From e1b3b1e6c9a89c8736c169bd97aafaf2cb32332b Mon Sep 17 00:00:00 2001
From: Daniel Clark <dan@thexamlguy.com>
Date: Mon, 8 Feb 2021 23:20:06 +0000
Subject: [PATCH] Added support for IsColorPrevalence background system accent
 color

---
 .../NotificationFlyoutContentPresenter.xaml   | 16 ++++++++
 .../NotificationFlyoutPresenter.cs            | 31 +++++++++-----
 .../NotificationFlyoutXamlHost.cs             | 39 ++++++++++++------
 .../Helpers/SystemPersonalisationHelper.cs    | 40 +++++++++++--------
 .../Helpers/ThemeChangedEventArgs.cs          |  8 +++-
 5 files changed, 94 insertions(+), 40 deletions(-)

diff --git a/NotificationFlyout.Uwp.UI.Controls/NotificationFlyoutPresenter/NotificationFlyoutContentPresenter.xaml b/NotificationFlyout.Uwp.UI.Controls/NotificationFlyoutPresenter/NotificationFlyoutContentPresenter.xaml
index 88ff298..bd13a0d 100644
--- a/NotificationFlyout.Uwp.UI.Controls/NotificationFlyoutPresenter/NotificationFlyoutContentPresenter.xaml
+++ b/NotificationFlyout.Uwp.UI.Controls/NotificationFlyoutPresenter/NotificationFlyoutContentPresenter.xaml
@@ -25,6 +25,12 @@
             <SolidColorBrush x:Key="NotificationFlyoutPresenterBackgroundBrush" Color="Green" />
         </ResourceDictionary>
     </ResourceDictionary.ThemeDictionaries>
+    <AcrylicBrush
+        x:Key="NotificationFlyoutPresenterBackgroundAccentBrush"
+        BackgroundSource="HostBackdrop"
+        FallbackColor="{ThemeResource SystemAccentColorDark1}"
+        TintColor="{ThemeResource SystemAccentColorDark1}"
+        TintOpacity="0.8" />
     <Style TargetType="controls:NotificationFlyoutContentPresenter">
         <Setter Property="Background" Value="{ThemeResource NotificationFlyoutPresenterBackgroundBrush}" />
         <Setter Property="Template">
@@ -54,6 +60,16 @@
                                 ContentTemplate="{TemplateBinding ContentTemplate}"
                                 ContentTransitions="{TemplateBinding ContentTransitions}" />
                         </ScrollViewer>
+                        <VisualStateManager.VisualStateGroups>
+                            <VisualStateGroup x:Name="ThemeStates">
+                                <VisualState x:Name="DefaultTheme" />
+                                <VisualState x:Name="ColorPrevalenceTheme">
+                                    <VisualState.Setters>
+                                        <Setter Target="Root.Background" Value="{ThemeResource NotificationFlyoutPresenterBackgroundAccentBrush}" />
+                                    </VisualState.Setters>
+                                </VisualState>
+                            </VisualStateGroup>
+                        </VisualStateManager.VisualStateGroups>
                     </Border>
                 </ControlTemplate>
             </Setter.Value>
diff --git a/NotificationFlyout.Uwp.UI.Controls/NotificationFlyoutPresenter/NotificationFlyoutPresenter.cs b/NotificationFlyout.Uwp.UI.Controls/NotificationFlyoutPresenter/NotificationFlyoutPresenter.cs
index 1edf63a..dd391d8 100644
--- a/NotificationFlyout.Uwp.UI.Controls/NotificationFlyoutPresenter/NotificationFlyoutPresenter.cs
+++ b/NotificationFlyout.Uwp.UI.Controls/NotificationFlyoutPresenter/NotificationFlyoutPresenter.cs
@@ -8,6 +8,7 @@ namespace NotificationFlyout.Uwp.UI.Controls
     {
         private NotificationFlyoutContentPresenter _contentPresenter;
 
+        private bool _isColorPrevalence;
         private ElementTheme _systemTheme;
 
         public NotificationFlyoutPresenter()
@@ -15,11 +16,9 @@ namespace NotificationFlyout.Uwp.UI.Controls
             DefaultStyleKey = typeof(NotificationFlyoutPresenter);       
             RegisterPropertyChangedCallback(RequestedThemeProperty, RequestedThemePropertyChanged);
         }
-
-        public void SetBackground(string theme)
+        public void UpdateFlyoutTheme(string theme, bool isColorPrevalence)
         {
-            if (_contentPresenter == null) return;
-
+            _isColorPrevalence = isColorPrevalence;
             switch (theme)
             {
                 case "Dark":
@@ -30,18 +29,21 @@ namespace NotificationFlyout.Uwp.UI.Controls
                     break;
             }
 
