[561973] Make CDO Editor node expansion asynchronous and resilient to failures

https://bugs.eclipse.org/bugs/show_bug.cgi?id=561973

12 files changed, 891 insertions, 608 deletions

diff --git a/plugins/org.eclipse.emf.cdo.explorer.ui/src/org/eclipse/emf/cdo/explorer/ui/bundle/OM.java b/plugins/org.eclipse.emf.cdo.explorer.ui/src/org/eclipse/emf/cdo/explorer/ui/bundle/OM.java
index 0a2d70a253..f7a446a19b 100644
--- a/plugins/org.eclipse.emf.cdo.explorer.ui/src/org/eclipse/emf/cdo/explorer/ui/bundle/OM.java
+++ b/plugins/org.eclipse.emf.cdo.explorer.ui/src/org/eclipse/emf/cdo/explorer/ui/bundle/OM.java
@@ -52,7 +52,7 @@ public abstract class OM
       PREFS.init("PREF_REPOSITORY_TIMEOUT_DISABLED", false); //$NON-NLS-1$
 
   public static final OMPreference<Boolean> PREF_REMEMBER_OPEN_EDITORS = //
-      PREFS.init("PREF_REMEMBER_OPEN_EDITORS", false); //$NON-NLS-1$
+      PREFS.init("PREF_REMEMBER_OPEN_EDITORS", true); //$NON-NLS-1$
 
   public static final OMPreference<Integer> PREF_DASHBOARD_HEIGHT = //
       PREFS.init("PREF_DASHBOARD_HEIGHT", 0); //$NON-NLS-1$
diff --git a/plugins/org.eclipse.emf.cdo.explorer.ui/src/org/eclipse/emf/cdo/explorer/ui/checkouts/CDOCheckoutContentProvider.java b/plugins/org.eclipse.emf.cdo.explorer.ui/src/org/eclipse/emf/cdo/explorer/ui/checkouts/CDOCheckoutContentProvider.java
index 8503036f5a..c654b54b96 100644
--- a/plugins/org.eclipse.emf.cdo.explorer.ui/src/org/eclipse/emf/cdo/explorer/ui/checkouts/CDOCheckoutContentProvider.java
+++ b/plugins/org.eclipse.emf.cdo.explorer.ui/src/org/eclipse/emf/cdo/explorer/ui/checkouts/CDOCheckoutContentProvider.java
@@ -11,11 +11,6 @@
 package org.eclipse.emf.cdo.explorer.ui.checkouts;
 
 import org.eclipse.emf.cdo.CDOElement;
-import org.eclipse.emf.cdo.CDOObject;
-import org.eclipse.emf.cdo.common.id.CDOID;
-import org.eclipse.emf.cdo.common.revision.CDOList;
-import org.eclipse.emf.cdo.common.revision.CDORevision;
-import org.eclipse.emf.cdo.common.revision.CDORevisionManager;
 import org.eclipse.emf.cdo.eresource.CDOResourceFolder;
 import org.eclipse.emf.cdo.eresource.CDOResourceNode;
 import org.eclipse.emf.cdo.explorer.CDOExplorerManager;
@@ -24,33 +19,19 @@ import org.eclipse.emf.cdo.explorer.CDOExplorerUtil;
 import org.eclipse.emf.cdo.explorer.checkouts.CDOCheckout;
 import org.eclipse.emf.cdo.explorer.checkouts.CDOCheckoutManager;
 import org.eclipse.emf.cdo.explorer.checkouts.CDOCheckoutManager.CheckoutStateEvent;
-import org.eclipse.emf.cdo.explorer.ui.ViewerUtil;
 import org.eclipse.emf.cdo.explorer.ui.bundle.OM;
 import org.eclipse.emf.cdo.explorer.ui.checkouts.actions.OpenWithActionProvider;
-import org.eclipse.emf.cdo.spi.common.revision.InternalCDORevision;
-import org.eclipse.emf.cdo.spi.common.revision.InternalCDORevisionCache;
+import org.eclipse.emf.cdo.internal.ui.CDOContentProvider;
+import org.eclipse.emf.cdo.internal.ui.RunnableViewerRefresh;
+import org.eclipse.emf.cdo.internal.ui.ViewerUtil;
 import org.eclipse.emf.cdo.ui.CDOItemProvider;
-import org.eclipse.emf.cdo.util.CDOUtil;
-import org.eclipse.emf.cdo.view.CDOView;
 
 import org.eclipse.net4j.util.container.IContainerEvent;
 import org.eclipse.net4j.util.event.IEvent;
 import org.eclipse.net4j.util.event.IListener;
-import org.eclipse.net4j.util.lifecycle.LifecycleException;
-import org.eclipse.net4j.util.lifecycle.LifecycleUtil;
-import org.eclipse.net4j.util.ui.UIUtil;
-import org.eclipse.net4j.util.ui.views.ItemProvider;
 
-import org.eclipse.emf.common.notify.Adapter;
 import org.eclipse.emf.ecore.EObject;
-import org.eclipse.emf.ecore.EStructuralFeature;
-import org.eclipse.emf.ecore.InternalEObject;
-import org.eclipse.emf.ecore.util.EcoreUtil;
 import org.eclipse.emf.edit.provider.ComposedAdapterFactory;
-import org.eclipse.emf.edit.provider.ITreeItemContentProvider;
-import org.eclipse.emf.edit.provider.ItemProviderAdapter;
-import org.eclipse.emf.spi.cdo.InternalCDOObject;
-import org.eclipse.emf.spi.cdo.InternalCDOView;
 
 import org.eclipse.core.resources.IResource;
 import org.eclipse.core.resources.IWorkspaceRoot;
@@ -60,7 +41,6 @@ import org.eclipse.core.runtime.IStatus;
 import org.eclipse.core.runtime.Status;
 import org.eclipse.core.runtime.jobs.Job;
 import org.eclipse.jface.action.IMenuManager;
-import org.eclipse.jface.dialogs.MessageDialog;
 import org.eclipse.jface.viewers.IOpenListener;
 import org.eclipse.jface.viewers.ISelection;
 import org.eclipse.jface.viewers.IStructuredSelection;
@@ -68,7 +48,6 @@ import org.eclipse.jface.viewers.ITreeContentProvider;
 import org.eclipse.jface.viewers.ITreeSelection;
 import org.eclipse.jface.viewers.OpenEvent;
 import org.eclipse.jface.viewers.StructuredSelection;
-import org.eclipse.jface.viewers.StructuredViewer;
 import org.eclipse.jface.viewers.TreeViewer;
 import org.eclipse.jface.viewers.Viewer;
 import org.eclipse.swt.SWT;
@@ -78,7 +57,6 @@ import org.eclipse.swt.widgets.Composite;
 import org.eclipse.swt.widgets.Control;
 import org.eclipse.swt.widgets.Display;
 import org.eclipse.swt.widgets.Shell;
-import org.eclipse.swt.widgets.TreeItem;
 import org.eclipse.ui.IMemento;
 import org.eclipse.ui.IViewPart;
 import org.eclipse.ui.IViewReference;
@@ -94,30 +72,23 @@ import org.eclipse.ui.views.properties.PropertySheet;
 import org.eclipse.ui.views.properties.PropertySheetPage;
 import org.eclipse.ui.views.properties.tabbed.TabbedPropertySheetPage;
 
-import java.lang.reflect.Method;
 import java.util.ArrayList;
 import java.util.Arrays;
-import java.util.Collection;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
-import java.util.concurrent.ConcurrentHashMap;
 
 /**
  * @author Eike Stepper
  */
-public class CDOCheckoutContentProvider implements ICommonContentProvider, IPropertySourceProvider, IOpenListener
+public class CDOCheckoutContentProvider extends CDOContentProvider<CDOCheckout> implements ICommonContentProvider, IPropertySourceProvider, IOpenListener
 {
-  private static final Map<String, CDOCheckoutContentProvider> INSTANCES = new HashMap<>();
-
-  private static final Set<Object> LOADING_OBJECTS = new HashSet<>();
-
-  private static final Method GET_CHILDREN_FEATURES_METHOD = getMethod(ItemProviderAdapter.class, "getChildrenFeatures", Object.class);
+  public static final String PROJECT_EXPLORER_ID = "org.eclipse.ui.navigator.ProjectExplorer";
 
-  private static final Method FIND_ITEM_METHOD = getMethod(StructuredViewer.class, "findItem", Object.class);
+  private static final Map<String, CDOCheckoutContentProvider> INSTANCES = new HashMap<>();
 
   private static final CDOCheckoutManager CHECKOUT_MANAGER = CDOExplorerUtil.getCheckoutManager();
 
