diff --git a/SourceGenWPF/HelpAccess.cs b/SourceGenWPF/HelpAccess.cs
index 1bb3800..ca7dd07 100644
--- a/SourceGenWPF/HelpAccess.cs
+++ b/SourceGenWPF/HelpAccess.cs
@@ -42,6 +42,9 @@ just opens the TOC, and individual UI items don't have help buttons.
 
 What we need in terms of API is a way to say, "show the help for XYZ".  The rest can be
 encapsulated here.
+
+TODO(maybe): the web viewer accessible from WPF appears to be much better, so we could create a
+simple browser window.
 */
 
 namespace SourceGenWPF {
diff --git a/SourceGenWPF/MainController.cs b/SourceGenWPF/MainController.cs
index c22ce89..90ac14f 100644
--- a/SourceGenWPF/MainController.cs
+++ b/SourceGenWPF/MainController.cs
@@ -978,6 +978,10 @@ namespace SourceGenWPF {
 
             // Some totals.
             public EntityCounts mEntityCounts;
+
+            public SelectionState() {
+                mEntityCounts = new EntityCounts();
+            }
         }
 
         /// <summary>
@@ -1134,7 +1138,6 @@ namespace SourceGenWPF {
             }
 
             int lastIndex = mMainWin.GetLastSelectedIndex();
-            Debug.WriteLine("CHECK: first=" + firstIndex + ", last=" + lastIndex);
             if (lastIndex == firstIndex) {
                 // only one line is selected
                 return true;
@@ -1150,6 +1153,59 @@ namespace SourceGenWPF {
             return false;
         }
 
+        public bool CanUndo() {
+            return (mProject != null && mProject.CanUndo);
+        }
+
+        /// <summary>
+        /// Handles Edit - Undo.
+        /// </summary>
+        public void UndoChanges() {
+            if (!mProject.CanUndo) {
+                Debug.Assert(false, "Nothing to undo");
+                return;
+            }
+            ChangeSet cs = mProject.PopUndoSet();
+            ApplyChanges(cs, true);
+#if false
+            UpdateMenuItemsAndTitle();
+
+            // If the debug dialog is visible, update it.
+            if (mShowUndoRedoHistoryDialog != null) {
+                mShowUndoRedoHistoryDialog.BodyText = mProject.DebugGetUndoRedoHistory();
+            }
+#endif
+        }
+
+        public bool CanRedo() {
+            return (mProject != null && mProject.CanRedo);
+        }
+
+        /// <summary>
+        /// Handles Edit - Redo.
+        /// </summary>
+        public void RedoChanges() {
+            if (!mProject.CanRedo) {
+                Debug.Assert(false, "Nothing to redo");
+                return;
+            }
+            ChangeSet cs = mProject.PopRedoSet();
+            ApplyChanges(cs, false);
+#if false
+            UpdateMenuItemsAndTitle();
+
+            // If the debug dialog is visible, update it.
+            if (mShowUndoRedoHistoryDialog != null) {
+                mShowUndoRedoHistoryDialog.BodyText = mProject.DebugGetUndoRedoHistory();
+            }
+#endif
+        }
+
+        /// <summary>
+        /// Handles the four Actions - edit hint commands.
+        /// </summary>
+        /// <param name="hint">Type of hint to apply.</param>
+        /// <param name="firstByteOnly">If set, only the first byte on each line is hinted.</param>
         public void MarkAsType(CodeAnalysis.TypeHint hint, bool firstByteOnly) {
             RangeSet sel;
 
@@ -1224,6 +1280,13 @@ namespace SourceGenWPF {
             return rs;
         }
 
+        /// <summary>
+        /// Handles Help - Help
+        /// </summary>
+        public void ShowHelp() {
+            HelpAccess.ShowHelp(HelpAccess.Topic.Contents);
+        }
+
         #endregion Main window UI event handlers
 
