Consider border thickness when rounding to pixel boundaries (#38).

ICSharpCode.AvalonEdit.Sample/ICSharpCode.AvalonEdit.Sample.csproj

@@ -16,7 +16,7 @@
     <TreatWarningsAsErrors>False</TreatWarningsAsErrors>
     <IntermediateOutputPath>obj\$(Configuration)\</IntermediateOutputPath>
     <WarningLevel>4</WarningLevel>
-    <PlatformTarget>AnyCPU</PlatformTarget>
+    <PlatformTarget>x86</PlatformTarget>
     <BaseAddress>4194304</BaseAddress>
     <RegisterForComInterop>False</RegisterForComInterop>
     <GenerateSerializationAssemblies>Auto</GenerateSerializationAssemblies>
@@ -40,8 +40,8 @@
     <Optimize>False</Optimize>
     <CheckForOverflowUnderflow>True</CheckForOverflowUnderflow>
     <BaseIntermediateOutputPath>obj\</BaseIntermediateOutputPath>
-	<DefineDebug>True</DefineDebug>
-	<DefineTrace>True</DefineTrace>
+    <DefineDebug>True</DefineDebug>
+    <DefineTrace>True</DefineTrace>
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)' == 'Release' ">
     <OutputPath>bin\Release\</OutputPath>
@@ -50,7 +50,7 @@
     <Optimize>True</Optimize>
     <CheckForOverflowUnderflow>False</CheckForOverflowUnderflow>
     <BaseIntermediateOutputPath>obj\</BaseIntermediateOutputPath>
-	<DefineTrace>True</DefineTrace>
+    <DefineTrace>True</DefineTrace>
   </PropertyGroup>
   <ItemGroup>
     <ProjectReference Include="..\..\NRefactory\ICSharpCode.NRefactory\ICSharpCode.NRefactory.csproj" Condition="$(DefineConstants.Contains('NREFACTORY'))">

ICSharpCode.AvalonEdit.Sample/Window1.xaml.cs

@@ -60,6 +60,8 @@ namespace ICSharpCode.AvalonEdit.Sample
 			#endif
 			propertyGridComboBox.SelectedIndex = 2;
 			
+			//textEditor.TextArea.SelectionBorder = null;
+			
 			//textEditor.SyntaxHighlighting = HighlightingManager.Instance.GetDefinition("C#");
 			//textEditor.SyntaxHighlighting = customHighlighting;
 			// initial highlighting now set by XAML

ICSharpCode.AvalonEdit/Editing/SelectionLayer.cs

@@ -21,6 +21,7 @@ using System.Windows;
 using System.Windows.Media;
 
 using ICSharpCode.AvalonEdit.Rendering;
+using ICSharpCode.AvalonEdit.Utils;
 
 namespace ICSharpCode.AvalonEdit.Editing
 {
@@ -52,8 +53,11 @@ namespace ICSharpCode.AvalonEdit.Editing
 		{
 			base.OnRender(drawingContext);
 			
+			var selectionBorder = textArea.SelectionBorder;
+			
 			BackgroundGeometryBuilder geoBuilder = new BackgroundGeometryBuilder();
-			geoBuilder.AlignToMiddleOfPixels = true;
+			geoBuilder.AlignToWholePixels = true;
+			geoBuilder.BorderThickness = selectionBorder != null ? selectionBorder.Thickness : 0;
 			geoBuilder.ExtendToFullWidthAtLineEnd = textArea.Selection.EnableVirtualSpace;
 			geoBuilder.CornerRadius = textArea.SelectionCornerRadius;
 			foreach (var segment in textArea.Selection.Segments) {
@@ -61,7 +65,7 @@ namespace ICSharpCode.AvalonEdit.Editing
 			}
 			Geometry geometry = geoBuilder.CreateGeometry();
 			if (geometry != null) {
-				drawingContext.DrawGeometry(textArea.SelectionBrush, textArea.SelectionBorder, geometry);
+				drawingContext.DrawGeometry(textArea.SelectionBrush, selectionBorder, geometry);
 			}
 		}
 	}

ICSharpCode.AvalonEdit/Editing/TextArea.cs

@@ -470,7 +470,7 @@ namespace ICSharpCode.AvalonEdit.Editing
 			DependencyProperty.Register("SelectionForeground", typeof(Brush), typeof(TextArea));
 		
 		/// <summary>
-		/// Gets/Sets the foreground brush used selected text.
+		/// Gets/Sets the foreground brush used for selected text.
 		/// </summary>
 		public Brush SelectionForeground {
 			get { return (Brush)GetValue(SelectionForegroundProperty); }
@@ -484,7 +484,7 @@ namespace ICSharpCode.AvalonEdit.Editing
 			DependencyProperty.Register("SelectionBorder", typeof(Pen), typeof(TextArea));
 		
