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This plug-in contains the bulk of the Workbench implementation, and depends on JFace, SWT, and Core Runtime. It cannot be used independently from org.eclipse.ui. Workbench client plug-ins should not depend directly on this plug-in.
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/*******************************************************************************
 * Copyright (c) 2000, 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.ui.internal;

import org.eclipse.core.runtime.Assert;
import org.eclipse.core.runtime.IConfigurationElement;
import org.eclipse.jface.action.IMenuManager;
import org.eclipse.jface.action.IToolBarManager;
import org.eclipse.jface.viewers.ISelection;
import org.eclipse.jface.viewers.ISelectionChangedListener;
import org.eclipse.jface.viewers.ISelectionProvider;
import org.eclipse.jface.viewers.IStructuredSelection;
import org.eclipse.jface.viewers.SelectionChangedEvent;
import org.eclipse.ui.IEditorPart;
import org.eclipse.ui.IViewPart;
import org.eclipse.ui.IWorkbenchPart;
import org.eclipse.ui.internal.registry.IWorkbenchRegistryConstants;

/**
 * This class reads the registry for extensions that plug into
 * 'popupMenus' extension point and deals only with the 'viewerContribution'
 * elements.
 */
public class ViewerActionBuilder extends PluginActionBuilder {
    

    private ISelectionProvider provider;

    private IWorkbenchPart part;

    /**
     * Basic contstructor
     */
    public ViewerActionBuilder() {
    }

    /* (non-Javadoc)
     * Method declared on PluginActionBuilder.
     */
    protected ActionDescriptor createActionDescriptor(
            IConfigurationElement element) {
        if (part instanceof IViewPart) {
			return new ActionDescriptor(element, ActionDescriptor.T_VIEW, part);
		}
		return new ActionDescriptor(element, ActionDescriptor.T_EDITOR, part);
    }

    /* (non-Javadoc)
     * Method declared on PluginActionBuilder.
     */
    protected BasicContribution createContribution() {
        return new ViewerContribution(provider);
    }

    /**
     * Dispose of the action builder
     */
    public void dispose() {
        if (cache != null) {
            for (int i = 0; i < cache.size(); i++) {
                ((BasicContribution) cache.get(i)).dispose();
            }
            cache = null;
        }
    }

    /* (non-Javadoc)
     * Method declared on PluginActionBuilder.
     */
    protected boolean readElement(IConfigurationElement element) {
        String tag = element.getName();

        // Found visibility sub-element
        if (currentContribution != null && tag.equals(IWorkbenchRegistryConstants.TAG_VISIBILITY)) {
            ((ViewerContribution) currentContribution)
                    .setVisibilityTest(element);
            return true;
        }

        return super.readElement(element);
    }

    /**
     * Reads the contributions for a viewer menu.
     * This method is typically used in conjunction with contribute to read
     * and then insert actions for a particular viewer menu.
     *
     * @param id the menu id
     * @param prov the selection provider for the control containing the menu
     * @param part the part containing the menu.
     * @return true if 1 or more items were read.  
     */
    public boolean readViewerContributions(String id, ISelectionProvider prov,
            IWorkbenchPart part) {
		Assert.isTrue(part instanceof IViewPart || part instanceof IEditorPart);
        provider = prov;
        this.part = part;
        readContributions(id, IWorkbenchRegistryConstants.TAG_VIEWER_CONTRIBUTION,
                IWorkbenchRegistryConstants.PL_POPUP_MENU);
        return (cache != null);
    }

    /**
     * Helper class to collect the menus and actions defined within a
     * contribution element.
     */
    private static class ViewerContribution extends BasicContribution implements ISelectionChangedListener {
        private ISelectionProvider selProvider;

        private ActionExpression visibilityTest;

        /**
         * Create a new ViewerContribution.
         * 
         * @param selProvider the selection provider
         */
        public ViewerContribution(ISelectionProvider selProvider) {
            super();
            this.selProvider = selProvider;
			if (selProvider != null) {
				selProvider.addSelectionChangedListener(this);
			}
        }

        /**
         * Set the visibility test.
         * 
         * @param element the element
         */
        public void setVisibilityTest(IConfigurationElement element) {
            visibilityTest = new ActionExpression(element);
        }

        /* (non-Javadoc)
         * Method declared on BasicContribution.
         */
        public void contribute(IMenuManager menu, boolean menuAppendIfMissing,
                IToolBarManager toolbar, boolean toolAppendIfMissing) {
            boolean visible = true;

            if (visibilityTest != null) {
                ISelection selection = selProvider.getSelection();
                if (selection instanceof IStructuredSelection) {
                    visible = visibilityTest
                            .isEnabledFor((IStructuredSelection) selection);
                } else {
                    visible = visibilityTest.isEnabledFor(selection);
                }
            }

            if (visible) {
				super.contribute(menu, menuAppendIfMissing, toolbar,
                        toolAppendIfMissing);
			}
        }
		
		/* (non-Javadoc)
		 * @see org.eclipse.ui.internal.PluginActionBuilder.BasicContribution#dispose()
		 */
		public void dispose() {
			if (selProvider != null) {
				selProvider.removeSelectionChangedListener(this);
			}
			disposeActions();
			super.dispose();
		}

		/**
		 * Rather than hooking up each action as a selection listener,
		 * the contribution itself is added, and propagates
		 * the selection changed notification to all actions.
		 * This simplifies cleanup, in addition to potentially reducing the number of listeners.
		 * 
		 * @see ISelectionChangedListener
		 * @since 3.1
		 */
		public void selectionChanged(SelectionChangedEvent event) {
			if (actions != null) {
				if (actions != null) {
					for (int i = 0; i < actions.size(); i++) {
						PluginAction proxy = ((ActionDescriptor) actions.get(i))
								.getAction();
						proxy.selectionChanged(event);
					}
				}
			}
		}
    }

}