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/* Copyright (C) 2000  Free Software Foundation

   This file is part of libgcj.

This software is copyrighted work licensed under the terms of the

Libgcj License.  Please consult the file "LIBGCJ_LICENSE" for

details.  */

package gnu.awt.j2d;

import java.awt.image.WritableRaster;

import java.awt.image.ColorModel;

/* The raster and associated properties of a mapped screen region.

 * The compositing capabilities of backends are often insufficient.

 * The backend may not support alpha blending, or may not support some

 * other special compositing rule.  This means that compositing must

 * sometimes be done within the rendering pipeline.  The general

 * compositing operation consists of combining new color and alpha

 * values with existing color values on the drawing surface, to find

 * the new color values for the drawing surface. The way the values

 * are combined, determines what kind of compositing operation that is

 * performed.  The default compositing operation is alpha compositing.

 *

 * <p>In order to perform alpha compositing and other compositing

 * operations, we need access to the color values of the imagery that

 * has already been drawn on the drawing surface.  The

 * DirectRasterGraphics interface must therefore contain methods that

 * makes it possible to gain access to the pixel values of the drawing

 * surface.  The methods are modeled after the POSIX mmap() and

 * munmap() functions.  But, instead of mapping and unmapping portions

 * of data from a file descriptor to memory, the methods in

 * DirectRasterGraphics maps and unmaps portions of the drawing

 * surface to data arrays within writable raster objects.  A call to

 * mapRaster() will return a writable raster object, encapsulating the

 * image data of the drawing surface in the requested domain. The data

 * encapsulated by this raster object can be modified using the

 * WritableRaster API, or the data buffers can be retrieved from the

 * raster, so that the data arrays can be manipulated directly.  When

 * the raster image has been modified as desired, the data can be

 * resynchronized with the drawing surface by calling mapRaster().

 *

 * <p>As with mmap() and munmap() the methods may work by direct

 * manipulation of shared memory, (i.e. the raster object directly

 * wraps the actual image data of the drawing surface), or may make a

 * private copy that is resynched when the raster is unmapped. The

 * backend may choose to implement either mechanism, and the pipeline

 * code should not care what mechanism is actually used.  This design

 * allows us to make full use of speedups such as X shared memory

 * extentions when available.

 */

public class MappedRaster

{

  WritableRaster raster;

  ColorModel cm;

  public MappedRaster(WritableRaster raster, ColorModel cm)

  {

    this.raster = raster;

    this.cm = cm;

  }

  public final WritableRaster getRaster()

  {

    return raster;

  }

  public final ColorModel getColorModel()

  {

    return cm;

  }

}