Initial revision

From-SVN: r102074

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

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+/* BufferStrategy.java -- describes image buffering resources
+   Copyright (C) 2002, 2005 Free Software Foundation, Inc.
+
+This file is part of GNU Classpath.
+
+GNU Classpath is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2, or (at your option)
+any later version.
+
+GNU Classpath is distributed in the hope that it will be useful, but
+WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GNU Classpath; see the file COPYING.  If not, write to the
+Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+02110-1301 USA.
+
+Linking this library statically or dynamically with other modules is
+making a combined work based on this library.  Thus, the terms and
+conditions of the GNU General Public License cover the whole
+combination.
+
+As a special exception, the copyright holders of this library give you
+permission to link this library with independent modules to produce an
+executable, regardless of the license terms of these independent
+modules, and to copy and distribute the resulting executable under
+terms of your choice, provided that you also meet, for each linked
+independent module, the terms and conditions of the license of that
+module.  An independent module is a module which is not derived from
+or based on this library.  If you modify this library, you may extend
+this exception to your version of the library, but you are not
+obligated to do so.  If you do not wish to do so, delete this
+exception statement from your version. */
+
+
+package java.awt.image;
+
+import java.awt.BufferCapabilities;
+import java.awt.Graphics;
+
+/**
+ * This class describes a strategy for managing image buffering
+ * resources on a Canvas or Window.  A given buffer strategy may make
+ * use of hardware acceleration or take advantage of features of the
+ * native graphics system.  Examples of buffering strategies are
+ * double or triple buffering using either flipping or blitting.  For
+ * the details of these algorithms see BufferCapabilities.
+ *
+ * To use a buffer strategy, you retrieve it from either the current
+ * GraphicsConfiguration or from the Component on which you'd like to
+ * draw.  Then you can query the strategy's capabilities to make sure
+ * they're suitable.
+ *
+ * If the strategy's capabilities are suitable, you can obtain a
+ * graphics object and use it to draw with this strategy.  Drawing
+ * with a buffer strategy requires extra care, however.  You'll need
+ * to manually cause the next buffer to be shown on the output device.
+ * And since buffer strategies are usually implemented with a
+ * VolatileImage, you must frequently check that the contents of the
+ * buffer are valid and that the buffer still exists.
+ *
+ * A buffer strategy is usually implemented using a VolatileImage.
+ *
+ * @see VolatileImage
+ * @since 1.4
+ */
+public abstract class BufferStrategy
+{
+  /**
+   * Creates a new buffer strategy.
+   */
+  public BufferStrategy()
+  {
+  }
+
+  /**
+   * Retrieves the capabilities of this buffer strategy.
+   *
+   * @return this buffer strategy's capabilities
+   */
+  public abstract BufferCapabilities getCapabilities();
+
+  /**
+   * Retrieves a graphics object that can be used to draw using this
+   * buffer strategy.  This method may not be synchronized so be
+   * careful when calling it from multiple threads.  You also must
+   * manually dispose of this graphics object.
+   *
+   * @return a graphics object that can be used to draw using this
+   * buffer strategy
+   */
+  public abstract Graphics getDrawGraphics();
+
+  /**
+   * Returns whether or not the buffer's resources have been reclaimed
+   * by the native graphics system.  If the buffer resources have been
+   * lost then you'll need to obtain new resources before drawing
+   * again.  For details, see the documentation for VolatileImage.
+   *
+   * @return true if the contents were lost, false otherwise
+   */
+  public abstract boolean contentsLost();
+
+  /**
+   * Returns whether or not the buffer's resources were re-created and
+   * cleared to the default background color.  If the buffer's
+   * resources have recently been re-created and initialized then the
+   * buffer's image may need to be re-rendered.  For details, see the
+   * documentation for VolatileImage.
+   *
+   * @return true if the contents were restored, false otherwise
+   */
+  public abstract boolean contentsRestored();
+
+  /**
+   * Applies this buffer strategy.  In other words, this method brings
+   * the contents of the back or intermediate buffers to the front
+   * buffer.
+   */
+  public abstract void show();
+}