ecommons/org.eclipse.statet.ecommons.uimisc/src/org/eclipse/statet/ecommons/ui/mpbv/ManagedPageBookView.java - gerrit/statet/org.eclipse.statet-commons - Git at Google

 /*=============================================================================#
  # Copyright (c) 2009, 2021 Stephan Wahlbrink and others.
  #
  # This program and the accompanying materials are made available under the
  # terms of the Eclipse Public License 2.0 which is available at
  # https://www.eclipse.org/legal/epl-2.0, or the Apache License, Version 2.0
  # which is available at https://www.apache.org/licenses/LICENSE-2.0.
  #
  # SPDX-License-Identifier: EPL-2.0 OR Apache-2.0
  #
  # Contributors:
  #     Stephan Wahlbrink <sw@wahlbrink.eu> - initial API and implementation
  #=============================================================================*/

 package org.eclipse.statet.ecommons.ui.mpbv;

 import static org.eclipse.statet.ecommons.ui.actions.UIActions.ADDITIONS_GROUP_ID;

 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.Comparator;
 import java.util.HashMap;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;

 import org.eclipse.core.commands.AbstractHandler;
 import org.eclipse.core.commands.ExecutionEvent;
 import org.eclipse.core.commands.ExecutionException;
 import org.eclipse.core.commands.IHandler2;
 import org.eclipse.e4.core.contexts.IEclipseContext;
 import org.eclipse.jface.action.IMenuManager;
 import org.eclipse.jface.action.IToolBarManager;
 import org.eclipse.jface.action.Separator;
 import org.eclipse.jface.resource.ImageDescriptor;
 import org.eclipse.swt.graphics.Image;
 import org.eclipse.swt.widgets.Composite;
 import org.eclipse.ui.IActionBars;
 import org.eclipse.ui.IPropertyListener;
 import org.eclipse.ui.IViewSite;
 import org.eclipse.ui.IWorkbenchPart;
 import org.eclipse.ui.IWorkbenchPartSite;
 import org.eclipse.ui.PartInitException;
 import org.eclipse.ui.handlers.IHandlerService;
 import org.eclipse.ui.internal.WorkbenchPlugin;
 import org.eclipse.ui.menus.CommandContributionItemParameter;
 import org.eclipse.ui.part.IPage;
 import org.eclipse.ui.part.IPageBookViewPage;
 import org.eclipse.ui.part.MessagePage;
 import org.eclipse.ui.part.PageBook;
 import org.eclipse.ui.part.PageBookView;
 import org.eclipse.ui.part.PageSite;
 import org.eclipse.ui.part.PageSwitcher;
 import org.eclipse.ui.services.IServiceLocator;

 import org.eclipse.statet.jcommons.collections.ImCollections;
 import org.eclipse.statet.jcommons.collections.ImList;
 import org.eclipse.statet.jcommons.lang.NonNull;
 import org.eclipse.statet.jcommons.lang.NonNullByDefault;
 import org.eclipse.statet.jcommons.lang.Nullable;

 import org.eclipse.statet.ecommons.ui.SharedUIResources;
 import org.eclipse.statet.ecommons.ui.actions.HandlerCollection;
 import org.eclipse.statet.ecommons.ui.actions.HandlerContributionItem;
 import org.eclipse.statet.ecommons.ui.actions.SimpleContributionItem;
 import org.eclipse.statet.ecommons.ui.util.StatusLineMessageManager;
 import org.eclipse.statet.ecommons.ui.workbench.ContextHandlers;


 @NonNullByDefault
 public abstract class ManagedPageBookView<S extends PageBookSession> extends PageBookView {


 	protected static final String PAGE_CONTROL_MENU_ID= "page_control"; //$NON-NLS-1$


 	private class SessionHandler implements IWorkbenchPart {


 		private final S session;


 		public SessionHandler(final S session) {
 			this.session= session;
 		}


 		ManagedPageBookView<S> getView() {
 			return ManagedPageBookView.this;
 		}

 		@Override
 		public IWorkbenchPartSite getSite() {
 			return ManagedPageBookView.this.getSite();
 		}

 		public S getSession() {
 			return this.session;
 		}


 		@Override
 		public String getTitle() {
 			return ""; //$NON-NLS-1$
 		}

 		@Override
 		public @Nullable Image getTitleImage() {
 			return null;
 		}

 		@Override
 		public String getTitleToolTip() {
 			return ""; //$NON-NLS-1$
 		}

 		@Override
 		public void addPropertyListener(final IPropertyListener listener) {
 		}

 		@Override
 		public void removePropertyListener(final IPropertyListener listener) {
 		}

