[578512] [UI] Provide an exemplary view for CDORemoteTopics

https://bugs.eclipse.org/bugs/show_bug.cgi?id=578512

6 files changed, 1562 insertions, 3 deletions

diff --git a/plugins/org.eclipse.emf.cdo.ui/src/org/eclipse/emf/cdo/internal/ui/bundle/OM.java b/plugins/org.eclipse.emf.cdo.ui/src/org/eclipse/emf/cdo/internal/ui/bundle/OM.java
index 57256e95e3..6e841ac14e 100644
--- a/plugins/org.eclipse.emf.cdo.ui/src/org/eclipse/emf/cdo/internal/ui/bundle/OM.java
+++ b/plugins/org.eclipse.emf.cdo.ui/src/org/eclipse/emf/cdo/internal/ui/bundle/OM.java
@@ -11,6 +11,7 @@
  */
 package org.eclipse.emf.cdo.internal.ui.bundle;
 
+import org.eclipse.emf.cdo.internal.ui.views.UserInfo;
 import org.eclipse.emf.cdo.ui.CDOEditorOpener;
 import org.eclipse.emf.cdo.ui.CDOLabelDecorator;
 import org.eclipse.emf.cdo.ui.OverlayImage;
@@ -72,6 +73,18 @@ public abstract class OM
   public static final OMPreference<Long> PREF_LOCK_TIMEOUT = //
       PREFS.init("PREF_LOCK_TIMEOUT", 10000L); //$NON-NLS-1$
 
+  public static final OMPreference<Boolean> PREF_TOPICS_LINK_WITH_EDITOR = //
+      PREFS.init("PREF_TOPICS_LINK_WITH_EDITOR", false); //$NON-NLS-1$
+
+  public static final OMPreference<String> PREF_USER_FIRST_NAME = //
+      PREFS.init("PREF_USER_FIRST_NAME", ""); //$NON-NLS-1$
+
+  public static final OMPreference<String> PREF_USER_LAST_NAME = //
+      PREFS.init("PREF_USER_LAST_NAME", ""); //$NON-NLS-1$
+
+  public static final OMPreference<String> PREF_USER_DISPLAY_NAME = //
+      PREFS.init("PREF_USER_DISPLAY_NAME", System.getProperty("user.name")); //$NON-NLS-1$
+
   private static Boolean historySupportAvailable;
 
   private static Boolean compareSupportAvailable;
@@ -148,11 +161,13 @@ public abstract class OM
     protected void doStart() throws Exception
     {
       CDOEditorOpener.Registry.INSTANCE.activate();
+      UserInfo.Manager.INSTANCE.activate();
     }
 
     @Override
     protected void doStop() throws Exception
     {
+      UserInfo.Manager.INSTANCE.deactivate();
       CDOEditorOpener.Registry.INSTANCE.deactivate();
     }
   }
diff --git a/plugins/org.eclipse.emf.cdo.ui/src/org/eclipse/emf/cdo/internal/ui/editor/CDOEditor.java b/plugins/org.eclipse.emf.cdo.ui/src/org/eclipse/emf/cdo/internal/ui/editor/CDOEditor.java
index 2519dd2a29..f5950fce67 100644
--- a/plugins/org.eclipse.emf.cdo.ui/src/org/eclipse/emf/cdo/internal/ui/editor/CDOEditor.java
+++ b/plugins/org.eclipse.emf.cdo.ui/src/org/eclipse/emf/cdo/internal/ui/editor/CDOEditor.java
@@ -14,12 +14,15 @@ package org.eclipse.emf.cdo.internal.ui.editor;
 
 import org.eclipse.emf.cdo.CDOObject;
 import org.eclipse.emf.cdo.CDOState;
+import org.eclipse.emf.cdo.common.branch.CDOBranch;
+import org.eclipse.emf.cdo.common.branch.CDOBranchPoint;
 import org.eclipse.emf.cdo.common.id.CDOID;
 import org.eclipse.emf.cdo.common.id.CDOIDUtil;
 import org.eclipse.emf.cdo.common.model.CDOPackageInfo;
 import org.eclipse.emf.cdo.common.model.CDOPackageRegistry;
 import org.eclipse.emf.cdo.common.model.CDOPackageUnit;
 import org.eclipse.emf.cdo.common.model.EMFUtil;
+import org.eclipse.emf.cdo.common.util.CDOCommonUtil;
 import org.eclipse.emf.cdo.eresource.CDOResource;
 import org.eclipse.emf.cdo.internal.ui.CDOContentProvider;
 import org.eclipse.emf.cdo.internal.ui.RunnableViewerRefresh;
@@ -37,6 +40,7 @@ import org.eclipse.emf.cdo.ui.CDOEditorInput3;
 import org.eclipse.emf.cdo.ui.CDOEventHandler;
 import org.eclipse.emf.cdo.ui.CDOInvalidRootAgent;
 import org.eclipse.emf.cdo.ui.CDOLabelProvider;
+import org.eclipse.emf.cdo.ui.CDOTopicProvider;
 import org.eclipse.emf.cdo.ui.CDOTreeExpansionAgent;
 import org.eclipse.emf.cdo.ui.shared.SharedIcons;
 import org.eclipse.emf.cdo.util.CDOURIUtil;
@@ -50,6 +54,7 @@ import org.eclipse.emf.internal.cdo.view.CDOStateMachine;
 import org.eclipse.net4j.util.AdapterUtil;
 import org.eclipse.net4j.util.ReflectUtil;
 import org.eclipse.net4j.util.StringUtil;
+import org.eclipse.net4j.util.collection.ConcurrentArray;
 import org.eclipse.net4j.util.lifecycle.LifecycleUtil;
 import org.eclipse.net4j.util.om.OMPlatform;
 import org.eclipse.net4j.util.om.trace.ContextTracer;
@@ -193,13 +198,14 @@ import java.util.Iterator;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Objects;
 import java.util.concurrent.atomic.AtomicBoolean;
 
 /**
  * @author Eike Stepper
- * @generated
+ * @generated not
  */
-public class CDOEditor extends MultiPageEditorPart implements IEditingDomainProvider, ISelectionProvider, IMenuListener, IViewerProvider
+public class CDOEditor extends MultiPageEditorPart implements IEditingDomainProvider, ISelectionProvider, IMenuListener, IViewerProvider, CDOTopicProvider
 {
   /**
    * The filters for file extensions supported by the editor.
@@ -529,6 +535,17 @@ public class CDOEditor extends MultiPageEditorPart implements IEditingDomainProv
 
   protected final AtomicBoolean pagesCreated = new AtomicBoolean();
 
