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
@@ -122,6 +122,28 @@ public sealed class CameraManager : IDisposable
        toStop.PreviewBitmap = null;
    }

+    /// <summary>
+    /// Releases a device unconditionally (every ref), regardless of how many scenes
+    /// hold it. Used on identity changes (webcam swap, layout reload) where the old
+    /// device's refcount isn't known after the scenes are replaced.
+    /// </summary>
+    public async Task ReleaseAllAsync(string deviceId)
+    {
+        CameraSession? toStop = null;
+        lock (_gate)
+        {
+            if (!_sessions.TryGetValue(deviceId, out var session)) return;
+            session.RefCount = 0;
+            _sessions.Remove(deviceId);
+            toStop = session;
+        }
+
+        if (toStop == null) return;
+        toStop.Source.FrameAvailable -= toStop.FrameHandler;
+        await SafeStopAsync(toStop.Source);
+        toStop.PreviewBitmap = null;
+    }
+
    public VideoFrame? GetLatestFrame(string deviceId)
    {
        lock (_gate)
@@ -12,6 +12,9 @@ public class LayoutStore : IDisposable
    private readonly SqliteConnection _connection;
    public string ActivePath { get; }

+    /// <summary>The app-wide webcam identity loaded with the last Load() (null = never picked).</summary>
+    public Webcam? Webcam { get; private set; }
+
    public LayoutStore(string path)
    {
        ActivePath = path;
@@ -31,7 +34,6 @@ public class LayoutStore : IDisposable
    {
        string[] statements =
        {
-            "PRAGMA user_version = 2;",
            """
            CREATE TABLE IF NOT EXISTS Scene (
                Id TEXT PRIMARY KEY,
@@ -70,6 +72,35 @@ public class LayoutStore : IDisposable
                SortOrder INTEGER NOT NULL DEFAULT 0
            );
            """,
+            """
+            CREATE TABLE IF NOT EXISTS Webcam (
+                Id TEXT PRIMARY KEY,
+                DeviceId TEXT NOT NULL UNIQUE,
+                Name TEXT NOT NULL
+            );
+            """,
+            """
+            CREATE TABLE IF NOT EXISTS WebcamSceneConfig (
+                SceneId TEXT NOT NULL REFERENCES Scene(Id) ON DELETE CASCADE,
+                WebcamId TEXT NOT NULL REFERENCES Webcam(Id) ON DELETE CASCADE,
+                IsVisible INTEGER NOT NULL DEFAULT 1,
+                X REAL NOT NULL DEFAULT 0,
+                Y REAL NOT NULL DEFAULT 0,
+                Width REAL NOT NULL DEFAULT 0,
+                Height REAL NOT NULL DEFAULT 0,
+                Opacity REAL NOT NULL DEFAULT 1,
+                ClipShape TEXT NOT NULL DEFAULT 'Traditional',
+                IsMirrored INTEGER NOT NULL DEFAULT 0,
+                RectWidth REAL,
+                RectHeight REAL,
+                BorderColor TEXT,
+                BorderOpacity REAL NOT NULL DEFAULT 1,
+                BorderWidth INTEGER NOT NULL DEFAULT 0,
+                BorderAnimation TEXT NOT NULL DEFAULT 'None',
+                SortOrder INTEGER NOT NULL DEFAULT 0,
+                PRIMARY KEY (SceneId, WebcamId)
+            );
+            """,
        };
        foreach (var sql in statements)
        {
@@ -78,6 +109,21 @@ public class LayoutStore : IDisposable
            cmd.ExecuteNonQuery();
        }
        MigrateSourceTable();
+        MigrateWebcamConfigTable();
+        if (GetUserVersion() < 3)
+            MigrateToV3();
+        using (var cmd = _connection.CreateCommand())
+        {
+            cmd.CommandText = "PRAGMA user_version = 4;";
+            cmd.ExecuteNonQuery();
+        }
+    }
+
+    private int GetUserVersion()
+    {
+        using var cmd = _connection.CreateCommand();
+        cmd.CommandText = "PRAGMA user_version;";
+        return Convert.ToInt32(cmd.ExecuteScalar());
    }

