Revert "Switch ColorPreviewer's AccentColorConverter to use the FluentTheme's HSL algorithm"

This reverts commit a91571aa49.

src/Avalonia.Controls.ColorPicker/Converters/AccentColorConverter.cs

@@ -13,6 +13,11 @@ namespace Avalonia.Controls.Primitives.Converters
     /// </remarks>
     public class AccentColorConverter : IValueConverter
     {
+        /// <summary>
+        /// The amount to change the Value component for each accent color step.
+        /// </summary>
+        public const double ValueDelta = 0.1;
+
         /// <inheritdoc/>
         public object? Convert(
             object? value,
@@ -96,54 +101,13 @@ namespace Avalonia.Controls.Primitives.Converters
         /// <returns>The new accent color.</returns>
         public static HsvColor GetAccent(HsvColor hsvColor, int accentStep)
         {
-            // Accent steps are taken from the FluentTheme:
-            //   SystemAccentColors.cs -> CalculateAccentShades()
-            //
-            // This is currently believed to be the most accurate representation of the algorithm in Windows.
-            // It replaces the previous implementation which adjusted Value +/- 10% per step.
-            // Any changes to FluentTheme's accent color calculation should be copied here.
-
-            const double dark1step = 28.5 / 255d;
-            const double dark2step = 49 / 255d;
-            const double dark3step = 74.5 / 255d;
-            const double light1step = 39 / 255d;
-            const double light2step = 70 / 255d;
-            const double light3step = 103 / 255d;
-
             if (accentStep != 0)
             {
-                // Temporary colors are used to preserve Hue through the RGB conversion
-                // Otherwise, at Black/White hue information would be lost
-                // This should be improved in the future with direct conversions to/from HSV/HSL.
-                var hslAccent = hsvColor.ToHsl();
-
-                double lightnessAdjustment = 0.0;
-                switch (accentStep)
-                {
-                    case -3:
-                        lightnessAdjustment = -dark3step;
-                        break;
-                    case -2:
-                        lightnessAdjustment = -dark2step;
-                        break;
-                    case -1:
-                        lightnessAdjustment = -dark1step;
-                        break;
-                    case 1:
-                        lightnessAdjustment = light1step;
-                        break;
-                    case 2:
-                        lightnessAdjustment = light2step;
-                        break;
-                    case 3:
-                        lightnessAdjustment = light3step;
-                        break;
-                }
-
-                var adjustedHsl = new HslColor(hslAccent.A, hslAccent.H, hslAccent.S, hslAccent.L + lightnessAdjustment);
-                // Rounding may be required here
+                double colorValue = hsvColor.V;
+                colorValue += (accentStep * AccentColorConverter.ValueDelta);
+                colorValue = Math.Round(colorValue, 2);
 
-                return adjustedHsl.ToHsv();
+                return new HsvColor(hsvColor.A, hsvColor.H, hsvColor.S, colorValue);
             }
             else
             {