@@ -126,7 +97,7 @@ public class CDOCheckoutContentProvider implements ICommonContentProvider, IProp
     @Override
     public void notifyEvent(IEvent event)
     {
-      CDOCheckoutViewerRefresh viewerRefresh = stateManager.getViewerRefresh();
+      RunnableViewerRefresh viewerRefresh = stateManager.getViewerRefresh();
 
       if (event instanceof IContainerEvent)
       {
@@ -141,23 +112,23 @@ public class CDOCheckoutContentProvider implements ICommonContentProvider, IProp
         if (state == CDOCheckout.State.Opening)
         {
           // Trigger hasChildren().
-          ViewerUtil.refresh(viewer, checkout);
+          ViewerUtil.refresh(getViewer(), checkout);
 
           // Trigger getChildren().
-          ViewerUtil.expand(viewer, checkout, true);
+          ViewerUtil.expand(getViewer(), checkout, true);
         }
         else
         {
           if (state == CDOCheckout.State.Closed)
           {
-            ViewerUtil.expand(viewer, checkout, false);
+            ViewerUtil.expand(getViewer(), checkout, false);
           }
 
           viewerRefresh.addNotification(checkout, true, true);
 
           if (state == CDOCheckout.State.Open)
           {
-            ViewerUtil.expand(viewer, checkout, true);
+            ViewerUtil.expand(getViewer(), checkout, true);
           }
 
           updatePropertySheetPage(checkout);
@@ -203,10 +174,11 @@ public class CDOCheckoutContentProvider implements ICommonContentProvider, IProp
       PropertySheet propertySheet = getPropertySheet(workbenchPage);
       if (propertySheet != null)
       {
-        final IPage currentPage = propertySheet.getCurrentPage();
+        IPage currentPage = propertySheet.getCurrentPage();
         if (currentPage instanceof PropertySheetPage || currentPage instanceof TabbedPropertySheetPage)
         {
-          final Control control = viewer.getControl();
+          TreeViewer viewer = getViewer();
+          Control control = viewer.getControl();
           if (!control.isDisposed())
           {
             control.getDisplay().asyncExec(new Runnable()
@@ -269,16 +241,8 @@ public class CDOCheckoutContentProvider implements ICommonContentProvider, IProp
 
   private final CDOCheckoutStateManager stateManager = new CDOCheckoutStateManager(this);
 
-  private final Map<Object, Object[]> childrenCache = new ConcurrentHashMap<>();
-
   private String viewerID;
 
-  private TreeViewer viewer;
-
-  private Object input;
-
-  public static final String PROJECT_EXPLORER_ID = "org.eclipse.ui.navigator.ProjectExplorer";
-
   public CDOCheckoutContentProvider()
   {
   }
@@ -327,497 +291,54 @@ public class CDOCheckoutContentProvider implements ICommonContentProvider, IProp
     return stateManager;
   }
 
-  public final TreeViewer getViewer()
-  {
-    return viewer;
-  }
-
   @Override
   public void inputChanged(Viewer newViewer, Object oldInput, Object newInput)
   {
-    TreeViewer newTreeViewer = null;
-    if (newViewer instanceof TreeViewer)
-    {
-      newTreeViewer = (TreeViewer)newViewer;
-    }
-
-    if (newTreeViewer != viewer)
-    {
-      if (viewer != null)
-      {
-        viewer.removeOpenListener(this);
-      }
-
-      viewer = newTreeViewer;
-
-      if (viewer != null)
-      {
-        viewer.addOpenListener(this);
-      }
-    }
-
-    input = newInput;
-    stateManager.inputChanged(newTreeViewer, oldInput, newInput);
-  }
-
-  public Object getInput()
-  {
-    return input;
-  }
-
-  @Override
-  public Object[] getElements(Object object)
-  {
-    return getChildren(object);
+    super.inputChanged(newViewer, oldInput, newInput);
+    stateManager.inputChanged(getViewer(), oldInput, newInput);
   }
 
   @Override
   public boolean hasChildren(Object object)
   {
-    try
-    {
-      if (object instanceof IResource)
-      {
-        if (object instanceof IWorkspaceRoot)
-        {
-          return !CHECKOUT_MANAGER.isEmpty();
-        }
-
-        return false;
-      }
-
-      if (object instanceof ViewerUtil.Pending)
-      {
-        return false;
-      }
-
-      if (object instanceof CDOCheckout)
-      {
-        CDOCheckout checkout = (CDOCheckout)object;
-        switch (checkout.getState())
-        {
-        case Closing:
-        case Closed:
-          return false;
-
-        case Opening:
-          // This must be the ViewerUtil.Pending element.
-          return true;
-
-        case Open:
-          object = checkout.getRootObject();
-          break;
-        }
-      }
-
-      if (object instanceof CDOElement)
-      {
-        CDOElement checkoutElement = (CDOElement)object;
-        return checkoutElement.hasChildren();
-      }
-
-      if (GET_CHILDREN_FEATURES_METHOD != null && object instanceof EObject)
-      {
-        EObject eObject = (EObject)object;
-
-        InternalCDOObject cdoObject = getCDOObject(eObject);
-        if (cdoObject != null)
-        {
-          InternalCDORevision revision = cdoObject.cdoRevision(false);
-          if (revision != null)
-          {
-            try
-            {
-              ITreeItemContentProvider provider = (ITreeItemContentProvider)stateManager.adapt(object, ITreeItemContentProvider.class);
-              if (provider instanceof ItemProviderAdapter)
-              {
-                return hasChildren(cdoObject, revision, (ItemProviderAdapter)provider);
-              }
-            }
-            catch (Exception ex)
-            {
-              //$FALL-THROUGH$
-            }
-          }
-        }
-      }
-
-      ITreeContentProvider contentProvider = stateManager.getContentProvider(object);
-      if (contentProvider != null)
-      {
-        return contentProvider.hasChildren(object);
-      }
-    }
-    catch (LifecycleException ex)
+    if (object instanceof IResource)
     {
-      //$FALL-THROUGH$
-    }
-    catch (RuntimeException ex)
-    {
-      if (LifecycleUtil.isActive(object))
+      if (object instanceof IWorkspaceRoot)
       {
-        throw ex;
+        return !CHECKOUT_MANAGER.isEmpty();
       }
 
-      //$FALL-THROUGH$
+      return false;
     }
 
-    return false;
+    return super.hasChildren(object);
   }
 
   @Override
   public Object[] getChildren(Object object)
   {
-    try
+    if (object instanceof IResource)
     {
-      if (object instanceof IResource)
-      {
-        if (object instanceof IWorkspaceRoot)
-        {
-          return CHECKOUT_MANAGER.getCheckouts();
-        }
-
-        return ViewerUtil.NO_CHILDREN;
-      }
-
-      if (object instanceof ViewerUtil.Pending)
+      if (object instanceof IWorkspaceRoot)
       {
-        return ViewerUtil.NO_CHILDREN;
+        return CHECKOUT_MANAGER.getCheckouts();
       }
 
