Add support for Surrogate Unicode sequences

src/Consolonia.Core/Consolonia.Core.csproj

@@ -6,8 +6,9 @@
         <PackageReference Include="Avalonia.FreeDesktop" Version="$(AvaloniaVersion)" />
         <PackageReference Include="Avalonia.Skia" Version="$(AvaloniaVersion)" />
         <PackageReference Include="Avalonia.Controls.DataGrid" Version="$(AvaloniaVersion)" />
-        <PackageReference Include="NullLib.ConsoleEx" Version="1.0.4.4" />
         <PackageReference Include="SkiaSharp.NativeAssets.Linux.NoDependencies" Version="2.88.8" />
+        <PackageReference Include="Unicode.net" Version="2.0.0" />
+        <PackageReference Include="Wcwidth" Version="2.0.0" />
     </ItemGroup>
 
 </Project>

src/Consolonia.Core/Drawing/ConsoleBrush.cs

@@ -1,11 +1,13 @@
 using System;
+using System.Diagnostics;
 using Avalonia;
 using Avalonia.Media;
 using Consolonia.Core.Drawing.PixelBufferImplementation;
 using Consolonia.Core.Infrastructure;
 
 namespace Consolonia.Core.Drawing
 {
+    [DebuggerDisplay("{Color} [{Mode}]")]
     public class ConsoleBrush : AvaloniaObject, IImmutableBrush
     {
         public static readonly StyledProperty<Color> ColorProperty =

src/Consolonia.Core/Drawing/DrawingContextImpl.cs

@@ -5,8 +5,10 @@
 using Avalonia;
 using Avalonia.Media;
 using Avalonia.Media.Immutable;
+using Avalonia.Media.TextFormatting;
 using Avalonia.Platform;
 using Consolonia.Core.Drawing.PixelBufferImplementation;
+using Consolonia.Core.Helpers;
 using Consolonia.Core.Infrastructure;
 using Consolonia.Core.InternalHelpers;
 using Consolonia.Core.Text;
@@ -24,7 +26,8 @@ internal class DrawingContextImpl : IDrawingContextImpl
         private const byte HorizontalEndPattern = 0b0001;
 
         public const int UnderlineThickness = 10;
-        public const int StrikthroughThickness = 11;
+        public const int StrikethroughThickness = 11;
+
         private readonly Stack<Rect> _clipStack = new(100);
         private readonly ConsoleWindow _consoleWindow;
         private readonly PixelBuffer _pixelBuffer;
@@ -91,7 +94,8 @@ public void DrawBitmap(IBitmapImpl source, double opacity, Rect sourceRect, Rect
                 Color foreground = GetForegroundColorForQuadPixel(quadColors, quadPixel);
                 Color background = GetBackgroundColorForQuadPixel(quadColors, quadPixel);
 
-                var imagePixel = new Pixel(new PixelForeground(new SimpleSymbol(quadPixel), color: foreground),
+                var imagePixel = new Pixel(
+                    new PixelForeground(new SimpleSymbol(quadPixel), color: foreground),
                     new PixelBackground(background));
                 CurrentClip.ExecuteWithClipping(new Point(px, py),
                     () =>
@@ -206,9 +210,9 @@ public void DrawGlyphRun(IBrush foreground, IGlyphRunImpl glyphRun)
                 return;
             }
 
-            string charactersDoDraw =
-                string.Concat(glyphRunImpl.GlyphIndices.Select(us => (char)us).ToArray());
-            DrawStringInternal(foreground, charactersDoDraw, glyphRun.GlyphTypeface);
+            var shapedBuffer = (ShapedBuffer)glyphRunImpl.GlyphInfos;
+            string text = shapedBuffer.Text.ToString();
+            DrawStringInternal(foreground, text, glyphRun.GlyphTypeface);
         }
 
         public IDrawingContextLayerImpl CreateLayer(Size size)
@@ -302,9 +306,12 @@ private void DrawLineInternal(IPen pen, Line line)
             line = TransformLineInternal(line);
 