+  protected final ConcurrentArray<Listener> topicListeners = new ConcurrentArray<>()
+  {
+    @Override
+    protected Listener[] newArray(int length)
+    {
+      return new Listener[length];
+    }
+  };
+
+  protected Topic currentTopic;
+
   /**
    * Handles activation of the editor or it's associated views.
    * <!-- begin-user-doc --> <!-- end-user-doc -->
@@ -1381,6 +1398,12 @@ public class CDOEditor extends MultiPageEditorPart implements IEditingDomainProv
       eventHandler = new CDOEventHandler(view, selectionViewer)
       {
         @Override
+        protected void viewTargetChanged(CDOBranchPoint branchPoint)
+        {
+          setCurrentTopic(createTopic());
+        }
+
+        @Override
         protected void objectInvalidated(InternalCDOObject cdoObject)
         {
           if (CDOUtil.isLegacyObject(cdoObject))
@@ -1467,6 +1490,8 @@ public class CDOEditor extends MultiPageEditorPart implements IEditingDomainProv
           fireDirtyPropertyChange();
         }
       };
+
+      setCurrentTopic(createTopic());
     }
     catch (RuntimeException ex)
     {
@@ -2261,6 +2286,80 @@ public class CDOEditor extends MultiPageEditorPart implements IEditingDomainProv
     setInputWithNotify(editorInput);
   }
 
