refactor: split Trax out of MainViewModel — Commit 7/12

MainViewModel.Trax.cs: music-player state (_musicPlayer/_music/_musicPlaying,
TraxIdleBrush), TRAX UI (IsMusicPlaying/TraxError/TraxDotBrush/TraxToolTip),
interaction (TraxLeftClick/TraxRightClick/PickTraxTrack), playback
(LoadTrax/PlayTrax/PauseTrax/OnTraxPlaybackEnded/RefreshTraxUi), local
loopback ducking (UpdateTraxLocalGain).

Core keeps the ctor event hookup, LoadLayout/Shutdown/SaveLayoutNow call
sites, and Scenes partial's hotkey dispatch.

Verify: 0 warnings, 246 passed, 2 known failures only.

ViewModels/MainViewModel.Trax.cs

@@ -0,0 +1,132 @@
+using System.IO;
+using System.Windows.Media;
+using Microsoft.Win32;
+using ytLive.Helpers;
+using ytLive.Models;
+using ytLive.Services.Audio;
+
+namespace ytLive.ViewModels;
+
+public partial class MainViewModel
+{
+    // TRAX (TASK 9): free background music at a fixed quiet volume, playing to
+    // the default device so it rides the loopback into the stream. The dot is
+    // red (no track) / yellow (loaded, stopped) / green (playing).
+    private readonly MusicPlayer _musicPlayer = new();
+    private Music? _music;
+    private bool _musicPlaying;
+
+    private static readonly SolidColorBrush TraxIdleBrush = CreateBrush("#555");
+    /// <summary>True while the TRAX background track is playing.</summary>
+    public bool IsMusicPlaying
+    {
+        get => _musicPlaying;
+        private set
+        {
+            if (SetProperty(ref _musicPlaying, value))
+            {
+                OnPropertyChanged(nameof(TraxDotBrush));
+                OnPropertyChanged(nameof(TraxToolTip));
+            }
+        }
+    }
+
+    private string? _traxError;
+
+    /// <summary>Error message from the last TRAX load/playback failure; null = no error.</summary>
+    public string? TraxError
+    {
+        get => _traxError;
+        private set => SetProperty(ref _traxError, value);
+    }
+
+    /// <summary>TRAX status dot: green = playing, gray = idle or no track.</summary>
+    public SolidColorBrush TraxDotBrush => _musicPlayer.IsPlaying
+        ? BarOnBrush
+        : TraxIdleBrush;
+
+    public string TraxToolTip => _musicPlayer.TrackName != null
+        ? $"TRAX: {_musicPlayer.TrackName} — left-click {(IsMusicPlaying ? "pauses" : "plays")}, right-click chooses a track"
+        : "No track — left-click or right-click to choose background music";
+
+    /// <summary>Left-click on TRAX: no track → pick one; otherwise toggle play/pause.</summary>
+    public void TraxLeftClick()
+    {
+        if (_music == null || string.IsNullOrWhiteSpace(_music.TrackPath))
+            PickTraxTrack();
+        else if (IsMusicPlaying)
+            PauseTrax();
+        else
+            PlayTrax();
+    }
+
+    /// <summary>Right-click on TRAX: always open the track picker (never the OS viewer).</summary>
+    public void TraxRightClick() => PickTraxTrack();
+
+    private void PickTraxTrack()
+    {
+        var dialog = new OpenFileDialog
+        {
+            Title = "Choose background music",
+            Filter = "Music (*.mp3;*.wav;*.m4a;*.aac;*.flac;*.ogg)|*.mp3;*.wav;*.m4a;*.aac;*.flac;*.ogg|All files (*.*)|*.*",
+        };
+        if (dialog.ShowDialog() != true)
+            return;
+
+        _music = new Music { TrackPath = dialog.FileName, IsEnabled = true };
+        LoadTrax(play: true);
+    }
+
+    private void LoadTrax(bool play)
+    {
+        if (_music == null || string.IsNullOrWhiteSpace(_music.TrackPath))
+            return;
+
+        try
+        {
+            _musicPlayer.Load(_music.TrackPath);
+            UpdateTraxLocalGain();
+            _music.IsEnabled = true;
+            TraxError = null;
+            if (play)
+                _musicPlayer.Play();
+        }
+        catch (Exception ex)
+        {
+            AppLog.Write($"TRAX: failed to load '{_music.TrackPath}': {ex.Message}");
+            TraxError = $"Failed to load: {Path.GetFileName(_music.TrackPath)} — {ex.Message}";
+        }
+        RefreshTraxUi();
+        ScheduleSave();
+    }
+
+    private void PlayTrax() => _musicPlayer.Play();
+
+    private void PauseTrax() => _musicPlayer.Pause();
+
+    private void OnTraxPlaybackEnded(Exception? ex)
+    {
+        if (ex != null)
+        {
+            AppLog.Write($"TRAX: playback error: {ex.Message}");
+            TraxError = $"Playback error: {ex.Message}";
+        }
+        RefreshTraxUi();
+    }
+
+    private void RefreshTraxUi()
+    {
+        IsMusicPlaying = _musicPlayer.IsPlaying;
+        OnPropertyChanged(nameof(TraxDotBrush));
+        OnPropertyChanged(nameof(TraxToolTip));
+    }
+
+    /// <summary>Mirrors the desktop/game audio bar's volume and mute onto the
+    /// music so the creator hears the controls work in the headphones (the
+    /// track rides the loopback channel, so it must duck the same way locally).
+    /// Called whenever the game volume/mute change and on TRAX load.</summary>
+    private void UpdateTraxLocalGain()
+    {
+        _musicPlayer.LocalGain = GameMuted ? 0f : 1f;
+    }
+}

