001    /* BufferCapabilities.java -- double-buffering capabilities descriptor
002       Copyright (C) 2002, 2005  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    
039    package java.awt;
040    
041    import java.awt.image.BufferStrategy;
042    
043    /**
044     * A double-buffering capability descriptor.  This class exposes
045     * details about the double-buffering algorithms used by image
046     * buffers.
047     *
048     * BufferCapabilities represents algorithms that involve at least two
049     * buffers but it can also specify so-called "multi-buffer" schemes
050     * involving more than two buffers.  This class describes the
051     * capabilities of the front and back buffers as well as the results
052     * of "flipping" -- that is, what happens when an image is transferred
053     * from the back buffer to the front buffer.
054     *
055     * Flipping may or may not be supported or may be supported only in
056     * fullscreen mode.  If it is not supported then "blitting" is implied
057     * -- that is, the contents of the back buffer are copied using a fast
058     * block transfer operation from the back buffer to the front buffer.
059     *
060     * The front buffer is the one that is displayed.
061     *
062     * @author Eric Blake (ebb9@email.byu.edu)
063     *
064     * @see BufferStrategy#getCapabilities()
065     * @see GraphicsConfiguration#getBufferCapabilities()
066     *
067     * @since 1.4
068     */
069    public class BufferCapabilities implements Cloneable
070    {
071      /**
072       * A type-safe enumeration of buffer flipping results.
073       *
074       * @see AttributeValue
075       */
076      public static final class FlipContents extends AttributeValue
077      {
078        /**
079         * The names of the different flipping results.
080         */
081        private static final String[] NAMES
082          = { "undefined", "background", "prior", "copied" };
083    
084        /**
085         * The contents of the back buffer are undefined after flipping.
086         */
087        public static final FlipContents UNDEFINED = new FlipContents(0);
088    
089        /**
090         * The back buffer is cleared with the background color after
091         * flipping.
092         */
093        public static final FlipContents BACKGROUND = new FlipContents(1);
094    
095        /**
096         * The back buffer contains the pre-flipping contents of the front
097         * buffer after flipping.  In other words a true "flip" has been
098         * performed.
099         */
100        public static final FlipContents PRIOR = new FlipContents(2);
101    
102        /**
103         * The back buffer has the same contents as the front buffer after
104         * flipping.
105         */
106        public static final FlipContents COPIED = new FlipContents(3);
107    
108        /**
109         * Create a new flipping result descriptor.
110         *
111         * @param value the enumeration value
112         */
113        private FlipContents(int value)
114        {
115          super(value, NAMES);
116        }
117      }
118    
119      /**
120       * Front buffer capabilities descriptor.
121       */
122      private final ImageCapabilities front;
123    
124      /**
125       * Back buffer capabilities descriptor.
126       */
127      private final ImageCapabilities back;
128    
129      /**
130       * Describes the results of a "flip" operation.
131       */
132      private final FlipContents flip;
133    
134      /**
135       * Creates a buffer capabilities object.
136       *
137       * @param frontCaps front buffer capabilities descriptor
138       * @param backCaps back buffer capabilities descriptor
139       * @param flip the results of a flip operation or null if
140       * flipping is not supported
141       *
142       * @exception IllegalArgumentException if frontCaps or backCaps is
143       * null
144       */
145      public BufferCapabilities(ImageCapabilities frontCaps,
146                                ImageCapabilities backCaps,
147                                FlipContents flip)
148      {
149        if (frontCaps ==  null || backCaps == null)
150          throw new IllegalArgumentException();
151        this.front = frontCaps;
152        this.back = backCaps;
153        this.flip = flip;
154      }
155    
156      /**
157       * Retrieve the front buffer's image capabilities.
158       *
159       * @return the front buffer's image capabilities
160       */
161      public ImageCapabilities getFrontBufferCapabilities()
162      {
163        return front;
164      }
165    
166      /**
167       * Retrieve the back buffer's image capabilities.
168       *
169       * @return the back buffer's image capabilities
170       */
171      public ImageCapabilities getBackBufferCapabilities()
172      {
173        return back;
174      }
175    
176      /**
177       * Return whether or not flipping is supported.
178       *
179       * @return true if flipping is supported, false otherwise
180       */
181      public boolean isPageFlipping()
182      {
183        return flip != null;
184      }
185    
186      /**
187       * Retrieve the result of a flipping operation.  If this method
188       * returns null then flipping is not supported.  This implies that
189       * "blitting", a fast block transfer, is used to copy the contents
190       * of the back buffer to the front buffer.  Other possible return
191       * values are:
192       * <ul>
193       *   <li><code>FlipContents.UNDEFINED</code> the contents of the
194       *   back buffer are undefined after flipping.</li>
195       *   <li><code>FlipContents.BACKGROUND</code> the contents of the
196       *   back buffer are cleared to the background color after
197       *   flipping.</li>
198       *   <li><code>FlipContents.PRIOR</code> the back buffer contains
199       *   the pre-flipping contents of the front * buffer after
200       *   flipping.</li>
201       *   <li><code>FlipContents.COPIED</code> the back buffer has the
202       *   same contents as the front buffer after flipping.</li>
203       * </ul>
204       *
205       * @return the result of a flipping operation or null if flipping is
206       * not supported
207       */
208      public FlipContents getFlipContents()
209      {
210        return flip;
211      }
212    
213      /**
214       * Returns true if flipping is only supported in fullscreen mode.
215       *
216       * @return true if flipping is only supported in fullscreen mode,
217       * false otherwise
218       */
219      public boolean isFullScreenRequired()
220      {
221        return true;
222      }
223    
224      /**
225       * Returns true if flipping can involve more than two buffers.  One
226       * or more intermediate buffers may be available in addition to the
227       * front and back buffers.
228       *
229       * @return true if there are more than two buffers available for
230       * flipping, false otherwise
231       */
232      public boolean isMultiBufferAvailable()
233      {
234        return false;
235      }
236    
237      /**
238       * Clone this buffering capability descriptor.
239       *
240       * @return a clone of this buffer capability descriptor
241       */
242      public Object clone()
243      {
244        try
245          {
246            return super.clone();
247          }
248        catch (CloneNotSupportedException e)
249          {
250            throw (Error) new InternalError().initCause(e);
251          }
252      }
253    }