 		/// <summary>
-		/// Gets/Sets the background brush used for the selection.
+		/// Gets/Sets the pen used for the border of the selection.
 		/// </summary>
 		public Pen SelectionBorder {
 			get { return (Pen)GetValue(SelectionBorderProperty); }

ICSharpCode.AvalonEdit/ICSharpCode.AvalonEdit.csproj

@@ -42,6 +42,7 @@
     <AssemblyOriginatorKeyFile>..\..\NRefactory\ICSharpCode.NRefactory.snk</AssemblyOriginatorKeyFile>
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)' == 'Debug' ">
+    <DefineConstants>DEBUG;$(DefineConstants)</DefineConstants>
     <OutputPath>bin\Debug\</OutputPath>
     <DocumentationFile>bin\Debug\ICSharpCode.AvalonEdit.xml</DocumentationFile>
     <DebugSymbols>true</DebugSymbols>

ICSharpCode.AvalonEdit/Properties/AssemblyInfo.cs

@@ -54,7 +54,7 @@ using System.Windows.Markup;
 [assembly: AssemblyCompany("ic#code")]
 [assembly: AssemblyProduct("SharpDevelop")]
 [assembly: AssemblyCopyright("2000-2014 AlphaSierraPapa for the SharpDevelop Team")]
-[assembly: AssemblyVersion("5.0.1")]
+[assembly: AssemblyVersion("5.0.3")]
 [assembly: NeutralResourcesLanguage("en-US")]
 
 [assembly: XmlnsPrefix("http://icsharpcode.net/sharpdevelop/avalonedit", "avalonedit")]

ICSharpCode.AvalonEdit/Rendering/BackgroundGeometryBuilder.cs

@@ -18,6 +18,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Diagnostics;
 using System.Linq;
 using System.Windows;
 using System.Windows.Controls.Primitives;
@@ -46,14 +47,41 @@ namespace ICSharpCode.AvalonEdit.Rendering
 		}
 		
 		/// <summary>
-		/// Gets/Sets whether to align the geometry to whole pixels.
+		/// Gets/Sets whether to align to whole pixels.
+		/// 
+		/// If BorderThickness is set to 0, the geometry is aligned to whole pixels.
+		/// If BorderThickness is set to a non-zero value, the outer edge of the border is aligned
+		/// to whole pixels.
+		/// 
+		/// The default value is <c>false</c>.
 		/// </summary>
 		public bool AlignToWholePixels { get; set; }
 		
+		/// <summary>
+		/// Gets/sets the border thickness.
+		/// 
+		/// This property only has an effect if <c>AlignToWholePixels</c> is enabled.
+		/// When using the resulting geometry to paint a border, set this property to the border thickness.
+		/// Otherwise, leave the property set to the default value <c>0</c>.
+		/// </summary>
+		public double BorderThickness { get; set; }
+		
+		bool alignToMiddleOfPixels;
+		
 		/// <summary>
 		/// Gets/Sets whether to align the geometry to the middle of pixels.
 		/// </summary>
-		public bool AlignToMiddleOfPixels { get; set; }
+		[Obsolete("Use the AlignToWholePixels and BorderThickness properties instead. "
+		          + "Setting AlignToWholePixels=true and setting the BorderThickness to the pixel size " 
+		          + "is equivalent to aligning the geometry to the middle of pixels.")]
+		public bool AlignToMiddleOfPixels {
+			get {
+				return alignToMiddleOfPixels;
+			}
+			set {
+				alignToMiddleOfPixels = value;
+			}
+		}
 		