+  private void setCurrentTopic(Topic topic)
+  {
+    if (!Objects.equals(currentTopic, topic))
+    {
+      if (currentTopic != null)
+      {
+        for (Listener listener : topicListeners.get())
+        {
+          listener.topicRemoved(this, currentTopic);
+        }
+      }
+
+      currentTopic = topic;
+
+      if (currentTopic != null)
+      {
+        for (Listener listener : topicListeners.get())
+        {
+          listener.topicAdded(this, currentTopic);
+        }
+      }
+    }
+  }
+
+  private Topic createTopic()
+  {
+    if (view != null)
+    {
+      ResourceSet resourceSet = view.getResourceSet();
+      Resource resource = resourceSet.getResources().get(0);
+
+      if (resource instanceof CDOResource)
+      {
+        CDOResource cdoResource = (CDOResource)resource;
+        String path = cdoResource.getPath();
+
+        CDOBranch branch = view.getBranch();
+        long timeStamp = view.getTimeStamp();
+
+        String id = "org.eclipse.emf.cdo.resource" + path + "/" + branch.getID() + "/" + timeStamp;
+        Image image = getTitleImage();
+        String text = path + "  [" + branch.getName() + "/" + CDOCommonUtil.formatTimeStamp(timeStamp) + "]";
+        String description = text;
+
+        return new Topic(view.getSession(), id, image, text, description);
+      }
+    }
+
+    return null;
+  }
+
+  @Override
+  public Topic[] getTopics()
+  {
+    if (currentTopic != null)
+    {
+      return new Topic[] { currentTopic };
+    }
+
+    return new Topic[0];
+  }
+
+  @Override
+  public void addTopicListener(Listener listener)
+  {
+    topicListeners.add(listener);
+  }
+
+  @Override
+  public void removeTopicListener(Listener listener)
+  {
+    topicListeners.remove(listener);
+  }
+
   /**
    * <!-- begin-user-doc --> <!-- end-user-doc -->
    * @generated
diff --git a/plugins/org.eclipse.emf.cdo.ui/src/org/eclipse/emf/cdo/internal/ui/views/CDORemoteTopicsView.java b/plugins/org.eclipse.emf.cdo.ui/src/org/eclipse/emf/cdo/internal/ui/views/CDORemoteTopicsView.java
new file mode 100644
index 0000000000..2161b119de
--- /dev/null
+++ b/plugins/org.eclipse.emf.cdo.ui/src/org/eclipse/emf/cdo/internal/ui/views/CDORemoteTopicsView.java
@@ -0,0 +1,758 @@
+/*
+ * Copyright (c) 2007-2013, 2015, 2016, 2019, 2020 Eike Stepper (Loehne, Germany) 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:
+ *    Eike Stepper - initial API and implementation
+ */
+package org.eclipse.emf.cdo.internal.ui.views;
+
+import org.eclipse.emf.cdo.internal.ui.bundle.OM;
+import org.eclipse.emf.cdo.internal.ui.views.UserInfo.Manager.UserChangedEvent;
+import org.eclipse.emf.cdo.session.CDOSession;
+import org.eclipse.emf.cdo.session.remote.CDORemoteSession;
+import org.eclipse.emf.cdo.session.remote.CDORemoteSessionManager;
+import org.eclipse.emf.cdo.session.remote.CDORemoteTopic;
+import org.eclipse.emf.cdo.ui.CDOTopicProvider;
+import org.eclipse.emf.cdo.ui.CDOTopicProvider.Listener;
+import org.eclipse.emf.cdo.ui.CDOTopicProvider.Topic;
+import org.eclipse.emf.cdo.ui.shared.SharedIcons;
+
+import org.eclipse.net4j.ui.shared.CollapseAllAction;
+import org.eclipse.net4j.ui.shared.ExpandAllAction;
+import org.eclipse.net4j.ui.shared.LinkWithEditorAction;
+import org.eclipse.net4j.util.AdapterUtil;
+import org.eclipse.net4j.util.container.IContainerEvent;
+import org.eclipse.net4j.util.container.IContainerEventVisitor;
+import org.eclipse.net4j.util.event.EventUtil;
+import org.eclipse.net4j.util.event.IEvent;
+import org.eclipse.net4j.util.event.IListener;
+import org.eclipse.net4j.util.lifecycle.ILifecycleEvent;
+import org.eclipse.net4j.util.lifecycle.ILifecycleEvent.Kind;
+import org.eclipse.net4j.util.om.OMPlatform;
+import org.eclipse.net4j.util.ui.GlobalPartAdapter;
+import org.eclipse.net4j.util.ui.UIUtil;
+import org.eclipse.net4j.util.ui.views.ContainerItemProvider;
+
+import org.eclipse.emf.common.notify.AdapterFactory;
+import org.eclipse.emf.common.notify.Notification;
+import org.eclipse.emf.edit.provider.ComposedAdapterFactory;
+import org.eclipse.emf.edit.provider.ItemProvider;
+import org.eclipse.emf.edit.ui.provider.AdapterFactoryContentProvider;
+import org.eclipse.emf.edit.ui.provider.AdapterFactoryLabelProvider;
+
+import org.eclipse.jface.action.Action;
+import org.eclipse.jface.action.IAction;
+import org.eclipse.jface.action.IMenuManager;
+import org.eclipse.jface.action.IToolBarManager;
+import org.eclipse.jface.action.MenuManager;
+import org.eclipse.jface.action.ToolBarManager;
+import org.eclipse.jface.dialogs.InputDialog;
+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.ITreeSelection;
+import org.eclipse.jface.viewers.StructuredSelection;
+import org.eclipse.jface.viewers.TreeViewer;
+import org.eclipse.jface.viewers.ViewerComparator;
+import org.eclipse.swt.SWT;
+import org.eclipse.swt.widgets.Composite;
+import org.eclipse.swt.widgets.Control;
+import org.eclipse.swt.widgets.Display;
+import org.eclipse.swt.widgets.Menu;
+import org.eclipse.swt.widgets.Shell;
+import org.eclipse.swt.widgets.ToolBar;
+import org.eclipse.ui.IActionBars;
+import org.eclipse.ui.IWorkbenchPage;
+import org.eclipse.ui.IWorkbenchPart;
+import org.eclipse.ui.IWorkbenchPartReference;
+import org.eclipse.ui.PartInitException;
+import org.eclipse.ui.PlatformUI;
+import org.eclipse.ui.part.ISetSelectionTarget;
+import org.eclipse.ui.part.ViewPart;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+
+/**
+ * @author Eike Stepper
+ */
+public class CDORemoteTopicsView extends ViewPart implements ISelectionProvider, ISetSelectionTarget
+{
+  public static final String ID = "org.eclipse.emf.cdo.ui.CDORemoteTopicsView"; //$NON-NLS-1$
+
+  private static final boolean LOCAL_USER_INFO_HIDE = //
+      OMPlatform.INSTANCE.isProperty("org.eclipse.emf.cdo.ui.CDORemoteTopicsView.LOCAL_USER_INFO_HIDE"); //$NON-NLS-1$
+
+  private static final boolean LOCAL_USER_INFO_DISABLE = //
+      OMPlatform.INSTANCE.isProperty("org.eclipse.emf.cdo.ui.CDORemoteTopicsView.LOCAL_USER_INFO_DISABLE"); //$NON-NLS-1$
+
+  private static final boolean EXPAND_SELECTION = //
+      OMPlatform.INSTANCE.isProperty("org.eclipse.emf.cdo.ui.CDORemoteTopicsView.EXPAND_SELECTION"); //$NON-NLS-1$
+
+  private AutoCloseable userInfoListener;
+
+  private final Map<Topic, CDORemoteTopic> remoteTopics = new HashMap<>();
+
+  private final Map<CDORemoteTopic, RemoteTopicItem> remoteTopicItems = new HashMap<>();
+
+  private GlobalPartAdapter workbenchListener = new GlobalPartAdapter(false)
+  {
+    @Override
+    public void partOpened(IWorkbenchPartReference partRef)
+    {
+      CDOTopicProvider provider = getTopicProvider(partRef);
+      if (provider != null)
+      {
+        addTopics(provider.getTopics());
+        provider.addTopicListener(topicListener);
+      }
+    }
+
+    @Override
+    public void partClosed(IWorkbenchPartReference partRef)
+    {
+      CDOTopicProvider provider = getTopicProvider(partRef);
+      if (provider != null)
+      {
+        provider.removeTopicListener(topicListener);
+        removeTopics(provider.getTopics());
+      }
+    }
+
+    @Override
+    public void partActivated(IWorkbenchPartReference partRef)
+    {
+      if (linkWithEditor)
+      {
+        CDOTopicProvider provider = getTopicProvider(partRef);
+        if (provider != null)
+        {
+          selectTopics(provider.getTopics());
+        }
+      }
+    }
+  };
+
+  private final Listener topicListener = new Listener()
+  {
+    @Override
+    public void topicAdded(CDOTopicProvider provider, Topic topic)
+    {
+      addTopics(topic);
+    }
+
+    @Override
+    public void topicRemoved(CDOTopicProvider provider, Topic topic)
+    {
+      removeTopics(topic);
+    }
+  };
+
+  private final AdapterFactory adapterFactory = new ComposedAdapterFactory();
+
+  private final ItemProvider root = new ItemProvider(adapterFactory);
+
+  private Shell shell;
+
+  private TreeViewer viewer;
+
+  private boolean linkWithEditor = OM.PREF_TOPICS_LINK_WITH_EDITOR.getValue();
+
+  private boolean inEditorActivation;
+
+  private ISelectionChangedListener selectionListener = event -> {
+    if (!inEditorActivation)
+    {
+      ITreeSelection selection = (ITreeSelection)event.getSelection();
+      IActionBars bars = getViewSite().getActionBars();
+      selectionChanged(bars, selection);
+    }
+  };
+
+  public CDORemoteTopicsView()
+  {
+  }
+
+  public Shell getShell()
+  {
+    return shell;
+  }
+
+  public TreeViewer getViewer()
+  {
+    return viewer;
+  }
+
+  @Override
+  public void setFocus()
+  {
+    viewer.getControl().setFocus();
+  }
+
+  @Override
+  public void dispose()
+  {
+    workbenchListener.dispose();
+
+    try
+    {
+      userInfoListener.close();
+    }
+    catch (Exception ex)
+    {
+      OM.LOG.error(ex);
+    }
+
+    super.dispose();
+  }
+
+  @Override
+  public ISelection getSelection()
+  {
+    if (viewer != null)
+    {
+      return viewer.getSelection();
+    }
+
+    return StructuredSelection.EMPTY;
+  }
+
+  @Override
+  public void setSelection(ISelection selection)
+  {
+    if (viewer != null)
+    {
+      viewer.setSelection(selection);
+    }
+  }
+
+  @Override
+  public void addSelectionChangedListener(ISelectionChangedListener listener)
+  {
+    if (viewer != null)
+    {
+      viewer.addSelectionChangedListener(listener);
+    }
+  }
+
+  @Override
+  public void removeSelectionChangedListener(ISelectionChangedListener listener)
+  {
+    if (viewer != null)
+    {
