/*******************************************************************************
 * Copyright (c) 2004 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials 
 * are made available under the terms of the Common Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/cpl-v10.html
 * 
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.ui.cheatsheets;

import org.eclipse.swt.widgets.Composite;

/**
 * Base class for adding controls to cheat sheet items.
 * <p>
 * Subclasses are used in conjunction with the
 * <code>org.eclipse.ui.cheatsheet.cheatSheetItemExtension</code> extension
 * point. Subclasses must be public and have a public 1-arg constructor 
 * that takes the name of the attribute type <code>String</code>. The
 * extension point specifies the name of the subclass and the name of the XML
 * attribute that it can handle. When the cheat sheet framework encounters an
 * item (or subitem) element in the cheat sheet content file with an attribute
 * with a matching name, an instance of the corresponding item extension subclass
 * is created. It is up to this instance to remember the attribute value if
 * required. Later, when creating the visual controls for the item
 * are being created, the instance is given the opportunity to add extra controls.
 * </p>
 * 
 * @since 3.0
 */
public abstract class AbstractItemExtensionElement {
	
	/**
	 * Name of the XML attribute that this item extension handles.
	 */
	private String attributeName;
	
	/**
	 * Creates a new item element extension for handling the
	 * XML attributes of the given name.
	 * 
	 * @param attributeName the name of the attribute that this item extension handles
	 * @exception IllegalArgumentException if <code>attributeName</code>
	 * is <code>null</code>
	 */
	public AbstractItemExtensionElement(String attributeName) {
		if (attributeName == null) {
			throw new IllegalArgumentException();
		}
		this.attributeName = attributeName;
	}

	/**
	 * Returns the name of the XML attribute that this item extension handles.
	 * 
	 * @return the name of the attribute that this item extension handles
	 */
	public final String getAttributeName() {
		return this.attributeName;
	}
	
	/**
	 * Called by the cheat sheet framework to parse and extract information
	 * from the string value of the XML attribute.
	 * 
	 * @param attributeValue the attribute value specified in the cheat sheet
	 * content file
	 */
	public abstract void handleAttribute(String attributeValue);

	/**
	 * Called by the cheat sheet framework when creating the visual
	 * representation of a step. This method should add a small button
	 * (suggested size 16x16 pixels) to the given composite to decorate the step.
	 * <p>
	 * Important note: In some presentations of the cheatsheet, the color of the
	 * background is varied to emphasize the current step. Because of this, it is
	 * important to always use the background color of the composite
	 * (<code>composite.getBackground()</code>) as the background color for any
	 * additional controls; otherwise the new controls will not match their
	 * surrounding.
	 * </p>
	 * 
	 * @param composite the composite to add extra controls to
	 */
	public abstract void createControl(Composite composite);

	/**
	 * Called by the cheat sheet framework to dispose of this item element extension.
	 * <p>
	 * This is the last method called on the <code>AbstractItemExtensionElement</code>.
	 * At this point the controls (if they were ever created) have been disposed as part 
	 * of an SWT composite.  There is no guarantee that createControl() has been called,
	 * so the controls may never have been created.
	 * </p>
	 * <p>
	 * Within this method an item element extension may release any resources, fonts,
	 * images, etc.&nbsp; held by this part.  It is also very important to deregister
	 * all listeners.
	 * </p>
	 * <p>
	 * Clients should not call this method (the cheat sheet framework calls this method
	 * at appropriate times).
	 * </p>
	 */
	public abstract void dispose();
}
