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

ViewModels/CameraPickerViewModel.cs

@@ -0,0 +1,86 @@
+using System.Collections.ObjectModel;
+using System.Windows.Input;
+using ytLive.Helpers;
+using ytLive.Services;
+
+namespace ytLive.ViewModels;
+
+public class CameraPickerCandidate
+{
+    public CameraDeviceInfo Device { get; }
+    public string Name => Device.DisplayName;
+
+    public CameraPickerCandidate(CameraDeviceInfo device)
+    {
+        Device = device;
+    }
+}
+
+public class CameraPickerViewModel : ViewModelBase
+{
+    private readonly ICameraEnumerator _enumerator;
+    private CameraPickerCandidate? _selectedCamera;
+    private bool _isLoading = true;
+
+    public ObservableCollection<CameraPickerCandidate> Cameras { get; } = new();
+
+    public bool IsLoading
+    {
+        get => _isLoading;
+        private set => SetProperty(ref _isLoading, value);
+    }
+
+    public bool HasCameras => !IsLoading && Cameras.Count > 0;
+    public bool NoCameras => !IsLoading && Cameras.Count == 0;
+
+    public CameraPickerCandidate? SelectedCamera
+    {
+        get => _selectedCamera;
+        set
+        {
+            if (SetProperty(ref _selectedCamera, value))
+                CommandManager.InvalidateRequerySuggested();
+        }
+    }
+
+    public ICommand UseSelectedCommand { get; }
+    public ICommand CancelCommand { get; }
+
+    public event Action<CameraDeviceInfo>? UseRequested;
+    public event Action? CancelRequested;
+
+    public CameraPickerViewModel(ICameraEnumerator enumerator)
+    {
+        _enumerator = enumerator;
+        UseSelectedCommand = new RelayCommand(
+            _ => { if (SelectedCamera != null) UseRequested?.Invoke(SelectedCamera.Device); },
+            _ => SelectedCamera != null);
+        CancelCommand = new RelayCommand(_ => CancelRequested?.Invoke());
+        _ = LoadAsync();
+    }
+
+    private async Task LoadAsync()
+    {
+        IsLoading = true;
+        try
+        {
+            var devices = await _enumerator.GetCamerasAsync();
+            Cameras.Clear();
+            foreach (var device in devices)
+                Cameras.Add(new CameraPickerCandidate(device));
+            if (Cameras.Count > 0)
+                SelectedCamera = Cameras[0];
+        }
+        catch (Exception ex)
+        {
+            AppLog.Write($"CameraPickerViewModel: enumerating cameras failed: {ex.Message}");
+        }
+        finally
+        {
+            IsLoading = false;
+            OnPropertyChanged(nameof(HasCameras));
+            OnPropertyChanged(nameof(NoCameras));
+            CommandManager.InvalidateRequerySuggested();
+        }
+    }
+}

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));

ViewModels/index.md

@@ -4,9 +4,10 @@ MVVM layer. See [`schema.md`](../schema.md) for the memory-map conventions.
 
 | File | Purpose |
 |------|---------|
-| `MainViewModel.cs` | The app brain: scenes/sources collections + commands, stream state (`IsLive`/`IsOffline`/`IsConnected`), chat feed, overlays, layout save/open, **resolution dropdown** (`QualityOptions`, `SelectedQuality`, `ResolutionHelp`, `ApplyStreamQuality`) that computes the output rect over the 1920×1080 master (`OutputRectX/Y/W/H`, `DimRects`, `IsOutputCropped`, `ResolutionBadgeText`). Auth: loads the saved DPAPI session at startup (`LoadSavedSessionAsync`), `SignInAsync` feeds the GoLive dialog; **End Livestream signs out** (`StopStream` clears session + token — crash-safe) |
+| `MainViewModel.cs` | The app brain: scenes/sources collections + commands, stream state (`IsLive`/`IsOffline`/`IsConnected`), chat feed, overlays, layout save/open, **resolution dropdown** (`QualityOptions`, `SelectedQuality`, `ResolutionHelp`, `ApplyStreamQuality`) that computes the output rect over the 1920×1080 master (`OutputRectX/Y/W/H`, `DimRects`, `IsOutputCropped`, `ResolutionBadgeText`). Auth: loads the saved DPAPI session at startup (`LoadSavedSessionAsync`), `SignInAsync` feeds the GoLive dialog; **End Livestream signs out** (`StopStream` clears session + token — crash-safe). **Webcam:** owns `CameraManager` (MediaCapture), `AddWebcamSourceAsync` (picker → default 480×270 bottom-right placement → acquire), one-camera app-wide (`CanAddWebcam` greys the menu), `ReacquireWebcam` after layout load, `OnCameraPreviewBitmapChanged` forwards the shared bitmap into `Source.VideoImageSource` |
 | `GoLiveViewModel.cs` | Start Stream dialog: **account row** (saved channel shown with Change Account, or Sign in to YouTube; Start gated on `IsSignedIn`/`IsBusy`) + title/description/visibility, start/cancel requests |
 | `ReuseImageViewModel.cs` | Add Image dialog: candidate list (`ReuseImageCandidate`), reuse/new/cancel |
+| `CameraPickerViewModel.cs` | Add Webcam dialog: async camera list (loading / has / none states), `UseRequested(CameraDeviceInfo)`/`CancelRequested` |
 
 Related: [`Models/index.md`](../Models/index.md) for the data; [`Services/index.md`](../Services/index.md)
 for what the ViewModels drive; base class in [`Helpers/ViewModelBase.cs`](../Helpers/ViewModelBase.cs).