128-131: Good addition of debug-time validation for shading operations.

The debug assertion ensures that shading operations are only performed with blank symbols, preventing undefined behavior early in development.

133-134: Improved efficiency of shaded pixel handling.

The direct return of the shaded pixel eliminates unnecessary blending operations, making the code more efficient and clearer in its intent.

145-161: ⚠️ Potential issue

Fix test inconsistencies and improve assertions.

1. The comment "foreground should be lighter" contradicts the assertions checking for lower RGB values (darker colors).
2. Consider using specific color value assertions for more precise testing.
3. Consider renaming the test to better describe the white background case.

Apply this diff to fix the issues:

-        public void BlendShadedBackground()
+        public void BlendShadedBackground_WithWhiteBackground_DarkensBothColors()
         {
             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
+            // 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 specific color values for more precise testing
+            var expectedForeground = Colors.DarkGray;  // Replace with actual expected color
+            var expectedBackground = Colors.LightGray;  // Replace with actual expected color
+            Assert.That(newPixel.Foreground.Color, Is.EqualTo(expectedForeground), "Foreground color should match expected darker shade");
+            Assert.That(newPixel.Background.Color, Is.EqualTo(expectedBackground), "Background color should match expected darker shade");

95-96: LGTM!

The indentation changes improve readability while preserving the correct cache initialization logic.

114-119: LGTM: Improved caret position validation

The new caret handling logic properly validates that only one caret position exists, throwing an exception if multiple carets are detected.

159-160: Verify handling of nullable font properties

The change from non-nullable to nullable font properties requires careful handling of default values. Please ensure:

1. The constructor properly initializes these nullable fields
2. All usage sites handle the null case appropriately

Let's check the usage of these properties:

_lastWeight != pixel.Foreground.Weight ||
_lastStyle != pixel.Foreground.Style

FontWeight = _lastWeight ?? FontWeight.Normal,
FontStyle = _lastStyle ?? FontStyle.Normal,

_lastStyle = pixel.Foreground.Style;
_lastWeight = pixel.Foreground.Weight;

#!/bin/bash
# Search for FontStyle and FontWeight usage
ast-grep --pattern 'FontStyle $_' 
ast-grep --pattern 'FontWeight $_'

# Check for null checks on these properties
rg '\b_lastStyle\b|\b_lastWeight\b' -A 2 -B 2

121-123: Address TODO comments regarding window invalidation and resize handling

There are two TODO comments that need attention:

1. Window invalidation logic needs to be updated due to API changes
2. Potential IndexOutOfRange exception during resize operations

These issues could affect the stability of the rendering system.

Let's check for any existing issues or discussions about these TODOs:

Would you like me to help create GitHub issues to track these TODOs?

Also applies to: 125-126

29-30: LGTM! Verify implementations across the codebase.

The change to make FontStyle and FontWeight nullable is well-reasoned and maintains backward compatibility.

Let's verify that all implementations of IConsole have been updated consistently:

#!/bin/bash
# Search for all Print method implementations to ensure consistent nullable parameters
ast-grep --pattern 'void Print(PixelBufferCoordinate $_, Color $_, Color $_, FontStyle $style, FontWeight $weight, $_)'

#!/bin/bash
# Let's try a broader search pattern to find Print method implementations
ast-grep --pattern 'void Print(PixelBufferCoordinate'

# Also search for files that might implement IConsole
rg "class.*:.*IConsole" -l

#!/bin/bash
# Let's examine the Print method implementation in each of these files
echo "=== UnitTestConsole.cs ==="
rg "void Print.*PixelBufferCoordinate" -A 2 src/Consolonia.NUnit/UnitTestConsole.cs

echo -e "\n=== DummyConsole.cs ==="
rg "void Print.*PixelBufferCoordinate" -A 2 src/Consolonia.Core/Dummy/DummyConsole.cs

echo -e "\n=== InputLessDefaultNetConsole.cs ==="
rg "void Print.*PixelBufferCoordinate" -A 2 src/Consolonia.Core/Infrastructure/InputLessDefaultNetConsole.cs

57-58: LGTM! Implementation matches interface changes.

The signature update correctly implements the nullable parameters from the interface.

17-18: LGTM! Proper initialization of nullable properties.

The default constructor correctly initializes nullable properties to null, which is consistent with the struct's new design.

