Improve way to respond to accent color change

Source/Monitorian.Core/Views/MainWindow.xaml.cs

@@ -44,7 +44,7 @@ public MainWindow(AppControllerCore controller)
 			{
 				ViewModel.MonitorsView.Refresh();
 			};
-			//controller.WindowPainter.ColorChanged += (_, _) =>
+			//controller.WindowPainter.AccentColorChanged += (_, _) =>
 			//{
 			//};
 

Source/ScreenFrame/Helper/ColorExtension.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using System.Runtime.InteropServices;
 using System.Text;
 using System.Threading.Tasks;
 using System.Windows.Media;
@@ -9,9 +10,31 @@ namespace ScreenFrame.Helper
 {
 	internal static class ColorExtension
 	{
+		#region Win32
+
+		[DllImport("Dwmapi.dll")]
+		private static extern int DwmGetColorizationColor(
+			out uint pcrColorization,
+			[MarshalAs(UnmanagedType.Bool)] out bool pfOpaqueBlend);
+
+		private const int S_OK = 0x0;
+
+		#endregion
+
+		public static Color GetColorizationColor()
+		{
+			if (DwmGetColorizationColor(
+				out uint pcrColorization,
+				out _) == S_OK)
+			{
+				return FromUInt32(pcrColorization);
+			}
+			return default;
+		}
+
 		public static uint ToUInt32(this Color color)
 		{
-			var bytes = new[] { color.B, color.G, color.R, color.A }.ToArray();
+			var bytes = new[] { color.B, color.G, color.R, color.A };
 			return BitConverter.ToUInt32(bytes, 0);
 		}
 

Source/ScreenFrame/Helper/Throttle.cs

@@ -11,7 +11,7 @@ namespace ScreenFrame.Helper
 	/// </summary>
 	internal class Throttle
 	{
-		private static readonly TimeSpan _dueTime = TimeSpan.FromSeconds(1);
+		private static readonly TimeSpan _dueTime = TimeSpan.FromSeconds(0.2);
 		private readonly Action _action;
 
 		public Throttle(Action action) => this._action = action;
@@ -29,4 +29,25 @@ public async Task PushAsync()
 			}
 		}
 	}
+
+	internal class Throttle<T>
+	{
+		private static readonly TimeSpan _dueTime = TimeSpan.FromSeconds(0.2);
+		private readonly Action<T> _action;
+
+		public Throttle(Action<T> action) => this._action = action;
+
+		private Task _lastWaitTask;
+
+		public async Task PushAsync(T value)
+		{
+			var currentWaitTask = Task.Delay(_dueTime);
+			_lastWaitTask = currentWaitTask;
+			await currentWaitTask;
+			if (_lastWaitTask == currentWaitTask)
+			{
+				_action?.Invoke(value);
+			}
+		}
+	}
 }

Source/ScreenFrame/Painter/WindowPainter.cs

@@ -38,11 +38,6 @@ public WindowPainter(IReadOnlyList<string> args)
 
 		private ColorTheme _theme;
 
-		/// <summary>
-		/// Whether to respond when the color theme of Windows is changed
-		/// </summary>
-		protected bool RespondsThemeChanged { get; set; } = true; // Default
-
 		/// <summary>
 		/// Background texture of window
 		/// </summary>
@@ -138,17 +133,15 @@ private void OnSourceInitialized(object sender, EventArgs e)
 			DisableTransitions(window);
 			PaintBackground(window);
 
-			if (RespondsThemeChanged)
-				AddHook(window);
+			AddHook(window);
 		}
 
 		private void OnClosed(object sender, EventArgs e)
 		{
 			var oldWindow = (Window)sender;
 			Remove(oldWindow);
 
-			if (RespondsThemeChanged &&
-				RemoveHook(oldWindow))
+			if (RemoveHook(oldWindow))
 			{
 				var newWindow = _windows.FirstOrDefault(x => x.IsInitialized);
 				if (newWindow is not null)
@@ -194,46 +187,53 @@ private IntPtr WndProc(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref b
 		{
 			switch (msg)
 			{
-				case WM_SETTINGCHANGE:
-					if (string.Equals(Marshal.PtrToStringAuto(lParam), "ImmersiveColorSet"))
-					{
-						OnThemeChanged();
-					}
+				case WM_SETTINGCHANGE when (Marshal.PtrToStringAuto(lParam) == "ImmersiveColorSet") && RespondsThemeChanged:
+					OnThemeChanged();
 					break;
 
