fix issue 158 Shading is computed wrong. (#160)

* fix issue 158 Shading is computed wrong.
* added unit tests

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

@@ -125,9 +125,15 @@ public Pixel Blend(Pixel pixelAbove)
                     newBackground = Background;
                     break;
                 case PixelBackgroundMode.Shaded:
+                    // shade the current pixel
                     (newForeground, newBackground) = Shade();
+
+                    // blend the pixelAbove foreground into the shaded pixel
                     newForeground = newForeground.Blend(pixelAbove.Foreground);
-                    break;
+
+                    // resulting in new pixel with shaded background and blended foreground
+                    return new Pixel(newForeground, newBackground);
+
                 default: throw new ArgumentOutOfRangeException(nameof(pixelAbove));
             }
 

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

@@ -1,5 +1,4 @@
 using System;
-using System.ComponentModel;
 using System.Diagnostics;
 using System.Diagnostics.CodeAnalysis;
 using Avalonia.Media;
@@ -14,13 +13,13 @@ public PixelForeground()
         {
             Symbol = new SimpleSymbol(" ");
             Color = Colors.Transparent;
-            Weight = FontWeight.Normal;
-            Style = FontStyle.Normal;
+            Weight = null;
+            Style = null;
             TextDecoration = null;
         }
 
         public PixelForeground(ISymbol symbol, Color color,
-            FontWeight weight = FontWeight.Normal, FontStyle style = FontStyle.Normal,
+            FontWeight? weight = null, FontStyle? style = null,
             TextDecorationLocation? textDecoration = null)
         {
             ArgumentNullException.ThrowIfNull(symbol);
@@ -36,15 +35,13 @@ public PixelForeground(ISymbol symbol, Color color,
         [JsonConverter(typeof(ColorConverter))]
         public Color Color { get; init; }
 
-        [DefaultValue(FontWeight.Normal)]
-        [JsonProperty(DefaultValueHandling = DefaultValueHandling.IgnoreAndPopulate)]
-        public FontWeight Weight { get; init; }
+        [JsonProperty(NullValueHandling = NullValueHandling.Ignore)]
+        public FontWeight? Weight { get; init; }
 
-        [DefaultValue(FontStyle.Normal)]
-        [JsonProperty(DefaultValueHandling = DefaultValueHandling.Ignore)]
-        public FontStyle Style { get; init; }
+        [JsonProperty(NullValueHandling = NullValueHandling.Ignore)]
+        public FontStyle? Style { get; init; }
 
-        [JsonProperty(DefaultValueHandling = DefaultValueHandling.Ignore)]
+        [JsonProperty(NullValueHandling = NullValueHandling.Ignore)]
         public TextDecorationLocation? TextDecoration { get; init; }
 
         public bool Equals(PixelForeground other)
@@ -68,10 +65,15 @@ public PixelForeground Blend(PixelForeground pixelAboveForeground)
             ISymbol symbolAbove = pixelAboveForeground.Symbol;
             ArgumentNullException.ThrowIfNull(symbolAbove);
 
-            ISymbol newSymbol = Symbol.Blend(ref symbolAbove);
+            if (pixelAboveForeground.Color == Colors.Transparent)
+                // if pixelAbove is transparent then the foreground below should be unchanged.
+                return this;
 
-            return new PixelForeground(newSymbol, pixelAboveForeground.Color, pixelAboveForeground.Weight,
-                pixelAboveForeground.Style, pixelAboveForeground.TextDecoration);
+            return new PixelForeground(Symbol.Blend(ref symbolAbove),
+                pixelAboveForeground.Color,
+                pixelAboveForeground.Weight ?? Weight,
+                pixelAboveForeground.Style ?? Style,
+                pixelAboveForeground.TextDecoration ?? TextDecoration);
         }
 
         public override bool Equals([NotNullWhen(true)] object obj)
@@ -81,7 +83,8 @@ public override bool Equals([NotNullWhen(true)] object obj)
 
         public override int GetHashCode()
         {
-            return HashCode.Combine(Symbol, Color, (int)Weight, (int)Style, TextDecoration);
+            return HashCode.Combine(Symbol, Color, (int)(Weight ?? FontWeight.Normal), (int)(Style ?? FontStyle.Normal),
+                TextDecoration);
         }
 
