1 /*
2 * Copyright (c) 1997, 2014, 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.AWTError;
29 import java.awt.LayoutManager;
30 import java.awt.Component;
31 import java.awt.Container;
32 import java.awt.Rectangle;
33 import java.awt.Point;
34 import java.awt.Dimension;
35 import java.awt.Insets;
36 import java.io.Serializable;
37
38 /**
39 * The default layout manager for <code>JViewport</code>.
40 * <code>ViewportLayout</code> defines
41 * a policy for layout that should be useful for most applications.
42 * The viewport makes its view the same size as the viewport,
43 * however it will not make the view smaller than its minimum size.
44 * As the viewport grows the view is kept bottom justified until
45 * the entire view is visible, subsequently the view is kept top
46 * justified.
47 * <p>
48 * <strong>Warning:</strong>
49 * Serialized objects of this class will not be compatible with
50 * future Swing releases. The current serialization support is
51 * appropriate for short term storage or RMI between applications running
52 * the same version of Swing. As of 1.4, support for long term storage
53 * of all JavaBeans™
54 * has been added to the <code>java.beans</code> package.
55 * Please see {@link java.beans.XMLEncoder}.
56 *
57 * @author Hans Muller
58 */
59 @SuppressWarnings("serial") // Same-version serialization only
60 public class ViewportLayout implements LayoutManager, Serializable
61 {
62 // Single instance used by JViewport.
63 static ViewportLayout SHARED_INSTANCE = new ViewportLayout();
64
65 /**
66 * Adds the specified component to the layout. Not used by this class.
67 * @param name the name of the component
68 * @param c the the component to be added
69 */
70 public void addLayoutComponent(String name, Component c) { }
71
72 /**
73 * Removes the specified component from the layout. Not used by
74 * this class.
75 * @param c the component to remove
76 */
77 public void removeLayoutComponent(Component c) { }
78
79
80 /**
81 * Returns the preferred dimensions for this layout given the components
82 * in the specified target container.
83 * @param parent the component which needs to be laid out
84 * @return a <code>Dimension</code> object containing the
85 * preferred dimensions
86 * @see #minimumLayoutSize
87 */
88 public Dimension preferredLayoutSize(Container parent) {
89 Component view = ((JViewport)parent).getView();
90 if (view == null) {
91 return new Dimension(0, 0);
92 }
93 else if (view instanceof Scrollable) {
94 return ((Scrollable)view).getPreferredScrollableViewportSize();
95 }
96 else {
97 return view.getPreferredSize();
98 }
99 }
100
101
102 /**
103 * Returns the minimum dimensions needed to layout the components
104 * contained in the specified target container.
105 *
106 * @param parent the component which needs to be laid out
107 * @return a <code>Dimension</code> object containing the minimum
108 * dimensions
109 * @see #preferredLayoutSize
110 */
111 public Dimension minimumLayoutSize(Container parent) {
112 return new Dimension(4, 4);
113 }
114
115
116 /**
117 * Called by the AWT when the specified container needs to be laid out.
118 *
119 * @param parent the container to lay out
120 *
121 * @throws AWTError if the target isn't the container specified to the
122 * <code>BoxLayout</code> constructor
123 */
124 public void layoutContainer(Container parent)
125 {
126 JViewport vp = (JViewport)parent;
127 Component view = vp.getView();
128 Scrollable scrollableView = null;
129
130 if (view == null) {
131 return;
132 }
133 else if (view instanceof Scrollable) {
134 scrollableView = (Scrollable) view;
135 }
136
137 /* All of the dimensions below are in view coordinates, except
138 * vpSize which we're converting.
139 */
140
141 Insets insets = vp.getInsets();
142 Dimension viewPrefSize = view.getPreferredSize();
143 Dimension vpSize = vp.getSize();
144 Dimension extentSize = vp.toViewCoordinates(vpSize);
145 Dimension viewSize = new Dimension(viewPrefSize);
146
147 if (scrollableView != null) {
148 if (scrollableView.getScrollableTracksViewportWidth()) {
149 viewSize.width = vpSize.width;
150 }
151 if (scrollableView.getScrollableTracksViewportHeight()) {
152 viewSize.height = vpSize.height;
153 }
154 }
155
156 Point viewPosition = vp.getViewPosition();
157
158 /* If the new viewport size would leave empty space to the
159 * right of the view, right justify the view or left justify
160 * the view when the width of the view is smaller than the
161 * container.
162 */
163 if (scrollableView == null ||
164 vp.getParent() == null ||
165 vp.getParent().getComponentOrientation().isLeftToRight()) {
166 if ((viewPosition.x + extentSize.width) > viewSize.width) {
167 viewPosition.x = Math.max(0, viewSize.width - extentSize.width);
168 }
169 } else {
170 if (extentSize.width > viewSize.width) {
171 viewPosition.x = viewSize.width - extentSize.width;
172 } else {
173 viewPosition.x = Math.max(0, Math.min(viewSize.width - extentSize.width, viewPosition.x));
174 }
175 }
176
177 /* If the new viewport size would leave empty space below the
178 * view, bottom justify the view or top justify the view when
179 * the height of the view is smaller than the container.
180 */
181 if ((viewPosition.y + extentSize.height) > viewSize.height) {
182 viewPosition.y = Math.max(0, viewSize.height - extentSize.height);
183 }
184
185 /* If we haven't been advised about how the viewports size
186 * should change wrt to the viewport, i.e. if the view isn't
187 * an instance of Scrollable, then adjust the views size as follows.
188 *
189 * If the origin of the view is showing and the viewport is
190 * bigger than the views preferred size, then make the view
191 * the same size as the viewport.
192 */
193 if (scrollableView == null) {
194 if ((viewPosition.x == 0) && (vpSize.width > viewPrefSize.width)) {
195 viewSize.width = vpSize.width;
196 }
197 if ((viewPosition.y == 0) && (vpSize.height > viewPrefSize.height)) {
198 viewSize.height = vpSize.height;
199 }
200 }
201 vp.setViewPosition(viewPosition);
202 vp.setViewSize(viewSize);
203 }
204 }