Overstrike mode - with options

data/resources/StringResources.resx

@@ -2400,6 +2400,9 @@ system. I don't think that it needs translation.</comment>
   <data name="Dialog.Options.IDEOptions.TextEditor.General.HideCursorWhileTypingCheckBoxCheckBox" xml:space="preserve">
     <value>Hide cursor while typing</value>
   </data>
+  <data name="Dialog.Options.IDEOptions.TextEditor.General.UseOverstrikeModeCheckBox" xml:space="preserve">
+    <value>Use overstrike mode</value>
+  </data>
   <data name="Dialog.Options.IDEOptions.TextEditor.General.ShowQuickClassBrowserCheckBox" xml:space="preserve">
     <value>Show &amp;Quick ClassBrowser Panel</value>
   </data>

src/AddIns/DisplayBindings/AvalonEdit.AddIn/Src/Options/GeneralEditorOptions.xaml

@@ -27,6 +27,9 @@
 				<CheckBox 
 					IsChecked="{core:OptionBinding local:CodeEditorOptions.ShowHiddenDefinitions}" 
 					Content="{core:Localize Dialog.Options.IDEOptions.TextEditor.Markers.ShowHiddenDefinitionsCheckBox}" />
+				<CheckBox 
+					IsChecked="{core:OptionBinding local:CodeEditorOptions.UseOverstrikeMode}" 
+					Content="{core:Localize Dialog.Options.IDEOptions.TextEditor.General.UseOverstrikeModeCheckBox}" />
 			</widgets:StackPanelWithSpacing>
 		</GroupBox>
 	</StackPanel>

src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Editing/TextArea.cs

@@ -866,8 +866,11 @@ namespace ICSharpCode.AvalonEdit.Editing
 			if (!e.Handled) {
 				if (e.Text == "\n" || e.Text == "\r" || e.Text == "\r\n")
 					ReplaceSelectionWithNewLine();
-				else
+				else {
+					if (overstrikeMode && Selection.IsEmpty && Document.GetLineByNumber(Caret.Line).EndOffset > Caret.Offset)
+						Selection = Selection.Create(this, Caret.Offset, Caret.Offset+e.Text.Length);
 					ReplaceSelectionWithText(e.Text);
+				}
 				OnTextEntered(e);
 				caret.BringCaretToView();
 			}
@@ -952,6 +955,15 @@ namespace ICSharpCode.AvalonEdit.Editing
 		protected override void OnPreviewKeyDown(KeyEventArgs e)
 		{
 			base.OnPreviewKeyDown(e);
+			
+			if (!this.Options.UseOverstrikeMode) {
+				this.overstrikeMode = false;
+			} else if (!e.Handled && e.Key == Key.Insert) {
+				this.overstrikeMode = !this.overstrikeMode;
+				e.Handled = true;
+				return;
+			}
+			
 			HideMouseCursor();
 			foreach (TextAreaStackedInputHandler h in stackedInputHandlers) {
 				if (e.Handled)
@@ -1017,6 +1029,12 @@ namespace ICSharpCode.AvalonEdit.Editing
 		
 		#endregion
 		
+		#region Overstrike mode
+		
+		bool overstrikeMode = false;
+		
+		#endregion
+		
 		/// <inheritdoc/>
 		protected override HitTestResult HitTestCore(PointHitTestParameters hitTestParameters)
 		{

src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/TextEditorOptions.cs

@@ -462,5 +462,21 @@ namespace ICSharpCode.AvalonEdit
 				}
 			}
 		}
+		
+		bool useOverstrikeMode = false;
+		
+		[DefaultValue(false)]
+		/// <summary>
+		/// Gets/Sets if overstrike mode is enabled to use
+		/// </summary>
+		public bool UseOverstrikeMode {
+			get { return useOverstrikeMode; }
+			set {
+				if (useOverstrikeMode != value) {
+					useOverstrikeMode = value;
+					OnPropertyChanged("UseOverstrikeMode");
+				}
+			}
+		}
 	}
 }