    // v1 → v2: Source gains ClipShape + IsMirrored (webcam clip/mirror prefs).
@@ -109,10 +155,117 @@ public class LayoutStore : IDisposable
        }
    }

+    // v3 → v4: WebcamSceneConfig gains RectWidth/RectHeight (the pre-Round rect,
+    // so a reloaded Round webcam restores its aspect on toggle-back).
+    private void MigrateWebcamConfigTable()
+    {
+        var columns = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
+        using (var cmd = _connection.CreateCommand())
+        {
+            cmd.CommandText = "PRAGMA table_info(WebcamSceneConfig);";
+            using var reader = cmd.ExecuteReader();
+            while (reader.Read())
+                columns.Add(reader.GetString(1));
+        }
+
+        if (!columns.Contains("RectWidth"))
+        {
+            using var cmd = _connection.CreateCommand();
+            cmd.CommandText = "ALTER TABLE WebcamSceneConfig ADD COLUMN RectWidth REAL;";
+            cmd.ExecuteNonQuery();
+        }
+
+        if (!columns.Contains("RectHeight"))
+        {
+            using var cmd = _connection.CreateCommand();
+            cmd.CommandText = "ALTER TABLE WebcamSceneConfig ADD COLUMN RectHeight REAL;";
+            cmd.ExecuteNonQuery();
+        }
+    }
+
+    // v2 → v3: the webcam leaves the Source table. Any webcam Source rows become
+    // one Webcam identity (first row — one camera app-wide) + a WebcamSceneConfig
+    // per scene that had one, then the webcam rows are deleted. No backfill:
+    // scenes without the webcam stay webcam-free.
+    private void MigrateToV3()
+    {
+        var rows = new List<(string Id, string SceneId, string Name, double X, double Y, double W, double H, double Opacity, string DeviceId, string ClipShape, bool IsMirrored)>();
+        using (var cmd = _connection.CreateCommand())
+        {
+            cmd.CommandText = """
+                SELECT Id, SceneId, Name, X, Y, Width, Height, Opacity, DeviceId, ClipShape, IsMirrored
+                FROM Source WHERE Type = 'Webcam' ORDER BY SortOrder;
+                """;
+            using var reader = cmd.ExecuteReader();
+            while (reader.Read())
+            {
+                rows.Add((
+                    reader.GetString(0),
+                    reader.GetString(1),
+                    reader.GetString(2),
+                    reader.GetDouble(3),
+                    reader.GetDouble(4),
+                    reader.GetDouble(5),
+                    reader.GetDouble(6),
+                    reader.GetDouble(7),
+                    reader.IsDBNull(8) ? string.Empty : reader.GetString(8),
+                    reader.GetString(9),
+                    reader.GetInt32(10) != 0));
+            }
+        }
+        if (rows.Count == 0) return;
+
+        using var tx = _connection.BeginTransaction();
+        var webcamId = Guid.NewGuid().ToString();
+
+        using (var cmd = _connection.CreateCommand())
+        {
+            cmd.CommandText = "INSERT INTO Webcam (Id, DeviceId, Name) VALUES ($id, $device, $name);";
+            cmd.Transaction = tx;
+            cmd.Parameters.AddWithValue("$id", webcamId);
+            cmd.Parameters.AddWithValue("$device", rows[0].DeviceId);
+            cmd.Parameters.AddWithValue("$name", rows[0].Name);
+            cmd.ExecuteNonQuery();
+        }
+
+        foreach (var row in rows)
+        {
+            using var cmd = _connection.CreateCommand();
+            cmd.CommandText = """
+                INSERT INTO WebcamSceneConfig
+                    (SceneId, WebcamId, IsVisible, X, Y, Width, Height, Opacity,
+                     ClipShape, IsMirrored, BorderColor, BorderOpacity, BorderWidth, BorderAnimation, SortOrder)
+                VALUES ($sceneId, $webcamId, 1, $x, $y, $w, $h, $opacity,
+                        $clip, $mirrored, NULL, 1, 0, 'None', 0);
+                """;
+            cmd.Transaction = tx;
+            cmd.Parameters.AddWithValue("$sceneId", row.SceneId);
+            cmd.Parameters.AddWithValue("$webcamId", webcamId);
+            cmd.Parameters.AddWithValue("$x", row.X);
+            cmd.Parameters.AddWithValue("$y", row.Y);
+            cmd.Parameters.AddWithValue("$w", row.W);
+            cmd.Parameters.AddWithValue("$h", row.H);
+            cmd.Parameters.AddWithValue("$opacity", row.Opacity);
+            cmd.Parameters.AddWithValue("$clip", row.ClipShape);
+            cmd.Parameters.AddWithValue("$mirrored", row.IsMirrored ? 1 : 0);
+            cmd.ExecuteNonQuery();
+        }
+
+        using (var cmd = _connection.CreateCommand())
+        {
+            cmd.CommandText = "DELETE FROM Source WHERE Type = 'Webcam';";
+            cmd.Transaction = tx;
+            cmd.ExecuteNonQuery();
+        }
+        tx.Commit();
+    }
+
    public List<Scene> Load()
    {
+        Webcam = null;
        var scenes = new List<Scene>();
        var sourcesByScene = new Dictionary<string, List<Source>>();
+        var configsByScene = new Dictionary<string, List<WebcamSceneConfig>>();

