trunk/libjava/classpath/java/awt/image/BufferStrategy.java

   1 /* BufferStrategy.java -- describes image buffering resources
   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.image;
  40
  41 import java.awt.BufferCapabilities;
  42 import java.awt.Graphics;
  43
  44 /**
  45  * This class describes a strategy for managing image buffering
  46  * resources on a Canvas or Window.  A given buffer strategy may make
  47  * use of hardware acceleration or take advantage of features of the
  48  * native graphics system.  Examples of buffering strategies are
  49  * double or triple buffering using either flipping or blitting.  For
  50  * the details of these algorithms see BufferCapabilities.
  51  *
  52  * To use a buffer strategy, you retrieve it from either the current
  53  * GraphicsConfiguration or from the Component on which you'd like to
  54  * draw.  Then you can query the strategy's capabilities to make sure
  55  * they're suitable.
  56  *
  57  * If the strategy's capabilities are suitable, you can obtain a
  58  * graphics object and use it to draw with this strategy.  Drawing
  59  * with a buffer strategy requires extra care, however.  You'll need
  60  * to manually cause the next buffer to be shown on the output device.
  61  * And since buffer strategies are usually implemented with a
  62  * VolatileImage, you must frequently check that the contents of the
  63  * buffer are valid and that the buffer still exists.
  64  *
  65  * A buffer strategy is usually implemented using a VolatileImage.
  66  *
  67  * @see VolatileImage
  68  * @since 1.4
  69  */
  70 public abstract class BufferStrategy
  71 {
  72   /**
  73    * Creates a new buffer strategy.
  74    */
  75   public BufferStrategy()
  76   {
  77   }
  78
  79   /**
  80    * Retrieves the capabilities of this buffer strategy.
  81    *
  82    * @return this buffer strategy's capabilities
  83    */
  84   public abstract BufferCapabilities getCapabilities();
  85
  86   /**
  87    * Retrieves a graphics object that can be used to draw using this
  88    * buffer strategy.  This method may not be synchronized so be
  89    * careful when calling it from multiple threads.  You also must
  90    * manually dispose of this graphics object.
  91    *
  92    * @return a graphics object that can be used to draw using this
  93    * buffer strategy
  94    */
  95   public abstract Graphics getDrawGraphics();
  96
  97   /**
  98    * Returns whether or not the buffer's resources have been reclaimed
  99    * by the native graphics system.  If the buffer resources have been
 100    * lost then you'll need to obtain new resources before drawing
 101    * again.  For details, see the documentation for VolatileImage.
 102    *
 103    * @return true if the contents were lost, false otherwise
 104    */
 105   public abstract boolean contentsLost();
 106
 107   /**
 108    * Returns whether or not the buffer's resources were re-created and
 109    * cleared to the default background color.  If the buffer's
 110    * resources have recently been re-created and initialized then the
 111    * buffer's image may need to be re-rendered.  For details, see the
 112    * documentation for VolatileImage.
 113    *
 114    * @return true if the contents were restored, false otherwise
 115    */
 116   public abstract boolean contentsRestored();
 117
 118   /**
 119    * Applies this buffer strategy.  In other words, this method brings
 120    * the contents of the back or intermediate buffers to the front
 121    * buffer.
 122    */
 123   public abstract void show();
 124 }