-				case WM_DWMCOLORIZATIONCOLORCHANGED:
-					OnColorChanged();
+				case WM_DWMCOLORIZATIONCOLORCHANGED when RespondsAccentColorChanged:
+					OnAccentColorChanged(ColorExtension.FromUInt32((uint)wParam));
 					break;
 			}
 			return IntPtr.Zero;
 		}
 
-		private Throttle _themeChange;
-		private Throttle _colorChange;
+		private Throttle _applyChangedTheme;
+		private Throttle<Color> _applyChangedAccentColor;
 
 		private async void OnThemeChanged()
 		{
-			_themeChange ??= new Throttle(() =>
+			_applyChangedTheme ??= new Throttle(() =>
 			{
 				if (ApplyChangedTheme())
 				{
 					ThemeChanged?.Invoke(null, EventArgs.Empty);
 				}
 			});
-			await _themeChange.PushAsync();
+			await _applyChangedTheme.PushAsync();
 		}
 
-		private async void OnColorChanged()
+		private async void OnAccentColorChanged(Color color)
 		{
-			_colorChange ??= new Throttle(() =>
+			_applyChangedAccentColor ??= new Throttle<Color>(c =>
 			{
-				ColorChanged?.Invoke(null, EventArgs.Empty);
+				if (ApplyChangedAccentColor(c))
+				{
+					AccentColorChanged?.Invoke(null, EventArgs.Empty);
+				}
 			});
-			await _colorChange.PushAsync();
+			await _applyChangedAccentColor.PushAsync(color);
 		}
 
 		#endregion
 
+		#region Theme
+
+		/// <summary>
+		/// Whether to respond when the color theme for Windows is changed
+		/// </summary>
+		protected bool RespondsThemeChanged { get; set; } = true; // Default
+
 		/// <summary>
 		/// Occurs when the color theme for Windows is changed.
 		/// </summary>
@@ -352,13 +352,6 @@ private void ResetTranslucent()
 			_translucentBrush = null;
 		}
 
-		/// <summary>
-		/// Occurs when the accent color for Windows is changed.
-		/// </summary>
-		public event EventHandler ColorChanged;
-
-		#region Resources
-
 		/// <summary>
 		/// Changes color themes.
 		/// </summary>
@@ -397,6 +390,50 @@ protected static void ChangeResources(string oldUriString, string newUriString)
 
 		#endregion
 
+		#region Accent color
+
+		/// <summary>
+		/// Whether to respond when the accent color for Windows is changed
+		/// </summary>
+		protected bool RespondsAccentColorChanged
+		{
+			get => _respondsAccentColorChanged;
+			set
+			{
+				_respondsAccentColorChanged = value;
+				if (_respondsAccentColorChanged)
+					_accentColor = ColorExtension.GetColorizationColor();
+			}
+		}
+		private bool _respondsAccentColorChanged;
+
+		/// <summary>
+		/// Occurs when the accent color for Windows is changed.
+		/// </summary>
+		public event EventHandler AccentColorChanged;
+
+		private static Color _accentColor;
+
+		private bool ApplyChangedAccentColor(Color accentColor)
+		{
+			if (_accentColor == accentColor)
+				return false;
+
+			// Color provided with WM_DWMCOLORIZATIONCOLORCHANGED and by DwmGetColorizationColor
+			// will not match that provided by UISettings.
+			ChangeAccentColors();
+			_accentColor = accentColor;
+			return true;
+		}
+
+		/// <summary>
+		/// Changes accent colors.
+		/// </summary>
+		protected virtual void ChangeAccentColors()
+		{ }
+
+		#endregion
+
 		#region IDisposable
 
 		private bool _isDisposed = false;
@@ -422,7 +459,7 @@ protected virtual void Dispose(bool disposing)
 			{
 				RemoveHook();
 				ThemeChanged = null;
-				ColorChanged = null;
+				AccentColorChanged = null;
 			}
 
 			_isDisposed = true;