 		@Override
 		public void createPartControl(final Composite parent) {
 		}

 		@Override
 		public void setFocus() {
 		}

 		@Override
 		public void dispose() {
 		}

 		@Override
 		public <T> @Nullable T getAdapter(final Class<T> adapterType) {
 			return null;
 		}

 		@Override
 		public int hashCode() {
 			return this.session.hashCode();
 		}

 		@Override
 		public boolean equals(final @Nullable Object obj) {
 			return (this == obj
 					|| ((obj instanceof ManagedPageBookView<?>.SessionHandler)
 							&& (this.session == ((SessionHandler) obj).session) ));
 		}

 	}

 	private class NewPageHandler extends AbstractHandler {

 		public NewPageHandler() {
 		}

 		@Override
 		public void setEnabled(final @Nullable Object evaluationContext) {
 		}

 		@Override
 		public @Nullable Object execute(final ExecutionEvent event) throws ExecutionException {
 			newPage(null, true);
 			return null;
 		}

 	}

 	private class CloseCurrentPageHandler extends AbstractHandler {

 		public CloseCurrentPageHandler() {
 		}

 		@Override
 		public void setEnabled(final @Nullable Object evaluationContext) {
 			setBaseEnabled(!ManagedPageBookView.this.sessionList.isEmpty());
 		}

 		@Override
 		public @Nullable Object execute(final ExecutionEvent event) throws ExecutionException {
 			final S session= getCurrentSession();
 			if (session != null) {
 				closePage(session);
 			}
 			return null;
 		}

 	}

 	public class CloseAllPagesHandler extends AbstractHandler {


 		@Override
 		public void setEnabled(final @Nullable Object evaluationContext) {
 			setBaseEnabled(!ManagedPageBookView.this.sessionList.isEmpty());
 		}

 		@Override
 		public @Nullable Object execute(final ExecutionEvent event) throws ExecutionException {
 			ManagedPageBookView.this.sessionHistory.clear();
 			final List<S> sessions= getSessions();
 			for (final S session : sessions) {
 				closePage(session);
 			}
 			return null;
 		}

 	}


 	private final List<@NonNull S> sessionList= new ArrayList<>();
 	private final Map<S, SessionHandler> sessionMap= new HashMap<>();
 	private Comparator<S> sessionComparator;

 	private final List<S> sessionHistory= new LinkedList<>();

 	private @Nullable SessionHandler activeSession;

 	private ContextHandlers handlers;

 	private StatusLineMessageManager statusManager;


 	public ManagedPageBookView() {
 	}


 	protected void setSessionComparator(final Comparator<S> comparator) {
 		this.sessionComparator= comparator;
 	}

 	@Override
 	protected boolean isImportant(final IWorkbenchPart part) {
 		return ( (part instanceof ManagedPageBookView<?>.SessionHandler)
 				&& ((ManagedPageBookView<?>.SessionHandler) part).getView() == this );
 	}

 	@Override
 	protected @Nullable IWorkbenchPart getBootstrapPart() {
 		return null;
 	}

 	@Override
 	protected void initPage(final IPageBookViewPage page) {
 		// E-Bug 473941
 		try {
 			page.init(new PageSite(getViewSite()) {
 				@Override
 				public void activate() {
 					super.activate();

 					final IEclipseContext context= getService(IEclipseContext.class);
 					if (context != null) {
 						context.activate();
 					}
 				}
 				@Override
 				public void deactivate() {
 					super.deactivate();

 					final IEclipseContext context= getService(IEclipseContext.class);
 					if (context != null) {
 						context.deactivate();
 					}
 				}
 			});
 		}
 		catch (final PartInitException e) {
 			WorkbenchPlugin.log(getClass(), "initPage", e); //$NON-NLS-1$
 		}
 	}

 	@Override
 	public void createPartControl(final Composite parent) {
 		super.createPartControl(parent);

 		final IViewSite site= getViewSite();
 		this.statusManager= new StatusLineMessageManager(site.getActionBars().getStatusLineManager());
 		initActions(site,
 				this.handlers= new ContextHandlers(site.getService(IHandlerService.class)) );
 		initPageSwitcher();
 		contributeToActionBars(site, site.getActionBars(), this.handlers);

 		updateState();
 	}

 	@Override
 	protected IPage createDefaultPage(final PageBook book) {
 		final MessagePage page= new MessagePage();
 		page.createControl(getPageBook());
 		initPage(page);
 		return page;
 	}

 	@Override
 	protected @Nullable PageRec doCreatePage(final IWorkbenchPart part) {
 		final SessionHandler sessionHandler= (SessionHandler) part;
 		final S session= sessionHandler.getSession();

 		final IPageBookViewPage page= doCreatePage(session);
 		if (page != null) {
 			initPage(page);
 			page.createControl(getPageBook());

 			final PageRec pageRecord= new PageRec(part, page);
 			return pageRecord;
 		}
 		return null;
 	}

 	protected /* abstract */ @Nullable IPageBookViewPage doCreatePage(final S session) {
 		throw new UnsupportedOperationException();
 	}

