Fix strikethrough implementation

src/Consolonia.Core/Drawing/DrawingContextImpl.cs

@@ -23,6 +23,8 @@
         private const byte HorizontalLinePattern = 0b0101;
         private const byte HorizontalEndPattern = 0b0001;
 
+        public const int UnderlineThickness = 10;
+        public const int StrikthroughThickness = 11;
         private readonly Stack<Rect> _clipStack = new(100);
         private readonly ConsoleWindow _consoleWindow;
         private readonly PixelBuffer _pixelBuffer;
@@ -304,6 +306,13 @@
             if (IfMoveConsoleCaretMove(pen, head))
                 return;
 
+            if (line.Vertical == false && pen.Thickness > 1)
+            {
+                // horizontal lines with thickness larger than one are text decorations
+                ApplyTextDecorationLineInternal(ref head, pen, line);
+                return;
+            }
+
             var extractColorCheckPlatformSupported = ExtractColorOrNullWithPlatformCheck(pen, out var lineStyle);
             if (extractColorCheckPlatformSupported == null)
                 return;
@@ -314,6 +323,36 @@
             DrawPixelAndMoveHead(ref head, line, lineStyle, pattern, color, line.Length); //line
         }
 
+        private void ApplyTextDecorationLineInternal(ref Point head, IPen pen, Line line)
+        {
+            TextDecorationCollection textDecoration = pen.Thickness switch
+            {
+                UnderlineThickness => TextDecorations.Underline,
+                StrikthroughThickness => TextDecorations.Strikethrough,
+                _ => throw new ArgumentOutOfRangeException($"Unsupported thickness {pen.Thickness}")
+            };
+
+            for (int x = 0; x < line.Length; x++)
+            {
+                Point h = head;
+                CurrentClip.ExecuteWithClipping(h, () =>
+                {
+                    // ReSharper disable once AccessToModifiedClosure todo: pass as a parameter
+                    _pixelBuffer.Set((PixelBufferCoordinate)h,
+                        pixel =>
+                        {
+                            var newPixelForeground = new PixelForeground(pixel.Foreground.Symbol,
+                                pixel.Foreground.Weight,
+                                pixel.Foreground.Style,
+                                textDecoration,
+                                pixel.Foreground.Color);
+                            return pixel.Blend(new Pixel(newPixelForeground, pixel.Background));
+                        });
+                });
+                head = head.WithX(head.X + 1);
+            }
+        }
+
         /// <summary>
         ///     Draw a rectangle line with corners
         /// </summary>
@@ -388,7 +427,7 @@
             if (pen is not
                 {
                     Brush: ConsoleBrush or LineBrush or ImmutableSolidColorBrush,
-                    Thickness: 1,
+                    // Thickness: 1,
                     DashStyle: null or { Dashes: { Count: 0 } },
                     LineCap: PenLineCap.Flat,
                     LineJoin: PenLineJoin.Miter
@@ -671,7 +710,7 @@
                     var clusteredColors = colors.Where((_, i) => clusters[i] == cluster).ToList();
                     if (clusteredColors.Any())
                         newClusterCenters[cluster] = GetAverageColor(clusteredColors);
                     if (clusteredColors.Count == 4)
                         if (clusteredColors.All(c => c.Alpha == 0))
                             return "FFFF";
                     //    return "TTTT";

src/Consolonia.Core/Drawing/PixelBufferImplementation/Pixel.cs

@@ -72,17 +72,7 @@ public Pixel Blend(Pixel pixelAbove)
                         new PixelBackground(mergedColors));
 
                 case PixelBackgroundMode.Transparent:
-                    // when a textdecoration of underline happens a DrawLine() is called over the top of the a pixel with non-zero symbol.
-                    // this detects this situation and eats the draw line, turning it into a textdecoration
-                    if (pixelAbove.Foreground.Symbol is DrawingBoxSymbol &&
-                        Foreground.Symbol is SimpleSymbol simpleSymbol &&
-                        ((ISymbol)simpleSymbol).GetCharacter() != (char)0)
-                        // this is a line being draw through text. add TextDecoration for underline.
-                        newForeground = new PixelForeground(Foreground.Symbol, Foreground.Weight, Foreground.Style,
-                            TextDecorations.Underline, Foreground.Color);
-                    else
-                        // do normal blend.
-                        newForeground = Foreground.Blend(pixelAbove.Foreground);
+                    newForeground = Foreground.Blend(pixelAbove.Foreground);
                     newBackground = Background;
                     break;
                 case PixelBackgroundMode.Shaded:

src/Consolonia.Core/Text/GlyphTypeface.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Linq;
 using Avalonia.Media;
+using Consolonia.Core.Drawing;
 
