Multi-scene webcam (schema v3/v4): singleton Webcam + per-scene WebcamSceneConfig, right-click OBS-style border/context menu, persisted round-to-rect restore + legacy-square 16:9 heal, dark MenuItem template, tests (25 passing)

2026-08-07 08:24:18 -07:00
parent f31ce9fdb7
commit e037ba027b
23 changed files with 1405 additions and 287 deletions
@@ -23,7 +23,7 @@ public class MainViewModel : ViewModelBase
    private readonly DispatcherTimer _liveTimer;

    private Scene? _activeScene;
-    private Source? _selectedSource;
+    private SceneElement? _selectedElement;
    private ImageSource? _activeBackgroundImage;
    private bool _isConnected;
    private StreamStatus _streamStatus = StreamStatus.Offline;
@@ -57,11 +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.
+    // Webcam: one camera input app-wide. The identity (DeviceId) lives on the
+    // Webcam entity; each scene that shows the webcam has a WebcamSceneConfig
+    // (webcam.{scene}.config). CameraManager still owns the single session.
    private readonly ICameraEnumerator _cameraEnumerator;
    private readonly CameraManager _cameraManager;
-    private Source? _webcamSource;
+    private Webcam? _webcam;

    // Branding flash (monetization): a full-frame "made with ytLlive!" shown
    // for ~1s every 300s on the live output, ~25% opacity. Paid unlock sets
@@ -87,11 +88,13 @@ public class MainViewModel : ViewModelBase
            if (value != null && value.IsHidden) return;
            if (SetProperty(ref _activeScene, value))
            {
-                SelectedSource = null;
+                SelectedElement = null;
                OnPropertyChanged(nameof(ShowChatInactiveMessage));
                OnPropertyChanged(nameof(ShowEmptySceneHint));
                OnPropertyChanged(nameof(ShowPreviewPlaceholder));
                OnPropertyChanged(nameof(ShowSourcesEmptyHint));
+                OnPropertyChanged(nameof(CanAddWebcamToActiveScene));
+                OnPropertyChanged(nameof(CanShowWebcamInActiveScene));
                UpdateActiveBackground();
            }
        }
@@ -103,21 +106,31 @@ public class MainViewModel : ViewModelBase
        private set => SetProperty(ref _activeBackgroundImage, value);
    }

-    public Source? SelectedSource
+    public SceneElement? SelectedElement
    {
-        get => _selectedSource;
+        get => _selectedElement;
        set
        {
-            if (SetProperty(ref _selectedSource, value))
+            if (SetProperty(ref _selectedElement, 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>The Add → Webcam menu item: enabled when the active scene doesn't show the webcam yet.</summary>
+    public bool CanAddWebcamToActiveScene => ActiveScene?.WebcamConfig == null;
+
+    /// <summary>
+    /// Right-click-on-preview → "Show Webcam": offered when the active scene has no
+    /// webcam config (add one) or hides it (unhide — keeps the config row).
+    /// </summary>
+    public bool CanShowWebcamInActiveScene
+        => ActiveScene is { } scene && (scene.WebcamConfig == null || !scene.WebcamConfig.IsVisible);
+
+    /// <summary>Swap-the-device item: enabled once a camera has been picked at all.</summary>
+    public bool CanChangeWebcam => _webcam != 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 bool IsWebcamSelected => SelectedElement is WebcamSceneConfig;

    public StreamStatus StreamStatus
    {
@@ -152,9 +165,9 @@ public class MainViewModel : ViewModelBase
    public bool LiveIndicatorVisible => IsLive;
    public bool ShowStartStream => IsOffline;
    public bool ShowChatInactiveMessage => !IsLive;
-    public bool ShowEmptySceneHint => ActiveScene != null && ActiveScene.Sources.Count == 0;
+    public bool ShowEmptySceneHint => ActiveScene != null && ActiveScene.Elements.Count == 0;
    public bool ShowPreviewPlaceholder => !ShowEmptySceneHint && ActiveBackgroundImage == null;
-    public bool ShowSourcesEmptyHint => ActiveScene == null || ActiveScene.Sources.Count == 0;
+    public bool ShowSourcesEmptyHint => ActiveScene == null || ActiveScene.Elements.Count == 0;