 	@Override
 	protected void showPageRec(final PageRec pageRec) {
 		if ((this.activeSession != null) ? (pageRec.part != this.activeSession) : (pageRec.part != null)) {
 			onPageHiding((IPageBookViewPage) getCurrentPage(), (this.activeSession != null) ? this.activeSession.getSession() : null);
 			this.activeSession= null;

 			super.showPageRec(pageRec);

 			this.activeSession= (SessionHandler) pageRec.part;

 			final S session;
 			if (this.activeSession != null) {
 				session= this.activeSession.getSession();
 				this.sessionHistory.remove(session);
 				this.sessionHistory.add(0, session);
 			}
 			else {
 				session= null;
 			}
 			onPageShowing((IPageBookViewPage) pageRec.page, session);
 		}
 		updateTitle();
 	}

 	protected void updateTitle() {
 		final @Nullable S session= getCurrentSession();
 		if (session == null) {
 			setContentDescription(getNoPageTitle());
 		}
 		else {
 			setContentDescription(session.getLabel());
 		}
 	}

 	protected String getNoPageTitle() {
 		return "No page at this time.";
 	}

 	@Override
 	public void partClosed(final IWorkbenchPart part) {
 		if (part instanceof ManagedPageBookView<?>.SessionHandler) {
 			final SessionHandler sessionHandler= (SessionHandler) part;
 			final S session= sessionHandler.getSession();

 			this.sessionList.remove(session);
 			this.sessionHistory.remove(session);

 			if (this.activeSession == part) {
 				if (!this.sessionHistory.isEmpty()) {
 					showPage(this.sessionHistory.get(0));
 				}
 				else if (!this.sessionList.isEmpty()) {
 					showPage(this.sessionList.get(this.sessionList.size()-1));
 				}
 			}
 			super.partClosed(part);
 		}
 	}

 	@Override
 	protected void doDestroyPage(final IWorkbenchPart part, final PageRec pageRecord) {
 		final SessionHandler sessionHandler= (SessionHandler) part;
 		final S session= sessionHandler.getSession();

 		pageRecord.page.dispose();
 		pageRecord.dispose();

 		this.sessionMap.remove(session);
 		if (sessionHandler == this.activeSession) {
 			this.activeSession= null;
 		}
 	}


 	private void initPageSwitcher() {
 		new PageSwitcher(this) {
 			@Override
 			public Object[] getPages() {
 				return ManagedPageBookView.this.sessionList.toArray();
 			}
 			@Override
 			public String getName(final Object page) {
 				return ((S) page).getLabel();
 			}
 			@Override
 			public @Nullable ImageDescriptor getImageDescriptor(final Object page) {
 				return ((S) page).getImageDescriptor();
 			}
 			@Override
 			public int getCurrentPageIndex() {
 				return (ManagedPageBookView.this.activeSession != null) ?
 						ManagedPageBookView.this.sessionList.indexOf(
 								ManagedPageBookView.this.activeSession.getSession() ) :
 						-1;
 			}
 			@Override
 			public void activatePage(final Object page) {
 				showPage((S) page);
 			}
 		};
 	}


 	protected boolean getPageControlByUser() {
 		return true;
 	}

 	protected void initActions(final IServiceLocator serviceLocator, final ContextHandlers handlers) {
 		if (getPageControlByUser()) {
 			final IHandler2 newPageHandler= createNewPageHandler();
 			if (newPageHandler != null) {
 				handlers.addActivate(SharedUIResources.NEW_PAGE_COMMAND_ID, newPageHandler);
 			}
 			final IHandler2 closePageHandler= new CloseCurrentPageHandler();
 			handlers.addActivate(SharedUIResources.CLOSE_PAGE_COMMAND_ID, closePageHandler);
 			final IHandler2 closeAllPagesHandler= new CloseAllPagesHandler();
 			handlers.addActivate(SharedUIResources.CLOSE_ALL_PAGES_COMMAND_ID, closeAllPagesHandler);
 		}
 	}

 	protected @Nullable IHandler2 createNewPageHandler() {
 		return new NewPageHandler();
 	}

 	protected void contributeToActionBars(final IServiceLocator serviceLocator,
 			final IActionBars actionBars, final HandlerCollection handlers) {
 		final IToolBarManager toolBarManager= actionBars.getToolBarManager();