-      if (object instanceof CDOElement)
-      {
-        CDOElement checkoutElement = (CDOElement)object;
-        return checkoutElement.getChildren();
-      }
-
-      final Object originalObject = object;
-      Object[] children = childrenCache.remove(originalObject);
-      if (children != null)
-      {
-        return children;
-      }
-
-      CDOCheckout openingCheckout = null;
-      CDOCheckout checkout = null;
-
-      if (object instanceof CDOCheckout)
-      {
-        checkout = (CDOCheckout)object;
-
-        switch (checkout.getState())
-        {
-        case Closing:
-        case Closed:
-          return ViewerUtil.NO_CHILDREN;
-
-        case Opening:
-          openingCheckout = checkout;
-          break;
-
-        case Open:
-          object = checkout.getRootObject();
-          break;
-        }
-      }
-
-      final Object finalObject = object;
-      final CDOCheckout finalOpeningCheckout = openingCheckout;
-
-      final ITreeContentProvider contentProvider = stateManager.getContentProvider(finalObject);
-      if (contentProvider == null)
-      {
-        return ItemProvider.NO_ELEMENTS;
-      }
-
-      final List<CDORevision> loadedRevisions = new ArrayList<>();
-      final List<CDOID> missingIDs = new ArrayList<>();
-
-      if (openingCheckout == null)
-      {
-        children = determineChildRevisions(object, loadedRevisions, missingIDs);
-        if (children != null)
-        {
-          return CDOCheckoutContentModifier.Registry.INSTANCE.modifyChildren(object, children);
-        }
-      }
-
-      boolean firstLoad;
-      synchronized (LOADING_OBJECTS)
-      {
-        firstLoad = LOADING_OBJECTS.add(originalObject);
-      }
-
-      if (firstLoad || finalOpeningCheckout == null)
-      {
-        Job job = new Job("Load " + finalObject)
-        {
-          @Override
-          protected IStatus run(IProgressMonitor monitor)
-          {
-            try
-            {
-              if (finalOpeningCheckout != null)
-              {
-                finalOpeningCheckout.open();
-                determineChildRevisions(finalObject, loadedRevisions, missingIDs);
-              }
-
-              if (!missingIDs.isEmpty())
-              {
-                CDOObject cdoObject = getCDOObject((EObject)finalObject);
-                CDOView view = cdoObject.cdoView();
-                CDORevisionManager revisionManager = view.getSession().getRevisionManager();
-
-                List<CDORevision> revisions = revisionManager.getRevisions(missingIDs, view, CDORevision.UNCHUNKED, CDORevision.DEPTH_NONE, true);
-                loadedRevisions.addAll(revisions);
-              }
-
-              Object[] children = contentProvider.getChildren(finalObject);
-
-              // Adjust possible legacy adapters.
-              for (int i = 0; i < children.length; i++)
-              {
-                Object child = children[i];
-                if (child instanceof InternalCDOObject)
-                {
-                  InternalCDOObject cdoObject = (InternalCDOObject)child;
-                  InternalEObject instance = cdoObject.cdoInternalInstance();
-                  if (instance != cdoObject)
-                  {
-                    children[i] = instance;
-                  }
-                }
-              }
-
-              children = CDOCheckoutContentModifier.Registry.INSTANCE.modifyChildren(finalObject, children);
-              childrenCache.put(originalObject, children);
-            }
-            catch (final Exception ex)
-            {
-              childrenCache.remove(originalObject);
-
-              if (finalOpeningCheckout != null)
-              {
-                finalOpeningCheckout.close();
-              }
-
-              OM.LOG.error(ex);
-
-              final Control control = viewer.getControl();
-              if (!control.isDisposed())
-              {
-                UIUtil.getDisplay().asyncExec(new Runnable()
-                {
-                  @Override
-                  public void run()
-                  {
-                    try
-                    {
-                      if (!control.isDisposed())
-                      {
-                        Shell shell = control.getShell();
-                        String title = (finalOpeningCheckout != null ? "Open" : "Load") + " Error";
-                        MessageDialog.openError(shell, title, ex.getMessage());
-                      }
-                    }
-                    catch (Exception ex)
-                    {
-                      OM.LOG.error(ex);
-                    }
-                  }
-                });
-              }
-            }
-
-            CDOCheckoutViewerRefresh viewerRefresh = stateManager.getViewerRefresh();
-            viewerRefresh.addNotification(originalObject, true, true, new Runnable()
-            {
-              @Override
-              public void run()
-              {
-                synchronized (LOADING_OBJECTS)
-                {
-                  LOADING_OBJECTS.remove(originalObject);
-                }
-              }
-            });
-
-            return Status.OK_STATUS;
-          }
-        };
-
-        job.schedule();
-      }
-
-      if (FIND_ITEM_METHOD != null)
-      {
-        try
-        {
-          Object widget = FIND_ITEM_METHOD.invoke(viewer, originalObject);
-          if (widget instanceof TreeItem)
-          {
-            TreeItem item = (TreeItem)widget;
-            TreeItem[] childItems = item.getItems();
-
-            int childCount = childItems.length;
-            if (childCount != 0)
-            {
-              List<Object> result = new ArrayList<>();
-              for (int i = 0; i < childCount; i++)
-              {
-                TreeItem childItem = childItems[i];
-                Object child = childItem.getData();
-                if (child != null)
-                {
-                  result.add(child);
-                }
-              }
-
-              int size = result.size();
-              if (size != 0)
-              {
-                return result.toArray(new Object[size]);
-              }
-            }
-          }
-        }
-        catch (Exception ex)
-        {
-          //$FALL-THROUGH$
-        }
-      }
-
-      String text = "Loading...";
-      if (finalOpeningCheckout != null)
-      {
-        text = "Opening...";
-      }
-
-      return new Object[] { new ViewerUtil.Pending(originalObject, text) };
+      return ViewerUtil.NO_CHILDREN;
     }
-    catch (LifecycleException ex)
-    {
-      //$FALL-THROUGH$
-    }
-    catch (RuntimeException ex)
-    {
-      if (LifecycleUtil.isActive(object))
-      {
-        throw ex;
-      }
 
-      //$FALL-THROUGH$
-    }
-
-    return ItemProvider.NO_ELEMENTS;
-  }
-
-  private Object[] determineChildRevisions(Object object, List<CDORevision> loadedRevisions, List<CDOID> missingIDs)
-  {
-    if (GET_CHILDREN_FEATURES_METHOD != null && object instanceof EObject)
-    {
-      EObject eObject = (EObject)object;
-
-      InternalCDOObject cdoObject = getCDOObject(eObject);
-      if (cdoObject != null)
-      {
-        InternalCDORevision revision = cdoObject.cdoRevision(false);
-        if (revision != null)
-        {
-          try
-          {
-            ITreeItemContentProvider provider = (ITreeItemContentProvider)stateManager.adapt(object, ITreeItemContentProvider.class);
-            if (provider instanceof ItemProviderAdapter)
-            {
-              determineChildRevisions(cdoObject, revision, (ItemProviderAdapter)provider, loadedRevisions, missingIDs);
-
-              if (missingIDs.isEmpty())
-              {
-                // All revisions are cached. Just return the objects without server round-trips.
-                ITreeContentProvider contentProvider = stateManager.getContentProvider(object);
-                if (contentProvider != null)
-                {
-                  return contentProvider.getChildren(object);
-                }
-              }
-            }
-          }
-          catch (Exception ex)
-          {
-            //$FALL-THROUGH$
-          }
-        }
-      }
-    }
-
-    return null;
+    return super.getChildren(object);
   }
 
   @Override
   public Object getParent(Object object)
   {
-    try
-    {
-      if (object instanceof CDOCheckout)
-      {
-        return ResourcesPlugin.getWorkspace().getRoot();
-      }
-
-      if (object instanceof ViewerUtil.Pending)
-      {
-        return ((ViewerUtil.Pending)object).getParent();
-      }
-
-      if (object instanceof CDOElement)
-      {
-        CDOElement checkoutElement = (CDOElement)object;
-        return checkoutElement.getParent();
-      }
-
-      if (object instanceof EObject)
-      {
-        EObject eObject = CDOUtil.getEObject((EObject)object);
-
-        CDOElement element = CDOElement.getFor(eObject);
-        if (element != null)
-        {
-          return element;
-        }
-
-        ITreeContentProvider contentProvider = stateManager.getContentProvider(object);
-        if (contentProvider != null)
-        {
-          Object parent = contentProvider.getParent(object);
-          if (parent instanceof EObject)
-          {
-            EObject eParent = (EObject)parent;
-            Adapter adapter = EcoreUtil.getAdapter(eParent.eAdapters(), CDOCheckout.class);
-            if (adapter != null)
-            {
-              return adapter;
-            }
-          }
-
-          return parent;
-        }
-      }
-    }
-    catch (LifecycleException ex)
+    if (object instanceof CDOCheckout)
     {
-      //$FALL-THROUGH$
-    }
-    catch (RuntimeException ex)
-    {
-      if (LifecycleUtil.isActive(object))
-      {
-        throw ex;
-      }
-
-      //$FALL-THROUGH$
+      return ResourcesPlugin.getWorkspace().getRoot();
     }
 
-    return null;
+    return super.getParent(object);
   }
 
   @Override
@@ -834,7 +355,8 @@ public class CDOCheckoutContentProvider implements ICommonContentProvider, IProp
 
   public void selectObjects(final Object... objects)
   {
-    final Control control = viewer.getControl();
+    TreeViewer viewer = getViewer();
+    Control control = viewer.getControl();
     if (!control.isDisposed())
     {
       final long end = System.currentTimeMillis() + 5000L;
@@ -943,121 +465,96 @@ public class CDOCheckoutContentProvider implements ICommonContentProvider, IProp
     }
   }
 
