examples/org.eclipse.swt.examples/src/org/eclipse/swt/examples/graphics/CustomAlphaTab.java

/*******************************************************************************
 * Copyright (c) 2006 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.examples.graphics;

import org.eclipse.swt.*;
import org.eclipse.swt.graphics.*;
import org.eclipse.swt.layout.*;
import org.eclipse.swt.widgets.*;

/**
 * This tab demonstrates the use of alpha blending. It allows a user to specify
 * a custom alpha value.
 */
public class CustomAlphaTab extends AnimatedGraphicsTab {
	
	private Spinner alphaSpinner;
	private Button colorButton;
	private GraphicsBackground background;
	private Menu menu;
	private int angle;

public CustomAlphaTab(GraphicsExample example) {
	super(example);
}

public String getCategory() {
	return GraphicsExample.getResourceString("Alpha"); //$NON-NLS-1$
}

public String getText() {
	return GraphicsExample.getResourceString("CustomAlpha"); //$NON-NLS-1$
}

public String getDescription() {
	return GraphicsExample.getResourceString("CustomAlphaDescription"); //$NON-NLS-1$
}

public void dispose() {
	if (menu != null) {
		menu.dispose();
		menu = null;
	}
}

/** 
 * Creates the widgets used to control the drawing.
 */
public void createControlPanel(Composite parent) {
	super.createControlPanel(parent);
	
	// create drop down combo for choosing clipping
	Composite comp;
	
	// create spinner for line width
	comp = new Composite(parent, SWT.NONE);
	comp.setLayout(new GridLayout(2, false));
	new Label(comp, SWT.CENTER).setText(GraphicsExample
				.getResourceString("Alpha")); //$NON-NLS-1$
	alphaSpinner = new Spinner(comp, SWT.BORDER | SWT.WRAP);
	alphaSpinner.setMinimum(0);
	alphaSpinner.setMaximum(255);
	alphaSpinner.setSelection(127);
	alphaSpinner.addListener(SWT.Selection, new Listener() {
		public void handleEvent(Event event) {
				example.redraw();
		}
	});
	
	// color menu
	ColorMenu cm = new ColorMenu();
	cm.setPatternItems(example.checkAdvancedGraphics());
	menu = cm.createMenu(parent.getParent(), new ColorListener() {
		public void setColor(GraphicsBackground gb) {
			background = gb;		
			colorButton.setImage(gb.getThumbNail());
			example.redraw();
		}
	});

	// initialize the background to the 5th item in the menu (blue)
	background = (GraphicsBackground)menu.getItem(4).getData();
	
	// color button
	comp = new Composite(parent, SWT.NONE);
	comp.setLayout(new GridLayout(2, false));
	
	colorButton = new Button(comp, SWT.PUSH);
	colorButton.setText(GraphicsExample
			.getResourceString("Color")); //$NON-NLS-1$
	colorButton.setImage(background.getThumbNail());
	colorButton.addListener(SWT.Selection, new Listener() { 
		public void handleEvent(Event event) {
			final Button button = (Button) event.widget;
			final Composite parent = button.getParent(); 
			Rectangle bounds = button.getBounds();
			Point point = parent.toDisplay(new Point(bounds.x, bounds.y));
			menu.setLocation(point.x, point.y + bounds.height);
			menu.setVisible(true);
		}
	});
}

public void next(int width, int height) {
	
	angle = (angle+1)%360;
}

public void paint(GC gc, int width, int height) {
	if (!example.checkAdvancedGraphics()) return;
	Device device = gc.getDevice();

	Pattern pattern = null;
	if (background.getBgColor1() != null) {
		gc.setBackground(background.getBgColor1());
	} else if (background.getBgImage() != null) {
		pattern = new Pattern(device, background.getBgImage());
		gc.setBackgroundPattern(pattern);
	}
	
	gc.setAntialias(SWT.ON);
	gc.setAlpha(alphaSpinner.getSelection());
	
	// rotate on center
	Transform transform = new Transform(device);
	transform.translate(width/2, height/2);
	transform.rotate(-angle);
	transform.translate(-width/2, -height/2);
	gc.setTransform(transform);
	transform.dispose();
	
	// choose the smallest between height and width
	int diameter = (height < width) ? height : width;
	
	Path path = new Path(device);
	path.addArc((width-diameter/5)/2, (height-diameter/5)/2, diameter/5, diameter/5, 0, 360);
	path.addArc(5*(width-diameter/8)/12, 4*(height-diameter/8)/12, diameter/8, diameter/8, 0, 360);
	path.addArc(7*(width-diameter/8)/12, 8*(height-diameter/8)/12, diameter/8, diameter/8, 0, 360);
	path.addArc(6*(width-diameter/12)/12, 3*(height-diameter/12)/12, diameter/12, diameter/12, 0, 360);
	path.addArc(6*(width-diameter/12)/12, 9*(height-diameter/12)/12, diameter/12, diameter/12, 0, 360);
	path.addArc(11.5f*(width-diameter/18)/20, 5*(height-diameter/18)/18, diameter/18, diameter/18, 0, 360);	
	path.addArc(8.5f*(width-diameter/18)/20, 13*(height-diameter/18)/18, diameter/18, diameter/18, 0, 360);
	path.addArc(62f*(width-diameter/25)/100, 32*(height-diameter/25)/100, diameter/25, diameter/25, 0, 360);
	path.addArc(39f*(width-diameter/25)/100, 67*(height-diameter/25)/100, diameter/25, diameter/25, 0, 360);
		
	gc.fillPath(path);
	path.dispose();
			
    if (pattern != null) pattern.dispose();
}
}