-            if (RequestedTheme == ElementTheme.Default)
-            {
-                _contentPresenter.SetValue(RequestedThemeProperty, _systemTheme);
-            }
+            UpdateThemeVisualState();
         }
 
         protected override void OnApplyTemplate()
         {
             _contentPresenter = GetTemplateChild("ContentPresenter") as NotificationFlyoutContentPresenter;
+            Loaded += OnLoaded;
         }
 
-        private void RequestedThemePropertyChanged(DependencyObject sender, DependencyProperty dp)
+        private void OnLoaded(object sender, RoutedEventArgs args)
+        {
+            UpdateThemeVisualState();
+        }
+
+        private void RequestedThemePropertyChanged(DependencyObject sender, DependencyProperty dependencyProperty)
         {
             if (RequestedTheme == ElementTheme.Default)
             {
@@ -52,5 +54,16 @@ namespace NotificationFlyout.Uwp.UI.Controls
                 _contentPresenter.SetValue(RequestedThemeProperty, RequestedTheme);
             }
         }
+
+        private void UpdateThemeVisualState()
+        {
+            if (_contentPresenter == null) return;
+            if (RequestedTheme == ElementTheme.Default)
+            {
+                _contentPresenter.SetValue(RequestedThemeProperty, _systemTheme);
+            }
+
+            VisualStateManager.GoToState(_contentPresenter, _isColorPrevalence ? "ColorPrevalenceTheme" : "DefaultTheme", true);
+        }
     }
 }
\ No newline at end of file
diff --git a/NotificationFlyout.Wpf.UI.Controls/NotificationFlyout/NotificationFlyoutXamlHost.cs b/NotificationFlyout.Wpf.UI.Controls/NotificationFlyout/NotificationFlyoutXamlHost.cs
index f76d082..794c5cb 100644
--- a/NotificationFlyout.Wpf.UI.Controls/NotificationFlyout/NotificationFlyoutXamlHost.cs
+++ b/NotificationFlyout.Wpf.UI.Controls/NotificationFlyout/NotificationFlyoutXamlHost.cs
@@ -15,12 +15,12 @@ namespace NotificationFlyout.Wpf.UI.Controls
         private const double WindowSize = 5;
 
         private ImageSource _defaultIconSource;
+        private bool _isLoaded;
         private ImageSource _lightIconSource;
         private NotificationIconHelper _notificationIconHelper;
         private SystemPersonalisationHelper _systemPersonalisationHelper;
         private TaskbarHelper _taskbarHelper;
         private WindowsXamlHost _xamlHost;
-        private bool _isLoaded;
 
         public NotificationFlyoutXamlHost()
         {
@@ -36,6 +36,11 @@ namespace NotificationFlyout.Wpf.UI.Controls
             if (flyoutHost != null)
             {
                 flyoutHost.FlyoutPresenter = flyoutPresenter;
+
+                var theme = _systemPersonalisationHelper.Theme.ToString();
+                var isColorPrevalence = _systemPersonalisationHelper.IsColorPrevalence;
+
+                flyoutHost.FlyoutPresenter.UpdateFlyoutTheme(theme, isColorPrevalence);
             }
         }
 
@@ -104,6 +109,25 @@ namespace NotificationFlyout.Wpf.UI.Controls
             UpdateWindow();
         }
 
+        private void OnThemeChanged(object sender, SystemPersonalisationChangedEventArgs args)
+        {
+            NewMethod(args);
+
+            UpdateIcon();
+        }
+
+        private void NewMethod(SystemPersonalisationChangedEventArgs args)
+        {
+            var flyoutHost = GetFlyoutHost();
+            if (flyoutHost != null)
+            {
+                var theme = args.Theme.ToString();
+                var isColorPrevalence = args.IsColorPrevalence;
+
+                flyoutHost.FlyoutPresenter.UpdateFlyoutTheme(theme, isColorPrevalence);
+            }
+        }
+
         private void PrepareDefaultWindow()
         {
             ShowInTaskbar = false;
@@ -125,17 +149,6 @@ namespace NotificationFlyout.Wpf.UI.Controls
             _systemPersonalisationHelper.ThemeChanged += OnThemeChanged;
         }
 
-        private void OnThemeChanged(object sender, ThemeChangedEventArgs args)
-        {
-            var flyoutHost = GetFlyoutHost();
-            if (flyoutHost != null)
-            {
-                flyoutHost.FlyoutPresenter.SetBackground(args.Theme.ToString());
-            }
-
-            UpdateIcon();
-        }
-
         private void PrepareTaskbar()
         {
             _taskbarHelper = TaskbarHelper.Create(this);
@@ -164,7 +177,7 @@ namespace NotificationFlyout.Wpf.UI.Controls
 
             var dpi = WindowHelper.GetDpi(shellTrayHandle);
 
