Disable sleep idle timeout when audio is playing via SetThreadExecutionState.

Harmonia.WinUI/Harmonia.WinUI.csproj

@@ -102,5 +102,6 @@
 		<PublishReadyToRun Condition="'$(Configuration)' != 'Debug'">True</PublishReadyToRun>
 		<PublishTrimmed Condition="'$(Configuration)' == 'Debug'">False</PublishTrimmed>
 		<PublishTrimmed Condition="'$(Configuration)' != 'Debug'">True</PublishTrimmed>
+		<AllowUnsafeBlocks>true</AllowUnsafeBlocks>
 	</PropertyGroup>
 </Project>

Harmonia.WinUI/MainWindow.xaml.cs

@@ -1,6 +1,9 @@
+using Harmonia.Core.Player;
 using Harmonia.WinUI.Session;
 using Microsoft.UI.Windowing;
 using Microsoft.UI.Xaml;
+using System;
+using System.Runtime.InteropServices;
 
 namespace Harmonia.WinUI;
 
@@ -8,16 +11,23 @@ public sealed partial class MainWindow : Window
 {
     private const string ApplicationTitle = "Harmonia";
 
+    [LibraryImport("kernel32.dll", SetLastError = true)]
+    private static partial EXECUTION_STATE SetThreadExecutionState(EXECUTION_STATE esFlags);
+
     private readonly ISessionService _sessionService;
     private readonly ISessionTracker _sessionTracker;
+    private readonly IAudioPlayer _audioPlayer;
 
     private bool _isSaved;
 
-    public MainWindow(ISessionService sessionService, ISessionTracker sessionTracker)
+    public MainWindow(ISessionService sessionService, ISessionTracker sessionTracker, IAudioPlayer audioPlayer)
     {
         _sessionService = sessionService;
         _sessionTracker = sessionTracker;
 
+        _audioPlayer = audioPlayer;
+        _audioPlayer.PropertyChanged += OnAudioPlayerPropertyChanged;
+
         InitializeComponent();
         InitializeTitleBar();
         InitializeWindowState();
@@ -54,6 +64,8 @@ public sealed partial class MainWindow : Window
 
     private async void OnMainWindowClosed(object sender, WindowEventArgs args)
     {
+        EnableSleepIdleTimeout();
+
         if (_isSaved)
             return;
 
@@ -65,4 +77,53 @@ public sealed partial class MainWindow : Window
         _isSaved = true;
         Close();
     }
+
+    private void OnAudioPlayerPropertyChanged(object? sender, System.ComponentModel.PropertyChangedEventArgs e)
+    {
+        switch (e.PropertyName)
+        {
+            case nameof(_audioPlayer.State):
+                OnAudioPlayerStateChanged(sender, e);
+                break;
+        }
+    }
+
+    private void OnAudioPlayerStateChanged(object? sender, EventArgs e)
+    {
+        // SetThreadExecutionState is per-thread, so always marshal to the UI thread to
+        // guarantee the ES_CONTINUOUS flags are set and cleared on the same thread.
+        DispatcherQueue.TryEnqueue(() =>
+        {
+            switch (_audioPlayer.State)
+            {
+                case Core.Engine.AudioPlaybackState.Playing:
+                    DisableSleepIdleTimeout();
+                    break;
+                default:
+                    EnableSleepIdleTimeout();
+                    break;
+            }
+        });
+    }
+
+    private static void EnableSleepIdleTimeout()
+    {
+        // Clear EXECUTION_STATE flags to allow the system to idle to sleep normally.
+        SetThreadExecutionState(EXECUTION_STATE.ES_CONTINUOUS);
+    }
+
+    private static void DisableSleepIdleTimeout()
+    {
+        // Prevent the system sleep idle time-out while still allowing the display to sleep.
+        SetThreadExecutionState(EXECUTION_STATE.ES_CONTINUOUS | EXECUTION_STATE.ES_SYSTEM_REQUIRED);
+    }
+
+    [Flags]
+    private enum EXECUTION_STATE : uint
+    {
+        ES_CONTINUOUS        = 0x80000000,
+        ES_SYSTEM_REQUIRED   = 0x00000001,
+        ES_DISPLAY_REQUIRED  = 0x00000002,
+        ES_AWAYMODE_REQUIRED = 0x00000040
+    }
 }