 		toolBarManager.add(new Separator(ADDITIONS_GROUP_ID));
 		toolBarManager.add(new Separator(PAGE_CONTROL_MENU_ID));
 		{	final IHandler2 handler= handlers.get(SharedUIResources.NEW_PAGE_COMMAND_ID);
 			if (handler != null) {
 				toolBarManager.appendToGroup(PAGE_CONTROL_MENU_ID,
 						new HandlerContributionItem(new CommandContributionItemParameter(
 								serviceLocator, null, SharedUIResources.NEW_PAGE_COMMAND_ID, HandlerContributionItem.STYLE_PUSH),
 								handler));
 			}
 		}
 		toolBarManager.appendToGroup(PAGE_CONTROL_MENU_ID,
 				new SimpleContributionItem("page_control.change_page", //$NON-NLS-1$
 						"Pages", null,
 						SharedUIResources.getImages().getDescriptor(SharedUIResources.LOCTOOL_CHANGE_PAGE_IMAGE_ID), null,
 						SimpleContributionItem.STYLE_PULLDOWN) {
 			@Override
 			protected void dropDownMenuAboutToShow(final IMenuManager manager) {
 				manager.add(new ShowPageDropdownContribution<>(ManagedPageBookView.this));
 			}
 			@Override
 			protected void execute() throws ExecutionException {
 				if (ManagedPageBookView.this.sessionHistory.size() >= 2) {
 					showPage(ManagedPageBookView.this.sessionHistory.get(1));
 				}
 			}
 		});
 		{	final IHandler2 handler= handlers.get(SharedUIResources.CLOSE_PAGE_COMMAND_ID);
 			if (handler != null) {
 				toolBarManager.appendToGroup(PAGE_CONTROL_MENU_ID,
 						new HandlerContributionItem(new CommandContributionItemParameter(
 								serviceLocator, null, SharedUIResources.CLOSE_PAGE_COMMAND_ID, HandlerContributionItem.STYLE_PUSH),
 								handler));
 			}
 		}
 		{	final IHandler2 handler= handlers.get(SharedUIResources.CLOSE_ALL_PAGES_COMMAND_ID);
 			if (handler != null) {
 				toolBarManager.appendToGroup(PAGE_CONTROL_MENU_ID,
 						new HandlerContributionItem(new CommandContributionItemParameter(
 								serviceLocator, null, SharedUIResources.CLOSE_ALL_PAGES_COMMAND_ID, HandlerContributionItem.STYLE_PUSH),
 								handler));
 			}
 		}
 	}

 	@Override
 	public void dispose() {
 		if (this.handlers != null) {
 			this.handlers.dispose();
 			this.handlers= null;
 		}

 		super.dispose();
 	}


 	public @Nullable IPage newPage(@Nullable S session, final boolean show) {
 		session= checkNewSession(session);
 		if (session == null || this.sessionList.contains(session)) {
 			return null;
 		}
 		final SessionHandler sessionHandler= new SessionHandler(session);
 		if (this.sessionComparator != null) {
 			final int idx= Collections.binarySearch(this.sessionList, session, this.sessionComparator);
 			this.sessionList.add((idx >= 0) ? idx : -(idx+1), session);
 		}
 		else {
 			this.sessionList.add(session);
 		}
 		this.sessionMap.put(session, sessionHandler);
 		if (show) {
 			partActivated(sessionHandler);
 			final PageRec pageRec= getPageRec(sessionHandler);
 			if (pageRec != null) {
 				return pageRec.page;
 			}
 			else {
 				this.sessionMap.remove(sessionHandler);
 				this.sessionList.remove(session);
 				return null;
 			}
 		}
 		else {
 			return null;
 		}
 	}

 	protected @Nullable S checkNewSession(final @Nullable S session) {
 		return session;
 	}

 	public @Nullable IPage getPage(final S session) {
 		final SessionHandler sessionHandler= this.sessionMap.get(session);
 		if (sessionHandler != null) {
 			final PageRec pageRec= getPageRec(sessionHandler);
 			if (pageRec != null) {
 				return pageRec.page;
 			}
 		}
 		return null;
 	}

 	public void showPage(final S session) {
 		final SessionHandler sessionHandler= this.sessionMap.get(session);
 		if (sessionHandler != null) {
 			partActivated(sessionHandler);
 		}
 	}

 	public void closePage(final S session) {
 		final SessionHandler sessionHandler= this.sessionMap.get(session);
 		if (sessionHandler != null) {
 			partClosed(sessionHandler);
 		}
 	}

 	public final ImList<S> getSessions() {
 		return ImCollections.toList(this.sessionList);
 	}

 	public final @Nullable S getCurrentSession() {
 		final SessionHandler sessionHandler= this.activeSession;
 		if (sessionHandler != null) {
 			return sessionHandler.getSession();
 		}
 		return null;
 	}

 	protected void onPageHiding(final IPageBookViewPage page, final S session) {
 		updateState();
 	}

