001/* BufferCapabilities.java -- double-buffering capabilities descriptor
002   Copyright (C) 2002, 2005  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
038
039package java.awt;
040
041import 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 */
069public 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}