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/*******************************************************************************
 * Copyright (c) 2000, 2013 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.jface.util.Policy;
import org.eclipse.swt.SWT;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Control;
import org.eclipse.swt.widgets.Menu;
import org.eclipse.swt.widgets.ToolBar;
import org.eclipse.swt.widgets.ToolItem;

/**
 * An abstract contribution item implementation for adding an arbitrary 
 * SWT control to a tool bar. 
 * Note, however, that these items cannot be contributed to menu bars.
 * 
 * The createControl framework method must be implemented
 * by concrete subclasses.
 * 
 */
public abstract class ControlContribution extends ContributionItem {
    /**
     * Creates a control contribution item with the given id.
     *
     * @param id the contribution item id
     */
    protected ControlContribution(String id) {
        super(id);
    }

    /**
     * Computes the width of the given control which is being added
     * to a tool bar.  This is needed to determine the width of the tool bar item
     * containing the given control.
     * 
     * The default implementation of this framework method returns 
     * control.computeSize(SWT.DEFAULT, SWT.DEFAULT, true).x.
     * Subclasses may override if required.
     * 
     *
     * @param control the control being added
     * @return the width of the control
     */
    protected int computeWidth(Control control) {
        return control.computeSize(SWT.DEFAULT, SWT.DEFAULT, true).x;
    }

    /**
     * Creates and returns the control for this contribution item
     * under the given parent composite.
     * 
     * This framework method must be implemented by concrete
     * subclasses.
     * 
     *
     * @param parent the parent composite
     * @return the new control, must not be null
     */
    protected abstract Control createControl(Composite parent);

    /**
     * The control item implementation of this IContributionItem
     * method calls the createControl framework method.
     * Subclasses must implement createControl rather than
     * overriding this method.
     */
    @Override
	public final void fill(Composite parent) {
        createControl(parent);
    }

    /**
     * The control item implementation of this IContributionItem
     * method throws an exception since controls cannot be added to menus.
     */
    @Override
	public final void fill(Menu parent, int index) {
        Assert.isTrue(false, "Can't add a control to a menu");//$NON-NLS-1$
    }

    /**
     * The control item implementation of this IContributionItem
     * method calls the createControl framework method to
     * create a control under the given parent, and then creates
     * a new tool item to hold it.
     * Subclasses must implement createControl rather than
     * overriding this method.
     */
    @Override
	public final void fill(ToolBar parent, int index) {
        Control control = createControl(parent);
		if (control == null) {
			Policy.logException(new IllegalStateException(
					"createControl(Composite) of " + getClass() //$NON-NLS-1$
							+ " returned null, cannot fill toolbar")); //$NON-NLS-1$
		} else {
			ToolItem ti = new ToolItem(parent, SWT.SEPARATOR, index);
			ti.setControl(control);
			ti.setWidth(computeWidth(control));
		}
    }
}