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    }