gomp-20050608-branch/libjava/classpath/java/awt/BufferCapabilities.java

   1 /* BufferCapabilities.java -- double-buffering capabilities descriptor
   2    Copyright (C) 2002, 2005  Free Software Foundation, Inc.
   3
   4 This file is part of GNU Classpath.
   5
   6 GNU Classpath is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2, or (at your option)
   9 any later version.
  10
  11 GNU Classpath is distributed in the hope that it will be useful, but
  12 WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14 General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GNU Classpath; see the file COPYING.  If not, write to the
  18 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  19 02110-1301 USA.
  20
  21 Linking this library statically or dynamically with other modules is
  22 making a combined work based on this library.  Thus, the terms and
  23 conditions of the GNU General Public License cover the whole
  24 combination.
  25
  26 As a special exception, the copyright holders of this library give you
  27 permission to link this library with independent modules to produce an
  28 executable, regardless of the license terms of these independent
  29 modules, and to copy and distribute the resulting executable under
  30 terms of your choice, provided that you also meet, for each linked
  31 independent module, the terms and conditions of the license of that
  32 module.  An independent module is a module which is not derived from
  33 or based on this library.  If you modify this library, you may extend
  34 this exception to your version of the library, but you are not
  35 obligated to do so.  If you do not wish to do so, delete this
  36 exception statement from your version. */
  37
  38
  39 package java.awt;
  40
  41 import java.awt.image.BufferStrategy;
  42
  43 /**
  44  * A double-buffering capability descriptor.  This class exposes
  45  * details about the double-buffering algorithms used by image
  46  * buffers.
  47  *
  48  * BufferCapabilities represents algorithms that involve at least two
  49  * buffers but it can also specify so-called "multi-buffer" schemes
  50  * involving more than two buffers.  This class describes the
  51  * capabilities of the front and back buffers as well as the results
  52  * of "flipping" -- that is, what happens when an image is transferred
  53  * from the back buffer to the front buffer.
  54  *
  55  * Flipping may or may not be supported or may be supported only in
  56  * fullscreen mode.  If it is not supported then "blitting" is implied
  57  * -- that is, the contents of the back buffer are copied using a fast
  58  * block transfer operation from the back buffer to the front buffer.
  59  *
  60  * The front buffer is the one that is displayed.
  61  *
  62  * @author Eric Blake (ebb9@email.byu.edu)
  63  *
  64  * @see BufferStrategy#getCapabilities()
  65  * @see GraphicsConfiguration#getBufferCapabilities()
  66  *
  67  * @since 1.4
  68  */
  69 public class BufferCapabilities implements Cloneable
  70 {
  71   /**
  72    * A type-safe enumeration of buffer flipping results.
  73    *
  74    * @see AttributeValue
  75    */
  76   public static final class FlipContents extends AttributeValue
  77   {
  78     /**
  79      * The names of the different flipping results.
  80      */
  81     private static final String[] NAMES
  82       = { "undefined", "background", "prior", "copied" };
  83
  84     /**
  85      * The contents of the back buffer are undefined after flipping.
  86      */
  87     public static final FlipContents UNDEFINED = new FlipContents(0);
  88
  89     /**
  90      * The back buffer is cleared with the background color after
  91      * flipping.
  92      */
  93     public static final FlipContents BACKGROUND = new FlipContents(1);
  94
  95     /**
  96      * The back buffer contains the pre-flipping contents of the front
  97      * buffer after flipping.  In other words a true "flip" has been
  98      * performed.
  99      */
 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 }