 	protected void onPageShowing(final IPageBookViewPage page, final S session) {
 		updateState();
 	}

 	protected StatusLineMessageManager getStatusManager() {
 		return this.statusManager;
 	}

 	protected void updateState() {
 		final Object evaluationContext= null;
 		this.handlers.update(evaluationContext);

 		final IPage currentPage= getCurrentPage();
 		if (currentPage instanceof ManagedPage<?>) {
 			((ManagedPage<?>) currentPage).updateState(evaluationContext);
 		}

 		getViewSite().getActionBars().getToolBarManager().update(true);
 	}

 }
	/*=============================================================================#
	# Copyright (c) 2009, 2021 Stephan Wahlbrink and others.
	#
	# This program and the accompanying materials are made available under the
	# terms of the Eclipse Public License 2.0 which is available at
	# https://www.eclipse.org/legal/epl-2.0, or the Apache License, Version 2.0
	# which is available at https://www.apache.org/licenses/LICENSE-2.0.
	#
	# SPDX-License-Identifier: EPL-2.0 OR Apache-2.0
	#
	# Contributors:
	# Stephan Wahlbrink <sw@wahlbrink.eu> - initial API and implementation
	#=============================================================================*/

	package org.eclipse.statet.ecommons.ui.mpbv;

	import static org.eclipse.statet.ecommons.ui.actions.UIActions.ADDITIONS_GROUP_ID;

	import java.util.ArrayList;
	import java.util.Collections;
	import java.util.Comparator;
	import java.util.HashMap;
	import java.util.LinkedList;
	import java.util.List;
	import java.util.Map;

	import org.eclipse.core.commands.AbstractHandler;
	import org.eclipse.core.commands.ExecutionEvent;
	import org.eclipse.core.commands.ExecutionException;
	import org.eclipse.core.commands.IHandler2;
	import org.eclipse.e4.core.contexts.IEclipseContext;
	import org.eclipse.jface.action.IMenuManager;
	import org.eclipse.jface.action.IToolBarManager;
	import org.eclipse.jface.action.Separator;
	import org.eclipse.jface.resource.ImageDescriptor;
	import org.eclipse.swt.graphics.Image;
	import org.eclipse.swt.widgets.Composite;
	import org.eclipse.ui.IActionBars;
	import org.eclipse.ui.IPropertyListener;
	import org.eclipse.ui.IViewSite;
	import org.eclipse.ui.IWorkbenchPart;
	import org.eclipse.ui.IWorkbenchPartSite;
	import org.eclipse.ui.PartInitException;
	import org.eclipse.ui.handlers.IHandlerService;
	import org.eclipse.ui.internal.WorkbenchPlugin;
	import org.eclipse.ui.menus.CommandContributionItemParameter;
	import org.eclipse.ui.part.IPage;
	import org.eclipse.ui.part.IPageBookViewPage;
	import org.eclipse.ui.part.MessagePage;
	import org.eclipse.ui.part.PageBook;
	import org.eclipse.ui.part.PageBookView;
	import org.eclipse.ui.part.PageSite;
	import org.eclipse.ui.part.PageSwitcher;
	import org.eclipse.ui.services.IServiceLocator;

	import org.eclipse.statet.jcommons.collections.ImCollections;
	import org.eclipse.statet.jcommons.collections.ImList;
	import org.eclipse.statet.jcommons.lang.NonNull;
	import org.eclipse.statet.jcommons.lang.NonNullByDefault;
	import org.eclipse.statet.jcommons.lang.Nullable;

	import org.eclipse.statet.ecommons.ui.SharedUIResources;
	import org.eclipse.statet.ecommons.ui.actions.HandlerCollection;
	import org.eclipse.statet.ecommons.ui.actions.HandlerContributionItem;
	import org.eclipse.statet.ecommons.ui.actions.SimpleContributionItem;
	import org.eclipse.statet.ecommons.ui.util.StatusLineMessageManager;
	import org.eclipse.statet.ecommons.ui.workbench.ContextHandlers;


	@NonNullByDefault
	public abstract class ManagedPageBookView<S extends PageBookSession> extends PageBookView {


	protected static final String PAGE_CONTROL_MENU_ID= "page_control"; //$NON-NLS-1$


	private class SessionHandler implements IWorkbenchPart {


	private final S session;


	public SessionHandler(final S session) {
	this.session= session;
	}


	ManagedPageBookView<S> getView() {
	return ManagedPageBookView.this;
	}

	@Override
	public IWorkbenchPartSite getSite() {
	return ManagedPageBookView.this.getSite();
	}

	public S getSession() {
	return this.session;
	}


	@Override
	public String getTitle() {
	return ""; //$NON-NLS-1$
	}

	@Override
	public @Nullable Image getTitleImage() {
	return null;
	}

	@Override
	public String getTitleToolTip() {
	return ""; //$NON-NLS-1$
	}

	@Override
	public void addPropertyListener(final IPropertyListener listener) {
	}