39-43: LGTM! Proper JSON serialization handling.

The NullValueHandling.Ignore attribute ensures that null style values won't be included in serialized output, reducing payload size.

89-89: LGTM! Proper null handling in GetHashCode.

The null-coalescing operator ensures consistent hash codes by using FontWeight.Normal and FontStyle.Normal as defaults.

69-79: Key fix for shading computation.

The new transparency check and blending logic fixes the core issue:

1. Transparent pixels no longer affect the foreground below them
2. Style inheritance is properly handled with null-coalescing

Let's verify the impact of this change on shading behavior:

#!/bin/bash
# Search for tests that verify the transparency behavior
rg -l "Colors\.Transparent.*Blend" --type cs

# Search for other potential shading-related code that might need updates
ast-grep --pattern 'Shade()'

#!/bin/bash
# Let's examine the Shade() implementation and its usage context
ast-grep --pattern 'Shade() {
  $$$
}'

# Also check for test files related to shading or transparency
rg -l "test.*shade|test.*transparent" --type cs -i

# Look for any direct usage of the PixelForeground class
rg "new PixelForeground" -A 3 --type cs

#!/bin/bash
# Let's check the implementation of Shade() method and its context
rg -A 10 "Shade\(\)" --type cs

# Also check for any transparency-related tests
rg -A 5 "Colors\.Transparent.*test" --type cs

58-59: LGTM: Parameter nullability changes are correctly implemented.

The changes to make FontStyle and FontWeight nullable are properly implemented and align with the interface changes.

62-64: LGTM: Null assertions are correctly updated.

The assertions have been properly updated to check for null values, aligning with the changes to make Style, Weight, and TextDecoration nullable.

153-156: Fix inconsistency between comment and assertions.

The comment states "foreground should be lighter" but the assertions check for lower RGB values (darker colors).

175-178: Fix inconsistency between comment and assertions.

The comment states "background should be darker" but the assertions check for higher RGB values (lighter colors).

32-34: LGTM: Consistent null handling across all constructors

The changes consistently implement the new nullable property design across all constructor test cases. This systematic approach helps ensure reliable behavior when these properties are unspecified.

Also applies to: 45-47, 56-58, 69-70, 82-84

20-22: Verify the intention behind making font properties nullable

The change from asserting specific default values to checking for null values indicates a significant design change in how font properties are handled. This could affect how shading is computed when these properties are null.

#!/bin/bash
# Check for other occurrences of these properties to ensure consistent handling
ast-grep --pattern 'Assert.That($_, Is.EqualTo(FontWeight.Normal))'
ast-grep --pattern 'Assert.That($_, Is.EqualTo(FontStyle.Normal))'

#!/bin/bash
# Check the implementation of Pixel and PixelForeground classes
ast-grep --pattern 'class PixelForeground'
ast-grep --pattern 'class Pixel'

# Check for any other tests related to these properties
rg "Weight|Style|TextDecoration" src/Tests/Consolonia.Core.Tests/PixelForegroundTests.cs -A 2

376-378: LGTM: Field types updated to match the new nullable design

The changes to make _lastStyle and _lastWeight nullable are consistent with the modifications in the test file, maintaining design consistency across the codebase.

376-378: Please clarify the connection to shading computation

While the changes to make font properties nullable are well-implemented and consistent, it's not immediately clear how these changes address the incorrect shading computation mentioned in issue #158. Could you please explain the relationship between font property nullability and shading computation?

Also applies to: 436-437

16-17: LGTM: Nullable property initialization

The initialization of Weight and Style to null aligns with making these properties nullable and removes implicit defaults, providing more flexibility in styling.

86-87: LGTM: Proper null handling in GetHashCode

The implementation correctly handles null values by providing appropriate defaults, ensuring consistent hash codes across instances.

68-76: Improved blending logic with proper transparency handling

The changes correctly handle transparent colors and provide clean fallback behavior for nullable properties. The early return for transparent colors is an optimization that prevents unnecessary object creation.

Let's verify the transparency handling with some test cases:

Line range hint 20-34: LGTM: Updated assertions for nullable properties

The test cases correctly verify the null state of Weight, Style, and TextDecoration properties in both default and parameterized constructors.

82-84: LGTM: Wide character handling with nullable properties

The test properly verifies that wide character handling maintains the expected null state of optional properties.