-  private IWorkbenchPage getWorkbenchPage()
+  @Override
+  protected void hookViewer(TreeViewer viewer)
   {
-    if (viewer instanceof CommonViewer)
-    {
-      CommonViewer commonViewer = (CommonViewer)viewer;
-      return commonViewer.getCommonNavigator().getSite().getPage();
-    }
+    viewer.addOpenListener(this);
+  }
 
-    return PlatformUI.getWorkbench().getActiveWorkbenchWindow().getActivePage();
+  @Override
+  protected void unhookViewer(TreeViewer viewer)
+  {
+    viewer.removeOpenListener(this);
   }
 
-  private static InternalCDOObject getCDOObject(EObject eObject)
+  @Override
+  protected Object adapt(Object target, Object type)
   {
-    return (InternalCDOObject)CDOUtil.getCDOObject(eObject, false);
+    return stateManager.adapt(target, type);
   }
 
-  private static boolean hasChildren(InternalCDOObject cdoObject, InternalCDORevision revision, ItemProviderAdapter provider) throws Exception
+  @Override
+  protected Object[] modifyChildren(Object parent, Object[] children)
   {
-    for (EStructuralFeature feature : getChildrenFeatures(cdoObject, provider))
-    {
-      if (feature.isMany())
-      {
-        if (!revision.isEmpty(feature))
-        {
-          return true;
-        }
-      }
-      else if (revision.getValue(feature) != null)
-      {
-        return true;
-      }
-    }
+    return CDOCheckoutContentModifier.Registry.INSTANCE.modifyChildren(parent, children);
+  }
 
-    return false;
+  @Override
+  protected ITreeContentProvider getContentProvider(Object object)
+  {
+    return stateManager.getContentProvider(object);
   }
 
-  private static void determineChildRevisions(InternalCDOObject cdoObject, InternalCDORevision revision, ItemProviderAdapter provider,
-      List<CDORevision> loadedRevisions, List<CDOID> missingIDs) throws Exception
+  @Override
+  protected RunnableViewerRefresh getViewerRefresh()
   {
-    InternalCDOView view = cdoObject.cdoView();
-    InternalCDORevisionCache revisionCache = view.getSession().getRevisionManager().getCache();
+    return stateManager.getViewerRefresh();
+  }
 
-    for (EStructuralFeature feature : getChildrenFeatures(cdoObject, provider))
-    {
-      if (feature.isMany())
-      {
-        CDOList list = revision.getListOrNull(feature);
-        if (list != null)
-        {
-          for (Object object : list)
-          {
-            determineChildRevision(loadedRevisions, missingIDs, view, revisionCache, object);
-          }
-        }
-      }
-      else
-      {
-        Object value = revision.getValue(feature);
-        determineChildRevision(loadedRevisions, missingIDs, view, revisionCache, value);
-      }
-    }
+  @Override
+  protected boolean isContext(Object object)
+  {
+    return object instanceof CDOCheckout;
   }
 
-  private static void determineChildRevision(List<CDORevision> loadedRevisions, List<CDOID> missingIDs, InternalCDOView view, InternalCDORevisionCache cache,
-      Object object)
+  @Override
+  protected ContextState getContextState(CDOCheckout checkout)
   {
-    if (object instanceof CDOID)
+    switch (checkout.getState())
     {
-      CDOID id = (CDOID)object;
-      CDORevision childRevision = cache.getRevision(id, view);
-      if (childRevision != null)
-      {
-        loadedRevisions.add(childRevision);
-      }
-      else
-      {
-        missingIDs.add(id);
-      }
+    case Closing:
+    case Closed:
+      return ContextState.Closed;
+
+    case Opening:
+      return ContextState.Opening;
+
+    case Open:
+      return ContextState.Open;
+
+    default:
+      throw new IllegalStateException("Unexpected checkout state: " + checkout);
     }
   }
 
-  @SuppressWarnings("unchecked")
-  private static Collection<? extends EStructuralFeature> getChildrenFeatures(InternalCDOObject cdoObject, ItemProviderAdapter provider) throws Exception
+  @Override
+  protected void openContext(CDOCheckout checkout)
   {
-    return (Collection<? extends EStructuralFeature>)GET_CHILDREN_FEATURES_METHOD.invoke(provider, cdoObject);
+    checkout.open();
   }
 
-  private static Method getMethod(Class<?> c, String methodName, Class<?>... parameterTypes)
+  @Override
+  protected void closeContext(CDOCheckout checkout)
   {
-    try
-    {
-      Method method = c.getDeclaredMethod(methodName, parameterTypes);
-      method.setAccessible(true);
-      return method;
-    }
-    catch (Throwable ex)
-    {
-      return null;
-    }
+    checkout.close();
   }
 
-  private static boolean isObjectLoading(Object... objects)
+  @Override
+  protected Object getRootObject(CDOCheckout checkout)
   {
-    synchronized (LOADING_OBJECTS)
-    {
-      for (Object object : objects)
-      {
-        if (LOADING_OBJECTS.contains(object))
-        {
-          return true;
-        }
-      }
+    return checkout.getRootObject();
+  }
 
-      return false;
+  private IWorkbenchPage getWorkbenchPage()
+  {
+    TreeViewer viewer = getViewer();
+    if (viewer instanceof CommonViewer)
+    {
+      CommonViewer commonViewer = (CommonViewer)viewer;
+      return commonViewer.getCommonNavigator().getSite().getPage();
     }
+
+    return PlatformUI.getWorkbench().getActiveWorkbenchWindow().getActivePage();
   }
 
   public static TreeViewer createTreeViewer(Composite container)
diff --git a/plugins/org.eclipse.emf.cdo.explorer.ui/src/org/eclipse/emf/cdo/explorer/ui/checkouts/CDOCheckoutEditorInput.java b/plugins/org.eclipse.emf.cdo.explorer.ui/src/org/eclipse/emf/cdo/explorer/ui/checkouts/CDOCheckoutEditorInput.java
index 1ed275bc07..c1574b4db7 100644
--- a/plugins/org.eclipse.emf.cdo.explorer.ui/src/org/eclipse/emf/cdo/explorer/ui/checkouts/CDOCheckoutEditorInput.java
+++ b/plugins/org.eclipse.emf.cdo.explorer.ui/src/org/eclipse/emf/cdo/explorer/ui/checkouts/CDOCheckoutEditorInput.java
@@ -24,6 +24,7 @@ import org.eclipse.emf.cdo.util.CDOURIUtil;
 import org.eclipse.emf.cdo.util.CDOUtil;
 import org.eclipse.emf.cdo.view.CDOView;
 
+import org.eclipse.net4j.util.CheckUtil;
 import org.eclipse.net4j.util.om.monitor.EclipseMonitor;
 import org.eclipse.net4j.util.om.monitor.OMMonitor;
 import org.eclipse.net4j.util.om.monitor.OMMonitor.Async;
@@ -58,6 +59,7 @@ public class CDOCheckoutEditorInput extends PlatformObject implements CDOEditorI
 
   public CDOCheckoutEditorInput(URI uri)
   {
+    CheckUtil.checkArg(uri, "uri is null");
     this.uri = uri;
   }
 
diff --git a/plugins/org.eclipse.emf.cdo.explorer.ui/src/org/eclipse/emf/cdo/explorer/ui/checkouts/CDOCheckoutLabelProvider.java b/plugins/org.eclipse.emf.cdo.explorer.ui/src/org/eclipse/emf/cdo/explorer/ui/checkouts/CDOCheckoutLabelProvider.java
index 113545c88c..ea479db7b2 100644
--- a/plugins/org.eclipse.emf.cdo.explorer.ui/src/org/eclipse/emf/cdo/explorer/ui/checkouts/CDOCheckoutLabelProvider.java
+++ b/plugins/org.eclipse.emf.cdo.explorer.ui/src/org/eclipse/emf/cdo/explorer/ui/checkouts/CDOCheckoutLabelProvider.java
@@ -11,7 +11,7 @@
 package org.eclipse.emf.cdo.explorer.ui.checkouts;
 
 import org.eclipse.emf.cdo.explorer.CDOExplorerElement;
-import org.eclipse.emf.cdo.explorer.ui.ViewerUtil;
+import org.eclipse.emf.cdo.internal.ui.ViewerUtil;
 import org.eclipse.emf.cdo.transfer.CDOTransferElement;
 
