001 /* OverlayLayout.java -- A layout manager
002 Copyright (C) 2002, 2004, 2005, 2006, Free Software Foundation, Inc.
003
004 This file is part of GNU Classpath.
005
006 GNU Classpath is free software; you can redistribute it and/or modify
007 it under the terms of the GNU General Public License as published by
008 the Free Software Foundation; either version 2, or (at your option)
009 any later version.
010
011 GNU Classpath is distributed in the hope that it will be useful, but
012 WITHOUT ANY WARRANTY; without even the implied warranty of
013 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
014 General Public License for more details.
015
016 You should have received a copy of the GNU General Public License
017 along with GNU Classpath; see the file COPYING. If not, write to the
018 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
019 02110-1301 USA.
020
021 Linking this library statically or dynamically with other modules is
022 making a combined work based on this library. Thus, the terms and
023 conditions of the GNU General Public License cover the whole
024 combination.
025
026 As a special exception, the copyright holders of this library give you
027 permission to link this library with independent modules to produce an
028 executable, regardless of the license terms of these independent
029 modules, and to copy and distribute the resulting executable under
030 terms of your choice, provided that you also meet, for each linked
031 independent module, the terms and conditions of the license of that
032 module. An independent module is a module which is not derived from
033 or based on this library. If you modify this library, you may extend
034 this exception to your version of the library, but you are not
035 obligated to do so. If you do not wish to do so, delete this
036 exception statement from your version. */
037
038 package javax.swing;
039
040 import java.awt.AWTError;
041 import java.awt.Component;
042 import java.awt.Container;
043 import java.awt.Dimension;
044 import java.awt.Insets;
045 import java.awt.LayoutManager2;
046 import java.io.Serializable;
047
048 /**
049 * A layout manager that lays out the components of a container one over
050 * another.
051 *
052 * The components take as much space as is available in the container, but not
053 * more than specified by their maximum size.
054 *
055 * The overall layout is mainly affected by the components
056 * <code>alignmentX</code> and <code>alignmentY</code> properties. All
057 * components are aligned, so that their alignment points (for either
058 * direction) are placed in one line (the baseline for this direction).
059 *
060 * For example: An X alignment of 0.0 means that the component's alignment
061 * point is at it's left edge, an X alignment of 0.5 means that the alignment
062 * point is in the middle, an X alignment of 1.0 means, the aligment point is
063 * at the right edge. So if you have three components, the first with 0.0, the
064 * second with 0.5 and the third with 1.0, then they are laid out like this:
065 *
066 * <pre>
067 * +-------+
068 * | 1 |
069 * +-------+
070 * +-------+
071 * | 2 |
072 * +-------+
073 * +---------+
074 * | 3 +
075 * +---------+
076 * </pre>
077 * The above picture shows the X alignment between the components. An Y
078 * alignment like shown above cannot be achieved with this layout manager. The
079 * components are place on top of each other, with the X alignment shown above.
080 *
081 * @author Roman Kennke (kennke@aicas.com)
082 * @author Andrew Selkirk
083 */
084 public class OverlayLayout implements LayoutManager2, Serializable
085 {
086 private static final long serialVersionUID = 18082829169631543L;
087
088 /**
089 * The container to be laid out.
090 */
091 private Container target;
092
093 /**
094 * The size requirements of the containers children for the X direction.
095 */
096 private SizeRequirements[] xChildren;
097
098 /**
099 * The size requirements of the containers children for the Y direction.
100 */
101 private SizeRequirements[] yChildren;
102
103 /**
104 * The size requirements of the container to be laid out for the X direction.
105 */
106 private SizeRequirements xTotal;
107
108 /**
109 * The size requirements of the container to be laid out for the Y direction.
110 */
111 private SizeRequirements yTotal;
112
113 /**
114 * The offsets of the child components in the X direction.
115 */
116 private int[] offsetsX;
117
118 /**
119 * The offsets of the child components in the Y direction.
120 */
121 private int[] offsetsY;
122
123 /**
124 * The spans of the child components in the X direction.
125 */
126 private int[] spansX;
127
128 /**
129 * The spans of the child components in the Y direction.
