001/* OverlayLayout.java -- A layout manager
002   Copyright (C) 2002, 2004, 2005, 2006, Free Software Foundation, Inc.
003
004This file is part of GNU Classpath.
005
006GNU Classpath is free software; you can redistribute it and/or modify
007it under the terms of the GNU General Public License as published by
008the Free Software Foundation; either version 2, or (at your option)
009any later version.
010
011GNU Classpath is distributed in the hope that it will be useful, but
012WITHOUT ANY WARRANTY; without even the implied warranty of
013MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014General Public License for more details.
015
016You should have received a copy of the GNU General Public License
017along with GNU Classpath; see the file COPYING.  If not, write to the
018Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
01902110-1301 USA.
020
021Linking this library statically or dynamically with other modules is
022making a combined work based on this library.  Thus, the terms and
023conditions of the GNU General Public License cover the whole
024combination.
025
026As a special exception, the copyright holders of this library give you
027permission to link this library with independent modules to produce an
028executable, regardless of the license terms of these independent
029modules, and to copy and distribute the resulting executable under
030terms of your choice, provided that you also meet, for each linked
031independent module, the terms and conditions of the license of that
032module.  An independent module is a module which is not derived from
033or based on this library.  If you modify this library, you may extend
034this exception to your version of the library, but you are not
035obligated to do so.  If you do not wish to do so, delete this
036exception statement from your version. */
037
038package javax.swing;
039
040import java.awt.AWTError;
041import java.awt.Component;
042import java.awt.Container;
043import java.awt.Dimension;
044import java.awt.Insets;
045import java.awt.LayoutManager2;
046import 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 */
084public 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}