    // Paid unlock flips this off (see ai.md "Monetization"). When disabled the
    // cadence timer is stopped and any active flash is hidden immediately.
@@ -185,7 +198,7 @@ public class MainViewModel : ViewModelBase

    private void UpdateActiveBackground()
    {
-        var background = ActiveScene?.Sources.FirstOrDefault(s => s.Type == SourceType.Background);
+        var background = ActiveScene?.Elements.OfType<Source>().FirstOrDefault(s => s.Type == SourceType.Background);
        ActiveBackgroundImage = background != null && !string.IsNullOrWhiteSpace(background.AssetId)
            ? ImageCache.Get(background.AssetId)
            : null;
@@ -315,6 +328,44 @@ public class MainViewModel : ViewModelBase
    private const double MasterFrameWidth = 1920;
    private const double MasterFrameHeight = 1080;

+    // Webcam size safeguard: no more than half the frame in any dimension
+    // (960x540 over the 1920x1080 master), and no less than 10% of it
+    // (192x108). Enforced at resize and on layout load.
+    public const double WebcamMaxWidth = 960;
+    public const double WebcamMaxHeight = 540;
+    public const double WebcamMinWidth = MasterFrameWidth * 0.1;
+    public const double WebcamMinHeight = MasterFrameHeight * 0.1;
+
+    internal static void ClampWebcamToBounds(WebcamSceneConfig config)
+    {
+        var scale = Math.Min(WebcamMaxWidth / config.Width, WebcamMaxHeight / config.Height);
+        if (scale < 1)
+        {
+            config.Width = Math.Round(config.Width * scale);
+            config.Height = Math.Round(config.Height * scale);
+            return;
+        }
+
+        var minScale = Math.Max(WebcamMinWidth / config.Width, WebcamMinHeight / config.Height);
+        if (minScale > 1)
+        {
+            config.Width = Math.Round(config.Width * minScale);
+            config.Height = Math.Round(config.Height * minScale);
+        }
+    }
+
+    // One-time heal for layouts saved before the rect dims were persisted (v3→v4):
+    // a Traditional webcam that ended up square (Round resize then reload lost the
+    // pre-Round rect) gets widened to 16:9, keeping the height. Round is skipped —
+    // a square bounding box is correct there — and an explicit pre-Round rect wins.
+    internal static void HealLegacySquareRect(WebcamSceneConfig config)
+    {
+        if (config.ClipShape != ClipShape.Traditional) return;
+        if (config.RectWidth != null || config.RectHeight != null) return;
+        if (Math.Abs(config.Width - config.Height) >= 1) return;
+        config.Width = Math.Round(config.Height * 16.0 / 9.0);
+    }
+
    public QualityOption[] QualityOptions { get; } =
    {
        new("1080p60", 60, 8.0, 1920, 1080),
@@ -419,6 +470,8 @@ public class MainViewModel : ViewModelBase
    public ICommand AddSourceCommand { get; }
    public ICommand AddImageCommand { get; }
    public ICommand RemoveSourceCommand { get; }
+    public ICommand ChangeWebcamCommand { get; }
+    public ICommand ShowWebcamCommand { get; }
    public ICommand StartStreamCommand { get; }
    public ICommand EndStreamCommand { get; }
    public ICommand OpenSettingsCommand { get; }
@@ -466,7 +519,9 @@ public class MainViewModel : ViewModelBase
        ToggleSceneVisibilityCommand = new RelayCommand(scene => ToggleSceneVisibility(scene as Scene));
        AddSourceCommand = new RelayCommand(type => AddSource(type as string));
        AddImageCommand = new RelayCommand(_ => AddImage());
-        RemoveSourceCommand = new RelayCommand(source => RemoveSource(source as Source));
+        RemoveSourceCommand = new RelayCommand(element => RemoveElement(element as SceneElement));
+        ChangeWebcamCommand = new RelayCommand(_ => _ = ChangeWebcamAsync(), _ => CanChangeWebcam);
+        ShowWebcamCommand = new RelayCommand(_ => ShowWebcamInActiveScene(), _ => CanShowWebcamInActiveScene);
        OpenSettingsCommand = new RelayCommand(_ => ShowOverlay(nameof(IsSettingsOpen), "App Settings"));
        OpenBugCommand = new RelayCommand(_ => ShowOverlay(nameof(IsBugOpen), "Report Bug"));
        OpenFeatureCommand = new RelayCommand(_ => ShowOverlay(nameof(IsFeatureOpen), "Feature Request"));
@@ -555,6 +610,12 @@ public class MainViewModel : ViewModelBase
                AddScene("Chat", isChatScene: true);
                AddScene("Ending");
            }
+            foreach (var scene in Scenes)
+                foreach (var config in scene.Elements.OfType<WebcamSceneConfig>())
+                {
+                    ClampWebcamToBounds(config);
+                    HealLegacySquareRect(config);
+                }
            AppLog.Write($"LoadLayout: {Scenes.Count} scenes loaded");
        }
        finally
@@ -568,29 +629,35 @@ public class MainViewModel : ViewModelBase
        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.
+    // After a layout load / file open: re-point the webcam identity, stop the
+    // previous device if it changed, and acquire the current one once per scene
+    // that uses it (CameraManager refcounts by DeviceId — one camera session).
    private void ReacquireWebcam()
    {
-        var webcam = Scenes.SelectMany(s => s.Sources).FirstOrDefault(s => s.Type == SourceType.Webcam);
-        if (ReferenceEquals(_webcamSource, webcam)) return;
+        var previousDevice = _webcam?.DeviceId;
+        _webcam = _layoutStore.Webcam;
+        var newDevice = _webcam?.DeviceId;