	@Override
	public void removePropertyListener(final IPropertyListener listener) {
	}

	@Override
	public void createPartControl(final Composite parent) {
	}

	@Override
	public void setFocus() {
	}

	@Override
	public void dispose() {
	}

	@Override
	public <T> @Nullable T getAdapter(final Class<T> adapterType) {
	return null;
	}

	@Override
	public int hashCode() {
	return this.session.hashCode();
	}

	@Override
	public boolean equals(final @Nullable Object obj) {
	return (this == obj
	\|\| ((obj instanceof ManagedPageBookView<?>.SessionHandler)
	&& (this.session == ((SessionHandler) obj).session) ));
	}

	}

	private class NewPageHandler extends AbstractHandler {

	public NewPageHandler() {
	}

	@Override
	public void setEnabled(final @Nullable Object evaluationContext) {
	}

	@Override
	public @Nullable Object execute(final ExecutionEvent event) throws ExecutionException {
	newPage(null, true);
	return null;
	}

	}

	private class CloseCurrentPageHandler extends AbstractHandler {

	public CloseCurrentPageHandler() {
	}

	@Override
	public void setEnabled(final @Nullable Object evaluationContext) {
	setBaseEnabled(!ManagedPageBookView.this.sessionList.isEmpty());
	}

	@Override
	public @Nullable Object execute(final ExecutionEvent event) throws ExecutionException {
	final S session= getCurrentSession();
	if (session != null) {
	closePage(session);
	}
	return null;
	}

	}

	public class CloseAllPagesHandler extends AbstractHandler {


	@Override
	public void setEnabled(final @Nullable Object evaluationContext) {
	setBaseEnabled(!ManagedPageBookView.this.sessionList.isEmpty());
	}

	@Override
	public @Nullable Object execute(final ExecutionEvent event) throws ExecutionException {
	ManagedPageBookView.this.sessionHistory.clear();
	final List<S> sessions= getSessions();
	for (final S session : sessions) {
	closePage(session);
	}
	return null;
	}

	}


	private final List<@NonNull S> sessionList= new ArrayList<>();
	private final Map<S, SessionHandler> sessionMap= new HashMap<>();
	private Comparator<S> sessionComparator;

	private final List<S> sessionHistory= new LinkedList<>();

	private @Nullable SessionHandler activeSession;

	private ContextHandlers handlers;

	private StatusLineMessageManager statusManager;


	public ManagedPageBookView() {
	}


	protected void setSessionComparator(final Comparator<S> comparator) {
	this.sessionComparator= comparator;
	}

	@Override
	protected boolean isImportant(final IWorkbenchPart part) {
	return ( (part instanceof ManagedPageBookView<?>.SessionHandler)
	&& ((ManagedPageBookView<?>.SessionHandler) part).getView() == this );
	}

	@Override
	protected @Nullable IWorkbenchPart getBootstrapPart() {
	return null;
	}

	@Override
	protected void initPage(final IPageBookViewPage page) {
	// E-Bug 473941
	try {
	page.init(new PageSite(getViewSite()) {
	@Override
	public void activate() {
	super.activate();

	final IEclipseContext context= getService(IEclipseContext.class);
	if (context != null) {
	context.activate();
	}
	}
	@Override
	public void deactivate() {
	super.deactivate();

	final IEclipseContext context= getService(IEclipseContext.class);
	if (context != null) {
	context.deactivate();
	}
	}
	});
	}
	catch (final PartInitException e) {
	WorkbenchPlugin.log(getClass(), "initPage", e); //$NON-NLS-1$
	}
	}

	@Override
	public void createPartControl(final Composite parent) {
	super.createPartControl(parent);

	final IViewSite site= getViewSite();
	this.statusManager= new StatusLineMessageManager(site.getActionBars().getStatusLineManager());
	initActions(site,
	this.handlers= new ContextHandlers(site.getService(IHandlerService.class)) );
	initPageSwitcher();
	contributeToActionBars(site, site.getActionBars(), this.handlers);

	updateState();
	}

	@Override
	protected IPage createDefaultPage(final PageBook book) {
	final MessagePage page= new MessagePage();
	page.createControl(getPageBook());
	initPage(page);
	return page;
	}

	@Override
	protected @Nullable PageRec doCreatePage(final IWorkbenchPart part) {
	final SessionHandler sessionHandler= (SessionHandler) part;
	final S session= sessionHandler.getSession();

	final IPageBookViewPage page= doCreatePage(session);
	if (page != null) {
	initPage(page);
	page.createControl(getPageBook());

	final PageRec pageRecord= new PageRec(part, page);
	return pageRecord;
	}
	return null;
	}

	protected /* abstract */ @Nullable IPageBookViewPage doCreatePage(final S session) {
	throw new UnsupportedOperationException();
	}