         #region References panel
diff --git a/SourceGenWPF/ProjWin/MainWindow.xaml b/SourceGenWPF/ProjWin/MainWindow.xaml
index d1ca76c..96f625a 100644
--- a/SourceGenWPF/ProjWin/MainWindow.xaml
+++ b/SourceGenWPF/ProjWin/MainWindow.xaml
@@ -47,16 +47,27 @@ limitations under the License.
                 </RoutedUICommand.InputGestures>
             </RoutedUICommand>
             <RoutedUICommand x:Key="CloseCmd" Text="Close"/>
-            <RoutedUICommand x:Key="HintAsCodeEntryPoint" Text="Hint As Code Entry Point"/>
-            <RoutedUICommand x:Key="HintAsDataStart" Text="Hint As Data Start"/>
-            <RoutedUICommand x:Key="HintAsInlineData" Text="Hint As Inline Data"/>
-            <RoutedUICommand x:Key="RemoveHints" Text="Remove Hints"/>
+            <RoutedUICommand x:Key="HintAsCodeEntryPointCmd" Text="Hint As Code Entry Point"/>
+            <RoutedUICommand x:Key="HintAsDataStartCmd" Text="Hint As Data Start"/>
+            <RoutedUICommand x:Key="HintAsInlineDataCmd" Text="Hint As Inline Data"/>
+            <RoutedUICommand x:Key="RemoveHintsCmd" Text="Remove Hints"/>
             <RoutedUICommand x:Key="RecentProjectCmd"/>
+            <RoutedUICommand x:Key="RedoCmd" Text="Redo">
+                <RoutedUICommand.InputGestures>
+                    <KeyGesture>Ctrl+Y</KeyGesture>
+                    <KeyGesture>Ctrl+Shift+Z</KeyGesture>
+                </RoutedUICommand.InputGestures>
+            </RoutedUICommand>
             <RoutedUICommand x:Key="SelectAllCmd" Text="Select All">
                 <RoutedUICommand.InputGestures>
                     <KeyGesture>Ctrl+A</KeyGesture>
                 </RoutedUICommand.InputGestures>
             </RoutedUICommand>
+            <RoutedUICommand x:Key="UndoCmd" Text="Undo">
+                <RoutedUICommand.InputGestures>
+                    <KeyGesture>Ctrl+Z</KeyGesture>
+                </RoutedUICommand.InputGestures>
+            </RoutedUICommand>
         </ResourceDictionary>
     </Window.Resources>
 
@@ -65,18 +76,24 @@ limitations under the License.
                         CanExecute="IsProjectOpen" Executed="AssembleCmd_Executed"/>
         <CommandBinding Command="{StaticResource CloseCmd}"
                         CanExecute="IsProjectOpen" Executed="CloseCmd_Executed"/>
-        <CommandBinding Command="{StaticResource HintAsCodeEntryPoint}"
-                        CanExecute="CanHintAsCodeEntryPoint" Executed="HintAsCodeEntryPoint_Executed"/>
-        <CommandBinding Command="{StaticResource HintAsDataStart}"
-                        CanExecute="CanHintAsDataStart" Executed="HintAsDataStart_Executed"/>
-        <CommandBinding Command="{StaticResource HintAsInlineData}"
-                        CanExecute="CanHintAsInlineData" Executed="HintAsInlineData_Executed"/>
-        <CommandBinding Command="{StaticResource RemoveHints}"
-                        CanExecute="CanRemoveHints" Executed="RemoveHints_Executed"/>
+        <CommandBinding Command="Help"
+                        Executed="HelpCmd_Executed"/>
+        <CommandBinding Command="{StaticResource HintAsCodeEntryPointCmd}"
+                        CanExecute="CanHintAsCodeEntryPoint" Executed="HintAsCodeEntryPointCmd_Executed"/>
+        <CommandBinding Command="{StaticResource HintAsDataStartCmd}"
+                        CanExecute="CanHintAsDataStart" Executed="HintAsDataStartCmd_Executed"/>
+        <CommandBinding Command="{StaticResource HintAsInlineDataCmd}"
+                        CanExecute="CanHintAsInlineData" Executed="HintAsInlineDataCmd_Executed"/>
+        <CommandBinding Command="{StaticResource RemoveHintsCmd}"
+                        CanExecute="CanRemoveHints" Executed="RemoveHintsCmd_Executed"/>
         <CommandBinding Command="{StaticResource RecentProjectCmd}" Executed="RecentProjectCmd_Executed"/>
-        <!-- ListView has a built-in Ctrl+A handler; this only fires when codeListView not in focus -->
+        <CommandBinding Command="{StaticResource RedoCmd}"
+                        CanExecute="CanRedo" Executed="RedoCmd_Executed"/>
+        <!-- ListView has a built-in Ctrl+A handler; this only fires when codeListView is not in focus -->
         <CommandBinding Command="{StaticResource SelectAllCmd}"
                         CanExecute="IsProjectOpen" Executed="SelectAllCmd_Executed"/>
+        <CommandBinding Command="{StaticResource UndoCmd}"
+                        CanExecute="CanUndo" Executed="UndoCmd_Executed"/>
     </Window.CommandBindings>
     
