ShrlAlgoToolkit/WPFluent/Appearance/ApplicationThemeManager.cs

using WPFluent.Controls;
using WPFluent.Extensions;

namespace WPFluent.Appearance;

/// <summary>
/// 允许通过交换包含动态资源的资源字典来管理应用程序主题。
/// </summary>
/// <example>
/// <code lang="csharp"> ApplicationThemeManager.Apply( ApplicationTheme.Light );</code> <code lang="csharp"> if
/// (ApplicationThemeManager.GetAppTheme() == ApplicationTheme.Dark) { ApplicationThemeManager.Apply(
/// ApplicationTheme.Light ); }</code> <code> ApplicationThemeManager.Changed += (theme, accent) => {
/// Debug.WriteLine($"Application theme changed to {theme.ToString()}"); };</code>
/// </example>
public static class ApplicationThemeManager
{
    internal const string LibraryNamespace = "WPFluent;";

    public const string ThemesDictionaryPath = "pack://application:,,,/WPFluent;component/Themes/";

    private static ApplicationTheme _cachedApplicationTheme = ApplicationTheme.Unknown;

    /// <summary>
    /// Event triggered when the application's theme is changed.
    /// </summary>
    public static event ThemeChangedEvent? Changed;

    /// <summary>
    /// 尝试猜测当前设置的应用程序主题。
    /// </summary>
    private static void FetchApplicationTheme()
    {
        ResourceDictionaryManager appDictionaries = new(LibraryNamespace);
        ResourceDictionary? themeDictionary = appDictionaries.GetDictionary("themes");

        if (themeDictionary == null)
        {
            return;
        }

        var themeUri = themeDictionary.Source.ToString();

        if (themeUri.Contains("light", StringComparison.OrdinalIgnoreCase))
        {
            _cachedApplicationTheme = ApplicationTheme.Light;
        }

        if (themeUri.Contains("dark", StringComparison.OrdinalIgnoreCase))
        {
            _cachedApplicationTheme = ApplicationTheme.Dark;
        }
    }

    /// <summary>
    /// 将资源应用于 <paramref name="frameworkElement"/>.
    /// </summary>
    public static void Apply(FrameworkElement frameworkElement)
    {
        if (frameworkElement.Resources.MergedDictionaries.Count <
            UiApplication.Current.Resources.MergedDictionaries.Count)
        {
            foreach (var dictionary in UiApplication.Current.Resources.MergedDictionaries)
            {
                frameworkElement.Resources.MergedDictionaries.Add(dictionary);
            }
        }
    }

    /// <summary>
    /// 更改当前应用程序主题。
    /// </summary>
    /// <param name="applicationTheme">Theme to set.</param>
    /// <param name="backgroundEffect">Whether the custom background effect should be applied.</param>
    /// <param name="updateAccent">Whether the color accents should be changed.</param>
    public static void Apply(
        ApplicationTheme applicationTheme,
        WindowBackdropType backgroundEffect = WindowBackdropType.Mica,
        bool updateAccent = true)
    {
        if (updateAccent)
        {
            //TODO
            ApplicationAccentColorManager.Apply(
                Color.FromRgb(194, 115, 37),
                applicationTheme,
                false);
        }

        if (applicationTheme == ApplicationTheme.Unknown)
        {
            return;
        }

        ResourceDictionaryManager appDictionaries = new(LibraryNamespace);

        string themeDictionaryName = "Light";

        switch (applicationTheme)
        {
            case ApplicationTheme.Dark:
                themeDictionaryName = "Dark";
                break;
            case ApplicationTheme.Auto:
                break;
            case ApplicationTheme.Unknown:
                break;
            case ApplicationTheme.Light:
                themeDictionaryName = "Light";
                break;
            case ApplicationTheme.HC1:
                themeDictionaryName = "HC1";
                break;
            case ApplicationTheme.HC2:
                themeDictionaryName = "HC2";
                break;
            case ApplicationTheme.HCBlack:
                themeDictionaryName = "HCBlack";

                break;
            case ApplicationTheme.HCWhite:
                themeDictionaryName = "HCWhite";
                break;
        }


        if (!appDictionaries.UpdateDictionary(
            "themes",
            new Uri($"{ThemesDictionaryPath}{themeDictionaryName}.xaml", UriKind.Absolute)))
        {
            return;
        }

        _cachedApplicationTheme = applicationTheme;

        Changed?.Invoke(applicationTheme, ApplicationAccentColorManager.SystemAccent);

        if (UiApplication.Current.MainWindow is Window mainWindow)
        {
            WindowBackgroundManager.UpdateBackground(mainWindow, applicationTheme, backgroundEffect);
        }
    }

    /// <summary>
    /// 获取当前设置的应用程序主题。
    /// </summary>
    /// <returns><see cref="ApplicationTheme.Unknown"/> if something goes wrong.</returns>
    public static ApplicationTheme GetAppTheme()
    {
        if (_cachedApplicationTheme == ApplicationTheme.Unknown)
        {
            FetchApplicationTheme();
        }

        return _cachedApplicationTheme;
    }
}