+      viewer.removeSelectionChangedListener(listener);
+    }
+  }
+
+  @Override
+  public void selectReveal(ISelection selection)
+  {
+    if (viewer != null)
+    {
+      viewer.setSelection(selection, true);
+    }
+  }
+
+  @Override
+  public final void createPartControl(Composite parent)
+  {
+    shell = parent.getShell();
+    Composite composite = UIUtil.createGridComposite(parent, 1);
+
+    Control control = createUI(composite);
+    control.setLayoutData(UIUtil.createGridData());
+
+    hookContextMenu();
+    hookDoubleClick();
+    contributeToActionBars();
+
+    workbenchListener.register(true);
+    getSite().setSelectionProvider(this);
+  }
+
+  protected Control createUI(Composite parent)
+  {
+    AdapterFactoryLabelProvider labelProvider = new AdapterFactoryLabelProvider(adapterFactory);
+    labelProvider.setFireLabelUpdateNotifications(true);
+
+    viewer = new TreeViewer(parent, SWT.MULTI | SWT.H_SCROLL | SWT.V_SCROLL);
+    viewer.setContentProvider(new AdapterFactoryContentProvider(adapterFactory));
+    viewer.setLabelProvider(labelProvider);
+    viewer.setComparator(new ViewerComparator());
+    viewer.setInput(root);
+    viewer.addSelectionChangedListener(selectionListener);
+
+    userInfoListener = EventUtil.addListener(UserInfo.Manager.INSTANCE, UserChangedEvent.class, e -> {
+      CDORemoteSession remoteSession = e.getRemoteSession();
+      if (remoteSession != null)
+      {
+        for (Object topic : root.getChildren())
+        {
+          for (Object child : ((RemoteTopicItem)topic).getChildren())
+          {
+            RemoteMemberItem member = (RemoteMemberItem)child;
+            if (member.getRemoteSession() == remoteSession)
+            {
+              UIUtil.asyncExec(() -> member.updateText());
+            }
+          }
+        }
+      }
+    });
+
+    return viewer.getControl();
+  }
+
+  protected void hookDoubleClick()
+  {
+    viewer.addDoubleClickListener(e -> doubleClicked(((ITreeSelection)viewer.getSelection()).getFirstElement()));
+  }
+
+  protected void hookContextMenu()
+  {
+    MenuManager manager = new MenuManager("#PopupMenu"); //$NON-NLS-1$
+    manager.setRemoveAllWhenShown(true);
+    manager.addMenuListener(m -> fillContextMenu(m, (ITreeSelection)viewer.getSelection()));
+
+    Menu menu = manager.createContextMenu(viewer.getControl());
+    viewer.getControl().setMenu(menu);
+    getViewSite().registerContextMenu(manager, viewer);
+  }
+
+  protected void contributeToActionBars()
+  {
+    IActionBars bars = getViewSite().getActionBars();
+    fillLocalPullDown(bars.getMenuManager());
+    fillLocalToolBar(bars.getToolBarManager());
+  }
+
+  protected void fillLocalPullDown(IMenuManager manager)
+  {
+  }
+
+  protected void fillLocalToolBar(IToolBarManager manager)
+  {
+    if (!LOCAL_USER_INFO_HIDE)
+    {
+      UserInfo localUser = UserInfo.Manager.INSTANCE.getLocalUser();
+
+      manager.add(new Action(localUser.getDisplayName(), IAction.AS_PUSH_BUTTON)
+      {
+        {
+          setToolTipText("Change Local Name");
+          setEnabled(!LOCAL_USER_INFO_DISABLE);
+        }
+
+        @Override
+        public void run()
+        {
+          String displayName = localUser.getDisplayName();
+          InputDialog dialog = new InputDialog(getShell(), getToolTipText(), "Local name:", displayName, null);
+          if (dialog.open() == InputDialog.OK)
+          {
+            String newDisplayName = dialog.getValue();
+            UserInfo.Manager.INSTANCE.changeLocalUser(localUser.getFirstName(), localUser.getLastName(), newDisplayName);
+
+            newDisplayName = localUser.getDisplayName(); // Could be different if it was originally empty.
+            if (!Objects.equals(newDisplayName, displayName))
+            {
+              setText(newDisplayName);
+
+              if (manager instanceof ToolBarManager)
+              {
+                ToolBar toolBar = ((ToolBarManager)manager).getControl();
+                toolBar.getParent().pack(true);
+              }
+            }
+          }
+        }
+      });
+    }
+
+    manager.add(new ExpandAllAction(viewer));
+    manager.add(new CollapseAllAction(viewer));
+
+    LinkWithEditorAction linkAction = new LinkWithEditorAction()
+    {
+      @Override
+      protected void linkWithEditorChanged(boolean linkWithEditor)
+      {
+        CDORemoteTopicsView.this.linkWithEditor = linkWithEditor;
+        OM.PREF_TOPICS_LINK_WITH_EDITOR.setValue(linkWithEditor);
+      }
+    };
+
+    linkAction.setChecked(linkWithEditor);
+    manager.add(linkAction);
+  }
+
+  protected void fillContextMenu(IMenuManager manager, ITreeSelection selection)
+  {
+  }
+
+  protected void selectionChanged(IActionBars bars, ITreeSelection selection)
+  {
+    if (linkWithEditor)
+    {
+      Object element = selection.getFirstElement();
+      if (element instanceof RemoteMemberItem)
+      {
+        element = ((RemoteMemberItem)element).getParent();
+      }
+
+      if (element instanceof RemoteTopicItem)
+      {
+        RemoteTopicItem remoteTopicItem = (RemoteTopicItem)element;
+        Topic topic = remoteTopicItem.getTopic();
+
+        IWorkbenchPage activePage = PlatformUI.getWorkbench().getActiveWorkbenchWindow().getActivePage();
+        if (!activatePart(topic, activePage.getEditorReferences()))
+        {
+          activatePart(topic, activePage.getViewReferences());
+        }
+      }
+    }
+  }
+
+  protected void doubleClicked(Object object)
+  {
+    if (object instanceof ContainerItemProvider.ErrorElement)
+    {
+      try
+      {
+        UIUtil.getActiveWorkbenchPage().showView(UIUtil.ERROR_LOG_ID);
+      }
+      catch (PartInitException ex)
+      {
+        OM.LOG.error(ex);
+      }
+    }
+    else if (object != null && viewer.isExpandable(object))
+    {
+      if (viewer.getExpandedState(object))
+      {
+        viewer.collapseToLevel(object, TreeViewer.ALL_LEVELS);
+      }
+      else
+      {
+        viewer.expandToLevel(object, 1);
+      }
+    }
+  }
+
+  /**
+   * @since 3.1
+   */
+  protected void refreshPressed()
+  {
+    UIUtil.refreshViewer(viewer);
+  }
+
+  /**
+   * @since 3.3
+   */
+  protected void collapseAllPressed()
+  {
+    getViewer().collapseAll();
+  }
+
+  protected void closeView()
+  {
+    UIUtil.syncExec(getDisplay(), () -> {
+      getSite().getPage().hideView(CDORemoteTopicsView.this);
+      dispose();
+    });
+  }
+
+  protected Display getDisplay()
+  {
+    Display display = viewer.getControl().getDisplay();
+    if (display == null)
+    {
+      display = UIUtil.getDisplay();
+    }
+
+    return display;
+  }
+
+  public Topic getTopic(CDORemoteTopic remoteTopic)
+  {
+    synchronized (remoteTopics)
+    {
+      RemoteTopicItem item = remoteTopicItems.get(remoteTopic);
+      return item == null ? null : item.getTopic();
+    }
+  }
+
+  protected void addTopics(Topic... topics)
+  {
+    synchronized (remoteTopics)
+    {
+      for (Topic topic : topics)
+      {
+        CDORemoteTopic remoteTopic = remoteTopics.computeIfAbsent(topic, k -> {
+          CDOSession session = topic.getSession();
+          String id = topic.getId();
+
+          CDORemoteSessionManager remoteSessionManager = session.getRemoteSessionManager();
+          return remoteSessionManager.subscribeTopic(id);
+        });
+
+        RemoteTopicItem item = remoteTopicItems.computeIfAbsent(remoteTopic, k -> {
+          RemoteTopicItem newItem = new RemoteTopicItem(topic, remoteTopic);
+          root.getChildren().add(newItem);
+          return newItem;
+        });
+
+        item.reference();
+      }
+    }
+  }
+
+  protected void removeTopics(Topic... topics)
+  {
+    synchronized (remoteTopics)
+    {
+      for (Topic topic : topics)
+      {
+        CDORemoteTopic remoteTopic = remoteTopics.get(topic);
+        if (remoteTopic != null)
+        {
+          RemoteTopicItem item = remoteTopicItems.get(remoteTopic);
+          if (item.dereference() == 0)
+          {
+            remoteTopic.unsubscribe();
+
+            remoteTopics.remove(topic);
+            remoteTopicItems.remove(remoteTopic);
+            root.getChildren().remove(item);
+          }
+        }
+      }
+    }
+  }
+
+  protected void selectTopics(Topic... topics)
+  {
+    List<RemoteTopicItem> items = new ArrayList<>();
+
+    synchronized (remoteTopics)
+    {
+      for (Topic topic : topics)
+      {
+        CDORemoteTopic remoteTopic = remoteTopics.get(topic);
+        if (remoteTopic != null)
+        {
+          RemoteTopicItem item = remoteTopicItems.get(remoteTopic);
+          if (item != null)
+          {
+            items.add(item);
+          }
+        }
+      }
+    }
+
+    try
+    {
+      inEditorActivation = true;
+
+      IStructuredSelection selection = new StructuredSelection(items);
+      viewer.setSelection(selection);
+
+      if (EXPAND_SELECTION)
+      {
+        viewer.setExpandedElements(items.toArray());
+      }
+    }
+    finally
+    {
+      inEditorActivation = false;
+    }
+  }
+
+  private static CDOTopicProvider getTopicProvider(IWorkbenchPartReference partRef)
+  {
+    IWorkbenchPart part = partRef.getPart(true);
+    return AdapterUtil.adapt(part, CDOTopicProvider.class);
+  }
+
+  private static boolean activatePart(Topic selectedTopic, IWorkbenchPartReference[] partRefs)
+  {
+    for (IWorkbenchPartReference partRef : partRefs)
+    {
+      CDOTopicProvider topicProvider = getTopicProvider(partRef);
+      if (topicProvider != null)
