/*******************************************************************************
 * Copyright (c) 2000, 2015 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.ui;

/**
 * A part service tracks the creation and activation of parts within a workbench
 * page.
 * <p>
 * This service can be acquired from your service locator:
 * </p>
 *
 * <pre>
 * IPartService service = (IPartService) getSite().getService(IPartService.class);
 * </pre>
 *
 * This service is not available globally, only from the workbench window level
 * down.
 *
 * @see IWorkbenchPage
 * @see org.eclipse.ui.services.IServiceLocator#getService(Class)
 * @noimplement This interface is not intended to be implemented by clients.
 */
public interface IPartService {

	/**
	 * Adds the given listener for part lifecycle events. Has no effect if an
	 * identical listener is already registered.
	 * <p>
	 * <b>Note:</b> listeners should be removed when no longer necessary. If not,
	 * they will be removed when the IServiceLocator used to acquire this service is
	 * disposed.
	 * </p>
	 *
	 * @param listener a part listener
	 * @see #removePartListener(IPartListener)
	 */
	void addPartListener(IPartListener listener);

	/**
	 * Adds the given listener for part lifecycle events. Has no effect if an
	 * identical listener is already registered.
	 * <p>
	 * As of 3.5, the IPartListener2 can also implement IPageChangedListener to be
	 * notified about any parts that implement IPageChangeProvider and post
	 * PageChangedEvents.
	 * </p>
	 * <p>
	 * <b>Note:</b> listeners should be removed when no longer necessary. If not,
	 * they will be removed when the IServiceLocator used to acquire this service is
	 * disposed.
	 * </p>
	 *
	 * @param listener a part listener
	 * @see #removePartListener(IPartListener2)
	 * @see org.eclipse.jface.dialogs.IPageChangeProvider
	 * @see org.eclipse.jface.dialogs.IPageChangedListener
	 */
	void addPartListener(IPartListener2 listener);

	/**
	 * Returns the active part.
	 *
	 * @return the active part, or <code>null</code> if no part is currently active
	 */
	IWorkbenchPart getActivePart();

	/**
	 * Returns the active part reference.
	 *
	 * @return the active part reference, or <code>null</code> if no part is
	 *         currently active
	 */
	IWorkbenchPartReference getActivePartReference();

	/**
	 * Removes the given part listener. Has no effect if an identical listener is
	 * not registered.
	 *
	 * @param listener a part listener
	 */
	void removePartListener(IPartListener listener);

	/**
	 * Removes the given part listener. Has no effect if an identical listener is
	 * not registered.
	 *
	 * @param listener a part listener
	 */
	void removePartListener(IPartListener2 listener);
}
