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SWT is an open source widget toolkit for Java designed to provide efficient, portable access to the user-interface facilities of the operating systems on which it is implemented.

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/*******************************************************************************
 * Copyright (c) 2000, 2012 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.swt.graphics;


import org.eclipse.swt.internal.win32.*;
import org.eclipse.swt.*;

/**
 * Instances of this class manage the operating system resources that
 * implement SWT's RGB color model. To create a color you can either
 * specify the individual color components as integers in the range 
 * 0 to 255 or provide an instance of an RGB. 
 * 

 * Application code must explicitly invoke the Color.dispose() 
 * method to release the operating system resources managed by each instance
 * when those instances are no longer required.
 * 

 *
 * @see RGB
 * @see Device#getSystemColor
 * @see Color and RGB snippets
 * @see SWT Example: PaintExample
 * @see Sample code and further information
 */

public final class Color extends Resource {
	
	/**
	 * the handle to the OS color resource 
	 * (Warning: This field is platform dependent)
	 * 

	 * IMPORTANT: This field is not part of the SWT
	 * public API. It is marked public only so that it can be shared
	 * within the packages provided by SWT. It is not available on all
	 * platforms and should never be accessed from application code.
	 * 

	 * 
	 * @noreference This field is not intended to be referenced by clients.
	 */
	public int handle;

/**
 * Prevents uninitialized instances from being created outside the package.
 */
Color(Device device) {
	super(device);
}

/**	 
 * Constructs a new instance of this class given a device and the
 * desired red, green and blue values expressed as ints in the range
 * 0 to 255 (where 0 is black and 255 is full brightness). On limited
 * color devices, the color instance created by this call may not have
 * the same RGB values as the ones specified by the arguments. The
 * RGB values on the returned instance will be the color values of 
 * the operating system color.
 * 

 * You must dispose the color when it is no longer required. 
 * 

 *
 * @param device the device on which to allocate the color
 * @param red the amount of red in the color
 * @param green the amount of green in the color
 * @param blue the amount of blue in the color
 *
 * @exception IllegalArgumentException 
    
 *    
  • ERROR_NULL_ARGUMENT - if device is null and there is no current device
    • 
 *    
  • ERROR_INVALID_ARGUMENT - if the red, green or blue argument is not between 0 and 255
    • 
 * 

 *
 * @see #dispose
 */
public Color (Device device, int red, int green, int blue) {
	super(device);
	init(red, green, blue);
	init();
}

/**	 
 * Constructs a new instance of this class given a device and an
 * RGB describing the desired red, green and blue values.
 * On limited color devices, the color instance created by this call
 * may not have the same RGB values as the ones specified by the
 * argument. The RGB values on the returned instance will be the color
 * values of the operating system color.
 * 

 * You must dispose the color when it is no longer required. 
 * 

 *
 * @param device the device on which to allocate the color
 * @param rgb the RGB values of the desired color
 *
 * @exception IllegalArgumentException 
    
 *    
  • ERROR_NULL_ARGUMENT - if device is null and there is no current device
    • 
 *    
  • ERROR_NULL_ARGUMENT - if the rgb argument is null
    • 
 *    
  • ERROR_INVALID_ARGUMENT - if the red, green or blue components of the argument are not between 0 and 255
    • 
 * 

 *
 * @see #dispose
 */
public Color (Device device, RGB rgb) {
	super(device);
	if (rgb == null) SWT.error(SWT.ERROR_NULL_ARGUMENT);
	init(rgb.red, rgb.green, rgb.blue);
	init();
}

void destroy() {
	/*
	 * If this is a palette-based device,
	 * Decrease the reference count for this color.
	 * If the reference count reaches 0, the slot may
	 * be reused when another color is allocated.
	 */
	int /*long*/ hPal = device.hPalette;
	if (hPal != 0) {
		int index = OS.GetNearestPaletteIndex(hPal, handle);
		int[] colorRefCount = device.colorRefCount;
		if (colorRefCount[index] > 0) {
			colorRefCount[index]--;
		}
	}
	handle = -1;
}

/**
 * Compares the argument to the receiver, and returns true
 * if they represent the same object using a class
 * specific comparison.
 *
 * @param object the object to compare with this object
 * @return true if the object is the same as this object and false otherwise
 *
 * @see #hashCode
 */
public boolean equals (Object object) {
	if (object == this) return true;
	if (!(object instanceof Color)) return false;
	Color color = (Color) object;
	return device == color.device && (handle & 0xFFFFFF) == (color.handle & 0xFFFFFF);
}

/**
 * Returns the amount of blue in the color, from 0 to 255.
 *
 * @return the blue component of the color
 *
 * @exception SWTException 
    
 *    
  • ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed
    • 
 * 

 */
public int getBlue () {
	if (isDisposed()) SWT.error(SWT.ERROR_GRAPHIC_DISPOSED);
	return (handle & 0xFF0000) >> 16;
}

/**
 * Returns the amount of green in the color, from 0 to 255.
 *
 * @return the green component of the color
 *
 * @exception SWTException 
    