         public static bool operator ==(PixelForeground left, PixelForeground right)

src/Consolonia.Core/Drawing/RenderTarget.cs

@@ -156,8 +156,8 @@ private struct FlushingBuffer
             private readonly StringBuilder _stringBuilder;
             private Color _lastBackgroundColor;
             private Color _lastForegroundColor;
-            private FontStyle _lastStyle = FontStyle.Normal;
-            private FontWeight _lastWeight = FontWeight.Normal;
+            private FontStyle? _lastStyle;
+            private FontWeight? _lastWeight;
             private TextDecorationLocation? _lastTextDecoration;
             private PixelBufferCoordinate _currentBufferPoint;
             private PixelBufferCoordinate _lastBufferPointStart;

src/Consolonia.Core/Dummy/DummyConsole.cs

@@ -54,8 +54,8 @@ public void PauseIO(Task task)
         {
         }
 
-        public void Print(PixelBufferCoordinate bufferPoint, Color background, Color foreground, FontStyle style,
-            FontWeight weight, TextDecorationLocation? textDecoration, string str)
+        public void Print(PixelBufferCoordinate bufferPoint, Color background, Color foreground, FontStyle? style,
+            FontWeight? weight, TextDecorationLocation? textDecoration, string str)
         {
         }
 

src/Consolonia.Core/Infrastructure/IConsole.cs

@@ -26,8 +26,8 @@ public interface IConsole : IDisposable
         void SetCaretPosition(PixelBufferCoordinate bufferPoint);
         PixelBufferCoordinate GetCaretPosition();
 
-        void Print(PixelBufferCoordinate bufferPoint, Color background, Color foreground, FontStyle style,
-            FontWeight weight, TextDecorationLocation? textDecoration, string str);
+        void Print(PixelBufferCoordinate bufferPoint, Color background, Color foreground, FontStyle? style,
+            FontWeight? weight, TextDecorationLocation? textDecoration, string str);
 
         void WriteText(string str);
 

src/Consolonia.Core/Infrastructure/InputLessDefaultNetConsole.cs

@@ -97,8 +97,8 @@ public PixelBufferCoordinate GetCaretPosition()
             return _headBufferPoint;
         }
 
-        public void Print(PixelBufferCoordinate bufferPoint, Color background, Color foreground, FontStyle style,
-            FontWeight weight, TextDecorationLocation? textDecoration, string str)
+        public void Print(PixelBufferCoordinate bufferPoint, Color background, Color foreground, FontStyle? style,
+            FontWeight? weight, TextDecorationLocation? textDecoration, string str)
         {
             PauseTask?.Wait();
             SetCaretPosition(bufferPoint);

src/Consolonia.Designer/ConsolePreview.cs

@@ -373,9 +373,9 @@ private class TextBlockComposer
             private readonly StringBuilder _textBuilder;
             private Color _lastBackgroundColor;
             private Color _lastForegroundColor;
-            private FontStyle _lastStyle = FontStyle.Normal;
+            private FontStyle? _lastStyle;
             private TextDecorationLocation? _lastTextDecorations;
-            private FontWeight _lastWeight = FontWeight.Normal;
+            private FontWeight? _lastWeight;
             private double _textRunCharWidth;
 
             public TextBlockComposer(StackPanel panel, double charWidth)
@@ -433,8 +433,8 @@ public void Flush()
                     Text = text,
                     Foreground = new SolidColorBrush(_lastForegroundColor),
                     Background = new SolidColorBrush(_lastBackgroundColor),
-                    FontWeight = _lastWeight,
-                    FontStyle = _lastStyle,
+                    FontWeight = _lastWeight ?? FontWeight.Normal,
+                    FontStyle = _lastStyle ?? FontStyle.Normal,
                     FontSize = 17,
                     TextDecorations = _lastTextDecorations switch
                     {

src/Consolonia.NUnit/UnitTestConsole.cs

@@ -55,8 +55,8 @@ PixelBufferCoordinate IConsole.GetCaretPosition()
             return _fakeCaretPosition;
         }
 