+      {
+        for (Topic topic : topicProvider.getTopics())
+        {
+          if (Objects.equals(topic, selectedTopic))
+          {
+            partRef.getPage().activate(partRef.getPart(true));
+            return true;
+          }
+        }
+      }
+    }
+
+    return false;
+  }
+
+  /**
+   * @author Eike Stepper
+   */
+  private class Item extends ItemProvider
+  {
+    protected Item()
+    {
+      super(CDORemoteTopicsView.this.adapterFactory);
+    }
+
+    /**
+     * Work around EMF bug 578508.
+     */
+    @Override
+    public void setText(Object object, String text)
+    {
+      this.text = text;
+
+      fireNotifyChanged(new ItemProviderNotification(Notification.SET, null, text, Notification.NO_INDEX, false, false, true)
+      {
+        @Override
+        public boolean isLabelUpdate()
+        {
+          return isLabelUpdate;
+        }
+      });
+    }
+  }
+
+  /**
+   * @author Eike Stepper
+   */
+  private final class RemoteTopicItem extends Item implements IListener
+  {
+    private final Topic topic;
+
+    private final CDORemoteTopic remoteTopic;
+
+    private int refCount;
+
+    public RemoteTopicItem(Topic topic, CDORemoteTopic remoteTopic)
+    {
+      this.topic = topic;
+      this.remoteTopic = remoteTopic;
+
+      setImage(topic.getImage());
+      setText(topic.getText());
+
+      List<RemoteMemberItem> children = new ArrayList<>();
+      for (CDORemoteSession remoteSession : remoteTopic.getRemoteSessions())
+      {
+        RemoteMemberItem item = new RemoteMemberItem(remoteSession);
+        children.add(item);
+      }
+
+      getChildren().addAll(children);
+      remoteTopic.addListener(this);
+    }
+
+    public Topic getTopic()
+    {
+      return topic;
+    }
+
+    @Override
+    public void notifyEvent(IEvent event)
+    {
+      if (event instanceof ILifecycleEvent)
+      {
+        ILifecycleEvent e = (ILifecycleEvent)event;
+        if (e.getKind() == Kind.DEACTIVATED)
+        {
+          dispose();
+        }
+      }
+      else if (event instanceof IContainerEvent)
+      {
+        @SuppressWarnings("unchecked")
+        IContainerEvent<CDORemoteSession> e = (IContainerEvent<CDORemoteSession>)event;
+
+        UIUtil.asyncExec(() -> e.accept(new IContainerEventVisitor<>()
+        {
+          @Override
+          public void added(CDORemoteSession remoteSession)
+          {
+            RemoteMemberItem item = new RemoteMemberItem(remoteSession);
+            getChildren().add(item);
+          }
+
+          @Override
+          public void removed(CDORemoteSession remoteSession)
+          {
+            for (Iterator<Object> it = getChildren().iterator(); it.hasNext();)
+            {
+              RemoteMemberItem item = (RemoteMemberItem)it.next();
+              if (item.getRemoteSession() == remoteSession)
+              {
+                it.remove();
+                break;
+              }
+            }
+          }
+        }));
+      }
+    }
+
+    @Override
+    public void dispose()
+    {
+      remoteTopic.removeListener(this);
+    }
+
+    private void reference()
+    {
+      ++refCount;
+    }
+
+    private int dereference()
+    {
+      return --refCount;
+    }
+  }
+
+  /**
+   * @author Eike Stepper
+   */
+  private final class RemoteMemberItem extends Item
+  {
+    private final CDORemoteSession remoteSession;
+
+    public RemoteMemberItem(CDORemoteSession remoteSession)
+    {
+      this.remoteSession = remoteSession;
+
+      setImage(SharedIcons.getImage(SharedIcons.OBJ_PERSON));
+      updateText();
+    }
+
+    public void updateText()
+    {
+      UserInfo userInfo = UserInfo.Manager.INSTANCE.getRemoteUser(remoteSession);
+      setText(userInfo.getDisplayName());
+    }
+
+    public CDORemoteSession getRemoteSession()
+    {
+      return remoteSession;
+    }
+  }
+}
diff --git a/plugins/org.eclipse.emf.cdo.ui/src/org/eclipse/emf/cdo/internal/ui/views/UserInfo.java b/plugins/org.eclipse.emf.cdo.ui/src/org/eclipse/emf/cdo/internal/ui/views/UserInfo.java
new file mode 100644
index 0000000000..0d39f15f32
--- /dev/null
+++ b/plugins/org.eclipse.emf.cdo.ui/src/org/eclipse/emf/cdo/internal/ui/views/UserInfo.java
@@ -0,0 +1,539 @@
+/*
+ * Copyright (c) 2021 Eike Stepper (Loehne, Germany) 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:
+ *    Eike Stepper - initial API and implementation
+ */
+package org.eclipse.emf.cdo.internal.ui.views;
+
+import org.eclipse.emf.cdo.internal.ui.bundle.OM;
+import org.eclipse.emf.cdo.session.remote.CDORemoteSession;
+import org.eclipse.emf.cdo.session.remote.CDORemoteSessionRequest;
+import org.eclipse.emf.cdo.session.remote.CDORemoteSessionRequest.GlobalRequestHandler;
+
+import org.eclipse.net4j.util.StringUtil;
+import org.eclipse.net4j.util.container.IManagedContainer;
+import org.eclipse.net4j.util.container.IPluginContainer;
+import org.eclipse.net4j.util.event.Event;
+import org.eclipse.net4j.util.factory.ProductCreationException;
+import org.eclipse.net4j.util.io.IOUtil;
+import org.eclipse.net4j.util.lifecycle.Lifecycle;
+import org.eclipse.net4j.util.om.OMPlatform;
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.io.OutputStream;
+import java.nio.charset.StandardCharsets;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Properties;
+import java.util.StringTokenizer;
+
+/**
+ * @author Eike Stepper
+ */
+public final class UserInfo
+{
+  private static final String UNKNOWN = "Unknown";
+
+  private String firstName;
+
+  private String lastName;
+
+  private String displayName;
+
+  UserInfo()
+  {
+    this(null, null, null);
+  }
+
+  public UserInfo(String firstName, String lastName, String displayName)
+  {
+    change(firstName, lastName, displayName);
+  }
+
+  public String getFirstName()
+  {
+    return firstName;
+  }
+
+  public String getLastName()
+  {
+    return lastName;
+  }
+
+  public String getDisplayName()
+  {
+    return displayName;
+  }
+
+  @Override
+  public String toString()
+  {
+    return "UserInfo[" + displayName + "]";
+  }
+
+  void change(String firstName, String lastName, String displayName)
+  {
+    this.firstName = StringUtil.isEmpty(firstName) ? UNKNOWN : firstName;
+    this.lastName = StringUtil.isEmpty(lastName) ? UNKNOWN : lastName;
+    this.displayName = StringUtil.isEmpty(displayName) ? UNKNOWN : displayName;
+  }
+
+  void change(UserInfo userInfo)
+  {
+    change(userInfo.getFirstName(), userInfo.getLastName(), userInfo.getDisplayName());
+  }
+
+  byte[] serialize()
+  {
+    String string = firstName + StringUtil.NL + lastName + StringUtil.NL + displayName;
+    return string.getBytes(StandardCharsets.UTF_8);
+  }
+
+  void deserialize(byte[] data)
+  {
+    String string = new String(data, StandardCharsets.UTF_8);
+    StringTokenizer tokenizer = new StringTokenizer(string, StringUtil.NL);
+    change(tokenizer.nextToken(), tokenizer.nextToken(), tokenizer.nextToken());
+  }
+
+  /**
+   * @author Eike Stepper
+   */
+  public static final class Manager extends Lifecycle
+  {
+    public static final UserInfo.Manager INSTANCE = new Manager();
+
+    private final Map<CDORemoteSession, UserInfo> remoteUsers = new HashMap<>();
+
+    private UserInfoStorage localUserInfoStorage;
+
+    private UserInfo localUser;
+
+    private GlobalRequestHandler userInfoRequestHandler;
+
+    private GlobalRequestHandler userInfoNotificationHandler;
+
+    private Manager()
+    {
+    }
+
+    public synchronized UserInfo getLocalUser()
+    {
+      return localUser;
+    }
+
+    public void changeLocalUser(String firstName, String lastName, String displayName)
+    {
+      UserInfo userInfo;
+      CDORemoteSession[] remoteSessions;
+
+      synchronized (this)
+      {
+        if (localUser != null)
+        {
+          localUser.change(firstName, lastName, displayName);
+        }
+
+        userInfo = localUser;
+        remoteSessions = remoteUsers.keySet().toArray(new CDORemoteSession[remoteUsers.size()]);
+      }
+
+      if (userInfo != null)
+      {
+        if (localUserInfoStorage instanceof UserInfoStorage.Writable)
+        {
+          UserInfoStorage.Writable writable = (UserInfoStorage.Writable)localUserInfoStorage;
+
+          try
+          {
+            writable.saveUserInfo(userInfo);
+          }
+          catch (Exception ex)
+          {
+            OM.LOG.error(ex);
+          }
+        }
+
+        fireEvent(new UserChangedEvent(null, userInfo));
+
+        byte[] data = userInfo.serialize();
+        for (CDORemoteSession remoteSession : remoteSessions)
+        {
+          new CDORemoteSessionRequest(UserInfoNotificationHandler.TYPE, data) //
+              .send(remoteSession);
+        }
+      }
+    }
+
+    public synchronized UserInfo getRemoteUser(CDORemoteSession remoteSession)
+    {
+      return remoteUsers.computeIfAbsent(remoteSession, k -> {
+        UserInfo userInfo = new UserInfo();
+
+        new CDORemoteSessionRequest(UserInfoRequestHandler.TYPE) //
+            .onResponse(data -> changeRemoteUser(remoteSession, data)) //
+            .send(remoteSession);
+
+        return userInfo;
+      });
+    }
+
+    void changeRemoteUser(CDORemoteSession remoteSession, byte[] data)
+    {
+      UserInfo userInfo;
+      synchronized (this)
+      {
+        userInfo = remoteUsers.get(remoteSession);
+        if (userInfo != null)
+        {
+          userInfo.deserialize(data);
+        }
+      }
+
+      if (userInfo != null)
+      {