        using (var cmd = _connection.CreateCommand())
        {
@@ -130,11 +283,26 @@ public class LayoutStore : IDisposable
            }
        }

+        using (var cmd = _connection.CreateCommand())
+        {
+            cmd.CommandText = "SELECT Id, DeviceId, Name FROM Webcam;";
+            using var reader = cmd.ExecuteReader();
+            if (reader.Read())
+            {
+                Webcam = new Webcam
+                {
+                    Id = reader.GetString(0),
+                    DeviceId = reader.GetString(1),
+                    Name = reader.GetString(2),
+                };
+            }
+        }
+
        using (var cmd = _connection.CreateCommand())
        {
            cmd.CommandText = """
                SELECT Id, SceneId, AssetId, Type, Name, IsEnabled,
-                       X, Y, Width, Height, Opacity, MonitorIndex, DeviceId, ClipShape, IsMirrored
+                       X, Y, Width, Height, Opacity, MonitorIndex, ClipShape, IsMirrored
                FROM Source ORDER BY SortOrder
                """;
            using var reader = cmd.ExecuteReader();
@@ -154,9 +322,8 @@ public class LayoutStore : IDisposable
                    Height = reader.GetDouble(9),
                    Opacity = reader.GetDouble(10),
                    MonitorIndex = reader.IsDBNull(11) ? null : reader.GetInt32(11),
-                    DeviceId = reader.IsDBNull(12) ? null : reader.GetString(12),
-                    ClipShape = Enum.TryParse<ClipShape>(reader.GetString(13), out var clip) ? clip : ClipShape.Traditional,
-                    IsMirrored = reader.GetInt32(14) != 0,
+                    ClipShape = Enum.TryParse<ClipShape>(reader.GetString(12), out var clip) ? clip : ClipShape.Traditional,
+                    IsMirrored = reader.GetInt32(13) != 0,
                };
                if (!sourcesByScene.TryGetValue(sceneId, out var list))
                    sourcesByScene[sceneId] = list = new List<Source>();
@@ -164,26 +331,78 @@ public class LayoutStore : IDisposable
            }
        }

