org.mihalis.opal/src/main/java/org/mihalis/opal/gradientComposite/GradientComposite.java

/*******************************************************************************
 * Copyright (c) 2011 Laurent CARON
 * 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:
 *     Laurent CARON (laurent.caron at gmail dot com) - Initial implementation and API
 *******************************************************************************/
package org.mihalis.opal.gradientComposite;

import org.eclipse.swt.SWT;
import org.eclipse.swt.SWTException;
import org.eclipse.swt.graphics.Color;
import org.eclipse.swt.graphics.GC;
import org.eclipse.swt.graphics.Image;
import org.eclipse.swt.graphics.Rectangle;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Event;
import org.eclipse.swt.widgets.Listener;
import org.eclipse.swt.widgets.Widget;
import org.mihalis.opal.utils.SWTGraphicUtil;

/**
 * Instances of this class are controls which background's texture is a gradient
 * composite.
 */
public class GradientComposite extends Composite {
	
	/** The previous generated image. */
	private Image previousGeneratedImage;
	
	/** The gradient end. */
	private Color gradientEnd;
	
	/** The gradient start. */
	private Color gradientStart;

	/**
	 * Constructs a new instance of this class given its parent and a style
	 * value describing its behavior and appearance.
	 * <p>
	 * The style value is either one of the style constants defined in class
	 * <code>SWT</code> which is applicable to instances of this class, or must
	 * be built by <em>bitwise OR</em>'ing together (that is, using the
	 * <code>int</code> "|" operator) two or more of those <code>SWT</code>
	 * style constants. The class description lists the style constants that are
	 * applicable to the class. Style bits are also inherited from superclasses.
	 * </p>
	 *
	 * @param parent a widget which will be the parent of the new instance
	 *            (cannot be null)
	 * @param style the style of widget to construct
	 * @see Composite#Composite(Composite, int)
	 * @see SWT#NO_BACKGROUND
	 * @see SWT#NO_FOCUS
	 * @see SWT#NO_MERGE_PAINTS
	 * @see SWT#NO_REDRAW_RESIZE
	 * @see SWT#NO_RADIO_GROUP
	 * @see SWT#EMBEDDED
	 * @see SWT#DOUBLE_BUFFERED
	 * @see Widget#getStyle
	 * @exception IllegalArgumentException <ul>
	 *                <li>ERROR_NULL_ARGUMENT - if the parent is null</li>
	 *                </ul>
	 * @exception SWTException <ul>
	 *                <li>ERROR_THREAD_INVALID_ACCESS - if not called from the
	 *                thread that created the parent</li>
	 *                </ul>
	 */
	public GradientComposite(final Composite parent, final int style) {
		super(parent, style);
		this.addListener(SWT.Resize, new Listener() {
			@Override
			public void handleEvent(final Event event) {
				GradientComposite.this.redrawComposite();
			}
		});

		this.gradientStart = getDisplay().getSystemColor(SWT.COLOR_BLACK);
		this.gradientEnd = SWTGraphicUtil.getDefaultColor(this, 110, 110, 110);
	}

	/**
	 * Redraws the composite.
	 */
	private void redrawComposite() {
		final Display display = this.getDisplay();
		final Rectangle rect = this.getClientArea();
		final Image newImage = new Image(display, Math.max(1, rect.width), Math.max(1, rect.height));

		final GC gc = new GC(newImage);
		gc.setForeground(this.gradientStart);
		gc.setBackground(this.gradientEnd);
		gc.fillGradientRectangle(rect.x, rect.y, rect.width, rect.height / 2, true);

		gc.setForeground(this.gradientEnd);
		gc.setBackground(this.gradientStart);
		gc.fillGradientRectangle(rect.x, rect.height / 2, rect.width, rect.height / 2, true);
		gc.dispose();

		this.setBackgroundImage(newImage);
		if (this.previousGeneratedImage != null) {
			this.previousGeneratedImage.dispose();
		}
		this.previousGeneratedImage = newImage;

	}

	// ------------------------------------ Getters and Setters
	/**
	 * Gets the gradient end.
	 *
	 * @return the gradientEnd color
	 */
	public Color getGradientEnd() {
		return this.gradientEnd;
	}

	/**
	 * Sets the gradient end.
	 *
	 * @param gradientEnd the gradientEnd color to set
	 */
	public void setGradientEnd(final Color gradientEnd) {
		this.gradientEnd = gradientEnd;
	}

	/**
	 * Gets the gradient start.
	 *
	 * @return the gradientStart color
	 */
	public Color getGradientStart() {
		return this.gradientStart;
	}

	/**
	 * Sets the gradient start.
	 *
	 * @param gradientStart the gradientStart color to set
	 */
	public void setGradientStart(final Color gradientStart) {
		this.gradientStart = gradientStart;
	}
}