     <DockPanel>
@@ -98,8 +115,8 @@ limitations under the License.
                 <MenuItem Header="Exit"/>
             </MenuItem>
             <MenuItem Header="_Edit">
-                <MenuItem Command="Undo"/>
-                <MenuItem Command="Redo"/> <!-- want both Ctrl+Y and Ctrl+Shift+Z -->
+                <MenuItem Command="{StaticResource UndoCmd}"/>
+                <MenuItem Command="{StaticResource RedoCmd}"/>
                 <Separator/>
                 <MenuItem Command="Copy"/>
                 <Separator/>
@@ -124,10 +141,10 @@ limitations under the License.
                 <MenuItem Header="Edit Note..."/>
                 <MenuItem Header="Edit Project Symbol..."/>
                 <Separator/>
-                <MenuItem Command="{StaticResource HintAsCodeEntryPoint}" InputGestureText="Ctrl+H, Ctrl+C"/>
-                <MenuItem Command="{StaticResource HintAsDataStart}" InputGestureText="Ctrl+H, Ctrl+D"/>
-                <MenuItem Command="{StaticResource HintAsInlineData}" InputGestureText="Ctrl+H, Ctrl+I"/>
-                <MenuItem Command="{StaticResource RemoveHints}" InputGestureText="Ctrl+H, Ctrl+R"/>
+                <MenuItem Command="{StaticResource HintAsCodeEntryPointCmd}" InputGestureText="Ctrl+H, Ctrl+C"/>
+                <MenuItem Command="{StaticResource HintAsDataStartCmd}" InputGestureText="Ctrl+H, Ctrl+D"/>
+                <MenuItem Command="{StaticResource HintAsInlineDataCmd}" InputGestureText="Ctrl+H, Ctrl+I"/>
+                <MenuItem Command="{StaticResource RemoveHintsCmd}" InputGestureText="Ctrl+H, Ctrl+R"/>
                 <Separator/>
                 <MenuItem Header="Format Split-Address Table..."/>
                 <MenuItem Header="Toggle Single-Byte Format"/>
diff --git a/SourceGenWPF/ProjWin/MainWindow.xaml.cs b/SourceGenWPF/ProjWin/MainWindow.xaml.cs
index cbe74c2..9bf0d33 100644
--- a/SourceGenWPF/ProjWin/MainWindow.xaml.cs
+++ b/SourceGenWPF/ProjWin/MainWindow.xaml.cs
@@ -78,6 +78,8 @@ namespace SourceGenWPF.ProjWin {
 
             mMainCtrl = new MainController(this);
 
+            mSelectionState = new MainController.SelectionState();
+
             AddMultiKeyGestures();
 
             //GridView gv = (GridView)codeListView.View;
@@ -87,25 +89,25 @@ namespace SourceGenWPF.ProjWin {
         private void AddMultiKeyGestures() {
             RoutedUICommand ruic;
 
