Add ThemeWatcher

skiffWindowsApp/Skiff Desktop/MainWindow.xaml.cs

@@ -12,6 +12,7 @@
 using System.Net.Http.Headers;
 using System.Runtime.InteropServices;
 using System.Windows.Interop;
+using Skiff_Desktop.Utilities;
 
 namespace Skiff_Desktop
 {
@@ -34,13 +35,12 @@ public partial class MainWindow : Window
 
         #region Dark Theme
 
+        private ThemeWatcher _themeWatcher;
+
         [DllImport("dwmapi.dll", PreserveSig = true)]
         static extern int DwmSetWindowAttribute(IntPtr hwnd, int attr, ref int attrValue, int attrSize);
         const int DWMWA_CAPTION_COLOR = 35;
 
-        [DllImport("UXTheme.dll", SetLastError = true, EntryPoint = "#138")]
-        static extern bool ShouldSystemUseDarkMode();
-
         private void SetDarkMode(bool darkMode)
         {
             var value = darkMode;
@@ -70,16 +70,7 @@ public void SetTheme(string? theme)
         {
             bool darkMode = false;
             if (theme == null || theme.Contains("system"))
-            {
-                try
-                {
-                    darkMode = ShouldSystemUseDarkMode();
-                }
-                catch (EntryPointNotFoundException)
-                {
-                    // Not supported (old Windows version?)
-                }
-            }
+                darkMode = _themeWatcher.GetCurrentTheme() == ThemeMode.Dark;
             else
                 darkMode = (theme.Contains("dark"));
 
@@ -205,6 +196,17 @@ private async Task InitializeBrowser()
             WebView2.CoreWebView2.Settings.IsGeneralAutofillEnabled = true;
             WebView2.CoreWebView2.Settings.IsStatusBarEnabled = false;
 
+            // Watch for system theme changes
+            _themeWatcher = new ThemeWatcher();
+            _themeWatcher.ThemeChanged += (sender, theme) => Dispatcher.Invoke(() =>
+            {
+                // Update WebView default theme
+                WebView2.CoreWebView2.Profile.PreferredColorScheme =
+                    (theme == ThemeMode.Dark) ? CoreWebView2PreferredColorScheme.Dark : CoreWebView2PreferredColorScheme.Light;
+
+            });
+            _themeWatcher.Start();
+
             // this is needed to allow the webview to communicate with the app
             // right now, only for sending notifications
             WebView2.CoreWebView2.WebMessageReceived += _messageProcessor.CoreWebView2_WebMessageReceived;

skiffWindowsApp/Skiff Desktop/Skiff Desktop.csproj

@@ -19,6 +19,7 @@
 
   <ItemGroup>
     <PackageReference Include="Microsoft.Web.WebView2" Version="1.0.1988-prerelease" />
+    <PackageReference Include="System.Management" Version="7.0.2" />
     <PackageReference Include="ToastNotifications" Version="2.5.1" />
     <PackageReference Include="ToastNotifications.Messages" Version="2.5.1" />
   </ItemGroup>

skiffWindowsApp/Skiff Desktop/Utilities/ThemeWatcher.cs

@@ -0,0 +1,88 @@
+using Microsoft.Win32;
+using System;
+using System.Diagnostics;
+using System.Globalization;
+using System.Management;
+using System.Security.Principal;
+
+namespace Skiff_Desktop.Utilities
+{
+    public enum ThemeMode
+    {
+        Light = 0,
+        Dark = 1,
+    }
+
+    public class ThemeWatcher
+    {
+        public ThemeMode Theme
+        {
+            get => _theme;
+            private set {
+                _theme = value;
+                ThemeChanged?.Invoke(this, value);
+            }
+        }
+        public event EventHandler<ThemeMode>? ThemeChanged;
+
+        private const string RegistryPath = @"Software\Microsoft\Windows\CurrentVersion\Themes\Personalize";
+        private const string RegistryValueName = "AppsUseLightTheme";
+        private ManagementEventWatcher? watcher;
+        private ThemeMode _theme;
+
+        public void Start()
+        {
+            var currentUser = WindowsIdentity.GetCurrent();
+
+            // Based on https://stackoverflow.com/a/69604613
+            string query = string.Format(
+                CultureInfo.InvariantCulture,
+                @"SELECT * FROM RegistryValueChangeEvent WHERE Hive = 'HKEY_USERS' AND KeyPath = '{0}\\{1}' AND ValueName = '{2}'",
+                currentUser.User?.Value,
+                RegistryPath.Replace(@"\", @"\\"),
+                RegistryValueName);
+
+            try
+            {
+                Theme = GetCurrentTheme();
+
+                // Listen for events
+                watcher = new ManagementEventWatcher(query);
+                watcher.EventArrived += (sender, e) =>
+                {
+                    Theme = GetCurrentTheme();
+                    Debug.WriteLine("System theme changed: " + Theme);
+                };
+                watcher.Start();
+            }
+            catch (Exception)
+            {
+                // This can fail on Windows 7
+                Theme = ThemeMode.Light;
+            }
+        }
+
+        public ThemeMode GetCurrentTheme()
+        {
+            ThemeMode theme = ThemeMode.Light;
+
+            try
+            {
+                using (RegistryKey? key = Registry.CurrentUser?.OpenSubKey(RegistryPath))
+                {
+                    object? value = key?.GetValue(RegistryValueName);
+                    if (value == null)
+                        return ThemeMode.Light;
+
+                    theme = (int)value > 0 ? ThemeMode.Light : ThemeMode.Dark;
+                }
+
+                return theme;
+            }
+            catch (Exception)
+            {
+                return theme;
+            }
+        }
+    }
+}