             Point head = line.PStart;
-
-            if (IfMoveConsoleCaretMove(pen, head))
+            if (pen.Brush is MoveConsoleCaretToPositionBrush)
+            {
+                CurrentClip.ExecuteWithClipping(head,
+                    () => { _pixelBuffer.Set((PixelBufferCoordinate)head, pixel => pixel.Blend(new Pixel(true))); });
                 return;
+            }
 
             if (line.Vertical == false && pen.Thickness > 1)
             {
@@ -328,7 +335,7 @@ private void ApplyTextDecorationLineInternal(ref Point head, IPen pen, Line line
             TextDecorationCollection textDecoration = pen.Thickness switch
             {
                 UnderlineThickness => TextDecorations.Underline,
-                StrikthroughThickness => TextDecorations.Strikethrough,
+                StrikethroughThickness => TextDecorations.Strikethrough,
                 _ => throw new ArgumentOutOfRangeException($"Unsupported thickness {pen.Thickness}")
             };
 
@@ -366,8 +373,12 @@ private void DrawRectangleLineInternal(IPen pen, Line line)
 
             Point head = line.PStart;
 
-            if (IfMoveConsoleCaretMove(pen, head))
+            if (pen.Brush is MoveConsoleCaretToPositionBrush)
+            {
+                CurrentClip.ExecuteWithClipping(head,
+                    () => { _pixelBuffer.Set((PixelBufferCoordinate)head, pixel => pixel.Blend(new Pixel(true))); });
                 return;
+            }
 
             var extractColorCheckPlatformSupported = ExtractColorOrNullWithPlatformCheck(pen, out var lineStyle);
             if (extractColorCheckPlatformSupported == null)
@@ -398,22 +409,6 @@ private Line TransformLineInternal(Line line)
             return line;
         }
 
-        /// <summary>
-        ///     If the pen brush is a MoveConsoleCaretToPositionBrush, move the caret
-        /// </summary>
-        /// <param name="pen"></param>
-        /// <param name="head"></param>
-        /// <returns></returns>
-        private bool IfMoveConsoleCaretMove(IPen pen, Point head)
-        {
-            if (pen.Brush is not MoveConsoleCaretToPositionBrush)
-                return false;
-
-            CurrentClip.ExecuteWithClipping(head,
-                () => { _pixelBuffer.Set((PixelBufferCoordinate)head, pixel => pixel.Blend(new Pixel(true))); });
-            return true;
-        }
-
         /// <summary>
         ///     Extract color from pen brush
         /// </summary>
@@ -486,7 +481,7 @@ private void DrawPixelAndMoveHead(ref Point head, Line line, LineStyle? lineStyl
             }
         }
 
-        private void DrawStringInternal(IBrush foreground, string str, IGlyphTypeface typeface, Point origin = new())
+        private void DrawStringInternal(IBrush foreground, string text, IGlyphTypeface typeface, Point origin = new())
         {
             foreground = ConsoleBrush.FromBrush(foreground);
             if (foreground is not ConsoleBrush { Mode: PixelBackgroundMode.Colored } consoleBrush)
@@ -495,23 +490,27 @@ private void DrawPixelAndMoveHead(ref Point head, Line line, LineStyle? lineStyl
                 return;
             }
 
-            //if (!Transform.IsTranslateOnly()) ConsoloniaPlatform.RaiseNotSupported(15);
+            // if (!Transform.IsTranslateOnly()) ConsoloniaPlatform.RaiseNotSupported(15);
 
             Point whereToDraw = origin.Transform(Transform);
             int currentXPosition = 0;
+            int currentYPosition = 0;
 
-            //todo: support surrogates
-            foreach (char c in str)
+            // Each glyph maps to a pixel as a starting point.
+            // Emoji's and Ligatures are complex strings, so they start at a point and then overlap following pixels
+            // the x and y are adjusted accodingly.
+            foreach (string glyph in text.GetGlyphs())
             {
-                Point characterPoint = whereToDraw.Transform(Matrix.CreateTranslation(currentXPosition++, 0));
+                Point characterPoint =
+                    whereToDraw.Transform(Matrix.CreateTranslation(currentXPosition, currentYPosition));
                 Color foregroundColor = consoleBrush.Color;
 
