diff --git a/libjava/ChangeLog b/libjava/ChangeLog index 8380e6ce580..428d2fc1366 100644 --- a/libjava/ChangeLog +++ b/libjava/ChangeLog @@ -1,3 +1,7 @@ +2005-05-04 Thomas Fitzsimmons + + * java/awt/BufferCapabilities.java: Document. + 2005-05-04 Tom Tromey * java/nio/channels/FileLock.java (toString): Entirely avoid diff --git a/libjava/java/awt/BufferCapabilities.java b/libjava/java/awt/BufferCapabilities.java index 9f91711e18a..4ff2ba98d9f 100644 --- a/libjava/java/awt/BufferCapabilities.java +++ b/libjava/java/awt/BufferCapabilities.java @@ -1,4 +1,4 @@ -/* BufferCapabilities.java -- +/* BufferCapabilities.java -- double-buffering capabilities descriptor Copyright (C) 2002, 2005 Free Software Foundation, Inc. This file is part of GNU Classpath. @@ -39,79 +39,204 @@ exception statement from your version. */ package java.awt; /** - * Needs documentation... + * A double-buffering capability descriptor. This class exposes + * details about the double-buffering algorithms used by image + * buffers. + * + * BufferCapabilities represents algorithms that involve at least two + * buffers but it can also specify so-called "multi-buffer" schemes + * involving more than two buffers. This class describes the + * capabilities of the front and back buffers as well as the results + * of "flipping" -- that is, what happens when an image is transferred + * from the back buffer to the front buffer. + * + * Flipping may or may not be supported or may be supported only in + * fullscreen mode. If it is not supported then "blitting" is implied + * -- that is, the contents of the back buffer are copied using a fast + * block transfer operation from the back buffer to the front buffer. + * + * The front buffer is the one that is displayed. * * @author Eric Blake (ebb9@email.byu.edu) + * * @see BufferStrategy#getCapabilities() * @see GraphicsConfiguration#getCapabilities() + * * @since 1.4 - * @status updated to 1.4, lacks documentation */ public class BufferCapabilities implements Cloneable { + /** + * A type-safe enumeration of buffer flipping results. + * + * @see AttributeValue + */ public static final class FlipContents extends AttributeValue { + /** + * The names of the different flipping results. + */ private static final String[] NAMES = { "undefined", "background", "prior", "copied" }; + + /** + * The contents of the back buffer are undefined after flipping. + */ public static final FlipContents UNDEFINED = new FlipContents(0); + + /** + * The back buffer is cleared with the background color after + * flipping. + */ public static final FlipContents BACKGROUND = new FlipContents(1); + + /** + * The back buffer contains the pre-flipping contents of the front + * buffer after flipping. In other words a true "flip" has been + * performed. + */ public static final FlipContents PRIOR = new FlipContents(2); + + /** + * The back buffer has the same contents as the front buffer after + * flipping. + */ public static final FlipContents COPIED = new FlipContents(3); + + /** + * Create a new flipping result descriptor. + * + * @param value the enumeration value + */ private FlipContents(int value) { super(value, NAMES); } - } // class FlipContents + } + /** + * Front buffer capabilities descriptor. + */ private final ImageCapabilities front; + + /** + * Back buffer capabilities descriptor. + */ private final ImageCapabilities back; + + /** + * Describes the results of a "flip" operation. + */ private final FlipContents flip; /** * Creates a buffer capabilities object. * - * @exception IllegalArgumentException If frontCaps or backCaps are null. + * @param frontCaps front buffer capabilities descriptor + * @param backCaps back buffer capabilities descriptor + * @param flipContents the results of a flip operation or null if + * flipping is not supported + * + * @exception IllegalArgumentException if frontCaps or backCaps is + * null */ - public BufferCapabilities(ImageCapabilities front, ImageCapabilities back, - FlipContents flip) + public BufferCapabilities(ImageCapabilities frontCaps, + ImageCapabilities backCaps, + FlipContents flipContents) { + if (front == null || back == null) + throw new IllegalArgumentException(); this.front = front; this.back = back; this.flip = flip; - if (front == null || back == null) - throw new IllegalArgumentException(); } + /** + * Retrieve the front buffer's image capabilities. + * + * @return the front buffer's image capabilities + */ public ImageCapabilities getFrontBufferCapabilities() { return front; } + /** + * Retrieve the back buffer's image capabilities. + * + * @return the back buffer's image capabilities + */ public ImageCapabilities getBackBufferCapabilities() { return back; } + /** + * Return whether or not flipping is supported. + * + * @return true if flipping is supported, false otherwise + */ public boolean isPageFlipping() { return flip != null; } + /** + * Retrieve the result of a flipping operation. If this method + * returns null then flipping is not supported. This implies that + * "blitting", a fast block transfer, is used to copy the contents + * of the back buffer to the front buffer. Other possible return + * values are: + * + * + * @return the result of a flipping operation or null if flipping is + * not supported + */ public FlipContents getFlipContents() { return flip; } + /** + * Returns true if flipping is only supported in fullscreen mode. + * + * @return true if flipping is only supported in fullscreen mode, + * false otherwise + */ public boolean isFullScreenRequired() { return true; } + /** + * Returns true if flipping can involve more than two buffers. One + * or more intermediate buffers may be available in addition to the + * front and back buffers. + * + * @return true if there are more than two buffers available for + * flipping, false otherwise + */ public boolean isMultiBufferAvailable() { return false; } + /** + * Clone this buffering capability descriptor. + * + * @return a clone of this buffer capability descriptor + */ public Object clone() { try @@ -120,7 +245,7 @@ public class BufferCapabilities implements Cloneable } catch (CloneNotSupportedException e) { - throw (Error) new InternalError().initCause(e); // Impossible + throw (Error) new InternalError().initCause(e); } } -} // class BufferCapabilities +}