SystemThemeWatcher Documentation content changes (#1200)

docs/documentation/system-theme-watcher.md

@@ -0,0 +1,88 @@
+# SystemThemeWatcher
+
+SystemThemeWatcher automatically updates the application background if the system theme or color changes. This component is used to adapt the application's background effect and theme according to the system theme.
+
+## Features
+
+  * Automatic Theme Updates: Updates the application's background and theme when the system theme changes.
+
+  * Global Settings: Settings apply globally and cannot be changed for each System.Windows.Window.
+
+  * Supported Backdrop Types: Provides background effects compatible with WindowBackdropType types (e.g., Egg).
+
+
+## Usage
+
+You can use SystemThemeWatcher to start watching a window's background and theme like this:
+
+```cs
+SystemThemeWatcher.Watch(this as System.Windows.Window);
+SystemThemeWatcher.UnWatch(this as System.Windows.Window);
+```
+
+or
+```cs
+SystemThemeWatcher.Watch(
+    _serviceProvider.GetRequiredService<MainWindow>()
+);
+```
+
+## Example Usage
+
+Here's an example of using SystemThemeWatcher in the MainWindow class to start watching the theme when the window is loaded:
+
+```cs
+namespace MyApp;
+
+public partial class MainWindow : Window
+{
+    public MainWindow()
+    {
+        InitializeComponent();
+
+        Loaded += (sender, args) =>
+        {
+            Wpf.Ui.Appearance.SystemThemeWatcher.Watch(
+                this,                                    // Window class
+                Wpf.Ui.Controls.WindowBackdropType.Mica, // Background type
+                true                                     // Whether to change accents automatically
+            );
+        };
+    }
+}
+```
+
+## Methods
+
+### Watch
+
+Applies the background effect and theme according to the system theme to the observed window.
+
+```cs
+public static void Watch(
+    Window? window,
+    WindowBackdropType backdrop = WindowBackdropType.Mica,
+    bool updateAccents = true
+)
+```
+
+### UnWatch
+
+Stops watching the window and removes the hook to receive system messages.
+
+```cs
+public static void UnWatch(Window? window)
+
+```
+
+### WndProc
+
+Listens to system messages on the application windows.
+
+```cs
+private static IntPtr WndProc(IntPtr hWnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled)
+
+```
+
+> [!IMPORTANT]
+> If UnWatch is called on a window that has not yet loaded, an InvalidOperationException may occur. Ensure that the window is loaded before calling UnWatch.