 import org.eclipse.net4j.util.StringUtil;
diff --git a/plugins/org.eclipse.emf.cdo.explorer.ui/src/org/eclipse/emf/cdo/explorer/ui/checkouts/CDOCheckoutState.java b/plugins/org.eclipse.emf.cdo.explorer.ui/src/org/eclipse/emf/cdo/explorer/ui/checkouts/CDOCheckoutState.java
index f4943d57f3..05f54b52c0 100644
--- a/plugins/org.eclipse.emf.cdo.explorer.ui/src/org/eclipse/emf/cdo/explorer/ui/checkouts/CDOCheckoutState.java
+++ b/plugins/org.eclipse.emf.cdo.explorer.ui/src/org/eclipse/emf/cdo/explorer/ui/checkouts/CDOCheckoutState.java
@@ -16,8 +16,8 @@ import org.eclipse.emf.cdo.eresource.CDOResourceNode;
 import org.eclipse.emf.cdo.explorer.CDOExplorerUtil;
 import org.eclipse.emf.cdo.explorer.checkouts.CDOCheckout;
 import org.eclipse.emf.cdo.explorer.checkouts.CDOCheckoutManager;
-import org.eclipse.emf.cdo.explorer.ui.ViewerUtil;
 import org.eclipse.emf.cdo.explorer.ui.bundle.OM;
+import org.eclipse.emf.cdo.internal.ui.ViewerUtil;
 import org.eclipse.emf.cdo.internal.ui.editor.CDOEditor;
 import org.eclipse.emf.cdo.ui.CDOEditorUtil;
 import org.eclipse.emf.cdo.ui.CDOLabelDecorator;
diff --git a/plugins/org.eclipse.emf.cdo.explorer.ui/src/org/eclipse/emf/cdo/explorer/ui/checkouts/CDOCheckoutStateManager.java b/plugins/org.eclipse.emf.cdo.explorer.ui/src/org/eclipse/emf/cdo/explorer/ui/checkouts/CDOCheckoutStateManager.java
index 1ad21940fa..23a1cb650a 100644
--- a/plugins/org.eclipse.emf.cdo.explorer.ui/src/org/eclipse/emf/cdo/explorer/ui/checkouts/CDOCheckoutStateManager.java
+++ b/plugins/org.eclipse.emf.cdo.explorer.ui/src/org/eclipse/emf/cdo/explorer/ui/checkouts/CDOCheckoutStateManager.java
@@ -14,6 +14,7 @@ import org.eclipse.emf.cdo.explorer.CDOExplorerUtil;
 import org.eclipse.emf.cdo.explorer.checkouts.CDOCheckout;
 import org.eclipse.emf.cdo.explorer.ui.checkouts.CDOCheckoutState.ContentProvider;
 import org.eclipse.emf.cdo.explorer.ui.checkouts.CDOCheckoutState.LabelProvider;
+import org.eclipse.emf.cdo.internal.ui.RunnableViewerRefresh;
 
 import org.eclipse.net4j.util.lifecycle.LifecycleException;
 
@@ -38,7 +39,7 @@ public final class CDOCheckoutStateManager
 
   private final CDOCheckoutContentProvider mainContentProvider;
 
-  private CDOCheckoutViewerRefresh viewerRefresh;
+  private RunnableViewerRefresh viewerRefresh;
 
   public CDOCheckoutStateManager(CDOCheckoutContentProvider mainContentProvider)
   {
@@ -55,7 +56,7 @@ public final class CDOCheckoutStateManager
     return resourceManager;
   }
 
-  public CDOCheckoutViewerRefresh getViewerRefresh()
+  public RunnableViewerRefresh getViewerRefresh()
   {
     return viewerRefresh;
   }
@@ -98,7 +99,7 @@ public final class CDOCheckoutStateManager
 
   public void inputChanged(TreeViewer newTreeViewer, Object oldInput, Object newInput)
   {
-    viewerRefresh = new CDOCheckoutViewerRefresh(newTreeViewer);
+    viewerRefresh = new RunnableViewerRefresh(newTreeViewer);
 
     for (CDOCheckoutState state : getStates())
     {
diff --git a/plugins/org.eclipse.emf.cdo.explorer.ui/src/org/eclipse/emf/cdo/explorer/ui/repositories/CDORepositoryItemProvider.java b/plugins/org.eclipse.emf.cdo.explorer.ui/src/org/eclipse/emf/cdo/explorer/ui/repositories/CDORepositoryItemProvider.java
index ea95b72f15..17aecfa5cb 100644
--- a/plugins/org.eclipse.emf.cdo.explorer.ui/src/org/eclipse/emf/cdo/explorer/ui/repositories/CDORepositoryItemProvider.java
+++ b/plugins/org.eclipse.emf.cdo.explorer.ui/src/org/eclipse/emf/cdo/explorer/ui/repositories/CDORepositoryItemProvider.java
@@ -19,8 +19,8 @@ import org.eclipse.emf.cdo.explorer.repositories.CDORepository.IDGeneration;
 import org.eclipse.emf.cdo.explorer.repositories.CDORepository.VersioningMode;
 import org.eclipse.emf.cdo.explorer.repositories.CDORepositoryManager;
 import org.eclipse.emf.cdo.explorer.repositories.CDORepositoryManager.RepositoryConnectionEvent;
-import org.eclipse.emf.cdo.explorer.ui.ViewerUtil;
 import org.eclipse.emf.cdo.explorer.ui.bundle.OM;
+import org.eclipse.emf.cdo.internal.ui.ViewerUtil;
 import org.eclipse.emf.cdo.ui.shared.SharedIcons;
 
