bundles/org.eclipse.ui.workbench/Eclipse UI/org/eclipse/ui/internal/services/CurrentSelectionSourceProvider.java

/*******************************************************************************
 * Copyright (c) 2005, 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.services;

import java.util.Map;
import java.util.TreeMap;

import org.eclipse.jface.viewers.ISelection;
import org.eclipse.ui.AbstractSourceProvider;
import org.eclipse.ui.INullSelectionListener;
import org.eclipse.ui.ISelectionService;
import org.eclipse.ui.ISources;
import org.eclipse.ui.IWindowListener;
import org.eclipse.ui.IWorkbench;
import org.eclipse.ui.IWorkbenchPart;
import org.eclipse.ui.IWorkbenchWindow;

/**
 * <p>
 * This listens to changes to the current selection, and propagates them through
 * the <code>ISourceProvider</code> framework (a common language in which
 * events are communicated to expression-based services).
 * </p>
 * <p>
 * This class is not intended for use outside of the
 * <code>org.eclipse.ui.workbench</code> plug-in.
 * </p>
 * 
 * @since 3.2
 */
public final class CurrentSelectionSourceProvider extends
		AbstractSourceProvider implements INullSelectionListener {

	/**
	 * The names of the sources supported by this source provider.
	 */
	private static final String[] PROVIDED_SOURCE_NAMES = new String[] { ISources.ACTIVE_CURRENT_SELECTION_NAME };

	/**
	 * Monitors changes to the active workbench window, and swaps the selection
	 * listener to the active workbench window.
	 */
	private final IWindowListener windowListener = new IWindowListener() {
		public final void windowActivated(final IWorkbenchWindow window) {
			swapListeners(window, false);
		}

		public final void windowClosed(final IWorkbenchWindow window) {
			swapListeners(window, true);
		}

		public final void windowDeactivated(final IWorkbenchWindow window) {
			swapListeners(window, true);
		}

		public final void windowOpened(final IWorkbenchWindow window) {
			swapListeners(window, false);
		}
	};

	/**
	 * The workbench on which this source provider is acting. This value is
	 * never <code>null</code>.
	 */
	private final IWorkbench workbench;

	/**
	 * Constructs a new instance of <code>CurrentSelectionSourceProvider</code>.
	 * 
	 * @param workbench
	 *            The workbench on which this source provider should act; this
	 *            value must not be <code>null</code>.
	 */
	public CurrentSelectionSourceProvider(final IWorkbench workbench) {
		this.workbench = workbench;
		workbench.addWindowListener(windowListener);
	}

	public final void dispose() {
		workbench.removeWindowListener(windowListener);
	}

	public final Map getCurrentState() {
		final Map currentState = new TreeMap();
		final IWorkbenchWindow window = workbench.getActiveWorkbenchWindow();
		if (window != null) {
			final ISelectionService service = window.getSelectionService();
			final ISelection selection = service.getSelection();
			currentState.put(ISources.ACTIVE_CURRENT_SELECTION_NAME, selection);
		} else {
			currentState.put(ISources.ACTIVE_CURRENT_SELECTION_NAME, null);
		}
		return currentState;
	}

	public final String[] getProvidedSourceNames() {
		return PROVIDED_SOURCE_NAMES;
	}

	public final void selectionChanged(final IWorkbenchPart part,
			final ISelection selection) {
		if (DEBUG) {
			logDebuggingInfo("Selection changed to " + selection); //$NON-NLS-1$
		}

		fireSourceChanged(ISources.ACTIVE_CURRENT_SELECTION,
				ISources.ACTIVE_CURRENT_SELECTION_NAME, selection);
	}

	/**
	 * Swaps the selection listener. This either adds or removes a selection
	 * listener from the given window's selection service.
	 * 
	 * @param window
	 *            The workbench window to which the listener should be added or
	 *            from which the listener should be removed; must not be
	 *            <code>null</code>.
	 * @param remove
	 *            Whether the selection listener should be removed; otherwise,
	 *            it should be added.
	 */
	private final void swapListeners(final IWorkbenchWindow window,
			final boolean remove) {
		final ISelectionService selectionService = window.getSelectionService();
		if (remove) {
			window.getSelectionService().removeSelectionListener(
					CurrentSelectionSourceProvider.this);
			selectionChanged(null, null);
		} else {
			window.getSelectionService().addSelectionListener(
					CurrentSelectionSourceProvider.this);
			selectionChanged(null, selectionService.getSelection());
		}
	}
}