-            ruic = (RoutedUICommand)FindResource("HintAsCodeEntryPoint");
+            ruic = (RoutedUICommand)FindResource("HintAsCodeEntryPointCmd");
             ruic.InputGestures.Add(
                 new MultiKeyInputGesture(new KeyGesture[] {
                       new KeyGesture(Key.H, ModifierKeys.Control, "Ctrl+H"),
                       new KeyGesture(Key.C, ModifierKeys.Control, "Ctrl+C")
                 }));
-            ruic = (RoutedUICommand)FindResource("HintAsDataStart");
+            ruic = (RoutedUICommand)FindResource("HintAsDataStartCmd");
             ruic.InputGestures.Add(
                 new MultiKeyInputGesture(new KeyGesture[] {
                       new KeyGesture(Key.H, ModifierKeys.Control, "Ctrl+H"),
                       new KeyGesture(Key.D, ModifierKeys.Control, "Ctrl+D")
                 }));
-            ruic = (RoutedUICommand)FindResource("HintAsInlineData");
+            ruic = (RoutedUICommand)FindResource("HintAsInlineDataCmd");
             ruic.InputGestures.Add(
                 new MultiKeyInputGesture(new KeyGesture[] {
                       new KeyGesture(Key.H, ModifierKeys.Control, "Ctrl+H"),
                       new KeyGesture(Key.I, ModifierKeys.Control, "Ctrl+I")
                 }));
-            ruic = (RoutedUICommand)FindResource("RemoveHints");
+            ruic = (RoutedUICommand)FindResource("RemoveHintsCmd");
             ruic.InputGestures.Add(
                 new MultiKeyInputGesture(new KeyGesture[] {
                       new KeyGesture(Key.H, ModifierKeys.Control, "Ctrl+H"),
@@ -304,6 +306,7 @@ namespace SourceGenWPF.ProjWin {
             const int MAX_SEL_COUNT = 2000;
 
             if (sel.IsAllSelected()) {
+                Debug.WriteLine("SetSelection: re-selecting all items");
                 codeListView.SelectAll();
                 return;
             }
@@ -312,7 +315,7 @@ namespace SourceGenWPF.ProjWin {
 
             if (sel.Count > MAX_SEL_COUNT) {
                 // Too much for WPF -- only restore the first item.
-                Debug.WriteLine("Not restoring selection (" + sel.Count + " items)");
+                Debug.WriteLine("SetSelection: not restoring (" + sel.Count + " items)");
                 codeListView.SelectedItems.Add(CodeDisplayList[sel.GetFirstSelectedIndex()]);
                 return;
             }
@@ -360,30 +363,49 @@ namespace SourceGenWPF.ProjWin {
         }
 
         private void CanHintAsCodeEntryPoint(object sender, CanExecuteRoutedEventArgs e) {
+            if (!mMainCtrl.IsProjectOpen()) {
+                e.CanExecute = false;
+                return;
+            }
             MainController.EntityCounts counts = mSelectionState.mEntityCounts;
-            e.CanExecute = mMainCtrl.IsProjectOpen() &&
-                (counts.mDataLines > 0 || counts.mCodeLines > 0) &&
+            e.CanExecute = (counts.mDataLines > 0 || counts.mCodeLines > 0) &&
                 (counts.mDataHints != 0 || counts.mInlineDataHints != 0 || counts.mNoHints != 0);
         }
         private void CanHintAsDataStart(object sender, CanExecuteRoutedEventArgs e) {
+            if (!mMainCtrl.IsProjectOpen()) {
+                e.CanExecute = false;
+                return;
+            }
             MainController.EntityCounts counts = mSelectionState.mEntityCounts;
-            e.CanExecute = mMainCtrl.IsProjectOpen() &&
-                (counts.mDataLines > 0 || counts.mCodeLines > 0) &&
+            e.CanExecute = (counts.mDataLines > 0 || counts.mCodeLines > 0) &&
                 (counts.mCodeHints != 0 || counts.mInlineDataHints != 0 || counts.mNoHints != 0);
         }
         private void CanHintAsInlineData(object sender, CanExecuteRoutedEventArgs e) {
+            if (!mMainCtrl.IsProjectOpen()) {
+                e.CanExecute = false;
+                return;
+            }
             MainController.EntityCounts counts = mSelectionState.mEntityCounts;
-            e.CanExecute = mMainCtrl.IsProjectOpen() &&
-                (counts.mDataLines > 0 || counts.mCodeLines > 0) &&
+            e.CanExecute = (counts.mDataLines > 0 || counts.mCodeLines > 0) &&
                 (counts.mCodeHints != 0 || counts.mDataHints != 0 || counts.mNoHints != 0);
         }
         private void CanRemoveHints(object sender, CanExecuteRoutedEventArgs e) {
+            if (!mMainCtrl.IsProjectOpen()) {
+                e.CanExecute = false;
+                return;
+            }
             MainController.EntityCounts counts = mSelectionState.mEntityCounts;
-            e.CanExecute = mMainCtrl.IsProjectOpen() &&
-                (counts.mDataLines > 0 || counts.mCodeLines > 0) &&
+            e.CanExecute = (counts.mDataLines > 0 || counts.mCodeLines > 0) &&
                 (counts.mCodeHints != 0 || counts.mDataHints != 0 || counts.mInlineDataHints != 0);
         }
 