 import org.eclipse.net4j.util.container.IContainer;
diff --git a/plugins/org.eclipse.emf.cdo.explorer.ui/src/org/eclipse/emf/cdo/explorer/ui/repositories/wizards/MasterRepositoryController.java b/plugins/org.eclipse.emf.cdo.explorer.ui/src/org/eclipse/emf/cdo/explorer/ui/repositories/wizards/MasterRepositoryController.java
index b771327e82..d9059cb155 100644
--- a/plugins/org.eclipse.emf.cdo.explorer.ui/src/org/eclipse/emf/cdo/explorer/ui/repositories/wizards/MasterRepositoryController.java
+++ b/plugins/org.eclipse.emf.cdo.explorer.ui/src/org/eclipse/emf/cdo/explorer/ui/repositories/wizards/MasterRepositoryController.java
@@ -16,8 +16,8 @@ import org.eclipse.emf.cdo.admin.CDOAdminClientRepository;
 import org.eclipse.emf.cdo.admin.CDOAdminClientUtil;
 import org.eclipse.emf.cdo.explorer.repositories.CDORepository.IDGeneration;
 import org.eclipse.emf.cdo.explorer.repositories.CDORepository.VersioningMode;
-import org.eclipse.emf.cdo.explorer.ui.ViewerUtil;
 import org.eclipse.emf.cdo.explorer.ui.bundle.OM;
+import org.eclipse.emf.cdo.internal.ui.ViewerUtil;
 import org.eclipse.emf.cdo.net4j.CDONet4jSession;
 import org.eclipse.emf.cdo.net4j.CDONet4jSessionConfiguration;
 import org.eclipse.emf.cdo.net4j.CDONet4jUtil;
diff --git a/plugins/org.eclipse.emf.cdo.ui/src/org/eclipse/emf/cdo/internal/ui/CDOContentProvider.java b/plugins/org.eclipse.emf.cdo.ui/src/org/eclipse/emf/cdo/internal/ui/CDOContentProvider.java
new file mode 100644
index 0000000000..13311c66ac
--- /dev/null
+++ b/plugins/org.eclipse.emf.cdo.ui/src/org/eclipse/emf/cdo/internal/ui/CDOContentProvider.java
@@ -0,0 +1,670 @@
+/*
+ * Copyright (c) 2015, 2016, 2018, 2019 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;
+
+import org.eclipse.emf.cdo.CDOElement;
+import org.eclipse.emf.cdo.CDOObject;
+import org.eclipse.emf.cdo.common.id.CDOID;
+import org.eclipse.emf.cdo.common.revision.CDOList;
+import org.eclipse.emf.cdo.common.revision.CDORevision;
+import org.eclipse.emf.cdo.common.revision.CDORevisionManager;
+import org.eclipse.emf.cdo.internal.ui.bundle.OM;
+import org.eclipse.emf.cdo.spi.common.revision.InternalCDORevision;
+import org.eclipse.emf.cdo.spi.common.revision.InternalCDORevisionCache;
+import org.eclipse.emf.cdo.util.CDOUtil;
+import org.eclipse.emf.cdo.view.CDOView;
+
+import org.eclipse.net4j.util.lifecycle.LifecycleException;
+import org.eclipse.net4j.util.lifecycle.LifecycleUtil;
+import org.eclipse.net4j.util.ui.UIUtil;
+import org.eclipse.net4j.util.ui.views.ItemProvider;
+
+import org.eclipse.emf.ecore.EObject;
+import org.eclipse.emf.ecore.EStructuralFeature;
+import org.eclipse.emf.ecore.InternalEObject;
+import org.eclipse.emf.edit.provider.ITreeItemContentProvider;
+import org.eclipse.emf.edit.provider.ItemProviderAdapter;
+import org.eclipse.emf.spi.cdo.InternalCDOObject;
+import org.eclipse.emf.spi.cdo.InternalCDOView;
+
+import org.eclipse.core.runtime.IProgressMonitor;
+import org.eclipse.core.runtime.IStatus;
+import org.eclipse.core.runtime.Status;
+import org.eclipse.core.runtime.jobs.Job;
+import org.eclipse.jface.dialogs.MessageDialog;
+import org.eclipse.jface.viewers.ITreeContentProvider;
+import org.eclipse.jface.viewers.StructuredViewer;
+import org.eclipse.jface.viewers.TreeViewer;
+import org.eclipse.jface.viewers.Viewer;
+import org.eclipse.swt.widgets.Control;
+import org.eclipse.swt.widgets.Shell;
+import org.eclipse.swt.widgets.TreeItem;
+
+import java.lang.reflect.Method;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
+
+/**
+ * @author Eike Stepper
+ */
+public abstract class CDOContentProvider<CONTEXT> implements ITreeContentProvider
+{
+  private static final Set<Object> LOADING_OBJECTS = new HashSet<>();
+
+  private static final Method GET_CHILDREN_FEATURES_METHOD = getMethod(ItemProviderAdapter.class, "getChildrenFeatures", Object.class);
+
+  private static final Method FIND_ITEM_METHOD = getMethod(StructuredViewer.class, "findItem", Object.class);
+
+  private final Map<Object, Object[]> childrenCache = new ConcurrentHashMap<>();
+
+  private TreeViewer viewer;
+
+  private Object input;
+
+  public CDOContentProvider()
+  {
+  }
+
+  public final TreeViewer getViewer()
+  {
+    return viewer;
+  }
+
+  @Override
+  public void inputChanged(Viewer newViewer, Object oldInput, Object newInput)
+  {
+    TreeViewer newTreeViewer = null;
+    if (newViewer instanceof TreeViewer)
+    {
+      newTreeViewer = (TreeViewer)newViewer;
+    }
+
+    if (newTreeViewer != viewer)
+    {
+      if (viewer != null)
+      {
+        unhookViewer(viewer);
+      }
+
+      viewer = newTreeViewer;
+
+      if (viewer != null)
+      {
+        hookViewer(viewer);
+      }
+    }
+
+    input = newInput;
+  }
+
+  public Object getInput()
+  {
+    return input;
+  }
+
+  @Override
+  public Object[] getElements(Object object)
+  {
+    return getChildren(object);
+  }
+
+  @Override
+  public boolean hasChildren(Object object)
+  {
+    try
+    {
+      if (object instanceof ViewerUtil.Pending)
+      {
+        return false;
+      }
+
+      if (isContext(object))
+      {
+        @SuppressWarnings("unchecked")
+        CONTEXT context = (CONTEXT)object;
+
+        switch (getContextState(context))
+        {
+        case Closed:
+          return false;
+
+        case Opening:
+          // This must be the ViewerUtil.Pending element.
+          return true;
+
+        case Open:
+          object = getRootObject(context);
+          break;
+        }
+      }
+
+      if (object instanceof CDOElement)
+      {
+        CDOElement checkoutElement = (CDOElement)object;
+        return checkoutElement.hasChildren();
+      }
+
+      if (GET_CHILDREN_FEATURES_METHOD != null && object instanceof EObject)
+      {
+        EObject eObject = (EObject)object;
+
+        InternalCDOObject cdoObject = getCDOObject(eObject);
+        if (cdoObject != null)
+        {
+          InternalCDORevision revision = cdoObject.cdoRevision(false);
+          if (revision != null)
+          {
+            try
+            {
+              ITreeItemContentProvider provider = (ITreeItemContentProvider)adapt(object, ITreeItemContentProvider.class);
+              if (provider instanceof ItemProviderAdapter)
+              {
+                return hasChildren(cdoObject, revision, (ItemProviderAdapter)provider);
+              }
+            }
+            catch (Exception ex)
+            {
+              //$FALL-THROUGH$
+            }
+          }
+        }
+      }
+
+      ITreeContentProvider contentProvider = getContentProvider(object);
+      if (contentProvider != null)
+      {
+        return contentProvider.hasChildren(object);
+      }
+    }
+    catch (LifecycleException ex)
+    {
+      //$FALL-THROUGH$
+    }
+    catch (RuntimeException ex)
+    {
+      if (LifecycleUtil.isActive(object))
+      {
+        throw ex;
+      }
+
+      //$FALL-THROUGH$
+    }
+
+    return false;
+  }
+
+  @Override
+  public Object[] getChildren(Object object)
+  {
+    try
+    {
+      if (object instanceof ViewerUtil.Pending)
+      {
+        return ViewerUtil.NO_CHILDREN;
+      }
+
+      if (object instanceof CDOElement)
+      {
+        CDOElement checkoutElement = (CDOElement)object;
+        return checkoutElement.getChildren();
+      }
+
+      final Object originalObject = object;
+      Object[] children = childrenCache.remove(originalObject);
+      if (children != null)
+      {
+        return children;
+      }
+
+      CONTEXT openingCheckout = null;
+      if (isContext(object))
+      {
+        @SuppressWarnings("unchecked")
+        CONTEXT context = (CONTEXT)object;
+
+        switch (getContextState(context))
+        {
+        case Closed:
+          return ViewerUtil.NO_CHILDREN;
+
+        case Opening:
+          openingCheckout = context;
+          break;
+
+        case Open:
+          object = getRootObject(context);
+          break;
+        }
+      }
+
+      final Object finalObject = object;
+      final CONTEXT finalOpeningContext = openingCheckout;
+
+      final ITreeContentProvider contentProvider = getContentProvider(finalObject);
+      if (contentProvider == null)
+      {
+        return ItemProvider.NO_ELEMENTS;
+      }
+
+      final List<CDORevision> loadedRevisions = new ArrayList<>();
+      final List<CDOID> missingIDs = new ArrayList<>();
+
+      if (finalOpeningContext == null)
+      {
+        children = determineChildRevisions(object, loadedRevisions, missingIDs);
+        if (children != null)
+        {
+          return modifyChildren(object, children);
+        }
+      }
+
+      boolean firstLoad;
+      synchronized (LOADING_OBJECTS)
+      {
+        firstLoad = LOADING_OBJECTS.add(originalObject);
+      }
+
+      if (firstLoad || finalOpeningContext == null)
+      {
+        Job job = new Job("Load " + finalObject)
+        {
+          @Override
+          protected IStatus run(IProgressMonitor monitor)
+          {
+            try
+            {
+              if (finalOpeningContext != null)
+              {
+                openContext(finalOpeningContext);
+                determineChildRevisions(finalObject, loadedRevisions, missingIDs);
+              }
+
+              if (!missingIDs.isEmpty())
+              {
+                CDOObject cdoObject = getCDOObject((EObject)finalObject);
+                CDOView view = cdoObject.cdoView();
+                CDORevisionManager revisionManager = view.getSession().getRevisionManager();
+
+                List<CDORevision> revisions = revisionManager.getRevisions(missingIDs, view, CDORevision.UNCHUNKED, CDORevision.DEPTH_NONE, true);
+                loadedRevisions.addAll(revisions);
+              }
+
+              Object[] children = contentProvider.getChildren(finalObject);
+
+              // Adjust possible legacy adapters.
+              for (int i = 0; i < children.length; i++)
+              {
+                Object child = children[i];
+                if (child instanceof InternalCDOObject)
+                {
+                  InternalCDOObject cdoObject = (InternalCDOObject)child;
+                  InternalEObject instance = cdoObject.cdoInternalInstance();
+                  if (instance != cdoObject)
+                  {
+                    children[i] = instance;
