Initial commit: .NET MAUI Linux Platform

Complete Linux platform implementation for .NET MAUI with:

- 35+ Skia-rendered controls (Button, Label, Entry, CarouselView, etc.)
- Platform services (Clipboard, FilePicker, Notifications, DragDrop, etc.)
- Accessibility support (AT-SPI2, High Contrast)
- HiDPI and Input Method support
- 216 unit tests
- CI/CD workflows
- Project templates
- Documentation

🤖 Generated with Claude Code

Extensions/ColorExtensions.cs

@@ -0,0 +1,181 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using SkiaSharp;
+using Microsoft.Maui.Graphics;
+
+namespace Microsoft.Maui.Platform;
+
+/// <summary>
+/// Extension methods for color conversions between MAUI and SkiaSharp.
+/// </summary>
+public static class ColorExtensions
+{
+    /// <summary>
+    /// Converts a MAUI Color to an SKColor.
+    /// </summary>
+    public static SKColor ToSKColor(this Color color)
+    {
+        if (color == null)
+            return SKColors.Transparent;
+
+        return new SKColor(
+            (byte)(color.Red * 255),
+            (byte)(color.Green * 255),
+            (byte)(color.Blue * 255),
+            (byte)(color.Alpha * 255));
+    }
+
+    /// <summary>
+    /// Converts an SKColor to a MAUI Color.
+    /// </summary>
+    public static Color ToMauiColor(this SKColor color)
+    {
+        return new Color(
+            color.Red / 255f,
+            color.Green / 255f,
+            color.Blue / 255f,
+            color.Alpha / 255f);
+    }
+
+    /// <summary>
+    /// Creates a new SKColor with the specified alpha value.
+    /// </summary>
+    public static SKColor WithAlpha(this SKColor color, byte alpha)
+    {
+        return new SKColor(color.Red, color.Green, color.Blue, alpha);
+    }
+
+    /// <summary>
+    /// Creates a lighter version of the color.
+    /// </summary>
+    public static SKColor Lighter(this SKColor color, float factor = 0.2f)
+    {
+        return new SKColor(
+            (byte)Math.Min(255, color.Red + (255 - color.Red) * factor),
+            (byte)Math.Min(255, color.Green + (255 - color.Green) * factor),
+            (byte)Math.Min(255, color.Blue + (255 - color.Blue) * factor),
+            color.Alpha);
+    }
+
+    /// <summary>
+    /// Creates a darker version of the color.
+    /// </summary>
+    public static SKColor Darker(this SKColor color, float factor = 0.2f)
+    {
+        return new SKColor(
+            (byte)(color.Red * (1 - factor)),
+            (byte)(color.Green * (1 - factor)),
+            (byte)(color.Blue * (1 - factor)),
+            color.Alpha);
+    }
+
+    /// <summary>
+    /// Gets the luminance of the color.
+    /// </summary>
+    public static float GetLuminance(this SKColor color)
+    {
+        return 0.299f * color.Red / 255f +
+               0.587f * color.Green / 255f +
+               0.114f * color.Blue / 255f;
+    }
+
+    /// <summary>
+    /// Determines if the color is considered light.
+    /// </summary>
+    public static bool IsLight(this SKColor color)
+    {
+        return color.GetLuminance() > 0.5f;
+    }
+
+    /// <summary>
+    /// Gets a contrasting color (black or white) for text on this background.
+    /// </summary>
+    public static SKColor GetContrastingColor(this SKColor backgroundColor)
+    {
+        return backgroundColor.IsLight() ? SKColors.Black : SKColors.White;
+    }
+
+    /// <summary>
+    /// Converts a MAUI Paint to an SKColor if possible.
+    /// </summary>
+    public static SKColor? ToSKColorOrNull(this Paint? paint)
+    {
+        if (paint is SolidPaint solidPaint && solidPaint.Color != null)
+            return solidPaint.Color.ToSKColor();
+
+        return null;
+    }
+
+    /// <summary>
+    /// Converts a MAUI Paint to an SKColor, using a default if not a solid color.
+    /// </summary>
+    public static SKColor ToSKColor(this Paint? paint, SKColor defaultColor)
+    {
+        return paint.ToSKColorOrNull() ?? defaultColor;
+    }
+}
+
+/// <summary>
+/// Font extensions for converting MAUI fonts to SkiaSharp.
+/// </summary>
+public static class FontExtensions
+{
+    /// <summary>
+    /// Gets the SKFontStyle from a MAUI Font.
+    /// </summary>
+    public static SKFontStyle ToSKFontStyle(this Font font)
+    {
+        // Map MAUI FontWeight (enum with numeric values) to SKFontStyleWeight
+        var weight = (int)font.Weight switch
+        {
+            100 => SKFontStyleWeight.Thin,        // Thin
+            200 => SKFontStyleWeight.ExtraLight,  // UltraLight
+            300 => SKFontStyleWeight.Light,       // Light
+            400 => SKFontStyleWeight.Normal,      // Regular
+            500 => SKFontStyleWeight.Medium,      // Medium
+            600 => SKFontStyleWeight.SemiBold,    // Semibold
+            700 => SKFontStyleWeight.Bold,        // Bold
+            800 => SKFontStyleWeight.ExtraBold,   // Heavy
+            900 => SKFontStyleWeight.Black,       // Black
+            _ => font.Weight >= FontWeight.Bold ? SKFontStyleWeight.Bold : SKFontStyleWeight.Normal
+        };
+
+        var slant = font.Slant switch
+        {
+            FontSlant.Italic => SKFontStyleSlant.Italic,
+            FontSlant.Oblique => SKFontStyleSlant.Oblique,
+            _ => SKFontStyleSlant.Upright
+        };
+
+        return new SKFontStyle(weight, SKFontStyleWidth.Normal, slant);
+    }
+
+    /// <summary>
+    /// Creates an SKFont from a MAUI Font.
+    /// </summary>
+    public static SKFont ToSKFont(this Font font, float defaultSize = 14f)
+    {
+        var size = font.Size > 0 ? (float)font.Size : defaultSize;
+        var typeface = SKTypeface.FromFamilyName(font.Family ?? "sans-serif", font.ToSKFontStyle());
+        return new SKFont(typeface, size);
+    }
+}
+
+/// <summary>
+/// Thickness extensions for converting MAUI Thickness to SKRect.
+/// </summary>
+public static class ThicknessExtensions
+{
+    /// <summary>
+    /// Converts a MAUI Thickness to an SKRect representing padding/margin.
+    /// </summary>
+    public static SKRect ToSKRect(this Thickness thickness)
+    {
+        return new SKRect(
+            (float)thickness.Left,
+            (float)thickness.Top,
+            (float)thickness.Right,
+            (float)thickness.Bottom);
+    }
+}