-        if (_webcamSource != null && !string.IsNullOrWhiteSpace(_webcamSource.DeviceId))
-            _ = _cameraManager.ReleaseAsync(_webcamSource.DeviceId);
+        if (!string.IsNullOrWhiteSpace(previousDevice) && previousDevice != newDevice)
+            _ = _cameraManager.ReleaseAllAsync(previousDevice);

-        _webcamSource = webcam;
-        OnPropertyChanged(nameof(CanAddWebcam));
-        if (webcam != null && !string.IsNullOrWhiteSpace(webcam.DeviceId))
-            _ = _cameraManager.AcquireAsync(webcam.DeviceId);
+        OnPropertyChanged(nameof(CanChangeWebcam));
+        OnPropertyChanged(nameof(CanAddWebcamToActiveScene));
+
+        if (_webcam == null || string.IsNullOrWhiteSpace(newDevice)) return;
+        if (previousDevice == newDevice) return;
+        foreach (var unused in Scenes.SelectMany(s => s.Elements.OfType<WebcamSceneConfig>()))
+            _ = _cameraManager.AcquireAsync(newDevice);
    }

    // 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.
+    // device's frame size; every scene's webcam config picks it up from here.
    private void OnCameraPreviewBitmapChanged(string deviceId, WriteableBitmap bitmap)
    {
-        if (_webcamSource?.DeviceId == deviceId)
-            _webcamSource.VideoImageSource = bitmap;
+        if (_webcam?.DeviceId != deviceId) return;
+        foreach (var scene in Scenes)
+            foreach (var config in scene.Elements.OfType<WebcamSceneConfig>())
+                config.VideoImageSource = bitmap;
    }

    public void Shutdown()
@@ -606,7 +673,7 @@ public class MainViewModel : ViewModelBase
        _saveDebounce?.Stop();
        try
        {
-            _layoutStore.Save(Scenes);
+            _layoutStore.Save(Scenes, _webcam);
        }
        catch (Exception ex)
        {
@@ -661,31 +728,36 @@ public class MainViewModel : ViewModelBase
    private void WireScene(Scene scene)
    {
        scene.PropertyChanged += OnScenePropertyChanged;
-        scene.Sources.CollectionChanged += OnSourcesChanged;
+        scene.Elements.CollectionChanged += OnElementsChanged;
    }

    private void UnwireScene(Scene scene)
    {
        scene.PropertyChanged -= OnScenePropertyChanged;
-        scene.Sources.CollectionChanged -= OnSourcesChanged;
+        scene.Elements.CollectionChanged -= OnElementsChanged;
    }

    private void OnScenePropertyChanged(object? sender, PropertyChangedEventArgs e)
        => ScheduleSave();