	@Override
	protected void showPageRec(final PageRec pageRec) {
	if ((this.activeSession != null) ? (pageRec.part != this.activeSession) : (pageRec.part != null)) {
	onPageHiding((IPageBookViewPage) getCurrentPage(), (this.activeSession != null) ? this.activeSession.getSession() : null);
	this.activeSession= null;

	super.showPageRec(pageRec);

	this.activeSession= (SessionHandler) pageRec.part;

	final S session;
	if (this.activeSession != null) {
	session= this.activeSession.getSession();
	this.sessionHistory.remove(session);
	this.sessionHistory.add(0, session);
	}
	else {
	session= null;
	}
	onPageShowing((IPageBookViewPage) pageRec.page, session);
	}
	updateTitle();
	}

	protected void updateTitle() {
	final @Nullable S session= getCurrentSession();
	if (session == null) {
	setContentDescription(getNoPageTitle());
	}
	else {
	setContentDescription(session.getLabel());
	}
	}

	protected String getNoPageTitle() {
	return "No page at this time.";
	}

	@Override
	public void partClosed(final IWorkbenchPart part) {
	if (part instanceof ManagedPageBookView<?>.SessionHandler) {
	final SessionHandler sessionHandler= (SessionHandler) part;
	final S session= sessionHandler.getSession();

	this.sessionList.remove(session);
	this.sessionHistory.remove(session);

	if (this.activeSession == part) {
	if (!this.sessionHistory.isEmpty()) {
	showPage(this.sessionHistory.get(0));
	}
	else if (!this.sessionList.isEmpty()) {
	showPage(this.sessionList.get(this.sessionList.size()-1));
	}
	}
	super.partClosed(part);
	}
	}

	@Override
	protected void doDestroyPage(final IWorkbenchPart part, final PageRec pageRecord) {
	final SessionHandler sessionHandler= (SessionHandler) part;
	final S session= sessionHandler.getSession();

	pageRecord.page.dispose();
	pageRecord.dispose();

	this.sessionMap.remove(session);
	if (sessionHandler == this.activeSession) {
	this.activeSession= null;
	}
	}


	private void initPageSwitcher() {
	new PageSwitcher(this) {
	@Override
	public Object[] getPages() {
	return ManagedPageBookView.this.sessionList.toArray();
	}
	@Override
	public String getName(final Object page) {
	return ((S) page).getLabel();
	}
	@Override
	public @Nullable ImageDescriptor getImageDescriptor(final Object page) {
	return ((S) page).getImageDescriptor();
	}
	@Override
	public int getCurrentPageIndex() {
	return (ManagedPageBookView.this.activeSession != null) ?
	ManagedPageBookView.this.sessionList.indexOf(
	ManagedPageBookView.this.activeSession.getSession() ) :
	-1;
	}
	@Override
	public void activatePage(final Object page) {
	showPage((S) page);
	}
	};
	}


	protected boolean getPageControlByUser() {
	return true;
	}

	protected void initActions(final IServiceLocator serviceLocator, final ContextHandlers handlers) {
	if (getPageControlByUser()) {
	final IHandler2 newPageHandler= createNewPageHandler();
	if (newPageHandler != null) {
	handlers.addActivate(SharedUIResources.NEW_PAGE_COMMAND_ID, newPageHandler);
	}
	final IHandler2 closePageHandler= new CloseCurrentPageHandler();
	handlers.addActivate(SharedUIResources.CLOSE_PAGE_COMMAND_ID, closePageHandler);
	final IHandler2 closeAllPagesHandler= new CloseAllPagesHandler();
	handlers.addActivate(SharedUIResources.CLOSE_ALL_PAGES_COMMAND_ID, closeAllPagesHandler);
	}
	}

	protected @Nullable IHandler2 createNewPageHandler() {
	return new NewPageHandler();
	}

	protected void contributeToActionBars(final IServiceLocator serviceLocator,
	final IActionBars actionBars, final HandlerCollection handlers) {
	final IToolBarManager toolBarManager= actionBars.getToolBarManager();