-                switch (c)
+                switch (glyph)
                 {
-                    case '\t':
+                    case "\t":
                     {
                         const int tabSize = 8;
-                        var consolePixel = new Pixel(' ', foregroundColor);
+                        var consolePixel = new Pixel(new SimpleSymbol(' '), foregroundColor);
                         for (int j = 0; j < tabSize; j++)
                         {
                             Point newCharacterPoint = characterPoint.WithX(characterPoint.X + j);
@@ -525,26 +524,26 @@ private void DrawPixelAndMoveHead(ref Point head, Line line, LineStyle? lineStyl
                         currentXPosition += tabSize - 1;
                     }
                         break;
-                    case '\n':
-                    {
-                        /* it's not clear if we need to draw anything. Cursor can be placed at the end of the line
-                         var consolePixel =  new Pixel(' ', foregroundColor);
-
-                        _pixelBuffer.Set((PixelBufferCoordinate)characterPoint,
-                            (oldPixel, cp) => oldPixel.Blend(cp), consolePixel);*/
-                    }
-                        break;
-                    case '\u200B':
-                        currentXPosition--;
+                    case "\r":
+                    case "\f":
+                    case "\n":
+                        currentXPosition = 0;
+                        currentYPosition++;
                         break;
                     default:
                     {
-                        var consolePixel = new Pixel(c, foregroundColor, typeface.Style, typeface.Weight);
+                        var symbol = new SimpleSymbol(glyph);
+                        var consolePixel = new Pixel(symbol, foregroundColor, typeface.Style, typeface.Weight);
                         CurrentClip.ExecuteWithClipping(characterPoint, () =>
                         {
                             _pixelBuffer.Set((PixelBufferCoordinate)characterPoint,
                                 (oldPixel, cp) => oldPixel.Blend(cp), consolePixel);
                         });
+
+                        if (symbol.Width > 1)
+                            currentXPosition += symbol.Width;
+                        else
+                            currentXPosition++;
                     }
                         break;
                 }

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

@@ -1,10 +1,12 @@
 using System;
+using System.Diagnostics;
 
 namespace Consolonia.Core.Drawing.PixelBufferImplementation
 {
     /// <summary>
     ///     https://en.wikipedia.org/wiki/Box-drawing_character
     /// </summary>
+    [DebuggerDisplay("DrawingBox {Text}")]
     public struct DrawingBoxSymbol : ISymbol
     {
         // all 0bXXXX_0000 are special values
@@ -18,10 +20,14 @@ public DrawingBoxSymbol(byte upRightDownLeft)
 
         private byte _upRightDownLeft;
 
+        public string Text => GetBoxSymbol().ToString();
+
+        public ushort Width { get; } = 1;
+
         /// <summary>
         ///     https://en.wikipedia.org/wiki/Code_page_437
         /// </summary>
-        char ISymbol.GetCharacter()
+        private char GetBoxSymbol()
         {
             //DOS linedraw characters are not ordered in any programmatic manner, and calculating a particular character shape needs to use a look-up table. from https://en.wikipedia.org/wiki/Box-drawing_character
 
@@ -106,22 +112,21 @@ public ISymbol Blend(ref ISymbol symbolAbove)
                 _upRightDownLeft = BoldSymbol;
             else
                 _upRightDownLeft |= drawingBoxSymbol._upRightDownLeft;
-
             return this;
         }
 
-        public static byte UpRightDownLeftFromPattern(byte pattern, LineStyle lineStyle)
+        public static DrawingBoxSymbol UpRightDownLeftFromPattern(byte pattern, LineStyle lineStyle)
         {
-            if (pattern == EmptySymbol) return EmptySymbol;
+            if (pattern == EmptySymbol) return new DrawingBoxSymbol(EmptySymbol);
             switch (lineStyle)
             {
                 case LineStyle.SingleLine:
-                    return pattern;
+                    return new DrawingBoxSymbol(pattern);
                 case LineStyle.Bold:
-                    return BoldSymbol;
+                    return new DrawingBoxSymbol(BoldSymbol);
                 case LineStyle.DoubleLine:
                     byte leftPart = (byte)(pattern << 4);
-                    return (byte)(leftPart | pattern);
+                    return new DrawingBoxSymbol((byte)(leftPart | pattern));
                 default:
                     throw new ArgumentOutOfRangeException(nameof(lineStyle), lineStyle, null);
             }

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

@@ -2,8 +2,23 @@ namespace Consolonia.Core.Drawing.PixelBufferImplementation
 {
     public interface ISymbol
     {
-        char GetCharacter();
+        /// <summary>
+        ///     The text for the symbol (This can be single character or unicode encoding for Emoji's and the like)
+        /// </summary>
+        string Text { get; }
+
+        /// <summary>
+        ///     The number of characters the symbol takes up
+        /// </summary>
+        ushort Width { get; }
+
         bool IsWhiteSpace();
+
+        /// <summary>
+        ///     Blend 2 symbols together
+        /// </summary>
+        /// <param name="symbolAbove"></param>
+        /// <returns></returns>
         ISymbol Blend(ref ISymbol symbolAbove);
     }
 }