+        using (var cmd = _connection.CreateCommand())
+        {
+            cmd.CommandText = """
+                SELECT SceneId, WebcamId, IsVisible, X, Y, Width, Height, Opacity,
+                       ClipShape, IsMirrored, BorderColor, BorderOpacity, BorderWidth, BorderAnimation,
+                       RectWidth, RectHeight
+                FROM WebcamSceneConfig ORDER BY SortOrder
+                """;
+            using var reader = cmd.ExecuteReader();
+            while (reader.Read())
+            {
+                var sceneId = reader.GetString(0);
+                var config = new WebcamSceneConfig
+                {
+                    WebcamId = reader.GetString(1),
+                    Name = Webcam?.Name ?? "Webcam",
+                    IsVisible = reader.GetInt32(2) != 0,
+                    X = reader.GetDouble(3),
+                    Y = reader.GetDouble(4),
+                    Width = reader.GetDouble(5),
+                    Height = reader.GetDouble(6),
+                    Opacity = reader.GetDouble(7),
+                    ClipShape = Enum.TryParse<ClipShape>(reader.GetString(8), out var clip) ? clip : ClipShape.Traditional,
+                    IsMirrored = reader.GetInt32(9) != 0,
+                    BorderColor = reader.IsDBNull(10) ? string.Empty : reader.GetString(10),
+                    BorderOpacity = reader.IsDBNull(11) ? 1.0 : reader.GetDouble(11),
+                    BorderWidth = reader.IsDBNull(12) ? 0 : reader.GetInt32(12),
+                    BorderAnimation = Enum.TryParse<BorderAnimation>(reader.GetString(13), out var anim) ? anim : BorderAnimation.None,
+                    RectWidth = reader.IsDBNull(14) ? null : reader.GetDouble(14),
+                    RectHeight = reader.IsDBNull(15) ? null : reader.GetDouble(15),
+                };
+                if (!configsByScene.TryGetValue(sceneId, out var list))
+                    configsByScene[sceneId] = list = new List<WebcamSceneConfig>();
+                list.Add(config);
+            }
+        }
+
        foreach (var scene in scenes)
        {
-            if (sourcesByScene.TryGetValue(scene.Id, out var list))
-                foreach (var source in list)
-                    scene.Sources.Add(source);
+            if (sourcesByScene.TryGetValue(scene.Id, out var sources))
+                foreach (var source in sources)
+                    scene.Elements.Add(source);
+            if (configsByScene.TryGetValue(scene.Id, out var configs))
+                foreach (var config in configs)
+                    scene.Elements.Add(config);
        }

        return scenes;
    }

-    public void Save(IEnumerable<Scene> scenes)
+    public void Save(IEnumerable<Scene> scenes, Webcam? webcam)
    {
        using var tx = _connection.BeginTransaction();
        using (var cmd = _connection.CreateCommand())
+        {
+            cmd.CommandText = "DELETE FROM WebcamSceneConfig;";
+            cmd.Transaction = tx;
+            cmd.ExecuteNonQuery();
+        }
+        using (var cmd = _connection.CreateCommand())
        {
            cmd.CommandText = "DELETE FROM Source;";
            cmd.Transaction = tx;
            cmd.ExecuteNonQuery();
        }
        using (var cmd = _connection.CreateCommand())
+        {
+            cmd.CommandText = "DELETE FROM Webcam;";
+            cmd.Transaction = tx;
+            cmd.ExecuteNonQuery();
+        }
+        using (var cmd = _connection.CreateCommand())
        {
            cmd.CommandText = "DELETE FROM Scene;";
            cmd.Transaction = tx;
@@ -219,10 +438,10 @@ public class LayoutStore : IDisposable
        {
            cmd.CommandText = """
                INSERT INTO Source (Id, SceneId, AssetId, Type, Name, IsEnabled,
-                                    X, Y, Width, Height, Opacity, MonitorIndex, DeviceId,
+                                    X, Y, Width, Height, Opacity, MonitorIndex,
                                    ClipShape, IsMirrored, SortOrder)
                VALUES ($id, $sceneId, $assetId, $type, $name, $isEnabled,
-                        $x, $y, $w, $h, $opacity, $monitor, $device,
+                        $x, $y, $w, $h, $opacity, $monitor,
                        $clip, $mirrored, $sort)
                """;
            cmd.Transaction = tx;
@@ -238,7 +457,6 @@ public class LayoutStore : IDisposable
            var hP = cmd.Parameters.Add("$h", SqliteType.Real);
            var opacityP = cmd.Parameters.Add("$opacity", SqliteType.Real);
            var monitorP = cmd.Parameters.Add("$monitor", SqliteType.Integer);
-            var deviceP = cmd.Parameters.Add("$device", SqliteType.Text);
            var clipP = cmd.Parameters.Add("$clip", SqliteType.Text);
            var mirroredP = cmd.Parameters.Add("$mirrored", SqliteType.Integer);
            var sortP = cmd.Parameters.Add("$sort", SqliteType.Integer);
@@ -246,8 +464,9 @@ public class LayoutStore : IDisposable
            foreach (var scene in scenes)
            {
                var sort = 0;
-                foreach (var source in scene.Sources)
+                foreach (var element in scene.Elements)
                {
+                    if (element is not Source source) continue;
                    idP.Value = source.Id;
                    sceneIdP.Value = scene.Id;
                    assetIdP.Value = (object?)source.AssetId ?? DBNull.Value;
@@ -260,7 +479,6 @@ public class LayoutStore : IDisposable
                    hP.Value = source.Height;
                    opacityP.Value = source.Opacity;
                    monitorP.Value = (object?)source.MonitorIndex ?? DBNull.Value;
-                    deviceP.Value = (object?)source.DeviceId ?? DBNull.Value;
                    clipP.Value = source.ClipShape.ToString();
                    mirroredP.Value = source.IsMirrored ? 1 : 0;
                    sortP.Value = sort++;
@@ -269,6 +487,76 @@ public class LayoutStore : IDisposable
            }
        }