+        private void CanRedo(object sender, CanExecuteRoutedEventArgs e) {
+            e.CanExecute = mMainCtrl.CanRedo();
+        }
+        private void CanUndo(object sender, CanExecuteRoutedEventArgs e) {
+            e.CanExecute = mMainCtrl.CanUndo();
+        }
+
         #endregion Can-execute handlers
 
 
@@ -400,26 +422,34 @@ namespace SourceGenWPF.ProjWin {
             }
         }
 
-        private void HintAsCodeEntryPoint_Executed(object sender, ExecutedRoutedEventArgs e) {
+        private void HelpCmd_Executed(object sender, ExecutedRoutedEventArgs e) {
+            mMainCtrl.ShowHelp();
+        }
+
+        private void HintAsCodeEntryPointCmd_Executed(object sender, ExecutedRoutedEventArgs e) {
             Debug.WriteLine("hint as code entry point");
             mMainCtrl.MarkAsType(CodeAnalysis.TypeHint.Code, true);
         }
 
-        private void HintAsDataStart_Executed(object sender, ExecutedRoutedEventArgs e) {
+        private void HintAsDataStartCmd_Executed(object sender, ExecutedRoutedEventArgs e) {
             Debug.WriteLine("hint as data start");
             mMainCtrl.MarkAsType(CodeAnalysis.TypeHint.Data, true);
         }
 
-        private void HintAsInlineData_Executed(object sender, ExecutedRoutedEventArgs e) {
+        private void HintAsInlineDataCmd_Executed(object sender, ExecutedRoutedEventArgs e) {
             Debug.WriteLine("hint as inline data");
             mMainCtrl.MarkAsType(CodeAnalysis.TypeHint.InlineData, false);
         }
 
-        private void RemoveHints_Executed(object sender, ExecutedRoutedEventArgs e) {
+        private void RemoveHintsCmd_Executed(object sender, ExecutedRoutedEventArgs e) {
             Debug.WriteLine("remove hints");
             mMainCtrl.MarkAsType(CodeAnalysis.TypeHint.NoHint, false);
         }
 
+        private void RedoCmd_Executed(object sender, ExecutedRoutedEventArgs e) {
+            mMainCtrl.RedoChanges();
+        }
+
         private void SelectAllCmd_Executed(object sender, ExecutedRoutedEventArgs e) {
             DateTime start = DateTime.Now;
 
@@ -448,6 +478,10 @@ namespace SourceGenWPF.ProjWin {
             mMainCtrl.OpenRecentProject(recentIndex);
         }
 
+        private void UndoCmd_Executed(object sender, ExecutedRoutedEventArgs e) {
+            mMainCtrl.UndoChanges();
+        }
+
         #endregion Command handlers