1  // Copyright (c) Microsoft Corporation
 2  // The Microsoft Corporation licenses this file to you under the MIT license.
 3  // See the LICENSE file in the project root for more information.
 4  
 5  namespace Microsoft.CmdPal.UI.ViewModels.Services;
 6  
 7  /// <summary>
 8  /// Provides theme-related values for the Command Palette and notifies listeners about
 9  /// changes that affect visual appearance (theme, tint, background image, and backdrop).
10  /// </summary>
11  /// <remarks>
12  /// Implementations are expected to monitor system/app theme changes and raise
13  /// <see cref="ThemeChanged"/> accordingly. Consumers should call <see cref="Initialize"/>
14  /// once to hook required sources and then query properties/methods for the current visuals.
15  /// </remarks>
16  public interface IThemeService
17  {
18      /// <summary>
19      /// Occurs when the effective theme or any visual-affecting setting changes.
20      /// </summary>
21      /// <remarks>
22      /// Triggered for changes such as app theme (light/dark/default), background image,
23      /// tint/accent, or backdrop parameters that would require UI to refresh styling.
24      /// </remarks>
25      event EventHandler<ThemeChangedEventArgs>? ThemeChanged;
26  
27      /// <summary>
28      /// Initializes the theme service and starts listening for theme-related changes.
29      /// </summary>
30      /// <remarks>
31      /// Safe to call once during application startup before consuming the service.
32      /// </remarks>
33      void Initialize();
34  
35      /// <summary>
36      /// Gets the current theme settings.
37      /// </summary>
38      ThemeSnapshot Current { get; }
39  }