206}