	toolBarManager.add(new Separator(ADDITIONS_GROUP_ID));
	toolBarManager.add(new Separator(PAGE_CONTROL_MENU_ID));
	{ final IHandler2 handler= handlers.get(SharedUIResources.NEW_PAGE_COMMAND_ID);
	if (handler != null) {
	toolBarManager.appendToGroup(PAGE_CONTROL_MENU_ID,
	new HandlerContributionItem(new CommandContributionItemParameter(
	serviceLocator, null, SharedUIResources.NEW_PAGE_COMMAND_ID, HandlerContributionItem.STYLE_PUSH),
	handler));
	}
	}
	toolBarManager.appendToGroup(PAGE_CONTROL_MENU_ID,
	new SimpleContributionItem("page_control.change_page", //$NON-NLS-1$
	"Pages", null,
	SharedUIResources.getImages().getDescriptor(SharedUIResources.LOCTOOL_CHANGE_PAGE_IMAGE_ID), null,
	SimpleContributionItem.STYLE_PULLDOWN) {
	@Override
	protected void dropDownMenuAboutToShow(final IMenuManager manager) {
	manager.add(new ShowPageDropdownContribution<>(ManagedPageBookView.this));
	}
	@Override
	protected void execute() throws ExecutionException {
	if (ManagedPageBookView.this.sessionHistory.size() >= 2) {
	showPage(ManagedPageBookView.this.sessionHistory.get(1));
	}
	}
	});
	{ final IHandler2 handler= handlers.get(SharedUIResources.CLOSE_PAGE_COMMAND_ID);
	if (handler != null) {
	toolBarManager.appendToGroup(PAGE_CONTROL_MENU_ID,
	new HandlerContributionItem(new CommandContributionItemParameter(
	serviceLocator, null, SharedUIResources.CLOSE_PAGE_COMMAND_ID, HandlerContributionItem.STYLE_PUSH),
	handler));
	}
	}
	{ final IHandler2 handler= handlers.get(SharedUIResources.CLOSE_ALL_PAGES_COMMAND_ID);
	if (handler != null) {
	toolBarManager.appendToGroup(PAGE_CONTROL_MENU_ID,
	new HandlerContributionItem(new CommandContributionItemParameter(
	serviceLocator, null, SharedUIResources.CLOSE_ALL_PAGES_COMMAND_ID, HandlerContributionItem.STYLE_PUSH),
	handler));
	}
	}
	}

	@Override
	public void dispose() {
	if (this.handlers != null) {
	this.handlers.dispose();
	this.handlers= null;
	}

	super.dispose();
	}


	public @Nullable IPage newPage(@Nullable S session, final boolean show) {
	session= checkNewSession(session);
	if (session == null \|\| this.sessionList.contains(session)) {
	return null;
	}
	final SessionHandler sessionHandler= new SessionHandler(session);
	if (this.sessionComparator != null) {
	final int idx= Collections.binarySearch(this.sessionList, session, this.sessionComparator);
	this.sessionList.add((idx >= 0) ? idx : -(idx+1), session);
	}
	else {
	this.sessionList.add(session);
	}
	this.sessionMap.put(session, sessionHandler);
	if (show) {
	partActivated(sessionHandler);
	final PageRec pageRec= getPageRec(sessionHandler);
	if (pageRec != null) {
	return pageRec.page;
	}
	else {
	this.sessionMap.remove(sessionHandler);
	this.sessionList.remove(session);
	return null;
	}
	}
	else {
	return null;
	}
	}

	protected @Nullable S checkNewSession(final @Nullable S session) {
	return session;
	}

	public @Nullable IPage getPage(final S session) {
	final SessionHandler sessionHandler= this.sessionMap.get(session);
	if (sessionHandler != null) {
	final PageRec pageRec= getPageRec(sessionHandler);
	if (pageRec != null) {
	return pageRec.page;
	}
	}
	return null;
	}

	public void showPage(final S session) {
	final SessionHandler sessionHandler= this.sessionMap.get(session);
	if (sessionHandler != null) {
	partActivated(sessionHandler);
	}
	}

	public void closePage(final S session) {
	final SessionHandler sessionHandler= this.sessionMap.get(session);
	if (sessionHandler != null) {
	partClosed(sessionHandler);
	}
	}

	public final ImList<S> getSessions() {
	return ImCollections.toList(this.sessionList);
	}

	public final @Nullable S getCurrentSession() {
	final SessionHandler sessionHandler= this.activeSession;
	if (sessionHandler != null) {
	return sessionHandler.getSession();
	}
	return null;
	}

	protected void onPageHiding(final IPageBookViewPage page, final S session) {
	updateState();
	}

	protected void onPageShowing(final IPageBookViewPage page, final S session) {
	updateState();
	}

	protected StatusLineMessageManager getStatusManager() {
	return this.statusManager;
	}

	protected void updateState() {
	final Object evaluationContext= null;
	this.handlers.update(evaluationContext);

	final IPage currentPage= getCurrentPage();
	if (currentPage instanceof ManagedPage<?>) {
	((ManagedPage<?>) currentPage).updateState(evaluationContext);
	}

	getViewSite().getActionBars().getToolBarManager().update(true);
	}

	}