src/java.desktop/share/classes/java/awt/image/WritableRenderedImage.java

/*
 * Copyright (c) 1997, 2008, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code 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
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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/* ****************************************************************
 ******************************************************************
 ******************************************************************
 *** COPYRIGHT (c) Eastman Kodak Company, 1997
 *** As  an unpublished  work pursuant to Title 17 of the United
 *** States Code.  All rights reserved.
 ******************************************************************
 ******************************************************************
 ******************************************************************/

package java.awt.image;
import java.awt.Point;

/**
 * WritableRenderedImage is a common interface for objects which
 * contain or can produce image data in the form of Rasters and
 * which can be modified and/or written over.  The image
 * data may be stored/produced as a single tile or a regular array
 * of tiles.
 * <p>
 * WritableRenderedImage provides notification to other interested
 * objects when a tile is checked out for writing (via the
 * getWritableTile method) and when the last writer of a particular
 * tile relinquishes its access (via a call to releaseWritableTile).
 * Additionally, it allows any caller to determine whether any tiles
 * are currently checked out (via hasTileWriters), and to obtain a
 * list of such tiles (via getWritableTileIndices, in the form of a Vector
 * of Point objects).
 * <p>
 * Objects wishing to be notified of changes in tile writability must
 * implement the TileObserver interface, and are added by a
 * call to addTileObserver.  Multiple calls to
 * addTileObserver for the same object will result in multiple
 * notifications.  An existing observer may reduce its notifications
 * by calling removeTileObserver; if the observer had no
 * notifications the operation is a no-op.
 * <p>
 * It is necessary for a WritableRenderedImage to ensure that
 * notifications occur only when the first writer acquires a tile and
 * the last writer releases it.
 *
 */

public interface WritableRenderedImage extends RenderedImage
{

  /**
   * Adds an observer.  If the observer is already present,
   * it will receive multiple notifications.
   * @param to the specified {@code TileObserver}
   */
  public void addTileObserver(TileObserver to);

  /**
   * Removes an observer.  If the observer was not registered,
   * nothing happens.  If the observer was registered for multiple
   * notifications, it will now be registered for one fewer.
   * @param to the specified {@code TileObserver}
   */
  public void removeTileObserver(TileObserver to);

  /**
   * Checks out a tile for writing.
   *
   * The WritableRenderedImage is responsible for notifying all
   * of its TileObservers when a tile goes from having
   * no writers to having one writer.
   *
   * @param tileX the X index of the tile.
   * @param tileY the Y index of the tile.
   * @return a writable tile.
   */
  public WritableRaster getWritableTile(int tileX, int tileY);

  /**
   * Relinquishes the right to write to a tile.  If the caller
   * continues to write to the tile, the results are undefined.
   * Calls to this method should only appear in matching pairs
   * with calls to getWritableTile; any other use will lead
   * to undefined results.
   *
   * The WritableRenderedImage is responsible for notifying all of
   * its TileObservers when a tile goes from having one writer
   * to having no writers.
   *
   * @param tileX the X index of the tile.
   * @param tileY the Y index of the tile.
   */
  public void releaseWritableTile(int tileX, int tileY);

  /**
   * Returns whether a tile is currently checked out for writing.
   *
   * @param tileX the X index of the tile.
   * @param tileY the Y index of the tile.
   * @return {@code true} if specified tile is checked out
   *         for writing; {@code false} otherwise.
   */
  public boolean isTileWritable(int tileX, int tileY);

  /**
   * Returns an array of Point objects indicating which tiles
   * are checked out for writing.  Returns null if none are
   * checked out.
   * @return an array containing the locations of tiles that are
   *         checked out for writing.
   */
  public Point[] getWritableTileIndices();

  /**
   * Returns whether any tile is checked out for writing.
   * Semantically equivalent to (getWritableTileIndices() != null).
   * @return {@code true} if any tiles are checked out for
   *         writing; {@code false} otherwise.
   */
  public boolean hasTileWriters();

  /**
   * Sets a rect of the image to the contents of the Raster r, which is
   * assumed to be in the same coordinate space as the WritableRenderedImage.
   * The operation is clipped to the bounds of the WritableRenderedImage.
   * @param r the specified {@code Raster}
   */
  public void setData(Raster r);

}