ViewModels/MainViewModel.cs

@@ -31,12 +31,6 @@ public partial class MainViewModel : ViewModelBase
 
     private SceneElement? _selectedElement;
 
-    // TRAX (TASK 9): free background music at a fixed quiet volume, playing to
-    // the default device so it rides the loopback into the stream. The dot is
-    // red (no track) / yellow (loaded, stopped) / green (playing).
-    private readonly MusicPlayer _musicPlayer = new();
-    private Music? _music;
-    private bool _musicPlaying;
     private StreamStatus _streamStatus = StreamStatus.Offline;
     private StreamHealth _currentHealth = new();
     private string _streamTitle = string.Empty;
@@ -234,121 +228,6 @@ public partial class MainViewModel : ViewModelBase
         }
     }
 
-    private static readonly SolidColorBrush TraxIdleBrush = CreateBrush("#555");
-    /// <summary>True while the TRAX background track is playing.</summary>
-    public bool IsMusicPlaying
-    {
-        get => _musicPlaying;
-        private set
-        {
-            if (SetProperty(ref _musicPlaying, value))
-            {
-                OnPropertyChanged(nameof(TraxDotBrush));
-                OnPropertyChanged(nameof(TraxToolTip));
-            }
-        }
-    }
-
-    private string? _traxError;
-
-    /// <summary>Error message from the last TRAX load/playback failure; null = no error.</summary>
-    public string? TraxError
-    {
-        get => _traxError;
-        private set => SetProperty(ref _traxError, value);
-    }
-
-    /// <summary>TRAX status dot: green = playing, gray = idle or no track.</summary>
-    public SolidColorBrush TraxDotBrush => _musicPlayer.IsPlaying
-        ? BarOnBrush
-        : TraxIdleBrush;
-
-    public string TraxToolTip => _musicPlayer.TrackName != null
-        ? $"TRAX: {_musicPlayer.TrackName} — left-click {(IsMusicPlaying ? "pauses" : "plays")}, right-click chooses a track"
-        : "No track — left-click or right-click to choose background music";
-
-    /// <summary>Left-click on TRAX: no track → pick one; otherwise toggle play/pause.</summary>
-    public void TraxLeftClick()
-    {
-        if (_music == null || string.IsNullOrWhiteSpace(_music.TrackPath))
-            PickTraxTrack();
-        else if (IsMusicPlaying)
-            PauseTrax();
-        else
-            PlayTrax();
-    }
-
-    /// <summary>Right-click on TRAX: always open the track picker (never the OS viewer).</summary>
-    public void TraxRightClick() => PickTraxTrack();
-
-    private void PickTraxTrack()
-    {
-        var dialog = new OpenFileDialog
-        {
-            Title = "Choose background music",
-            Filter = "Music (*.mp3;*.wav;*.m4a;*.aac;*.flac;*.ogg)|*.mp3;*.wav;*.m4a;*.aac;*.flac;*.ogg|All files (*.*)|*.*",
-        };
-        if (dialog.ShowDialog() != true)
-            return;
-
-        _music = new Music { TrackPath = dialog.FileName, IsEnabled = true };
-        LoadTrax(play: true);
-    }
-
-    private void LoadTrax(bool play)
-    {
-        if (_music == null || string.IsNullOrWhiteSpace(_music.TrackPath))
-            return;
-
-        try
-        {
-            _musicPlayer.Load(_music.TrackPath);
-            UpdateTraxLocalGain();
-            _music.IsEnabled = true;
-            TraxError = null;
-            if (play)
-                _musicPlayer.Play();
-        }
-        catch (Exception ex)
-        {
-            AppLog.Write($"TRAX: failed to load '{_music.TrackPath}': {ex.Message}");
-            TraxError = $"Failed to load: {Path.GetFileName(_music.TrackPath)} — {ex.Message}";
-        }
-        RefreshTraxUi();
-        ScheduleSave();
-    }
-
-    private void PlayTrax() => _musicPlayer.Play();
-
-    private void PauseTrax() => _musicPlayer.Pause();
-
-    private void OnTraxPlaybackEnded(Exception? ex)
-    {
-        if (ex != null)
-        {
-            AppLog.Write($"TRAX: playback error: {ex.Message}");
-            TraxError = $"Playback error: {ex.Message}";
-        }
-        RefreshTraxUi();
-    }
-
-    private void RefreshTraxUi()
-    {
-        IsMusicPlaying = _musicPlayer.IsPlaying;
-        OnPropertyChanged(nameof(TraxDotBrush));
-        OnPropertyChanged(nameof(TraxToolTip));
-    }
-
-    /// <summary>Mirrors the desktop/game audio bar's volume and mute onto the
-    /// music so the creator hears the controls work in the headphones (the
-    /// track rides the loopback channel, so it must duck the same way locally).
-    /// Called whenever the game volume/mute change and on TRAX load.</summary>
-    private void UpdateTraxLocalGain()
-    {
-        _musicPlayer.LocalGain = GameMuted ? 0f : 1f;
-    }
-
-
     public bool IsOffline => StreamStatus == StreamStatus.Offline;
     public bool IsLive => StreamStatus == StreamStatus.Streaming;
     public bool IsLivePrivate => IsLive && string.Equals(StreamVisibility, "Private", StringComparison.OrdinalIgnoreCase);