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

@@ -1,11 +1,13 @@
 using System;
+using System.Diagnostics;
 using Avalonia.Media;
 
 // ReSharper disable MemberCanBePrivate.Global
 // ReSharper disable UnusedMember.Global
 
 namespace Consolonia.Core.Drawing.PixelBufferImplementation
 {
+    [DebuggerDisplay("'{Foreground.Symbol.Text}' [{Foreground.Color}, {Background.Color}]")]
     public readonly struct Pixel
     {
         public PixelForeground Foreground { get; }
@@ -14,22 +16,13 @@ public readonly struct Pixel
 
         public bool IsCaret { get; }
 
-        public Pixel(bool isCaret) : this(PixelBackgroundMode.Transparent)
+        public Pixel(bool isCaret)
         {
+            Foreground = new PixelForeground(new SimpleSymbol());
+            Background = new PixelBackground(PixelBackgroundMode.Transparent);
             IsCaret = isCaret;
         }
 
-        public Pixel(char character, Color foregroundColor, FontStyle style = FontStyle.Normal,
-            FontWeight weight = FontWeight.Normal) :
-            this(new SimpleSymbol(character), foregroundColor, style, weight)
-        {
-        }
-
-        public Pixel(byte drawingBoxSymbol, Color foregroundColor) : this(
-            new DrawingBoxSymbol(drawingBoxSymbol), foregroundColor)
-        {
-        }
-
         public Pixel(ISymbol symbol, Color foregroundColor, FontStyle style = FontStyle.Normal,
             FontWeight weight = FontWeight.Normal, TextDecorationCollection textDecorations = null) : this(
             new PixelForeground(symbol, weight, style, textDecorations, foregroundColor),
@@ -68,11 +61,17 @@ public Pixel Blend(Pixel pixelAbove)
                 case PixelBackgroundMode.Colored:
                     // merge pixelAbove into this pixel using alpha channel.
                     Color mergedColors = MergeColors(Background.Color, pixelAbove.Background.Color);
-                    return new Pixel(pixelAbove.Foreground,
-                        new PixelBackground(mergedColors));
+                    newForeground = pixelAbove.Foreground;
+                    newBackground = new PixelBackground(mergedColors);
+                    return new Pixel(newForeground, newBackground);
 
                 case PixelBackgroundMode.Transparent:
-                    newForeground = Foreground.Blend(pixelAbove.Foreground);
+                    // if the foreground is transparent, ignore pixelAbove foreground.
+                    newForeground = pixelAbove.Foreground.Color != Colors.Transparent
+                        ? Foreground.Blend(pixelAbove.Foreground)
+                        : Foreground;
+
+                    // background is transparent, ignore pixelAbove background.
                     newBackground = Background;
                     break;
                 case PixelBackgroundMode.Shaded:

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

@@ -1,8 +1,10 @@
 using System;
+using System.Diagnostics;
 using Avalonia.Media;
 
 namespace Consolonia.Core.Drawing.PixelBufferImplementation
 {
+    [DebuggerDisplay("[{Color}, {Mode}]")]
     public readonly struct PixelBackground
     {
         public PixelBackground(Color color)

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

@@ -1,8 +1,10 @@
 using System;
+using System.Diagnostics;
 using Avalonia.Media;
 
 namespace Consolonia.Core.Drawing.PixelBufferImplementation
 {
+    [DebuggerDisplay("'{Symbol.Text}' [{Color}]")]
     public readonly struct PixelForeground
     {
         public PixelForeground(ISymbol symbol, FontWeight weight = FontWeight.Normal,
@@ -38,8 +40,6 @@ public PixelForeground Blend(PixelForeground pixelAboveForeground)
             ISymbol symbolAbove = pixelAboveForeground.Symbol;
             ArgumentNullException.ThrowIfNull(symbolAbove);
 
-            if (symbolAbove.IsWhiteSpace()) return this;
-
             ISymbol newSymbol = Symbol.Blend(ref symbolAbove);
 
             return new PixelForeground(newSymbol, pixelAboveForeground.Weight, pixelAboveForeground.Style,