Taskbar-Launcher/Services/ThemeService.cs

using System.Windows;
using System.Windows.Media;
using Microsoft.Win32;
using TaskbarLauncher.Models;
using MediaColor = System.Windows.Media.Color;

namespace TaskbarLauncher.Services;

public static class ThemeService
{
    private const string PersonalizeKey = @"Software\Microsoft\Windows\CurrentVersion\Themes\Personalize";
    private const string DwmKey = @"Software\Microsoft\Windows\DWM";

    public static void Apply(LauncherThemeScheme scheme = LauncherThemeScheme.MarkHaven)
    {
        bool isLight = IsLightTheme();
        ThemePalette palette = GetPalette(scheme, isLight);
        MediaColor accent = palette.Accent;
        MediaColor selectedText = IsDark(accent) ? System.Windows.Media.Colors.White : System.Windows.Media.Colors.Black;

        SetBrush("AppWindowBrush", palette.Window);
        SetBrush("AppSurfaceBrush", palette.Surface);
        SetBrush("AppPanelBrush", palette.Panel);
        SetBrush("AppControlBrush", palette.Control);
        SetBrush("AppControlHoverBrush", palette.Hover);
        SetBrush("AppTextBrush", palette.Text);
        SetBrush("AppMutedTextBrush", palette.Muted);
        SetBrush("AppBorderBrush", palette.Border);
        SetBrush("AppAccentBrush", accent);
        SetBrush("AppAccentSoftBrush", palette.AccentSoft);
        SetBrush("AppOrangeBrush", palette.Orange);
        SetBrush("AppOrangeSoftBrush", palette.OrangeSoft);
        SetBrush("AppSelectedTextBrush", selectedText);

        SetBrush(System.Windows.SystemColors.WindowBrushKey, palette.Surface);
        SetBrush(System.Windows.SystemColors.WindowTextBrushKey, palette.Text);
        SetBrush(System.Windows.SystemColors.ControlBrushKey, palette.Control);
        SetBrush(System.Windows.SystemColors.ControlTextBrushKey, palette.Text);
        SetBrush(System.Windows.SystemColors.ControlDarkBrushKey, palette.Border);
        SetBrush(System.Windows.SystemColors.HighlightBrushKey, accent);
        SetBrush(System.Windows.SystemColors.HighlightTextBrushKey, selectedText);
    }

    private static bool IsLightTheme()
    {
        object? value = Registry.CurrentUser.OpenSubKey(PersonalizeKey)?.GetValue("AppsUseLightTheme");
        return value is null || Convert.ToInt32(value) != 0;
    }

    private static MediaColor GetAccentColor()
    {
        object? value = Registry.CurrentUser.OpenSubKey(DwmKey)?.GetValue("AccentColor");
        if (value is int colorValue)
        {
            byte r = (byte)(colorValue & 0xFF);
            byte g = (byte)((colorValue >> 8) & 0xFF);
            byte b = (byte)((colorValue >> 16) & 0xFF);
            return MediaColor.FromRgb(r, g, b);
        }

        return MediaColor.FromRgb(0x00, 0x78, 0xD4);
    }

    private static ThemePalette GetPalette(LauncherThemeScheme scheme, bool isLight)
    {
        MediaColor windowsAccent = GetAccentColor();
        MediaColor orange = MediaColor.FromRgb(0xD8, 0x78, 0x1D);

        return scheme switch
        {
            LauncherThemeScheme.System => CreatePalette(
                isLight,
                windowsAccent,
                orange,
                window: LightDark(isLight, 0xF7F7F7, 0x202020),
                surface: LightDark(isLight, 0xFFFFFF, 0x2B2B2B),
                panel: LightDark(isLight, 0xF3F3F3, 0x333333),
                control: LightDark(isLight, 0xF3F3F3, 0x333333),
                hover: LightDark(isLight, 0xEAF3FF, 0x3B4A5C),
                text: LightDark(isLight, 0x1A1A1A, 0xF3F3F3),
                muted: LightDark(isLight, 0x666666, 0xB8B8B8),
                border: LightDark(isLight, 0xC8C8C8, 0x555555)),

