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 * @since 1.2
59 */
60 @SuppressWarnings("serial") // Same-version serialization only
61 public class ViewportLayout implements LayoutManager, Serializable
62 {
63 // Single instance used by JViewport.
64 static ViewportLayout SHARED_INSTANCE = new ViewportLayout();
65
66 /**
67 * Adds the specified component to the layout. Not used by this class.
68 * @param name the name of the component
69 * @param c the component to be added
70 */
71 public void addLayoutComponent(String name, Component c) { }
72
73 /**
74 * Removes the specified component from the layout. Not used by
75 * this class.
76 * @param c the component to remove
77 */
78 public void removeLayoutComponent(Component c) { }
79
80
81 /**
82 * Returns the preferred dimensions for this layout given the components
83 * in the specified target container.
84 * @param parent the component which needs to be laid out
85 * @return a <code>Dimension</code> object containing the
86 * preferred dimensions
87 * @see #minimumLayoutSize
88 */
89 public Dimension preferredLayoutSize(Container parent) {
90 Component view = ((JViewport)parent).getView();
91 if (view == null) {
92 return new Dimension(0, 0);
93 }
94 else if (view instanceof Scrollable) {
95 return ((Scrollable)view).getPreferredScrollableViewportSize();
96 }
97 else {
98 return view.getPreferredSize();
99 }
100 }
101
102
103 /**
104 * Returns the minimum dimensions needed to layout the components
105 * contained in the specified target container.
106 *
107 * @param parent the component which needs to be laid out
108 * @return a <code>Dimension</code> object containing the minimum
109 * dimensions
110 * @see #preferredLayoutSize
111 */
112 public Dimension minimumLayoutSize(Container parent) {
113 return new Dimension(4, 4);
114 }
115
116
117 /**
118 * Called by the AWT when the specified container needs to be laid out.
119 *
120 * @param parent the container to lay out
121 *
122 * @throws AWTError if the target isn't the container specified to the
123 * <code>BoxLayout</code> constructor
124 */
125 public void layoutContainer(Container parent)
126 {
127 JViewport vp = (JViewport)parent;
128 Component view = vp.getView();
129 Scrollable scrollableView = null;
130
131 if (view == null) {
132 return;
133 }
134 else if (view instanceof Scrollable) {
135 scrollableView = (Scrollable) view;
136 }
137
138 /* All of the dimensions below are in view coordinates, except
139 * vpSize which we're converting.
140 */
141
142 Insets insets = vp.getInsets();
143 Dimension viewPrefSize = view.getPreferredSize();
144 Dimension vpSize = vp.getSize();
145 Dimension extentSize = vp.toViewCoordinates(vpSize);
146 Dimension viewSize = new Dimension(viewPrefSize);
147
148 if (scrollableView != null) {
149 if (scrollableView.getScrollableTracksViewportWidth()) {
150 viewSize.width = vpSize.width;
151 }
152 if (scrollableView.getScrollableTracksViewportHeight()) {
153 viewSize.height = vpSize.height;
154 }
155 }
156
157 Point viewPosition = vp.getViewPosition();
158
159 /* If the new viewport size would leave empty space to the
160 * right of the view, right justify the view or left justify
161 * the view when the width of the view is smaller than the
162 * container.
163 */
164 if (scrollableView == null ||
165 vp.getParent() == null ||
166 vp.getParent().getComponentOrientation().isLeftToRight()) {
167 if ((viewPosition.x + extentSize.width) > viewSize.width) {
168 viewPosition.x = Math.max(0, viewSize.width - extentSize.width);
169 }
170 } else {
171 if (extentSize.width > viewSize.width) {
172 viewPosition.x = viewSize.width - extentSize.width;
173 } else {
174 viewPosition.x = Math.max(0, Math.min(viewSize.width - extentSize.width, viewPosition.x));
175 }
176 }
177
178 /* If the new viewport size would leave empty space below the
179 * view, bottom justify the view or top justify the view when
180 * the height of the view is smaller than the container.
181 */
182 if ((viewPosition.y + extentSize.height) > viewSize.height) {
183 viewPosition.y = Math.max(0, viewSize.height - extentSize.height);
184 }
185
186 /* If we haven't been advised about how the viewports size
187 * should change wrt to the viewport, i.e. if the view isn't
188 * an instance of Scrollable, then adjust the views size as follows.
189 *
190 * If the origin of the view is showing and the viewport is
191 * bigger than the views preferred size, then make the view
192 * the same size as the viewport.
193 */
194 if (scrollableView == null) {
195 if ((viewPosition.x == 0) && (vpSize.width > viewPrefSize.width)) {
196 viewSize.width = vpSize.width;
197 }
198 if ((viewPosition.y == 0) && (vpSize.height > viewPrefSize.height)) {
199 viewSize.height = vpSize.height;
200 }
201 }
202 vp.setViewPosition(viewPosition);
203 vp.setViewSize(viewSize);
204 }
205 }