ViewModels/index.md

@@ -68,14 +68,20 @@ Progress (Commit N/12 · tag):
   `OnLoopbackLevelChanged`/`OnMicConnected`/`OnMicFailed`, `StartMicCaptureAsync`,
   audio fields + `ToggleMicMuteCommand`/`ToggleGameMuteCommand`/`OpenMicPickerCommand`).
   TRAX stays in core (next commit).
+- **Commit 7/12 · `refactor-commit-7`: Trax landed** → `MainViewModel.Trax.cs`
+  (`_musicPlayer`/`_music`/`_musicPlaying` + `TraxIdleBrush`, `IsMusicPlaying`/
+  `TraxError`/`TraxDotBrush`/`TraxToolTip`, `TraxLeftClick`/`TraxRightClick`/
+  `PickTraxTrack`/`LoadTrax`/`PlayTrax`/`PauseTrax`/`OnTraxPlaybackEnded`/
+  `RefreshTraxUi`/`UpdateTraxLocalGain`). Core keeps the ctor hookup
+  (`_musicPlayer.PlaybackEnded += ...`), the `LoadLayout`/`Shutdown`/
+  `SaveLayoutNow` call sites, and the Scenes partial's hotkey dispatch into `TraxLeftClick`.
 
 - Core file keeps: fields, ctor, `Shutdown`/`SaveLayoutNow`/`ScheduleSave`/`LoadLayout`,
   `SetPanel`/`ShowOverlay`/`ShowLicenses`, `CreateBrush`, `OpenUrl`/`ComposeEmail`,
   `SubmitBug`/`SubmitFeature`, window-geometry pass-through.
 - Partials: `Account` ✔ (Commit 1), `License` ✔ (Commit 2), `Scenes` ✔ (Commit 3), `Background` ✔ (Commit 4),
-  `Webcam` ✔ (Commit 5), `Audio` ✔ (Commit 6),
+  `Webcam` ✔ (Commit 5), `Audio` ✔ (Commit 6), `Trax` ✔ (Commit 7),
-  `Trax` (music player), `Socials` (social bar + dialog),
+  `Socials` (social bar + dialog), `Streaming` (go-live/record + health + quality tiers + media source pipeline),
-  `Streaming` (go-live/record + health + quality tiers + media source pipeline),
   `Chat` (YouTube chat + mock preview + chatbox render), `Overlays` (settings/bug/feature/about
   panels + license entry).