 *    
  • ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed
    • 
 * 

 */
public int getGreen () {
	if (isDisposed()) SWT.error(SWT.ERROR_GRAPHIC_DISPOSED);
	return (handle & 0xFF00) >> 8 ;
}

/**
 * Returns the amount of red in the color, from 0 to 255.
 *
 * @return the red component of the color
 *
 * @exception SWTException 
    
 *    
  • ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed
    • 
 * 

 */
public int getRed () {
	if (isDisposed()) SWT.error(SWT.ERROR_GRAPHIC_DISPOSED);
	return handle & 0xFF;
}

/**
 * Returns an RGB representing the receiver.
 *
 * @return the RGB for the color
 *
 * @exception SWTException 
    
 *    
  • ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed
    • 
 * 

 */
public RGB getRGB () {
	if (isDisposed()) SWT.error(SWT.ERROR_GRAPHIC_DISPOSED);
	return new RGB(handle & 0xFF, (handle & 0xFF00) >> 8, (handle & 0xFF0000) >> 16);
}

/**
 * Returns an integer hash code for the receiver. Any two 
 * objects that return true when passed to 
 * equals must return the same value for this
 * method.
 *
 * @return the receiver's hash
 *
 * @see #equals
 */
public int hashCode () {
	return handle;
}

/**
 * Allocates the operating system resources associated 
 * with the receiver.
 *
 * @param device the device on which to allocate the color
 * @param red the amount of red in the color
 * @param green the amount of green in the color
 * @param blue the amount of blue in the color
 *
 * @exception IllegalArgumentException 
    
 *    
  • ERROR_INVALID_ARGUMENT - if the red, green or blue argument is not between 0 and 255
    • 
 * 

 *
 * @see #dispose
 */
void init(int red, int green, int blue) {
	if (red > 255 || red < 0 || green > 255 || green < 0 || blue > 255 || blue < 0) {
		SWT.error(SWT.ERROR_INVALID_ARGUMENT);
	}
	handle = (red & 0xFF) | ((green & 0xFF) << 8) | ((blue & 0xFF) << 16);
	
	/* If this is not a palette-based device, return */
	int /*long*/ hPal = device.hPalette;
	if (hPal == 0) return;
	
	int[] colorRefCount = device.colorRefCount;
	/* Add this color to the default palette now */
	/* First find out if the color already exists */
	int index = OS.GetNearestPaletteIndex(hPal, handle);
	/* See if the nearest color actually is the color */
	byte[] entry = new byte[4];
	OS.GetPaletteEntries(hPal, index, 1, entry);
	if ((entry[0] == (byte)red) && (entry[1] == (byte)green) &&
		(entry[2] == (byte)blue)) {
			/* Found the color. Increment the ref count and return */
			colorRefCount[index]++;
			return;
	}
	/* Didn't find the color, allocate it now. Find the first free entry */
	int i = 0;
	while (i < colorRefCount.length) {
		if (colorRefCount[i] == 0) {
			index = i;
			break;
		}
		i++;
	}
	if (i == colorRefCount.length) {
		/* No free entries, use the closest one */
		/* Remake the handle from the actual rgbs */
		handle = (entry[0] & 0xFF) | ((entry[1] & 0xFF) << 8) |
				 ((entry[2] & 0xFF) << 16);
	} else {
		/* Found a free entry */
		entry = new byte[] { (byte)(red & 0xFF), (byte)(green & 0xFF), (byte)(blue & 0xFF), 0 };
		OS.SetPaletteEntries(hPal, index, 1, entry);
	}
	colorRefCount[index]++;
}

/**
 * Returns true if the color has been disposed,
 * and false otherwise.
 * 

 * This method gets the dispose state for the color.
 * When a color has been disposed, it is an error to
 * invoke any other method (except {@link #dispose()}) using the color.
 *
 * @return true when the color is disposed and false otherwise
 */
public boolean isDisposed() {
	return handle == -1;
}

/**
 * Returns a string containing a concise, human-readable
 * description of the receiver.
 *
 * @return a string representation of the receiver
 */
public String toString () {
	if (isDisposed()) return "Color {*DISPOSED*}"; //$NON-NLS-1$
	return "Color {" + getRed() + ", " + getGreen() + ", " + getBlue() + "}"; //$NON-NLS-1$//$NON-NLS-2$ //$NON-NLS-3$ //$NON-NLS-4$
}

/**	 
 * Invokes platform specific functionality to allocate a new color.
 * 

 * IMPORTANT: This method is not part of the public
 * API for Color. It is marked public only so that it
 * can be shared within the packages provided by SWT. It is not
 * available on all platforms, and should never be called from
 * application code.
 * 

 *
 * @param device the device on which to allocate the color
 * @param handle the handle for the color
 * @return a new color object containing the specified device and handle
 * 
 * @noreference This method is not intended to be referenced by clients.
 */
public static Color win32_new(Device device, int handle) {
	Color color = new Color(device);
	color.handle = handle;
	return color;
}

}




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