 namespace Consolonia.Core.Text
 {
@@ -73,11 +74,10 @@ public bool TryGetTable(uint tag, out byte[] table)
             Ascent = -1, //var height = (GlyphTypeface.Descent - GlyphTypeface.Ascent + GlyphTypeface.LineGap) * Scale; //todo: need to consult Avalonia guys
             Descent = 0,
             LineGap = 0,
-            UnderlinePosition =
-                -1, // this turns on TextDecorations="Underline", -1 is so it draws over the top of the text.
-            UnderlineThickness = 1, // this is the thickness of the underline, aka 1 char thick.
+            UnderlinePosition = -1,
+            UnderlineThickness = DrawingContextImpl.UnderlineThickness,
             StrikethroughPosition = -1,
-            StrikethroughThickness = 1,
+            StrikethroughThickness = DrawingContextImpl.StrikthroughThickness,
             IsFixedPitch = true
         };
 

src/Consolonia.Gallery/Gallery/GalleryViews/GalleryTextBlock.axaml

@@ -30,21 +30,20 @@
                    Text="Multiline TextBlock with TextWrapping.

Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vivamus magna. Cras in mi at felis aliquet congue. Ut a est eget ligula molestie gravida. Curabitur massa. Donec eleifend, libero at sagittis mollis, tellus est malesuada tellus, at luctus turpis elit sit amet quam. Vivamus pretium ornare est." />
         <TextBlock TextWrapping="Wrap"
                    Text="Special characters: Élève naïve: “𝔉𝔞𝔫𝔠𝔶” ligatures like ff, fi, and fl; numbers ½, ¼; symbols like @, #, and €; emoji 😊; and math symbols Ω, ∑, √…"/>
-        <StackPanel Orientation="Horizontal">
-            <TextBlock Text="TextDecoration=Underline" TextDecorations="Underline" HorizontalAlignment="Left"/>
-            <TextBlock Text="TextDecoration=Strikethrough" HorizontalAlignment="Left" TextDecorations="Strikethrough" />
-            <TextBlock Text="FontStyle=Italic" FontStyle="Italic" HorizontalAlignment="Left"/>
-        </StackPanel>
-        <StackPanel Orientation="Horizontal">
-            <TextBlock Text="FontWeight=BOLD" FontWeight="Bold" Foreground="Sienna"/>
-            <TextBlock Text="FontWeight=NORMAL" FontWeight="Normal" Foreground="Sienna"/>
-            <TextBlock Text="FontWeight=LIGHT" FontWeight="Light" Foreground="Sienna"/>
-        </StackPanel>
-        <StackPanel Orientation="Horizontal">
-            <TextBlock Text="FontWeight=BOLD" Background="DarkMagenta" Foreground="Yellow" FontWeight="Bold"/>
-            <TextBlock Text="FontWeight=NORMAL" Background="DarkMagenta" Foreground="Yellow" FontWeight="Normal"/>
-            <TextBlock Text="FontWeight=LIGHT" Background="DarkMagenta" Foreground="Yellow" FontWeight="Light"/>
-        </StackPanel>
+        <WrapPanel>
+            <TextBlock Text="Underline" TextDecorations="Underline" HorizontalAlignment="Left" Margin="1 0"/>
+            <TextBlock Text="Strikethrough" HorizontalAlignment="Left" TextDecorations="Strikethrough"  Margin="1 0"/>
+            <TextBlock Text="Italic" FontStyle="Italic" HorizontalAlignment="Left"  Margin="1 0"/>
+            <TextBlock Text="Italic and Underline" FontStyle="Italic" TextDecorations="Underline" HorizontalAlignment="Left"  Margin="1 0"/>
+        </WrapPanel>
+        <WrapPanel >
+            <TextBlock Text="BOLD" FontWeight="Bold" Foreground="Sienna" Margin="1 0"/>
+            <TextBlock Text="NORMAL" FontWeight="Normal" Foreground="Sienna" Margin="1 0"/>
+            <TextBlock Text="LIGHT" FontWeight="Light" Foreground="Sienna" Margin="1 0"/>
+            <TextBlock Text="BOLD" Background="DarkMagenta" Foreground="Yellow" FontWeight="Bold" Margin="1 0"/>
+            <TextBlock Text="NORMAL" Background="DarkMagenta" Foreground="Yellow" FontWeight="Normal" Margin="1 0"/>
+            <TextBlock Text="LIGHT" Background="DarkMagenta" Foreground="Yellow" FontWeight="Light" Margin="1 0"/>
+        </WrapPanel>
 
     </StackPanel>