+        fireEvent(new UserChangedEvent(remoteSession, userInfo));
+      }
+    }
+
+    @Override
+    protected void doActivate() throws Exception
+    {
+      super.doActivate();
+
+      localUserInfoStorage = UserInfoStorage.Factory.get(IPluginContainer.INSTANCE);
+      localUser = localUserInfoStorage == null ? null : localUserInfoStorage.loadUserInfo();
+
+      if (localUser == null)
+      {
+        localUser = new UserInfo();
+      }
+
+      userInfoRequestHandler = new UserInfoRequestHandler();
+      userInfoNotificationHandler = new UserInfoNotificationHandler();
+    }
+
+    @Override
+    protected void doDeactivate() throws Exception
+    {
+      userInfoNotificationHandler.deactivate();
+      userInfoNotificationHandler = null;
+
+      userInfoRequestHandler.deactivate();
+      userInfoRequestHandler = null;
+
+      localUser = null;
+      super.doDeactivate();
+    }
+
+    /**
+     * @author Eike Stepper
+     */
+    public final class UserChangedEvent extends Event
+    {
+      private static final long serialVersionUID = 1L;
+
+      private final CDORemoteSession remoteSession;
+
+      private final UserInfo userInfo;
+
+      protected UserChangedEvent(CDORemoteSession remoteSession, UserInfo userInfo)
+      {
+        super(Manager.this);
+        this.remoteSession = remoteSession;
+        this.userInfo = userInfo;
+      }
+
+      @Override
+      public UserInfo.Manager getSource()
+      {
+        return (UserInfo.Manager)super.getSource();
+      }
+
+      public CDORemoteSession getRemoteSession()
+      {
+        return remoteSession;
+      }
+
+      public UserInfo getUserInfo()
+      {
+        return userInfo;
+      }
+    }
+
+    /**
+     * @author Eike Stepper
+     */
+    private static final class UserInfoRequestHandler extends GlobalRequestHandler
+    {
+      private static final String TYPE = "org.eclipse.emf.cdo.ui.UserInfo";
+
+      public UserInfoRequestHandler()
+      {
+        super(TYPE);
+      }
+
+      @Override
+      protected byte[] createResponse(CDORemoteSession sender, byte[] request)
+      {
+        UserInfo userInfo = INSTANCE.getLocalUser();
+        return userInfo.serialize();
+      }
+    }
+
+    /**
+     * @author Eike Stepper
+     */
+    private static final class UserInfoNotificationHandler extends GlobalRequestHandler
+    {
+      private static final String TYPE = "org.eclipse.emf.cdo.ui.UserInfoChanged";
+
+      public UserInfoNotificationHandler()
+      {
+        super(TYPE);
+      }
+
+      @Override
+      protected byte[] createResponse(CDORemoteSession sender, byte[] request)
+      {
+        INSTANCE.changeRemoteUser(sender, request);
+        return null;
+      }
+    }
+
+    /**
+     * @author Eike Stepper
+     */
+    public interface UserInfoStorage
+    {
+      public UserInfo loadUserInfo() throws IOException;
+
+      /**
+       * @author Eike Stepper
+       */
+      public interface Writable extends UserInfoStorage
+      {
+        public void saveUserInfo(UserInfo userInfo) throws IOException;
+      }
+
+      /**
+       * @author Eike Stepper
+       */
+      public static abstract class Factory extends org.eclipse.net4j.util.factory.Factory
+      {
+        public static final String PRODUCT_GROUP = "org.eclipse.emf.cdo.ui.userInfoStorages";
+
+        private static final String DEFAULT_TYPE = OMPlatform.INSTANCE.getProperty("org.eclipse.emf.cdo.ui.UserInfoStorageFactory.DEFAULT_TYPE",
+            PreferencesUserInfoStorage.Factory.TYPE);
+
+        private static final String DEFAULT_DESCRIPTION = OMPlatform.INSTANCE.getProperty("org.eclipse.emf.cdo.ui.UserInfoStorageFactory.DEFAULT_DESCRIPTION");
+
+        public Factory(String type)
+        {
+          super(PRODUCT_GROUP, type);
+        }
+
+        @Override
+        public abstract UserInfoStorage create(String description) throws ProductCreationException;
+
+        public static UserInfoStorage get(IManagedContainer container)
+        {
+          return get(container, null);
+        }
+
+        public static UserInfoStorage get(IManagedContainer container, String type)
+        {
+          return get(container, type, null);
+        }
+
+        public static UserInfoStorage get(IManagedContainer container, String type, String description)
+        {
+          if (type == null)
+          {
+            type = DEFAULT_TYPE;
+          }
+
+          if (description == null)
+          {
+            description = DEFAULT_DESCRIPTION;
+          }
+
+          return container.getElementOrNull(PRODUCT_GROUP, type, description);
+        }
+      }
+    }
+
+    /**
+     * @author Eike Stepper
+     */
+    public static final class PreferencesUserInfoStorage implements UserInfoStorage.Writable
+    {
+      public PreferencesUserInfoStorage()
+      {
+      }
+
+      @Override
+      public UserInfo loadUserInfo() throws IOException
+      {
+        String firstName = OM.PREF_USER_FIRST_NAME.getValue();
+        String lastName = OM.PREF_USER_LAST_NAME.getValue();
+        String displayName = OM.PREF_USER_DISPLAY_NAME.getValue();
+        return new UserInfo(firstName, lastName, displayName);
+      }
+
+      @Override
+      public void saveUserInfo(UserInfo userInfo) throws IOException
+      {
+        OM.PREF_USER_FIRST_NAME.setValue(userInfo.getFirstName());
+        OM.PREF_USER_LAST_NAME.setValue(userInfo.getLastName());
+        OM.PREF_USER_DISPLAY_NAME.setValue(userInfo.getDisplayName());
+      }
+
+      /**
+       * @author Eike Stepper
+       */
+      public static final class Factory extends UserInfoStorage.Factory
+      {
+        public static final String TYPE = "preferences";
+
+        public Factory()
+        {
+          super(TYPE);
+        }
+
+        @Override
+        public UserInfoStorage create(String description) throws ProductCreationException
+        {
+          return new PreferencesUserInfoStorage();
+        }
+      }
+    }
+
+    /**
+     * @author Eike Stepper
+     */
+    public static final class HomeUserInfoStorage implements UserInfoStorage.Writable
+    {
+      private static final String PROP_FIRST_NAME = "firstName";
+
+      private static final String PROP_LAST_NAME = "lastName";
+
+      private static final String PROP_DISPLAY_NAME = "displayName";
+
+      private static final File FILE = new File(OM.BUNDLE.getUserLocation(), "user.properties");
+
+      public HomeUserInfoStorage()
+      {
+        FILE.getParentFile().mkdirs();
+      }
+
+      @Override
+      public UserInfo loadUserInfo() throws IOException
+      {
+        if (FILE.isFile())
+        {
+          FileInputStream in = null;
+
+          try
+          {
+            in = new FileInputStream(FILE);
+
+            Properties properties = new Properties();
+            properties.load(in);
+
+            String firstName = properties.getProperty(PROP_FIRST_NAME);
+            String lastName = properties.getProperty(PROP_LAST_NAME);
+            String displayName = properties.getProperty(PROP_DISPLAY_NAME);
+
+            return new UserInfo(firstName, lastName, displayName);
+          }
+          catch (Exception ex)
+          {
+            OM.LOG.error(ex);
+          }
+          finally
+          {
+            IOUtil.close(in);
+          }
+        }
+
+        return null;
+      }
+
+      @Override
+      public void saveUserInfo(UserInfo userInfo) throws IOException
+      {
+        OutputStream out = null;
+
+        try
+        {
+          out = new FileOutputStream(FILE);
+
+          Properties properties = new Properties();
+          properties.setProperty(PROP_FIRST_NAME, userInfo.getFirstName());
+          properties.setProperty(PROP_LAST_NAME, userInfo.getLastName());
+          properties.setProperty(PROP_DISPLAY_NAME, userInfo.getDisplayName());
+          properties.store(out, "Local user information");
+        }
+        catch (IOException ex)
+        {
+          OM.LOG.error(ex);
+        }
+        finally
+        {
+          IOUtil.close(out);
+        }
+      }
+
+      public static void saveProperties(File folder, String fileName, Properties properties, String comment)
+      {
+        OutputStream out = null;
+
+        try
+        {
+          folder.mkdirs();
+
+          File file = new File(folder, fileName);
+          out = new FileOutputStream(file);
+
+          properties.store(out, comment);
+        }
+        catch (IOException ex)
+        {
+          OM.LOG.error(ex);
+        }
+        finally
+        {
+          IOUtil.close(out);
+        }
+      }
+
+      /**
+       * @author Eike Stepper
+       */
+      public static final class Factory extends UserInfoStorage.Factory
+      {
+        public static final String TYPE = "home";
+
+        public Factory()
+        {
+          super(TYPE);
+        }
+
+        @Override
+        public UserInfoStorage create(String description) throws ProductCreationException
+        {
+          return new HomeUserInfoStorage();
+        }
+      }
+    }
+  }
+}
diff --git a/plugins/org.eclipse.emf.cdo.ui/src/org/eclipse/emf/cdo/ui/CDOEventHandler.java b/plugins/org.eclipse.emf.cdo.ui/src/org/eclipse/emf/cdo/ui/CDOEventHandler.java
index d997a6ae8c..440c97a433 100644
--- a/plugins/org.eclipse.emf.cdo.ui/src/org/eclipse/emf/cdo/ui/CDOEventHandler.java
+++ b/plugins/org.eclipse.emf.cdo.ui/src/org/eclipse/emf/cdo/ui/CDOEventHandler.java
@@ -14,6 +14,7 @@ package org.eclipse.emf.cdo.ui;
 