            LauncherThemeScheme.WindowsClassic => CreatePalette(
                isLight,
                windowsAccent,
                orange,
                window: LightDark(isLight, 0xF0F0F0, 0x1F1F1F),
                surface: LightDark(isLight, 0xFAFAFA, 0x2D2D30),
                panel: LightDark(isLight, 0xFFFFFF, 0x252526),
                control: LightDark(isLight, 0xF5F5F5, 0x333337),
                hover: LightDark(isLight, 0xEDEDED, 0x3E3E42),
                text: LightDark(isLight, 0x111111, 0xF1F1F1),
                muted: LightDark(isLight, 0x5F5F5F, 0xBDBDBD),
                border: LightDark(isLight, 0xD0D0D0, 0x565656)),

            LauncherThemeScheme.MGETOrange => CreatePalette(
                isLight,
                orange,
                orange,
                window: LightDark(isLight, 0xF6F1EA, 0x181614),
                surface: LightDark(isLight, 0xFFFCF8, 0x221F1B),
                panel: LightDark(isLight, 0xFFF7EE, 0x2A241E),
                control: LightDark(isLight, 0xFAF1E7, 0x322B24),
                hover: LightDark(isLight, 0xFFEDDA, 0x423428),
                text: LightDark(isLight, 0x241D17, 0xF8F2EA),
                muted: LightDark(isLight, 0x75685C, 0xC3B5A6),
                border: LightDark(isLight, 0xE4D1BC, 0x5B4B3C)),

            _ => CreatePalette(
                isLight,
                LightDark(isLight, 0x146B52, 0x58D0A3),
                LightDark(isLight, 0xB56B08, 0xF4BD54),
                window: LightDark(isLight, 0xEEF1F0, 0x111816),
                surface: LightDark(isLight, 0xFFFFFF, 0x18201E),
                panel: LightDark(isLight, 0xFBFCFB, 0x15201D),
                control: LightDark(isLight, 0xEEF3F0, 0x1A2A24),
                hover: LightDark(isLight, 0xE2F3EC, 0x183B30),
                text: LightDark(isLight, 0x1B2824, 0xEDF5F2),
                muted: LightDark(isLight, 0x66746F, 0x9CAAA5),
                border: LightDark(isLight, 0xDCE3E0, 0x33423D))
        };
    }

    private static ThemePalette CreatePalette(
        bool isLight,
        MediaColor accent,
        MediaColor orange,
        MediaColor window,
        MediaColor surface,
        MediaColor panel,
        MediaColor control,
        MediaColor hover,
        MediaColor text,
        MediaColor muted,
        MediaColor border)
    {
        return new ThemePalette(
            window,
            surface,
            panel,
            control,
            hover,
            text,
            muted,
            border,
            accent,
            Blend(accent, surface, isLight ? 0.14 : 0.24),
            orange,
            Blend(orange, surface, isLight ? 0.16 : 0.30));
    }

    private static MediaColor LightDark(bool isLight, int lightRgb, int darkRgb)
    {
        int rgb = isLight ? lightRgb : darkRgb;
        return MediaColor.FromRgb((byte)(rgb >> 16), (byte)(rgb >> 8), (byte)rgb);
    }

    private static MediaColor Blend(MediaColor foreground, MediaColor background, double foregroundAmount)
    {
        double amount = Math.Clamp(foregroundAmount, 0, 1);
        byte r = (byte)Math.Round((foreground.R * amount) + (background.R * (1 - amount)));
        byte g = (byte)Math.Round((foreground.G * amount) + (background.G * (1 - amount)));
        byte b = (byte)Math.Round((foreground.B * amount) + (background.B * (1 - amount)));
        return MediaColor.FromRgb(r, g, b);
    }

    private static void SetBrush(string key, MediaColor color)
    {
        SolidColorBrush brush = new(color);
        brush.Freeze();
        System.Windows.Application.Current.Resources[key] = brush;
    }

    private static void SetBrush(ResourceKey key, MediaColor color)
    {
        SolidColorBrush brush = new(color);
        brush.Freeze();
        System.Windows.Application.Current.Resources[key] = brush;
    }

    private static bool IsDark(MediaColor color)
    {
        double luminance = (0.299 * color.R) + (0.587 * color.G) + (0.114 * color.B);
        return luminance < 140;
    }

    private sealed record ThemePalette(
        MediaColor Window,
        MediaColor Surface,
        MediaColor Panel,
        MediaColor Control,
        MediaColor Hover,
        MediaColor Text,
        MediaColor Muted,
        MediaColor Border,
        MediaColor Accent,
        MediaColor AccentSoft,
        MediaColor Orange,
        MediaColor OrangeSoft);
}