 		/// <summary>
 		/// Gets/Sets whether to extend the rectangles to full width at line end.
@@ -96,17 +124,19 @@ namespace ICSharpCode.AvalonEdit.Rendering
 		void AddRectangle(Size pixelSize, Rect r)
 		{
 			if (AlignToWholePixels) {
-				AddRectangle(PixelSnapHelpers.Round(r.Left, pixelSize.Width),
-				             PixelSnapHelpers.Round(r.Top + 1, pixelSize.Height),
-				             PixelSnapHelpers.Round(r.Right, pixelSize.Width),
-				             PixelSnapHelpers.Round(r.Bottom + 1, pixelSize.Height));
-			} else if (AlignToMiddleOfPixels) {
+				double halfBorder = 0.5 * BorderThickness;
+				AddRectangle(PixelSnapHelpers.Round(r.Left - halfBorder, pixelSize.Width) + halfBorder,
+				             PixelSnapHelpers.Round(r.Top - halfBorder, pixelSize.Height) + halfBorder,
+				             PixelSnapHelpers.Round(r.Right + halfBorder, pixelSize.Width) - halfBorder,
+				             PixelSnapHelpers.Round(r.Bottom + halfBorder, pixelSize.Height) - halfBorder);
+				//Debug.WriteLine(r.ToString() + " -> " + new Rect(lastLeft, lastTop, lastRight-lastLeft, lastBottom-lastTop).ToString());
+			} else if (alignToMiddleOfPixels) {
 				AddRectangle(PixelSnapHelpers.PixelAlign(r.Left, pixelSize.Width),
-				             PixelSnapHelpers.PixelAlign(r.Top + 1, pixelSize.Height),
+				             PixelSnapHelpers.PixelAlign(r.Top, pixelSize.Height),
 				             PixelSnapHelpers.PixelAlign(r.Right, pixelSize.Width),
-				             PixelSnapHelpers.PixelAlign(r.Bottom + 1, pixelSize.Height));
+				             PixelSnapHelpers.PixelAlign(r.Bottom, pixelSize.Height));
 			} else {
-				AddRectangle(r.Left, r.Top + 1, r.Right, r.Bottom + 1);
+				AddRectangle(r.Left, r.Top, r.Right, r.Bottom);
 			}
 		}
 		

ICSharpCode.AvalonEdit/Rendering/VisualLine.cs

@@ -484,7 +484,7 @@ namespace ICSharpCode.AvalonEdit.Rendering
 		{
 			if (xPos > textLine.WidthIncludingTrailingWhitespace) {
 				if (allowVirtualSpace && textLine == TextLines[TextLines.Count - 1]) {
-					int virtualX = (int)Math.Round((xPos - textLine.WidthIncludingTrailingWhitespace) / textView.WideSpaceWidth);
+					int virtualX = (int)Math.Round((xPos - textLine.WidthIncludingTrailingWhitespace) / textView.WideSpaceWidth, MidpointRounding.AwayFromZero);
 					return VisualLengthWithEndOfLineMarker + virtualX;
 				}
 			}

ICSharpCode.AvalonEdit/Search/SearchResultBackgroundRenderer.cs

@@ -80,7 +80,8 @@ namespace ICSharpCode.AvalonEdit.Search
 			
 			foreach (SearchResult result in currentResults.FindOverlappingSegments(viewStart, viewEnd - viewStart)) {
 				BackgroundGeometryBuilder geoBuilder = new BackgroundGeometryBuilder();
-				geoBuilder.AlignToMiddleOfPixels = true;
+				geoBuilder.AlignToWholePixels = true;
+				geoBuilder.BorderThickness = markerPen != null ? markerPen.Thickness : 0;
 				geoBuilder.CornerRadius = 3;
 				geoBuilder.AddSegment(textView, result);
 				Geometry geometry = geoBuilder.CreateGeometry();

ICSharpCode.AvalonEdit/Snippets/SnippetReplaceableTextElement.cs

@@ -203,7 +203,8 @@ namespace ICSharpCode.AvalonEdit.Snippets
 				ISegment s = element.Segment;
 				if (s != null) {
 					BackgroundGeometryBuilder geoBuilder = new BackgroundGeometryBuilder();
-					geoBuilder.AlignToMiddleOfPixels = true;
+					geoBuilder.AlignToWholePixels = true;
+					geoBuilder.BorderThickness = activeBorderPen != null ? activeBorderPen.Thickness : 0;
 					if (Layer == KnownLayer.Background) {
 						geoBuilder.AddSegment(textView, s);
 						drawingContext.DrawGeometry(backgroundBrush, null, geoBuilder.CreateGeometry());

ICSharpCode.AvalonEdit/Utils/PixelSnapHelpers.cs

@@ -56,7 +56,7 @@ namespace ICSharpCode.AvalonEdit.Utils
 			// 0.5 -> 0.5
 			// 0.9 -> 0.5
 			// 1 -> 1.5
-			return pixelSize * (Math.Round((value / pixelSize) + 0.5) - 0.5);
+			return pixelSize * (Math.Round((value / pixelSize) + 0.5, MidpointRounding.AwayFromZero) - 0.5);
 		}
 		
 		/// <summary>
@@ -93,7 +93,7 @@ namespace ICSharpCode.AvalonEdit.Utils
 		/// </summary>
 		public static double Round(double value, double pixelSize)
 		{
-			return pixelSize * Math.Round(value / pixelSize);
+			return pixelSize * Math.Round(value / pixelSize, MidpointRounding.AwayFromZero);
 		}
 		
 		/// <summary>