-    private void OnSourcesChanged(object? sender, NotifyCollectionChangedEventArgs e)
+    private void OnElementsChanged(object? sender, NotifyCollectionChangedEventArgs e)
    {
        if (e.NewItems != null)
-            foreach (Source source in e.NewItems)
-                source.PropertyChanged += OnSourcePropertyChanged;
+            foreach (SceneElement element in e.NewItems)
+                element.PropertyChanged += OnElementPropertyChanged;
        if (e.OldItems != null)
-            foreach (Source source in e.OldItems)
-                source.PropertyChanged -= OnSourcePropertyChanged;
+            foreach (SceneElement element in e.OldItems)
+                element.PropertyChanged -= OnElementPropertyChanged;
+        OnPropertyChanged(nameof(CanAddWebcamToActiveScene));
        ScheduleSave();
    }

-    private void OnSourcePropertyChanged(object? sender, PropertyChangedEventArgs e)
-        => ScheduleSave();
+    private void OnElementPropertyChanged(object? sender, PropertyChangedEventArgs e)
+    {
+        if (sender is WebcamSceneConfig && e.PropertyName == nameof(SceneElement.IsVisible))
+            OnPropertyChanged(nameof(CanShowWebcamInActiveScene));
+        ScheduleSave();
+    }

    private void ScheduleSave()
    {
@@ -728,9 +800,14 @@ public class MainViewModel : ViewModelBase
        var scene = ActiveScene;
        if (scene == null) return;

+        if (string.Equals(type, "webcam", StringComparison.OrdinalIgnoreCase))
+        {
+            _ = AddWebcamToActiveSceneAsync();
+            return;
+        }
+
        var sourceType = type?.ToLowerInvariant() switch
        {
-            "webcam" => SourceType.Webcam,
            "screen" => SourceType.DisplayCapture,
            "window" => SourceType.WindowCapture,
            "background" => SourceType.Background,
@@ -739,7 +816,6 @@ public class MainViewModel : ViewModelBase
        };
        var baseName = sourceType switch
        {
-            SourceType.Webcam => "Webcam",
            SourceType.DisplayCapture => "Screen",
            SourceType.WindowCapture => "Window",
            SourceType.Background => "Background",
@@ -748,12 +824,6 @@ public class MainViewModel : ViewModelBase
            _ => "Source",
        };

-        if (sourceType == SourceType.Webcam)
-        {
-            _ = AddWebcamSourceAsync();
-            return;
-        }
-
        if (sourceType == SourceType.Background)
        {
            var bytes = PickImageBytes("Choose a backdrop image");
@@ -761,7 +831,7 @@ public class MainViewModel : ViewModelBase
            var assetId = AddAsset(bytes);
            if (assetId == null) return;

-            var existing = scene.Sources.FirstOrDefault(s => s.Type == SourceType.Background);
+            var existing = scene.Elements.OfType<Source>().FirstOrDefault(s => s.Type == SourceType.Background);
            if (existing != null)
            {
                existing.AssetId = assetId;
@@ -769,26 +839,73 @@ public class MainViewModel : ViewModelBase
                return;
            }

-            scene.Sources.Add(new Source { Name = baseName, Type = SourceType.Background, AssetId = assetId });
+            scene.Elements.Add(new Source { Name = baseName, Type = SourceType.Background, AssetId = assetId });
            OnPropertyChanged(nameof(ShowEmptySceneHint));
            OnPropertyChanged(nameof(ShowSourcesEmptyHint));
            UpdateActiveBackground();
            return;
        }

-        var count = scene.Sources.Count(s => s.Type == sourceType);
+        var count = scene.Elements.OfType<Source>().Count(s => s.Type == sourceType);
        var name = count == 0 ? baseName : $"{baseName} {count + 1}";

-        scene.Sources.Add(new Source { Name = name, Type = sourceType });
+        scene.Elements.Add(new Source { Name = name, Type = sourceType });
        OnPropertyChanged(nameof(ShowEmptySceneHint));
        OnPropertyChanged(nameof(ShowSourcesEmptyHint));
        UpdateActiveBackground();
    }