+                  }
+                }
+              }
+
+              children = modifyChildren(finalObject, children);
+              childrenCache.put(originalObject, children);
+            }
+            catch (final Exception ex)
+            {
+              childrenCache.remove(originalObject);
+
+              if (finalOpeningContext != null)
+              {
+                closeContext(finalOpeningContext);
+              }
+
+              OM.LOG.error(ex);
+
+              final Control control = viewer.getControl();
+              if (!control.isDisposed())
+              {
+                UIUtil.getDisplay().asyncExec(new Runnable()
+                {
+                  @Override
+                  public void run()
+                  {
+                    try
+                    {
+                      if (!control.isDisposed())
+                      {
+                        Shell shell = control.getShell();
+                        String title = (finalOpeningContext != null ? "Open" : "Load") + " Error";
+                        MessageDialog.openError(shell, title, ex.getMessage());
+                      }
+                    }
+                    catch (Exception ex)
+                    {
+                      OM.LOG.error(ex);
+                    }
+                  }
+                });
+              }
+            }
+
+            RunnableViewerRefresh viewerRefresh = getViewerRefresh();
+            viewerRefresh.addNotification(originalObject, true, true, () -> {
+              synchronized (LOADING_OBJECTS)
+              {
+                LOADING_OBJECTS.remove(originalObject);
+              }
+            });
+
+            return Status.OK_STATUS;
+          }
+        };
+
+        job.schedule();
+      }
+
+      if (FIND_ITEM_METHOD != null)
+      {
+        try
+        {
+          Object widget = FIND_ITEM_METHOD.invoke(viewer, originalObject);
+          if (widget instanceof TreeItem)
+          {
+            TreeItem item = (TreeItem)widget;
+            TreeItem[] childItems = item.getItems();
+
+            int childCount = childItems.length;
+            if (childCount != 0)
+            {
+              List<Object> result = new ArrayList<>();
+              for (int i = 0; i < childCount; i++)
+              {
+                TreeItem childItem = childItems[i];
+                Object child = childItem.getData();
+                if (child != null)
+                {
+                  result.add(child);
+                }
+              }
+
+              int size = result.size();
+              if (size != 0)
+              {
+                return result.toArray(new Object[size]);
+              }
+            }
+          }
+        }
+        catch (Exception ex)
+        {
+          //$FALL-THROUGH$
+        }
+      }
+
+      String text = "Loading...";
+      if (finalOpeningContext != null)
+      {
+        text = "Opening...";
+      }
+
+      return new Object[] { new ViewerUtil.Pending(originalObject, text) };
+    }
+    catch (LifecycleException ex)
+    {
+      //$FALL-THROUGH$
+    }
+    catch (RuntimeException ex)
+    {
+      if (LifecycleUtil.isActive(object))
+      {
+        throw ex;
+      }
+
+      //$FALL-THROUGH$
+    }
+
+    return ItemProvider.NO_ELEMENTS;
+  }
+
+  @Override
+  public Object getParent(Object object)
+  {
+    try
+    {
+      if (object instanceof ViewerUtil.Pending)
+      {
+        return ((ViewerUtil.Pending)object).getParent();
+      }
+
+      if (object instanceof CDOElement)
+      {
+        CDOElement checkoutElement = (CDOElement)object;
+        return checkoutElement.getParent();
+      }
+
+      if (object instanceof EObject)
+      {
+        EObject eObject = CDOUtil.getEObject((EObject)object);
+
+        CDOElement element = CDOElement.getFor(eObject);
+        if (element != null)
+        {
+          return element;
+        }
+
+        ITreeContentProvider contentProvider = getContentProvider(object);
+        if (contentProvider != null)
+        {
+          return contentProvider.getParent(object);
+        }
+      }
+    }
+    catch (LifecycleException ex)
+    {
+      //$FALL-THROUGH$
+    }
+    catch (RuntimeException ex)
+    {
+      if (LifecycleUtil.isActive(object))
+      {
+        throw ex;
+      }
+
+      //$FALL-THROUGH$
+    }
+
+    return null;
+  }
+
+  protected void hookViewer(TreeViewer viewer)
+  {
+  }
+
+  protected void unhookViewer(TreeViewer viewer)
+  {
+  }
+
+  protected abstract Object adapt(Object target, Object type);
+
+  protected abstract Object[] modifyChildren(Object parent, Object[] children);
+
+  protected abstract ITreeContentProvider getContentProvider(Object object);
+
+  protected abstract RunnableViewerRefresh getViewerRefresh();
+
+  protected abstract boolean isContext(Object object);
+
+  protected abstract ContextState getContextState(CONTEXT context);
+
+  protected abstract void openContext(CONTEXT context);
+
+  protected abstract void closeContext(CONTEXT context);
+
+  protected abstract Object getRootObject(CONTEXT context);
+
+  private Object[] determineChildRevisions(Object object, List<CDORevision> loadedRevisions, List<CDOID> missingIDs)
+  {
+    if (GET_CHILDREN_FEATURES_METHOD != null && object instanceof EObject)
+    {
+      EObject eObject = (EObject)object;
+
+      InternalCDOObject cdoObject = getCDOObject(eObject);
+      if (cdoObject != null)
+      {
+        InternalCDORevision revision = cdoObject.cdoRevision(false);
+        if (revision != null)
+        {
+          try
+          {
+            ITreeItemContentProvider provider = (ITreeItemContentProvider)adapt(object, ITreeItemContentProvider.class);
+            if (provider instanceof ItemProviderAdapter)
+            {
+              determineChildRevisions(cdoObject, revision, (ItemProviderAdapter)provider, loadedRevisions, missingIDs);
+
+              if (missingIDs.isEmpty())
+              {
+                // All revisions are cached. Just return the objects without server round-trips.
+                ITreeContentProvider contentProvider = getContentProvider(object);
+                if (contentProvider != null)
+                {
+                  return contentProvider.getChildren(object);
+                }
+              }
+            }
+          }
+          catch (Exception ex)
+          {
+            //$FALL-THROUGH$
+          }
+        }
+      }
+    }
+
+    return null;
+  }
+
+  protected static boolean isObjectLoading(Object... objects)
+  {
+    synchronized (LOADING_OBJECTS)
+    {
+      for (Object object : objects)
+      {
+        if (LOADING_OBJECTS.contains(object))
+        {
+          return true;
+        }
+      }
+
+      return false;
+    }
+  }
+
+  private static InternalCDOObject getCDOObject(EObject eObject)
+  {
+    return (InternalCDOObject)CDOUtil.getCDOObject(eObject, false);
+  }
+
+  private static boolean hasChildren(InternalCDOObject cdoObject, InternalCDORevision revision, ItemProviderAdapter provider) throws Exception
+  {
+    for (EStructuralFeature feature : getChildrenFeatures(cdoObject, provider))
+    {
+      if (feature.isMany())
+      {
+        if (!revision.isEmpty(feature))
+        {
+          return true;
+        }
+      }
+      else if (revision.getValue(feature) != null)
+      {
+        return true;
+      }
+    }
+
+    return false;
+  }
+
+  private static void determineChildRevisions(InternalCDOObject cdoObject, InternalCDORevision revision, ItemProviderAdapter provider,
+      List<CDORevision> loadedRevisions, List<CDOID> missingIDs) throws Exception
+  {
+    InternalCDOView view = cdoObject.cdoView();
+    InternalCDORevisionCache revisionCache = view.getSession().getRevisionManager().getCache();
+
+    for (EStructuralFeature feature : getChildrenFeatures(cdoObject, provider))
+    {
+      if (feature.isMany())
+      {
+        CDOList list = revision.getListOrNull(feature);
+        if (list != null)
+        {
+          for (Object object : list)
+          {
+            determineChildRevision(loadedRevisions, missingIDs, view, revisionCache, object);
+          }
+        }
+      }
+      else
+      {
+        Object value = revision.getValue(feature);
+        determineChildRevision(loadedRevisions, missingIDs, view, revisionCache, value);
+      }
+    }
+  }
+
+  private static void determineChildRevision(List<CDORevision> loadedRevisions, List<CDOID> missingIDs, InternalCDOView view, InternalCDORevisionCache cache,
+      Object object)
+  {
+    if (object instanceof CDOID)
+    {
+      CDOID id = (CDOID)object;
+      CDORevision childRevision = cache.getRevision(id, view);
+      if (childRevision != null)
+      {
+        loadedRevisions.add(childRevision);
+      }
+      else
+      {
+        missingIDs.add(id);
+      }
+    }
+  }
+
+  @SuppressWarnings("unchecked")
+  private static Collection<? extends EStructuralFeature> getChildrenFeatures(InternalCDOObject cdoObject, ItemProviderAdapter provider) throws Exception
+  {
+    return (Collection<? extends EStructuralFeature>)GET_CHILDREN_FEATURES_METHOD.invoke(provider, cdoObject);
+  }
+
+  private static Method getMethod(Class<?> c, String methodName, Class<?>... parameterTypes)
+  {
+    try
+    {
+      Method method = c.getDeclaredMethod(methodName, parameterTypes);
+      method.setAccessible(true);
+      return method;
+    }
+    catch (Throwable ex)
+    {
+      return null;
+    }
+  }
+
+  /**
+   * @author Eike Stepper
+   */
+  public static enum ContextState
+  {
+    Opening, Open, Closed
+  }
+}
diff --git a/plugins/org.eclipse.emf.cdo.explorer.ui/src/org/eclipse/emf/cdo/explorer/ui/checkouts/CDOCheckoutViewerRefresh.java b/plugins/org.eclipse.emf.cdo.ui/src/org/eclipse/emf/cdo/internal/ui/RunnableViewerRefresh.java
index 8b86b431f7..480598a18e 100644
--- a/plugins/org.eclipse.emf.cdo.explorer.ui/src/org/eclipse/emf/cdo/explorer/ui/checkouts/CDOCheckoutViewerRefresh.java
+++ b/plugins/org.eclipse.emf.cdo.ui/src/org/eclipse/emf/cdo/internal/ui/RunnableViewerRefresh.java
@@ -8,7 +8,7 @@
  * Contributors:
  *    Eike Stepper - initial API and implementation
  */
-package org.eclipse.emf.cdo.explorer.ui.checkouts;
+package org.eclipse.emf.cdo.internal.ui;
 
