TASK 3 milestone 1: webcam capture (MediaCapture CPU-first, CameraManager refcount, picker, clip/mirror, schema v2, tests)

ViewModels/MainViewModel.cs

@@ -6,6 +6,7 @@ using System.IO;
 using System.Windows;
 using System.Windows.Input;
 using System.Windows.Media;
+using System.Windows.Media.Imaging;
 using System.Windows.Threading;
 using Microsoft.Win32;
 using ytLive.Helpers;
@@ -56,6 +57,12 @@ public class MainViewModel : ViewModelBase
     private DispatcherTimer? _saveDebounce;
     private bool _isLoading;
 
+    // Webcam: one camera app-wide. The single Source is tracked here so the
+    // Add menu can be disabled and the live preview bitmap can be forwarded.
+    private readonly ICameraEnumerator _cameraEnumerator;
+    private readonly CameraManager _cameraManager;
+    private Source? _webcamSource;
+
     // Branding flash (monetization): a full-frame "made with ytLlive!" shown
     // for ~1s every 300s on the live output, ~25% opacity. Paid unlock sets
     // BrandFlashEnabled = false. See ai.md "Monetization".
@@ -99,9 +106,19 @@ public class MainViewModel : ViewModelBase
     public Source? SelectedSource
     {
         get => _selectedSource;
-        set => SetProperty(ref _selectedSource, value);
+        set
+        {
+            if (SetProperty(ref _selectedSource, value))
+                OnPropertyChanged(nameof(IsWebcamSelected));
+        }
     }
 
+    /// <summary>The Add → Webcam menu item. One webcam app-wide — once one exists it's greyed out.</summary>
+    public bool CanAddWebcam => _webcamSource == null;
+
+    /// <summary>Shows the mirror / clip-shape row in the source chip when a webcam is selected.</summary>
+    public bool IsWebcamSelected => SelectedSource?.Type == SourceType.Webcam;
+
     public StreamStatus StreamStatus
     {
         get => _streamStatus;
@@ -466,6 +483,14 @@ public class MainViewModel : ViewModelBase
 
         _layoutStore = new LayoutStore(DefaultLayoutPath);
         _activeLayoutPath = _layoutStore.ActivePath;
+
+        _cameraEnumerator = new MediaCaptureCameraEnumerator();
+        _cameraManager = new CameraManager(
+            _cameraEnumerator,
+            id => new MediaCaptureFrameSource(id),
+            System.Windows.Application.Current?.Dispatcher);
+        _cameraManager.PreviewBitmapChanged += OnCameraPreviewBitmapChanged;
+
         LoadLayout();
         _ = LoadSavedSessionAsync();
         AppLog.Write("MainViewModel ctor end");
@@ -533,14 +558,41 @@ public class MainViewModel : ViewModelBase
         }
         ActiveScene = Scenes.FirstOrDefault();
         UpdateActiveBackground();
+        ReacquireWebcam();
         ScheduleSave();
         AppLog.Write("LoadLayout end");
     }
 
+    // Finds the persisted webcam source (at most one app-wide) and re-acquires
+    // its camera after a layout load / file open. Releasing the previous session
+    // unconditionally keeps the refcount honest even when the device is unchanged.
+    private void ReacquireWebcam()
+    {
+        var webcam = Scenes.SelectMany(s => s.Sources).FirstOrDefault(s => s.Type == SourceType.Webcam);
+        if (ReferenceEquals(_webcamSource, webcam)) return;
+
+        if (_webcamSource != null && !string.IsNullOrWhiteSpace(_webcamSource.DeviceId))
+            _ = _cameraManager.ReleaseAsync(_webcamSource.DeviceId);
+
+        _webcamSource = webcam;
+        OnPropertyChanged(nameof(CanAddWebcam));
+        if (webcam != null && !string.IsNullOrWhiteSpace(webcam.DeviceId))
+            _ = _cameraManager.AcquireAsync(webcam.DeviceId);
+    }
+
+    // CameraManager creates the shared WriteableBitmap on the UI thread at the
+    // device's frame size; the webcam Source's preview picks it up from here.
+    private void OnCameraPreviewBitmapChanged(string deviceId, WriteableBitmap bitmap)
+    {
+        if (_webcamSource?.DeviceId == deviceId)
+            _webcamSource.VideoImageSource = bitmap;
+    }
+
     public void Shutdown()
     {
         _saveDebounce?.Stop();
         SaveLayoutNow();
+        _cameraManager.Dispose();
         _layoutStore.Dispose();
     }
 
@@ -691,6 +743,12 @@ public class MainViewModel : ViewModelBase
             _ => "Source",
         };
 
+        if (sourceType == SourceType.Webcam)
+        {
+            _ = AddWebcamSourceAsync();
+            return;
+        }
+
         if (sourceType == SourceType.Background)
         {
             var bytes = PickImageBytes("Choose a backdrop image");
@@ -722,6 +780,46 @@ public class MainViewModel : ViewModelBase
         UpdateActiveBackground();
     }
 
+    private async Task AddWebcamSourceAsync()
+    {
+        var scene = ActiveScene;
+        if (scene == null || _webcamSource != null) return;
+
+        var dialog = new CameraPickerDialog(new CameraPickerViewModel(_cameraEnumerator))
+        {
+            Owner = Application.Current.MainWindow
+        };
+        if (dialog.ShowDialog() != true || dialog.PickedDevice == null) return;
+
+        var device = dialog.PickedDevice;
+        var source = new Source
+        {
+            Name = "Webcam",
+            Type = SourceType.Webcam,
+            DeviceId = device.Id,
+            Width = 480,
+            Height = 270,
+            X = 1920 - 480 - 32,
+            Y = 1080 - 270 - 32,
+        };
+
+        _webcamSource = source;
+        OnPropertyChanged(nameof(CanAddWebcam));
+        scene.Sources.Add(source);
+        SelectedSource = source;
+        OnPropertyChanged(nameof(ShowEmptySceneHint));
+        OnPropertyChanged(nameof(ShowSourcesEmptyHint));
+        UpdateActiveBackground();
+
+        var started = await _cameraManager.AcquireAsync(device.Id);
+        if (!started)
+        {
+            MessageBox.Show(
+                "Couldn't start that camera. It may be in use by another app, or Windows camera access may be turned off.",
+                "ytLlive", MessageBoxButton.OK, MessageBoxImage.Warning);
+        }
+    }
+
     private void AddImage()
     {
         var scene = ActiveScene;
@@ -842,6 +940,13 @@ public class MainViewModel : ViewModelBase
     {
         var scene = ActiveScene;
         if (scene == null || source == null) return;
+        if (source.Type == SourceType.Webcam && ReferenceEquals(source, _webcamSource))
+        {
+            _webcamSource = null;
+            OnPropertyChanged(nameof(CanAddWebcam));
+            if (!string.IsNullOrWhiteSpace(source.DeviceId))
+                _ = _cameraManager.ReleaseAsync(source.DeviceId);
+        }
         scene.Sources.Remove(source);
         OnPropertyChanged(nameof(ShowEmptySceneHint));
         OnPropertyChanged(nameof(ShowSourcesEmptyHint));