-    private async Task AddWebcamSourceAsync()
+    // Adds the webcam to the active scene. The camera is picked once app-wide
+    // (first add); afterwards "Add Webcam" just places the existing webcam here
+    // at the default spot — each scene's config is independent (webcam.{scene}.config).
+    private async Task AddWebcamToActiveSceneAsync()
    {
        var scene = ActiveScene;
-        if (scene == null || _webcamSource != null) return;
+        if (scene == null || scene.WebcamConfig != null) return;
+
+        if (_webcam == null)
+        {
+            var dialog = new CameraPickerDialog(new CameraPickerViewModel(_cameraEnumerator))
+            {
+                Owner = Application.Current.MainWindow
+            };
+            if (dialog.ShowDialog() != true || dialog.PickedDevice == null) return;
+            var device = dialog.PickedDevice;
+            _webcam = new Webcam { DeviceId = device.Id, Name = device.DisplayName };
+            OnPropertyChanged(nameof(CanChangeWebcam));
+        }
+
+        var config = new WebcamSceneConfig
+        {
+            WebcamId = _webcam.Id,
+            Name = _webcam.Name,
+            Width = 480,
+            Height = 270,
+            X = MasterFrameWidth - 480 - 32,
+            Y = MasterFrameHeight - 270 - 32,
+        };
+
+        scene.Elements.Add(config);
+        SelectedElement = config;
+        OnPropertyChanged(nameof(ShowEmptySceneHint));
+        OnPropertyChanged(nameof(ShowSourcesEmptyHint));
+        UpdateActiveBackground();
+
+        var started = await _cameraManager.AcquireAsync(_webcam.DeviceId);
+        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);
+        }
+    }
+
+    // Swaps the device on the app-wide webcam identity. The old device is stopped
+    // unconditionally; each scene that uses the webcam re-acquires the new one so
+    // the per-config refcount stays honest.
+    private async Task ChangeWebcamAsync()
+    {
+        if (_webcam == null) return;

        var dialog = new CameraPickerDialog(new CameraPickerViewModel(_cameraEnumerator))
        {
@@ -796,35 +913,49 @@ public class MainViewModel : ViewModelBase
        };
        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,
-        };
+        var oldDevice = _webcam.DeviceId;
+        var newDevice = dialog.PickedDevice.Id;
+        if (oldDevice == newDevice) return;

-        _webcamSource = source;
-        OnPropertyChanged(nameof(CanAddWebcam));
-        scene.Sources.Add(source);
-        SelectedSource = source;
-        OnPropertyChanged(nameof(ShowEmptySceneHint));
-        OnPropertyChanged(nameof(ShowSourcesEmptyHint));
-        UpdateActiveBackground();
+        _webcam.DeviceId = newDevice;
+        _webcam.Name = dialog.PickedDevice.DisplayName;
+        ScheduleSave();

-        var started = await _cameraManager.AcquireAsync(device.Id);
-        if (!started)
+        if (!string.IsNullOrWhiteSpace(oldDevice))
+            await _cameraManager.ReleaseAllAsync(oldDevice);
+
+        foreach (var unused in Scenes.SelectMany(s => s.Elements.OfType<WebcamSceneConfig>()))
        {
-            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);
+            var started = await _cameraManager.AcquireAsync(newDevice);
+            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);
+                break;
+            }
        }
    }