 import org.eclipse.emf.common.notify.Notification;
 import org.eclipse.emf.edit.provider.IViewerNotification;
@@ -23,11 +23,11 @@ import java.util.List;
 /**
  * @author Eike Stepper
  */
-public final class CDOCheckoutViewerRefresh extends ViewerRefresh
+public final class RunnableViewerRefresh extends ViewerRefresh
 {
   private final Viewer viewer;
 
-  public CDOCheckoutViewerRefresh(Viewer viewer)
+  public RunnableViewerRefresh(Viewer viewer)
   {
     super(viewer);
     this.viewer = viewer;
diff --git a/plugins/org.eclipse.emf.cdo.explorer.ui/src/org/eclipse/emf/cdo/explorer/ui/ViewerUtil.java b/plugins/org.eclipse.emf.cdo.ui/src/org/eclipse/emf/cdo/internal/ui/ViewerUtil.java
index 3ed3d5492e..fa9831036b 100644
--- a/plugins/org.eclipse.emf.cdo.explorer.ui/src/org/eclipse/emf/cdo/explorer/ui/ViewerUtil.java
+++ b/plugins/org.eclipse.emf.cdo.ui/src/org/eclipse/emf/cdo/internal/ui/ViewerUtil.java
@@ -8,7 +8,7 @@
  * Contributors:
  *    Eike Stepper - initial API and implementation
  */
-package org.eclipse.emf.cdo.explorer.ui;
+package org.eclipse.emf.cdo.internal.ui;
 
 import org.eclipse.jface.viewers.ISelection;
 import org.eclipse.jface.viewers.StructuredViewer;
@@ -195,5 +195,11 @@ public final class ViewerUtil
     {
       return text;
     }
+
+    @Override
+    public String toString()
+    {
+      return text;
+    }
   }
 }
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 82364be6a6..2317f4e9cb 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
@@ -21,6 +21,9 @@ 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.eresource.CDOResource;
+import org.eclipse.emf.cdo.internal.ui.CDOContentProvider;
+import org.eclipse.emf.cdo.internal.ui.RunnableViewerRefresh;
+import org.eclipse.emf.cdo.internal.ui.ViewerUtil;
 import org.eclipse.emf.cdo.internal.ui.actions.TransactionalBackgroundAction;
 import org.eclipse.emf.cdo.internal.ui.bundle.OM;
 import org.eclipse.emf.cdo.internal.ui.dialogs.BulkAddDialog;
@@ -50,6 +53,7 @@ import org.eclipse.net4j.util.StringUtil;
 import org.eclipse.net4j.util.om.trace.ContextTracer;
 import org.eclipse.net4j.util.ui.actions.LongRunningAction;
 import org.eclipse.net4j.util.ui.actions.SafeAction;
+import org.eclipse.net4j.util.ui.views.ContainerItemProvider;
 
 import org.eclipse.emf.common.command.BasicCommandStack;
 import org.eclipse.emf.common.command.Command;
@@ -125,6 +129,7 @@ import org.eclipse.jface.viewers.ISelectionChangedListener;
 import org.eclipse.jface.viewers.ISelectionProvider;
 import org.eclipse.jface.viewers.IStructuredContentProvider;
 import org.eclipse.jface.viewers.IStructuredSelection;
+import org.eclipse.jface.viewers.ITreeContentProvider;
 import org.eclipse.jface.viewers.SelectionChangedEvent;
 import org.eclipse.jface.viewers.StructuredSelection;
 import org.eclipse.jface.viewers.StructuredViewer;
@@ -1508,8 +1513,33 @@ public class CDOEditor extends MultiPageEditorPart implements IEditingDomainProv
    */
   protected IContentProvider createContentProvider()
   {
-    return new AdapterFactoryContentProvider(adapterFactory)
+    class DelegateContentProvider extends AdapterFactoryContentProvider
     {
+      public DelegateContentProvider(AdapterFactory adapterFactory)
+      {
+        super(adapterFactory);
+      }
+
+      @Override
+      public void inputChanged(Viewer viewer, Object oldInput, Object newInput)
+      {
+        super.inputChanged(viewer, oldInput, newInput);
+
+        if (viewer != null)
+        {
+          viewerRefresh = new RunnableViewerRefresh(viewer);
+        }
+        else
+        {
+          viewerRefresh = null;
+        }
+      }
+
+      public RunnableViewerRefresh getViewerRefresh()
+      {
+        return (RunnableViewerRefresh)viewerRefresh;
+      }
+
       @Override
       public boolean hasChildren(Object object)
       {
@@ -1527,6 +1557,72 @@ public class CDOEditor extends MultiPageEditorPart implements IEditingDomainProv
           return false;
         }
       }
+    }
+
+    DelegateContentProvider delegate = new DelegateContentProvider(adapterFactory);
+
+    return new CDOContentProvider<CDOView>()
+    {
+      @Override
+      public void inputChanged(Viewer newViewer, Object oldInput, Object newInput)
+      {
+        super.inputChanged(newViewer, oldInput, newInput);
+        delegate.inputChanged(newViewer, oldInput, newInput);
+      }
+
+      @Override
+      protected Object adapt(Object target, Object type)
+      {
+        return adapterFactory.adapt(target, type);
+      }
+
+      @Override
+      protected Object[] modifyChildren(Object parent, Object[] children)
+      {
+        return children;
+      }
+
+      @Override
+      protected ITreeContentProvider getContentProvider(Object object)
+      {
+        return delegate;
+      }
+
+      @Override
+      protected RunnableViewerRefresh getViewerRefresh()
+      {
+        return delegate.getViewerRefresh();
+      }
+
+      @Override
+      protected boolean isContext(Object object)
+      {
+        return false;
+      }
+
+      @Override
+      protected ContextState getContextState(CDOView view)
+      {
+        throw new UnsupportedOperationException();
+      }
+
+      @Override
+      protected void openContext(CDOView view)
+      {
+        throw new UnsupportedOperationException();
+      }
+
+      @Override
+      protected void closeContext(CDOView view)
+      {
+        throw new UnsupportedOperationException();
+      }
+
+      @Override
+      protected Object getRootObject(CDOView view)
+      {
+        throw new UnsupportedOperationException();
+      }
     };
   }
 
@@ -1542,6 +1638,11 @@ public class CDOEditor extends MultiPageEditorPart implements IEditingDomainProv
       {
         try
         {
+          if (element instanceof ViewerUtil.Pending)
+          {
+            return ContainerItemProvider.PENDING_IMAGE;
+          }
+
           Image image = super.getImage(element);
           if (image != null)
           {
@@ -1564,6 +1665,12 @@ public class CDOEditor extends MultiPageEditorPart implements IEditingDomainProv
       {
         try
         {
+          if (element instanceof ViewerUtil.Pending)
+          {
+            ViewerUtil.Pending pending = (ViewerUtil.Pending)element;
+            return pending.getText();
+          }
+
           String text = super.getText(element);
           if (!StringUtil.isEmpty(text))
           {