130 */
131 private int[] spansY;
132
133 /**
134 * Creates a new OverlayLayout for the specified container.
135 *
136 * @param target the container to be laid out
137 */
138 public OverlayLayout(Container target)
139 {
140 this.target = target;
141 }
142
143 /**
144 * Notifies the layout manager that the layout has become invalid. It throws
145 * away cached layout information and recomputes it the next time it is
146 * requested.
147 *
148 * @param target not used here
149 */
150 public void invalidateLayout(Container target)
151 {
152 xChildren = null;
153 yChildren = null;
154 xTotal = null;
155 yTotal = null;
156 offsetsX = null;
157 offsetsY = null;
158 spansX = null;
159 spansY = null;
160 }
161
162 /**
163 * This method is not used in this layout manager.
164 *
165 * @param string not used here
166 * @param component not used here
167 */
168 public void addLayoutComponent(String string, Component component)
169 {
170 // Nothing to do here.
171 }
172
173 /**
174 * This method is not used in this layout manager.
175 *
176 * @param component not used here
177 * @param constraints not used here
178 */
179 public void addLayoutComponent(Component component, Object constraints)
180 {
181 // Nothing to do here.
182 }
183
184 /**
185 * This method is not used in this layout manager.
186 *
187 * @param component not used here
188 */
189 public void removeLayoutComponent(Component component)
190 {
191 // Nothing to do here.
192 }
193
194 /**
195 * Returns the preferred size of the container that is laid out. This is
196 * computed by the children's preferred sizes, taking their alignments into
197 * account.
198 *
199 * @param target not used here
200 *
201 * @return the preferred size of the container that is laid out
202 */
203 public Dimension preferredLayoutSize(Container target)
204 {
205 if (target != this.target)
206 throw new AWTError("OverlayLayout can't be shared");
207
208 checkTotalRequirements();
209 return new Dimension(xTotal.preferred, yTotal.preferred);
210 }
211
212 /**
213 * Returns the minimum size of the container that is laid out. This is
214 * computed by the children's minimum sizes, taking their alignments into
215 * account.
216 *
217 * @param target not used here
218 *
219 * @return the minimum size of the container that is laid out
220 */
221 public Dimension minimumLayoutSize(Container target)
222 {
223 if (target != this.target)
224 throw new AWTError("OverlayLayout can't be shared");
225
226 checkTotalRequirements();
227 return new Dimension(xTotal.minimum, yTotal.minimum);
228 }
229
230 /**
231 * Returns the maximum size of the container that is laid out. This is
232 * computed by the children's maximum sizes, taking their alignments into
233 * account.
234 *
235 * @param target not used here
236 *
237 * @return the maximum size of the container that is laid out
238 */
239 public Dimension maximumLayoutSize(Container target)
240 {
241 if (target != this.target)
242 throw new AWTError("OverlayLayout can't be shared");
243
244 checkTotalRequirements();
245 return new Dimension(xTotal.maximum, yTotal.maximum);
246 }
247
248 /**
249 * Returns the X alignment of the container that is laid out. This is
250 * computed by the children's preferred sizes, taking their alignments into
251 * account.
252 *
253 * @param target not used here
254 *
255 * @return the X alignment of the container that is laid out
256 */
257 public float getLayoutAlignmentX(Container target)
258 {
259 if (target != this.target)
260 throw new AWTError("OverlayLayout can't be shared");
261
262 checkTotalRequirements();
263 return xTotal.alignment;
264 }
265
266 /**
267 * Returns the Y alignment of the container that is laid out. This is
268 * computed by the children's preferred sizes, taking their alignments into
269 * account.
270 *
271 * @param target not used here
272 *
273 * @return the X alignment of the container that is laid out
274 */
275 public float getLayoutAlignmentY(Container target)
276 {
277 if (target != this.target)
278 throw new AWTError("OverlayLayout can't be shared");
279
280 checkTotalRequirements();
281 return yTotal.alignment;
282 }
283
284 /**
285 * Lays out the container and it's children.
286 *
287 * The children are laid out one over another.
288 *
289 * The components take as much space as is available in the container, but
290 * not more than specified by their maximum size.