+    // "Show Webcam" from a right-click on the empty preview. Unhides this scene's
+    // existing (hidden) config — the config row survives Hide in this scene — or
+    // adds the webcam here for the first time (which opens the camera picker).
+    private void ShowWebcamInActiveScene()
+    {
+        var scene = ActiveScene;
+        if (scene == null) return;
+
+        var config = scene.WebcamConfig;
+        if (config != null)
+        {
+            config.IsVisible = true;
+            SelectedElement = config;
+            return;
+        }
+
+        _ = AddWebcamToActiveSceneAsync();
+    }
+
    private void AddImage()
    {
        var scene = ActiveScene;
@@ -859,7 +990,7 @@ public class MainViewModel : ViewModelBase
    {
        var candidates = new List<ReuseImageCandidate>();
        foreach (var scene in Scenes)
-        foreach (var source in scene.Sources.Where(s => s.Type == SourceType.Image && !string.IsNullOrWhiteSpace(s.AssetId)))
+        foreach (var source in scene.Elements.OfType<Source>().Where(s => s.Type == SourceType.Image && !string.IsNullOrWhiteSpace(s.AssetId)))
        {
            candidates.Add(new ReuseImageCandidate
            {
@@ -919,7 +1050,7 @@ public class MainViewModel : ViewModelBase
        var scene = ActiveScene;
        if (scene == null || string.IsNullOrWhiteSpace(assetId)) return;

-        var count = scene.Sources.Count(s => s.Type == SourceType.Image);
+        var count = scene.Elements.OfType<Source>().Count(s => s.Type == SourceType.Image);
        var name = count == 0 ? "Image" : $"Image {count + 1}";

        var source = new Source { Name = name, Type = SourceType.Image, AssetId = assetId };
@@ -934,25 +1065,39 @@ public class MainViewModel : ViewModelBase
            source.Y = (1080 - source.Height) / 2;
        }

-        scene.Sources.Add(source);
-        SelectedSource = source;
+        scene.Elements.Add(source);
+        SelectedElement = source;
        OnPropertyChanged(nameof(ShowEmptySceneHint));
        OnPropertyChanged(nameof(ShowSourcesEmptyHint));
        UpdateActiveBackground();
    }

-    private void RemoveSource(Source? source)
+    // Removes an element from the active scene. For a webcam config this drops the
+    // scene's usage and releases one camera reference (CameraManager stops the
+    // session when the last using scene lets go). When the last config anywhere is
+    // removed, the webcam identity is cleared too — re-adding opens the picker
+    // again instead of silently resurrecting the old camera.
+    private void RemoveElement(SceneElement? element)
    {
        var scene = ActiveScene;
-        if (scene == null || source == null) return;
-        if (source.Type == SourceType.Webcam && ReferenceEquals(source, _webcamSource))
+        if (scene == null || element == null) return;
+        if (element is WebcamSceneConfig && _webcam != null)
        {
-            _webcamSource = null;
-            OnPropertyChanged(nameof(CanAddWebcam));
-            if (!string.IsNullOrWhiteSpace(source.DeviceId))
-                _ = _cameraManager.ReleaseAsync(source.DeviceId);
+            if (SelectedElement == element)
+                SelectedElement = null;
+            _ = _cameraManager.ReleaseAsync(_webcam.DeviceId);
        }
-        scene.Sources.Remove(source);
+        scene.Elements.Remove(element);
+
+        if (element is WebcamSceneConfig && _webcam != null
+            && !Scenes.Any(s => s.Elements.OfType<WebcamSceneConfig>().Any()))
+        {
+            _webcam = null;
+            OnPropertyChanged(nameof(CanChangeWebcam));
+            OnPropertyChanged(nameof(CanAddWebcamToActiveScene));
+            OnPropertyChanged(nameof(CanShowWebcamInActiveScene));
+        }
+
        OnPropertyChanged(nameof(ShowEmptySceneHint));
        OnPropertyChanged(nameof(ShowSourcesEmptyHint));
        UpdateActiveBackground();
@@ -4,7 +4,7 @@ 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). **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` |
+| `MainViewModel.cs` | The app brain: scenes/elements 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), `AddWebcamToActiveSceneAsync` (picker → default 480×270 bottom-right placement → acquire; greys out when the active scene already has a config via `CanAddWebcamToActiveScene`), `ChangeWebcamAsync` (device swap — `ReleaseAllAsync` old + re-acquire), `ShowWebcamInActiveScene` (reveal hidden config / empty-canvas right-click), `ReacquireWebcam` after layout load, `OnCameraPreviewBitmapChanged` forwards the shared bitmap into every `WebcamSceneConfig.VideoImageSource`; `SelectedElement` drives the preview overlay + `internal ClampWebcamToBounds` (50% cap seam) |
 | `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` |