-        void IConsole.Print(PixelBufferCoordinate bufferPoint, Color background, Color foreground, FontStyle style,
-            FontWeight weight, TextDecorationLocation? textDecoration, string str)
+        void IConsole.Print(PixelBufferCoordinate bufferPoint, Color background, Color foreground, FontStyle? style,
+            FontWeight? weight, TextDecorationLocation? textDecoration, string str)
         {
             (ushort x, ushort y) = bufferPoint;
 

src/Tests/Consolonia.Core.Tests/PixelForegroundTests.cs

@@ -17,9 +17,9 @@ public void Constructor()
             Assert.That(pixelForeground.Color, Is.EqualTo(Colors.Transparent));
             Assert.That(pixelForeground.Symbol.Text, Is.EqualTo(" "));
             Assert.That(pixelForeground.Symbol.Width, Is.EqualTo(1));
-            Assert.That(pixelForeground.Weight, Is.EqualTo(FontWeight.Normal));
-            Assert.That(pixelForeground.Style, Is.EqualTo(FontStyle.Normal));
-            Assert.That(pixelForeground.TextDecoration, Is.Null);
+            Assert.IsNull(pixelForeground.Weight);
+            Assert.IsNull(pixelForeground.Style);
+            Assert.IsNull(pixelForeground.TextDecoration);
         }
 
         [Test]
@@ -29,9 +29,9 @@ public void ConstructorWithSymbol()
             var pixelForeground = new PixelForeground(symbol, Colors.Red);
             Assert.That(pixelForeground.Color, Is.EqualTo(Colors.Red));
             Assert.That(pixelForeground.Symbol.Text, Is.EqualTo("a"));
-            Assert.That(pixelForeground.Weight, Is.EqualTo(FontWeight.Normal));
-            Assert.That(pixelForeground.Style, Is.EqualTo(FontStyle.Normal));
-            Assert.That(pixelForeground.TextDecoration, Is.Null);
+            Assert.IsNull(pixelForeground.Weight);
+            Assert.IsNull(pixelForeground.Style);
+            Assert.IsNull(pixelForeground.TextDecoration);
         }
 
         [Test]
@@ -42,8 +42,8 @@ public void ConstructorWithSymbolAndWeight()
             Assert.That(pixelForeground.Color, Is.EqualTo(Colors.Red));
             Assert.That(pixelForeground.Symbol.Text, Is.EqualTo("a"));
             Assert.That(pixelForeground.Weight, Is.EqualTo(FontWeight.Bold));
-            Assert.That(pixelForeground.Style, Is.EqualTo(FontStyle.Normal));
-            Assert.That(pixelForeground.TextDecoration, Is.Null);
+            Assert.IsNull(pixelForeground.Style);
+            Assert.IsNull(pixelForeground.TextDecoration);
         }
 
         [Test]
@@ -53,9 +53,9 @@ public void ConstructorWithSymbolAndStyle()
             var pixelForeground = new PixelForeground(symbol, Colors.Red, style: FontStyle.Italic);
             Assert.That(pixelForeground.Color, Is.EqualTo(Colors.Red));
             Assert.That(pixelForeground.Symbol.Text, Is.EqualTo("a"));
-            Assert.That(pixelForeground.Weight, Is.EqualTo(FontWeight.Normal));
+            Assert.IsNull(pixelForeground.Weight);
             Assert.That(pixelForeground.Style, Is.EqualTo(FontStyle.Italic));
-            Assert.That(pixelForeground.TextDecoration, Is.Null);
+            Assert.IsNull(pixelForeground.TextDecoration);
         }
 
         [Test]
@@ -66,8 +66,8 @@ public void ConstructorWithSymbolAndTextDecorations()
             var pixelForeground = new PixelForeground(symbol, Colors.Red, textDecoration: textDecoration);
             Assert.That(pixelForeground.Color, Is.EqualTo(Colors.Red));
             Assert.That(pixelForeground.Symbol.Text, Is.EqualTo("a"));
-            Assert.That(pixelForeground.Weight, Is.EqualTo(FontWeight.Normal));
-            Assert.That(pixelForeground.Style, Is.EqualTo(FontStyle.Normal));
+            Assert.IsNull(pixelForeground.Weight);
+            Assert.IsNull(pixelForeground.Style);
             Assert.That(pixelForeground.TextDecoration, Is.EqualTo(TextDecorationLocation.Underline));
         }
 