-            var iconSource = _systemPersonalisationHelper.SystemTheme == SystemTheme.Dark ? _defaultIconSource : _lightIconSource;
+            var iconSource = _systemPersonalisationHelper.Theme == SystemTheme.Dark ? _defaultIconSource : _lightIconSource;
             if (iconSource == null) return;
 
             using var icon = iconSource.ConvertToIcon(dpi);
diff --git a/NotificationFlyout.Wpf.UI/Helpers/SystemPersonalisationHelper.cs b/NotificationFlyout.Wpf.UI/Helpers/SystemPersonalisationHelper.cs
index 6607705..bb7631d 100644
--- a/NotificationFlyout.Wpf.UI/Helpers/SystemPersonalisationHelper.cs
+++ b/NotificationFlyout.Wpf.UI/Helpers/SystemPersonalisationHelper.cs
@@ -1,4 +1,5 @@
-using NotificationFlyout.Wpf.UI.Extensions;
+using Microsoft.Win32;
+using NotificationFlyout.Wpf.UI.Extensions;
 using System;
 using System.Runtime.InteropServices;
 using System.Windows;
@@ -10,22 +11,23 @@ namespace NotificationFlyout.Wpf.UI.Helpers
     public class SystemPersonalisationHelper
     {
         private readonly UISettings _settings = new();
-
+        private readonly string PersonalizeKey = @"Software\Microsoft\Windows\CurrentVersion\Themes\Personalize";
         private SystemTheme _currentTheme;
-
+        private bool _isColorPrevalence;
 
         private SystemPersonalisationHelper(Window window)
         {
             var source = HwndSource.FromHwnd(window.GetHandle());
             source.AddHook(new HwndSourceHook(WndProc));
 
-            _settings.ColorValuesChanged += OnColorValuesChanged;
-            _currentTheme = GetSystemTheme();
+            _currentTheme = GetTheme();
+            _isColorPrevalence = GetIsColorPrevalence();
         }
 
-        public event EventHandler<ThemeChangedEventArgs> ThemeChanged;
+        public event EventHandler<SystemPersonalisationChangedEventArgs> ThemeChanged;
 
-        public SystemTheme SystemTheme => GetSystemTheme();
+        public bool IsColorPrevalence => GetIsColorPrevalence();
+        public SystemTheme Theme => GetTheme();
 
         public static SystemPersonalisationHelper Create(Window window)
         {
@@ -35,24 +37,30 @@ namespace NotificationFlyout.Wpf.UI.Helpers
         [DllImport("user32.dll", SetLastError = true)]
         private static extern IntPtr DefWindowProcW(IntPtr handle, uint msg, IntPtr wParam, IntPtr lParam);
 
-        private SystemTheme GetSystemTheme()
+        private bool GetIsColorPrevalence()
+        {
+            using var baseKey = RegistryKey.OpenBaseKey(RegistryHive.CurrentUser, RegistryView.Registry64);
+            using var subKey = baseKey.OpenSubKey(PersonalizeKey);
+            return subKey.GetValue<int>("ColorPrevalence", 0) > 0;
+        }
+
+        private SystemTheme GetTheme()
         {
             var color = _settings.GetColorValue(UIColorType.Background).ToString();
             return color == "#FFFFFFFF" ? SystemTheme.Light : SystemTheme.Dark;
         }
 
-        private void OnColorValuesChanged(UISettings sender, object args)
-        {
-            RaiseThemeChangedEvent();
-        }
-
         private void RaiseThemeChangedEvent()
         {
-            var theme = GetSystemTheme();
-            if (theme != _currentTheme)
+            var theme = GetTheme();
+            var isColorPrevalence = GetIsColorPrevalence();
+
+            if (theme != _currentTheme || _isColorPrevalence != isColorPrevalence)
             {
-                ThemeChanged?.Invoke(this, new ThemeChangedEventArgs(theme));
                 _currentTheme = theme;
+                _isColorPrevalence = isColorPrevalence;
+
+                ThemeChanged?.Invoke(this, new SystemPersonalisationChangedEventArgs(theme, isColorPrevalence));
             }
         }
 
diff --git a/NotificationFlyout.Wpf.UI/Helpers/ThemeChangedEventArgs.cs b/NotificationFlyout.Wpf.UI/Helpers/ThemeChangedEventArgs.cs
index 6da9c84..8a14153 100644
--- a/NotificationFlyout.Wpf.UI/Helpers/ThemeChangedEventArgs.cs
+++ b/NotificationFlyout.Wpf.UI/Helpers/ThemeChangedEventArgs.cs
@@ -2,13 +2,17 @@
 
 namespace NotificationFlyout.Wpf.UI.Helpers
 {
-    public class ThemeChangedEventArgs : EventArgs
+    public class SystemPersonalisationChangedEventArgs : EventArgs
     {
-        internal ThemeChangedEventArgs(SystemTheme theme)
+        internal SystemPersonalisationChangedEventArgs(SystemTheme theme, bool isColorPrevalence)
         {
             Theme = theme;
+            IsColorPrevalence = isColorPrevalence;
         }
 
         public SystemTheme Theme { get; private set; }
+
+        public bool IsColorPrevalence { get; private set; }
+
     }
 }