StackLayout.java

/*******************************************************************************
 * Copyright (c) 2000, 2011 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.custom;


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

/**
 * This Layout stacks all the controls one on top of the other and resizes all controls
 * to have the same size and location.
 * The control specified in topControl is visible and all other controls are not visible.
 * Users must set the topControl value to flip between the visible items and then call 
 * layout() on the composite which has the StackLayout.
 * 
 * <p> Here is an example which places ten buttons in a stack layout and 
 * flips between them:
 * 
 * <pre><code>
 * 	public static void main(String[] args) {
 * 		Display display = new Display();
 * 		Shell shell = new Shell(display);
 * 		shell.setLayout(new GridLayout());
 * 	
 * 		final Composite parent = new Composite(shell, SWT.NONE);
 * 		parent.setLayoutData(new GridData(GridData.FILL_BOTH));
 * 		final StackLayout layout = new StackLayout();
 * 		parent.setLayout(layout);
 * 		final Button[] bArray = new Button[10];
 * 		for (int i = 0; i < 10; i++) {
 * 			bArray[i] = new Button(parent, SWT.PUSH);
 * 			bArray[i].setText("Button "+i);
 * 		}
 * 		layout.topControl = bArray[0];
 * 	
 * 		Button b = new Button(shell, SWT.PUSH);
 * 		b.setText("Show Next Button");
 * 		final int[] index = new int[1];
 * 		b.addListener(SWT.Selection, new Listener(){
 * 			public void handleEvent(Event e) {
 * 				index[0] = (index[0] + 1) % 10;
 * 				layout.topControl = bArray[index[0]];
 * 				parent.layout();
 * 			}
 * 		});
 * 	
 * 		shell.open();
 * 		while (shell != null && !shell.isDisposed()) {
 * 			if (!display.readAndDispatch())
 * 				display.sleep(); 
 * 		} 	
 * 	}
 * </code></pre>
 *
 * @see <a href="http://www.eclipse.org/swt/snippets/#stacklayout">StackLayout snippets</a>
 * @see <a href="http://www.eclipse.org/swt/examples.php">SWT Example: LayoutExample</a>
 * @see <a href="http://www.eclipse.org/swt/">Sample code and further information</a>
 */

public class StackLayout extends Layout {
	
 	/**
	 * marginWidth specifies the number of pixels of horizontal margin
	 * that will be placed along the left and right edges of the layout.
	 *
	 * The default value is 0.
	 */
 	public int marginWidth = 0;
	/**
	 * marginHeight specifies the number of pixels of vertical margin
	 * that will be placed along the top and bottom edges of the layout.
	 *
	 * The default value is 0.
	 */
	public int marginHeight = 0;

 	/**
 	 * topControl the Control that is displayed at the top of the stack.
 	 * All other controls that are children of the parent composite will not be visible.
 	 */
 	public Control topControl;

@Override
protected Point computeSize(Composite composite, int wHint, int hHint, boolean flushCache) {
	Control children[] = composite.getChildren();
	int maxWidth = 0;
	int maxHeight = 0;
	for (int i = 0; i < children.length; i++) {
		Point size = children[i].computeSize(wHint, hHint, flushCache);
		maxWidth = Math.max(size.x, maxWidth);
		maxHeight = Math.max(size.y, maxHeight);
	}
	int width = maxWidth + 2 * marginWidth;
	int height = maxHeight + 2 * marginHeight;
	if (wHint != SWT.DEFAULT) width = wHint;
	if (hHint != SWT.DEFAULT) height = hHint;
	return new Point(width, height);
}

@Override
protected boolean flushCache(Control control) {
	return true;
}

@Override
protected void layout(Composite composite, boolean flushCache) {
	Control children[] = composite.getChildren();
	Rectangle rect = composite.getClientArea();
	rect.x += marginWidth;
	rect.y += marginHeight;
	rect.width -= 2 * marginWidth;
	rect.height -= 2 * marginHeight;
	for (int i = 0; i < children.length; i++) {
		children[i].setBounds(rect);
		children[i].setVisible(children[i] == topControl);
	}
}

String getName () {
	String string = getClass ().getName ();
	int index = string.lastIndexOf ('.');
	if (index == -1) return string;
	return string.substring (index + 1, string.length ());
}

/**
 * Returns a string containing a concise, human-readable
 * description of the receiver.
 *
 * @return a string representation of the layout
 */
@Override
public String toString () {
 	String string = getName ()+" {";
 	if (marginWidth != 0) string += "marginWidth="+marginWidth+" ";
 	if (marginHeight != 0) string += "marginHeight="+marginHeight+" ";
 	if (topControl != null) string += "topControl="+topControl+" ";
 	string = string.trim();
 	string += "}";
 	return string;
}
}