@@ -79,9 +79,9 @@ public void ConstructorWithWideCharacter()
             var pixelForeground = new PixelForeground(symbol, Colors.Red);
             Assert.That(pixelForeground.Color, Is.EqualTo(Colors.Red));
             Assert.That(pixelForeground.Symbol.Text, Is.EqualTo("🎵"));
-            Assert.That(pixelForeground.Weight, Is.EqualTo(FontWeight.Normal));
-            Assert.That(pixelForeground.Style, Is.EqualTo(FontStyle.Normal));
-            Assert.That(pixelForeground.TextDecoration, Is.Null);
+            Assert.IsNull(pixelForeground.Weight);
+            Assert.IsNull(pixelForeground.Style);
+            Assert.IsNull(pixelForeground.TextDecoration);
         }
 
         [Test]

src/Tests/Consolonia.Core.Tests/PixelTests.cs

@@ -59,9 +59,9 @@ public void ConstructorDrawingBoxSymbolAndColor()
                 new PixelBackground(Colors.Blue));
             Assert.That(pixel.Foreground.Symbol.Text, Is.EqualTo("┼"));
             Assert.That(pixel.Foreground.Color, Is.EqualTo(Colors.Red));
-            Assert.That(pixel.Foreground.Style, Is.EqualTo(FontStyle.Normal));
-            Assert.That(pixel.Foreground.Weight, Is.EqualTo(FontWeight.Normal));
-            Assert.That(pixel.Foreground.TextDecoration, Is.Null);
+            Assert.IsNull(pixel.Foreground.Style);
+            Assert.IsNull(pixel.Foreground.Weight);
+            Assert.IsNull(pixel.Foreground.TextDecoration);
             Assert.That(pixel.Background.Color, Is.EqualTo(Colors.Blue));
             Assert.That(pixel.Background.Mode, Is.EqualTo(PixelBackgroundMode.Colored));
         }
@@ -142,6 +142,42 @@ public void BlendColoredBackground()
             Assert.That(newPixel.Background.Color, Is.EqualTo(Colors.Blue));
         }
 
+        [Test]
+        public void BlendShadedBackground()
+        {
+            var pixel = new Pixel(new PixelForeground(new SimpleSymbol("x"), Colors.Gray),
+                new PixelBackground(Colors.White));
+            var pixel2 = new Pixel(new PixelBackground(PixelBackgroundMode.Shaded));
+            Pixel newPixel = pixel.Blend(pixel2);
+            Assert.True(newPixel.Foreground.Symbol.Text == "x");
+            // foreground should be lighter than original
+            Assert.True(newPixel.Foreground.Color.R < pixel.Foreground.Color.R &&
+                        newPixel.Foreground.Color.G < pixel.Foreground.Color.G &&
+                        newPixel.Foreground.Color.B < pixel.Foreground.Color.B);
+            // background should be darker than original
+            Assert.True(newPixel.Background.Color.R < pixel.Background.Color.R &&
+                        newPixel.Background.Color.G < pixel.Background.Color.G &&
+                        newPixel.Background.Color.B < pixel.Background.Color.B);
+        }
+
+        [Test]
+        public void BlendShadedBackground2()
+        {
+            var pixel = new Pixel(new PixelForeground(new SimpleSymbol("x"), Colors.Gray),
+                new PixelBackground(Colors.Black));
+            var pixel2 = new Pixel(new PixelBackground(PixelBackgroundMode.Shaded));
+            Pixel newPixel = pixel.Blend(pixel2);
+            Assert.True(newPixel.Foreground.Symbol.Text == "x");
+            // foreground should be darker than original
+            Assert.True(newPixel.Foreground.Color.R < pixel.Foreground.Color.R &&
+                        newPixel.Foreground.Color.G < pixel.Foreground.Color.G &&
+                        newPixel.Foreground.Color.B < pixel.Foreground.Color.B);
+            // background should be darker than original
+            Assert.True(newPixel.Background.Color.R > pixel.Background.Color.R &&
+                        newPixel.Background.Color.G > pixel.Background.Color.G &&
+                        newPixel.Background.Color.B > pixel.Background.Color.B);
+        }
+
         [Test]
         public void HashCode()
         {