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/*******************************************************************************
 * Copyright (c) 2000, 2010 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.jface.action;

import org.eclipse.core.runtime.Assert;

import org.eclipse.swt.SWT;
import org.eclipse.swt.custom.CLabel;
import org.eclipse.swt.graphics.FontMetrics;
import org.eclipse.swt.graphics.GC;
import org.eclipse.swt.graphics.Point;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Label;

import org.eclipse.jface.util.Util;

/**
 * A contribution item to be used with status line managers.
 * 
 * This class may be instantiated; it is not intended to be subclassed.
 * 
 * 
 * @since 1.1
 */
public class StatusLineContributionItem extends ContributionItem {

	private final static int DEFAULT_CHAR_WIDTH = 40;
	
	/**
	 * A constant indicating that the contribution should compute its actual 
	 * size depending on the text. It will grab all space necessary to display 
	 * the whole text.
	 *
	 * @since 1.3
	 */
	public final static int CALC_TRUE_WIDTH = -1;

	private int charWidth;

	private CLabel label;

	/**
	 * The composite into which this contribution item has been placed. This
	 * will be null if this instance has not yet been
	 * initialized.
	 */
	private Composite statusLine = null;

	private String text = Util.ZERO_LENGTH_STRING;

	private int widthHint = -1;

	private int heightHint = -1;

	/**
	 * Creates a status line contribution item with the given id.
	 * 
	 * @param id
	 *            the contribution item's id, or null if it is to
	 *            have no id
	 */
	public StatusLineContributionItem(String id) {
		this(id, DEFAULT_CHAR_WIDTH);
	}

	/**
	 * Creates a status line contribution item with the given id that displays
	 * the given number of characters.
	 * 
	 * @param id
	 *            the contribution item's id, or null if it is to
	 *            have no id
	 * @param charWidth
	 *            the number of characters to display. If the value is
	 *            CALC_TRUE_WIDTH then the contribution will compute the
	 *            preferred size exactly. Otherwise the size will be based on the
	 *            average character size * 'charWidth'
	 */
	public StatusLineContributionItem(String id, int charWidth) {
		super(id);
		this.charWidth = charWidth;
		setVisible(false); // no text to start with
	}

	public void fill(Composite parent) {
		statusLine = parent;

		Label sep = new Label(parent, SWT.SEPARATOR);
		label = new CLabel(statusLine, SWT.SHADOW_NONE);
		label.setText(text);		
		
		if (charWidth == CALC_TRUE_WIDTH) {
			// compute the size of the label to get the width hint for the contribution
			Point preferredSize = label.computeSize(SWT.DEFAULT, SWT.DEFAULT);
			widthHint = preferredSize.x;
			heightHint = preferredSize.y;
		} else if (widthHint < 0) {
			// Compute the size base on 'charWidth' average char widths
			GC gc = new GC(statusLine);
			gc.setFont(statusLine.getFont());
			FontMetrics fm = gc.getFontMetrics();
			widthHint = fm.getAverageCharWidth() * charWidth;
			heightHint = fm.getHeight();
			gc.dispose();
		}

		StatusLineLayoutData data = new StatusLineLayoutData();
		data.widthHint = widthHint;
		label.setLayoutData(data);

		data = new StatusLineLayoutData();
		data.heightHint = heightHint;
		sep.setLayoutData(data);
	}

	/**
	 * An accessor for the current location of this status line contribution
	 * item -- relative to the display.
	 * 
	 * @return The current location of this status line; null if
	 *         not yet initialized.
	 */
	public Point getDisplayLocation() {
		if ((label != null) && (statusLine != null)) {
			return statusLine.toDisplay(label.getLocation());
		}

		return null;
	}

	/**
	 * Retrieves the text that is being displayed in the status line.
	 * 
	 * @return the text that is currently being displayed
	 */
	public String getText() {
		return text;
	}

	/**
	 * Sets the text to be displayed in the status line.
	 * 
	 * @param text
	 *            the text to be displayed, must not be null
	 */
	public void setText(String text) {
		Assert.isNotNull(text);

		this.text = LegacyActionTools.escapeMnemonics(text);

		if (label != null && !label.isDisposed()) {
			label.setText(this.text);
		}

		if (this.text.length() == 0) {
			if (isVisible()) {
				setVisible(false);
				IContributionManager contributionManager = getParent();

				if (contributionManager != null) {
					contributionManager.update(true);
				}
			}
		} else {
			// Always update if using 'CALC_TRUE_WIDTH'
			if (!isVisible() || charWidth == CALC_TRUE_WIDTH) {
				setVisible(true);
				IContributionManager contributionManager = getParent();

				if (contributionManager != null) {
					contributionManager.update(true);
				}
			}
		}
	}
}