bundles/org.eclipse.ui.workbench/Eclipse UI/org/eclipse/ui/internal/registry/CapabilityRegistryReader.java

package org.eclipse.ui.internal.registry;
 
/**********************************************************************
Copyright (c) 2002 IBM Corp. and others.
All rights reserved.   This program and the accompanying materials
are made available under the terms of the Common Public License v0.5
which accompanies this distribution, and is available at
http://www.eclipse.org/legal/cpl-v05.html
 
Contributors:
**********************************************************************/
import org.eclipse.core.runtime.IConfigurationElement;
import org.eclipse.core.runtime.IPluginRegistry;
import org.eclipse.ui.PlatformUI;
import org.eclipse.ui.WorkbenchException;
import org.eclipse.ui.internal.IWorkbenchConstants;
import org.eclipse.ui.internal.WorkbenchPlugin;

/**
 * This class is used to read project capabilities and capability
 * categories from the platform's plugin registry and store the results in
 * a capability registry.
 */
public class CapabilityRegistryReader extends RegistryReader{	
	private static final String TAG_CAPABILITY = "capability"; //$NON-NLS-1$
	private static final String TAG_CATEGORY = "category"; //$NON-NLS-1$
	private static final String TAG_HANDLE_UI = "handleUI"; //$NON-NLS-1$
	private static final String TAG_PERSPECTIVE_CHOICE = "perspectiveChoice"; //$NON-NLS-1$
	
	private static final String ATT_ID = "id"; //$NON-NLS-1$
	
	private CapabilityRegistry capabilityRegistry;
	private Capability currentCapability;
	
	/**
	 * Reads an element of the plugin registry and adds it to the capability
	 * registry if it is a capability or category (or a handleUI element, a
	 * child of a capability. A handleUI element represents another capability
	 * for which this capability controls the user interface).
	 */
	protected boolean readElement(IConfigurationElement element) {
		String name = element.getName();
		if (name.equals(TAG_CAPABILITY))
			return readCapability(element);
		if (name.equals(TAG_CATEGORY))
			return readCategory(element);
		if (name.equals(TAG_HANDLE_UI))
			return readHandleUI(element);
		if (name.equals(TAG_PERSPECTIVE_CHOICE))
			return readPerspectiveChoice(element);
		return false;
	}
	
	/**
	 * Reads a capability and adds it to the capability registry. Reads all
	 * children elements (which will be handleUI elements) as well and adds
	 * them to the capability.
	 */
	private boolean readCapability(IConfigurationElement element) {
		try {
			Capability capability = new Capability(element, this);
			capabilityRegistry.addCapability(capability);
			currentCapability = capability;
			readElementChildren(element);
			currentCapability = null;
			return true;
		} catch(WorkbenchException e) {
			currentCapability = null;
			return false;
		}
	}

	/**
	 * Reads a capability category and adds it to the capability registry.
	 */
	private boolean readCategory(IConfigurationElement element) {
		try {
			Category category = new Category(element);
			capabilityRegistry.addCategory(category);
		} catch (WorkbenchException e) {
			// log an error since its not safe to show a dialog here
			WorkbenchPlugin.log("Unable to create capability category. ", e.getStatus()); //$NON-NLS-1$
		}
		return true;		
	}
	
	/**
	 * Reads handleUI elements. These elements contain the ids of other
	 * capabilities. The capability that is the parent of the handleUI element
	 * controls the user interface for the capabilities whose ids are stored
	 * in the handleUI element.
	 */
	private boolean readHandleUI(IConfigurationElement element) {
		String capabilityId = element.getAttribute(ATT_ID);
		
		if (capabilityId == null) {
			logMissingAttribute(element, ATT_ID);
		}
		
		if (currentCapability != null)
			currentCapability.addHandleUI(capabilityId);		
		return true;	
	}
	
	/**
	 * Reads perspectiveChoice elements. These elements contain the ids of
	 * perspectives.
	 */
	private boolean readPerspectiveChoice(IConfigurationElement element) {
		String perspId = element.getAttribute(ATT_ID);
		
		if (perspId == null) {
			logMissingAttribute(element, ATT_ID);
		}
		
		if (currentCapability != null)
			currentCapability.addPerspectiveChoice(perspId);		
		return true;	
	}
	
	/**
	 * Reads project capabilities and capability categories from the provided
	 * plugin registry and stores them in the provided capability registry.
	 */
	public void read(IPluginRegistry registry, CapabilityRegistry out) {
		capabilityRegistry = out;
		readRegistry(registry, PlatformUI.PLUGIN_ID, IWorkbenchConstants.PL_CAPABILITIES);
	}
}