Source for java.awt.image.BufferStrategy

   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
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  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: }