 import org.eclipse.emf.cdo.CDOObject;
 import org.eclipse.emf.cdo.CDOState;
+import org.eclipse.emf.cdo.common.branch.CDOBranchPoint;
 import org.eclipse.emf.cdo.internal.ui.ItemsProcessor;
 import org.eclipse.emf.cdo.internal.ui.bundle.OM;
 import org.eclipse.emf.cdo.session.CDOSession;
@@ -24,6 +25,7 @@ import org.eclipse.emf.cdo.view.CDOObjectHandler;
 import org.eclipse.emf.cdo.view.CDOView;
 import org.eclipse.emf.cdo.view.CDOViewInvalidationEvent;
 import org.eclipse.emf.cdo.view.CDOViewLocksChangedEvent;
+import org.eclipse.emf.cdo.view.CDOViewTargetChangedEvent;
 
 import org.eclipse.net4j.util.container.IContainerDelta;
 import org.eclipse.net4j.util.container.IContainerEvent;
@@ -88,7 +90,12 @@ public class CDOEventHandler
     @Override
     public void notifyEvent(IEvent event)
     {
-      if (event instanceof CDOViewInvalidationEvent)
+      if (event instanceof CDOViewTargetChangedEvent)
+      {
+        CDOViewTargetChangedEvent e = (CDOViewTargetChangedEvent)event;
+        viewTargetChanged(e.getBranchPoint());
+      }
+      else if (event instanceof CDOViewInvalidationEvent)
       {
         CDOViewInvalidationEvent e = (CDOViewInvalidationEvent)event;
         // Remove detached object from selection, could incur into unwanted exceptions
@@ -375,6 +382,13 @@ public class CDOEventHandler
   {
   }
 
