chore: refactor window activated event

Screenbox/Pages/MainPage.xaml

@@ -15,6 +15,7 @@
     xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
     xmlns:muxc="using:Microsoft.UI.Xaml.Controls"
     xmlns:strings="using:Screenbox.Strings"
+    xmlns:triggers="using:Screenbox.Triggers"
     muxc:BackdropMaterial.ApplyToRootOrPageBackground="True"
     Loaded="MainPage_Loaded"
     mc:Ignorable="d">
@@ -412,9 +413,10 @@
 
         <VisualStateManager.VisualStateGroups>
             <VisualStateGroup x:Name="WindowActivationStates">
-                <VisualState x:Name="Activated" />
-
                 <VisualState x:Name="Deactivated">
+                    <VisualState.StateTriggers>
+                        <triggers:WindowActivationModeTrigger ActivationMode="Deactivated" />
+                    </VisualState.StateTriggers>
                     <VisualState.Setters>
                         <Setter Target="AppTitleText.Foreground" Value="{ThemeResource TextFillColorDisabledBrush}" />
                         <Setter Target="NavView.IsBackEnabled" Value="False" />

Screenbox/Pages/MainPage.xaml.cs

@@ -51,9 +51,6 @@ public MainPage()
             // For example, when the app moves to a screen with a different DPI.
             coreTitleBar.LayoutMetricsChanged += CoreTitleBar_LayoutMetricsChanged;
 
-            // Register a handler for when the window changes focus
-            Window.Current.CoreWindow.Activated += CoreWindow_Activated;
-
             NotificationView.Translation = new Vector3(0, 0, 16);
 
             _pages = new Dictionary<string, Type>
@@ -81,21 +78,6 @@ private void CoreTitleBar_LayoutMetricsChanged(CoreApplicationViewTitleBar sende
             RightPaddingColumn.Width = new GridLength(Math.Max(sender.SystemOverlayLeftInset, sender.SystemOverlayRightInset));
         }
 
-        /// <summary>
-        /// Change the <see cref="VisualState"/> depending on whether the app is active or inactive.
-        /// </summary>
-        private void CoreWindow_Activated(CoreWindow sender, WindowActivatedEventArgs args)
-        {
-            if (args.WindowActivationState == CoreWindowActivationState.Deactivated)
-            {
-                VisualStateManager.GoToState(this, "Deactivated", true);
-            }
-            else
-            {
-                VisualStateManager.GoToState(this, "Activated", true);
-            }
-        }
-
         protected override void OnNavigatedTo(NavigationEventArgs e)
         {
             PlayerFrame.Navigate(typeof(PlayerPage), e.Parameter);

Screenbox/Screenbox.csproj

@@ -309,6 +309,7 @@
     <Compile Include="Properties\AssemblyInfo.cs" />
     <Compile Include="Secrets.cs" />
     <Compile Include="Services\ResourceService.cs" />
+    <Compile Include="Triggers\WindowActivationModeTrigger.cs" />
   </ItemGroup>
   <ItemGroup>
     <AppxManifest Include="Package.appxmanifest">

Screenbox/Triggers/WindowActivationModeTrigger.cs

@@ -0,0 +1,101 @@
+#nullable enable
+
+using Windows.UI.Core;
+using Windows.UI.Xaml;
+
+namespace Screenbox.Triggers;
+
+/// <summary>
+/// Represents a declarative rule that applies visual states based on the <see cref="CoreWindow.ActivationMode"/> property.
+/// </summary>
+/// <remarks>
+/// Use WindowActivationModeTriggers to create rules that automatically triggers a VisualState change when
+/// the window is a specified activation state. When you use WindowActivationModeTriggers in your XAML markup,
+/// you don't need to handle the <see cref="CoreWindow.Activated"/> event and call <see cref="VisualStateManager.GoToState"/> in your code.
+/// </remarks>
+/// <example>
+/// This example shows how to use the <see cref="VisualState.StateTriggers"/> property with an <see cref="WindowActivationModeTrigger"/>
+/// to create a declarative rule in XAML markup based on the activation state of the window.
+/// <code lang="xaml">
+/// &lt;Grid&gt;
+///     &lt;StackPanel&gt;
+///         &lt;TextBlock x:Name="FirstText"
+///                    Foreground="{ThemeResource TextFillColorPrimaryBrush}"
+///                    Text="This is a block of text. It is the 1st text block." /&gt;
+///         &lt;TextBlock x:Name="LastText"
+///                    Foreground="{ThemeResource TextFillColorPrimaryBrush}"
+///                    Text="This is a block of text. It is the 2nd text block." /&gt;
+///     &lt;/StackPanel&gt;
+///     &lt;VisualStateManager.VisualStateGroups&gt;
+///         &lt;VisualStateGroup&gt;
+///             &lt;VisualState&gt;
+///                 &lt;VisualState.StateTriggers&gt;
+///                     &lt;!-- VisualState to be triggered when the activation state of the window is Deactivated. --&gt;
+///                     &lt;local:WindowActivationModeTrigger ActivationMode="Deactivated" /&gt;
+///                 &lt;/VisualState.StateTriggers&gt;
+/// 
+///                 &lt;VisualState.Setters&gt;
+///                     &lt;Setter Target="FirstText.Foreground" Value="{ThemeResource TextFillColorDisabledBrush}" /&gt;
+///                     &lt;Setter Target="LastText.Opacity" Value="0.4" /&gt;
+///                 &lt;/VisualState.Setters&gt;
+///             &lt;/VisualState&gt;
+///         &lt;/VisualStateGroup&gt;
+///     &lt;/VisualStateManager.VisualStateGroups&gt;
+/// &lt;/Grid&gt;
+/// </code>
+/// </example>
+[Windows.Foundation.Metadata.ContractVersion(typeof(Windows.Foundation.UniversalApiContract), 327680u)]
+public sealed class WindowActivationModeTrigger : StateTriggerBase
+{
+    private CoreWindow? _coreWindow;
+
+    /// <summary>
+    /// Identifies the <see cref="ActivationMode"/> dependency property.
+    /// </summary>
+    public static readonly DependencyProperty ActivationModeProperty = DependencyProperty.Register(
+        nameof(ActivationMode), typeof(CoreWindowActivationMode), typeof(WindowActivationModeTrigger), new PropertyMetadata(CoreWindowActivationMode.None, OnActivationModePropertyChanged));
+
+    /// <summary>
+    /// Gets or sets the activation mode that indicates whether the trigger should be applied.
+    /// </summary>
+    public CoreWindowActivationMode ActivationMode
+    {
+        get { return (CoreWindowActivationMode)GetValue(ActivationModeProperty); }
+        set { SetValue(ActivationModeProperty, value); }
+    }
+
+    private static void OnActivationModePropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
+    {
+        if (d is WindowActivationModeTrigger trigger)
+        {
+            trigger.UpdateActivatedEventHandler();
+            trigger.UpdateTrigger();
+        }
+    }
+
+    private void UpdateActivatedEventHandler()
+    {
+        _coreWindow = Window.Current?.CoreWindow;
+
+        var coreWindow = _coreWindow;
+        if (coreWindow != null)
+        {
+            coreWindow.Activated -= OnActivated;
+
+            if (ActivationMode is not CoreWindowActivationMode.None)
+            {
+                coreWindow.Activated += OnActivated;
+            }
+        }
+    }
+
+    private void OnActivated(CoreWindow sender, WindowActivatedEventArgs args)
+    {
+        UpdateTrigger();
+    }
+
+    private void UpdateTrigger()
+    {
+        SetActive(_coreWindow?.ActivationMode == ActivationMode);
+    }
+}