291 *
292 * The overall layout is mainly affected by the components
293 * <code>alignmentX</code> and <code>alignmentY</code> properties. All
294 * components are aligned, so that their alignment points (for either
295 * direction) are placed in one line (the baseline for this direction).
296 *
297 * For example: An X alignment of 0.0 means that the component's alignment
298 * point is at it's left edge, an X alignment of 0.5 means that the alignment
299 * point is in the middle, an X alignment of 1.0 means, the aligment point is
300 * at the right edge. So if you have three components, the first with 0.0,
301 * the second with 0.5 and the third with 1.0, then they are laid out like
302 * this:
303 *
304 * <pre>
305 * +-------+
306 * | 1 |
307 * +-------+
308 * +-------+
309 * | 2 |
310 * +-------+
311 * +---------+
312 * | 3 +
313 * +---------+
314 * </pre>
315 * The above picture shows the X alignment between the components. An Y
316 * alignment like shown above cannot be achieved with this layout manager.
317 * The components are place on top of each other, with the X alignment shown
318 * above.
319 *
320 * @param target not used here
321 */
322 public void layoutContainer(Container target)
323 {
324 if (target != this.target)
325 throw new AWTError("OverlayLayout can't be shared");
326
327 checkLayout();
328 Component[] children = target.getComponents();
329 for (int i = 0; i < children.length; i++)
330 children[i].setBounds(offsetsX[i], offsetsY[i], spansX[i], spansY[i]);
331 }
332
333 /**
334 * Makes sure that the xChildren and yChildren fields are correctly set up.
335 * A call to {@link #invalidateLayout(Container)} sets these fields to null,
336 * so they have to be set up again.
337 */
338 private void checkRequirements()
339 {
340 if (xChildren == null || yChildren == null)
341 {
342 Component[] children = target.getComponents();
343 xChildren = new SizeRequirements[children.length];
344 yChildren = new SizeRequirements[children.length];
345 for (int i = 0; i < children.length; i++)
346 {
347 if (! children[i].isVisible())
348 {
349 xChildren[i] = new SizeRequirements();
350 yChildren[i] = new SizeRequirements();
351 }
352 else
353 {
354 xChildren[i] =
355 new SizeRequirements(children[i].getMinimumSize().width,
356 children[i].getPreferredSize().width,
357 children[i].getMaximumSize().width,
358 children[i].getAlignmentX());
359 yChildren[i] =
360 new SizeRequirements(children[i].getMinimumSize().height,
361 children[i].getPreferredSize().height,
362 children[i].getMaximumSize().height,
363 children[i].getAlignmentY());
364 }
365 }
366 }
367 }
368
369 /**
370 * Makes sure that the xTotal and yTotal fields are set up correctly. A call
371 * to {@link #invalidateLayout} sets these fields to null and they have to be
372 * recomputed.
373 */
374 private void checkTotalRequirements()
375 {
376 if (xTotal == null || yTotal == null)
377 {
378 checkRequirements();
379 xTotal = SizeRequirements.getAlignedSizeRequirements(xChildren);
380 yTotal = SizeRequirements.getAlignedSizeRequirements(yChildren);
381 }
382 }
383
384 /**
385 * Makes sure that the offsetsX, offsetsY, spansX and spansY fields are set
386 * up correctly. A call to {@link #invalidateLayout} sets these fields
387 * to null and they have to be recomputed.
388 */
389 private void checkLayout()
390 {
391 if (offsetsX == null || offsetsY == null || spansX == null
392 || spansY == null)
393 {
394 checkRequirements();
395 checkTotalRequirements();
396 int len = target.getComponents().length;
397 offsetsX = new int[len];
398 offsetsY = new int[len];
399 spansX = new int[len];
400 spansY = new int[len];
401
402 Insets in = target.getInsets();
403 int width = target.getWidth() - in.left - in.right;
404 int height = target.getHeight() - in.top - in.bottom;
405
406 SizeRequirements.calculateAlignedPositions(width, xTotal,
407 xChildren, offsetsX, spansX);
408 SizeRequirements.calculateAlignedPositions(height, yTotal,
409 yChildren, offsetsY, spansY);
410 }
411 }
412 }