+  /**
+   * @since 4.12
+   */
+  protected void viewTargetChanged(CDOBranchPoint branchPoint)
+  {
+  }
+
   protected void viewClosed()
   {
   }
diff --git a/plugins/org.eclipse.emf.cdo.ui/src/org/eclipse/emf/cdo/ui/CDOTopicProvider.java b/plugins/org.eclipse.emf.cdo.ui/src/org/eclipse/emf/cdo/ui/CDOTopicProvider.java
new file mode 100644
index 0000000000..3b6d26603a
--- /dev/null
+++ b/plugins/org.eclipse.emf.cdo.ui/src/org/eclipse/emf/cdo/ui/CDOTopicProvider.java
@@ -0,0 +1,134 @@
+/*
+ * Copyright (c) 2022 Eike Stepper (Loehne, Germany) 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:
+ *    Eike Stepper - initial API and implementation
+ */
+package org.eclipse.emf.cdo.ui;
+
+import org.eclipse.emf.cdo.session.CDOSession;
+
+import org.eclipse.net4j.util.StringUtil;
+
+import org.eclipse.swt.graphics.Image;
+
+import java.util.Objects;
+
+/**
+ * @author Eike Stepper
+ * @since 4.12
+ */
+public interface CDOTopicProvider
+{
+  public Topic[] getTopics();
+
+  public void addTopicListener(Listener listener);
+
+  public void removeTopicListener(Listener listener);
+
+  /**
+   * @author Eike Stepper
+   */
+  public static final class Topic
+  {
+    private final CDOSession session;
+
+    private final String id;
+
+    private final Image image;
+
+    private final String text;
+
+    private final String description;
+
+    public Topic(CDOSession session, String id, Image image, String text, String description)
+    {
+      this.session = session;
+      this.id = id;
+      this.image = image;
+      this.text = text;
+      this.description = description;
+    }
+
+    public CDOSession getSession()
+    {
+      return session;
+    }
+
+    public String getId()
+    {
+      return id;
+    }
+
+    public Image getImage()
+    {
+      return image;
+    }
+
+    public String getText()
+    {
+      return text;
+    }
+
+    public String getDescription()
+    {
+      return description;
+    }
+
+    @Override
+    public int hashCode()
+    {
+      return Objects.hash(session, id);
+    }
+
+    @Override
+    public boolean equals(Object obj)
+    {
+      if (this == obj)
+      {
+        return true;
+      }
+
+      if (obj == null)
+      {
+        return false;
+      }
+
+      if (getClass() != obj.getClass())
+      {
+        return false;
+      }
+
+      Topic other = (Topic)obj;
+      return Objects.equals(session, other.session) && Objects.equals(id, other.id);
+    }
+
+    @Override
+    public String toString()
+    {
+      String string = session.getRepositoryInfo().getName() + "/" + id;
+
+      String userID = session.getUserID();
+      if (!StringUtil.isEmpty(userID))
+      {
+        string = userID + "@" + string;
+      }
+
+      return string;
+    }
+  }
+
+  /**
+   * @author Eike Stepper
+   */
+  public interface Listener
+  {
+    public void topicAdded(CDOTopicProvider provider, Topic topic);
+
+    public void topicRemoved(CDOTopicProvider provider, Topic topic);
+  }
+}