Overstrike mode visual effects

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

@@ -32,7 +32,7 @@ namespace ICSharpCode.AvalonEdit.Editing
 			this.textView = textArea.TextView;
 			position = new TextViewPosition(1, 1, 0);
 			
-			caretAdorner = new CaretLayer(textView);
+			caretAdorner = new CaretLayer(textArea);
 			textView.InsertLayer(caretAdorner, KnownLayer.Caret, LayerInsertionPosition.Replace);
 			textView.VisualLinesChanged += TextView_VisualLinesChanged;
 			textView.ScrollOffsetChanged += TextView_ScrollOffsetChanged;
@@ -367,6 +367,26 @@ namespace ICSharpCode.AvalonEdit.Editing
 			                lineBottom - lineTop);
 		}
 		
+		Rect CalcCaretOverstrikeRectangle(VisualLine visualLine)
+		{
+			if (!visualColumnValid) {
+				RevalidateVisualColumn(visualLine);
+			}
+			
+			TextLine textLine = visualLine.GetTextLine(position.VisualColumn, position.IsAtEndOfLine);
+			double xPos = visualLine.GetTextLineVisualXPosition(textLine, position.VisualColumn);
+			double lineTop = visualLine.GetTextLineVisualYPosition(textLine, VisualYPosition.TextTop);
+			double lineBottom = visualLine.GetTextLineVisualYPosition(textLine, VisualYPosition.TextBottom);
+			double charSize = 
+				visualLine.GetTextLineVisualXPosition(textLine, VisualColumn + 1) -
+				visualLine.GetTextLineVisualXPosition(textLine, VisualColumn);
+			
+			return new Rect(xPos,
+			                lineTop,
+			                charSize,
+			                lineBottom - lineTop);
+		}
+		
 		/// <summary>
 		/// Returns the caret rectangle. The coordinate system is in device-independent pixels from the top of the document.
 		/// </summary>
@@ -374,7 +394,8 @@ namespace ICSharpCode.AvalonEdit.Editing
 		{
 			if (textView != null && textView.Document != null) {
 				VisualLine visualLine = textView.GetOrConstructVisualLine(textView.Document.GetLineByNumber(position.Line));
-				return CalcCaretRectangle(visualLine);
+				return (this.textView.Options.UseOverstrikeMode && this.textArea.OverstrikeMode)
+					? CalcCaretOverstrikeRectangle(visualLine) : CalcCaretRectangle(visualLine);
 			} else {
 				return Rect.Empty;
 			}
@@ -429,7 +450,12 @@ namespace ICSharpCode.AvalonEdit.Editing
 			if (caretAdorner != null && textView != null) {
 				VisualLine visualLine = textView.GetVisualLine(position.Line);
 				if (visualLine != null) {
-					Rect caretRect = CalcCaretRectangle(visualLine);
+					Rect caretRect;
+					if (this.textView.Options.UseOverstrikeMode && this.textArea.OverstrikeMode) {
+						caretRect = CalcCaretOverstrikeRectangle(visualLine);
+					} else {
+						caretRect = CalcCaretRectangle(visualLine);
+					}
 					// Create Win32 caret so that Windows knows where our managed caret is. This is necessary for
 					// features like 'Follow text editing' in the Windows Magnifier.
 					if (!hasWin32Caret) {

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

@@ -15,14 +15,17 @@ namespace ICSharpCode.AvalonEdit.Editing
 {
 	sealed class CaretLayer : Layer
 	{
+		TextArea textArea;
+		
 		bool isVisible;
 		Rect caretRectangle;
 		
 		DispatcherTimer caretBlinkTimer = new DispatcherTimer();
 		bool blink;
 		
-		public CaretLayer(TextView textView) : base(textView, KnownLayer.Caret)
+		public CaretLayer(TextArea textArea) : base(textArea.TextView, KnownLayer.Caret)
 		{
+			this.textArea = textArea;
 			this.IsHitTestVisible = false;
 			caretBlinkTimer.Tick += new EventHandler(caretBlinkTimer_Tick);
 		}
@@ -75,6 +78,16 @@ namespace ICSharpCode.AvalonEdit.Editing
 				Brush caretBrush = this.CaretBrush;
 				if (caretBrush == null)
 					caretBrush = (Brush)textView.GetValue(TextBlock.ForegroundProperty);
+				
+				if (this.textArea.Options.UseOverstrikeMode && this.textArea.OverstrikeMode) {
+					SolidColorBrush scBrush = caretBrush as SolidColorBrush;
+					if (scBrush != null) {
+						Color brushColor = scBrush.Color;
+						Color newColor = Color.FromArgb(100, brushColor.R, brushColor.G, brushColor.B);
+						caretBrush = new SolidColorBrush(newColor);
+					}
+				}
+				
 				Rect r = new Rect(caretRectangle.X - textView.HorizontalOffset,
 				                  caretRectangle.Y - textView.VerticalOffset,
 				                  caretRectangle.Width,

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

@@ -960,6 +960,7 @@ namespace ICSharpCode.AvalonEdit.Editing
 				this.overstrikeMode = false;
 			} else if (!e.Handled && e.Key == Key.Insert) {
 				this.overstrikeMode = !this.overstrikeMode;
+				this.caret.Show();
 				e.Handled = true;
 				return;
 			}
@@ -1033,6 +1034,11 @@ namespace ICSharpCode.AvalonEdit.Editing
 		
 		bool overstrikeMode = false;
 		
+		public bool OverstrikeMode
+		{
+			get { return this.overstrikeMode; }
+		}
+		
 		#endregion
 		
 		/// <inheritdoc/>