1 /*
2 * Copyright (c) 2005, 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 package javax.swing.plaf.basic;
26
27 import java.awt.Toolkit;
28 import java.awt.event.*;
29 import java.awt.dnd.DragSource;
30 import javax.swing.*;
31 import sun.awt.dnd.SunDragSourceContextPeer;
32 import sun.awt.AppContext;
33
34 /**
35 * Drag gesture recognition support for classes that have a
36 * <code>TransferHandler</code>. The gesture for a drag in this class is a mouse
37 * press followed by movement by <code>DragSource.getDragThreshold()</code>
38 * pixels. An instance of this class is maintained per AppContext, and the
39 * public static methods call into the appropriate instance.
40 *
41 * @author Shannon Hickey
42 */
43 class DragRecognitionSupport {
44 private int motionThreshold;
45 private MouseEvent dndArmedEvent;
46 private JComponent component;
47
48 /**
49 * This interface allows us to pass in a handler to mouseDragged,
50 * so that we can be notified immediately before a drag begins.
51 */
52 public static interface BeforeDrag {
53 public void dragStarting(MouseEvent me);
54 }
55
56 /**
57 * Returns the DragRecognitionSupport for the caller's AppContext.
58 */
59 private static DragRecognitionSupport getDragRecognitionSupport() {
60 DragRecognitionSupport support =
61 (DragRecognitionSupport)AppContext.getAppContext().
62 get(DragRecognitionSupport.class);
63
64 if (support == null) {
65 support = new DragRecognitionSupport();
66 AppContext.getAppContext().put(DragRecognitionSupport.class, support);
67 }
68
69 return support;
70 }
71
72 /**
73 * Returns whether or not the event is potentially part of a drag sequence.
74 */
75 public static boolean mousePressed(MouseEvent me) {
76 return getDragRecognitionSupport().mousePressedImpl(me);
77 }
78
79 /**
80 * If a dnd recognition has been going on, return the MouseEvent
81 * that started the recognition. Otherwise, return null.
82 */
83 public static MouseEvent mouseReleased(MouseEvent me) {
84 return getDragRecognitionSupport().mouseReleasedImpl(me);
85 }
86
87 /**
88 * Returns whether or not a drag gesture recognition is ongoing.
89 */
90 public static boolean mouseDragged(MouseEvent me, BeforeDrag bd) {
91 return getDragRecognitionSupport().mouseDraggedImpl(me, bd);
92 }
93
94 private void clearState() {
95 dndArmedEvent = null;
96 component = null;
97 }
98
99 private int mapDragOperationFromModifiers(MouseEvent me,
100 TransferHandler th) {
101
102 if (th == null || !SwingUtilities.isLeftMouseButton(me)) {
103 return TransferHandler.NONE;
104 }
105
106 return SunDragSourceContextPeer.
107 convertModifiersToDropAction(me.getModifiersEx(),
108 th.getSourceActions(component));
109 }
110
111 /**
112 * Returns whether or not the event is potentially part of a drag sequence.
113 */
114 private boolean mousePressedImpl(MouseEvent me) {
115 component = (JComponent)me.getSource();
116
117 if (mapDragOperationFromModifiers(me, component.getTransferHandler())
118 != TransferHandler.NONE) {
119
120 motionThreshold = DragSource.getDragThreshold();
121 dndArmedEvent = me;
122 return true;
123 }
124
125 clearState();
126 return false;
127 }
128
129 /**
130 * If a dnd recognition has been going on, return the MouseEvent
131 * that started the recognition. Otherwise, return null.
132 */
133 private MouseEvent mouseReleasedImpl(MouseEvent me) {
134 /* no recognition has been going on */
135 if (dndArmedEvent == null) {
136 return null;
137 }
138
139 MouseEvent retEvent = null;
140
141 if (me.getSource() == component) {
142 retEvent = dndArmedEvent;
143 } // else component has changed unexpectedly, so return null
144
145 clearState();
146 return retEvent;
147 }
148
149 /**
150 * Returns whether or not a drag gesture recognition is ongoing.
151 */
152 private boolean mouseDraggedImpl(MouseEvent me, BeforeDrag bd) {
153 /* no recognition is in progress */
154 if (dndArmedEvent == null) {
155 return false;
156 }
157
158 /* component has changed unexpectedly, so bail */
159 if (me.getSource() != component) {
160 clearState();
161 return false;
162 }
163
164 int dx = Math.abs(me.getX() - dndArmedEvent.getX());
165 int dy = Math.abs(me.getY() - dndArmedEvent.getY());
166 if ((dx > motionThreshold) || (dy > motionThreshold)) {
167 TransferHandler th = component.getTransferHandler();
168 int action = mapDragOperationFromModifiers(me, th);
169 if (action != TransferHandler.NONE) {
170 /* notify the BeforeDrag instance */
171 if (bd != null) {
172 bd.dragStarting(dndArmedEvent);
173 }
174 th.exportAsDrag(component, dndArmedEvent, action);
175 clearState();
176 }
177 }
178
179 return true;
180 }
181 }