+        if (webcam != null)
+        {
+            using (var cmd = _connection.CreateCommand())
+            {
+                cmd.CommandText = "INSERT INTO Webcam (Id, DeviceId, Name) VALUES ($id, $device, $name);";
+                cmd.Transaction = tx;
+                cmd.Parameters.AddWithValue("$id", webcam.Id);
+                cmd.Parameters.AddWithValue("$device", webcam.DeviceId);
+                cmd.Parameters.AddWithValue("$name", webcam.Name);
+                cmd.ExecuteNonQuery();
+            }
+
+            using (var cmd = _connection.CreateCommand())
+            {
+                cmd.CommandText = """
+                    INSERT INTO WebcamSceneConfig
+                        (SceneId, WebcamId, IsVisible, X, Y, Width, Height, Opacity,
+                         ClipShape, IsMirrored, BorderColor, BorderOpacity, BorderWidth, BorderAnimation,
+                         RectWidth, RectHeight, SortOrder)
+                    VALUES ($sceneId, $webcamId, $isVisible, $x, $y, $w, $h, $opacity,
+                            $clip, $mirrored, $borderColor, $borderOpacity, $borderWidth, $borderAnimation,
+                            $rectWidth, $rectHeight, $sort)
+                    """;
+                cmd.Transaction = tx;
+                var sceneIdP = cmd.Parameters.Add("$sceneId", SqliteType.Text);
+                var webcamIdP = cmd.Parameters.Add("$webcamId", SqliteType.Text);
+                var visibleP = cmd.Parameters.Add("$isVisible", SqliteType.Integer);
+                var xP = cmd.Parameters.Add("$x", SqliteType.Real);
+                var yP = cmd.Parameters.Add("$y", SqliteType.Real);
+                var wP = cmd.Parameters.Add("$w", SqliteType.Real);
+                var hP = cmd.Parameters.Add("$h", SqliteType.Real);
+                var opacityP = cmd.Parameters.Add("$opacity", SqliteType.Real);
+                var clipP = cmd.Parameters.Add("$clip", SqliteType.Text);
+                var mirroredP = cmd.Parameters.Add("$mirrored", SqliteType.Integer);
+                var colorP = cmd.Parameters.Add("$borderColor", SqliteType.Text);
+                var borderOpacityP = cmd.Parameters.Add("$borderOpacity", SqliteType.Real);
+                var borderWidthP = cmd.Parameters.Add("$borderWidth", SqliteType.Integer);
+                var animationP = cmd.Parameters.Add("$borderAnimation", SqliteType.Text);
+                var rectWidthP = cmd.Parameters.Add("$rectWidth", SqliteType.Real);
+                var rectHeightP = cmd.Parameters.Add("$rectHeight", SqliteType.Real);
+                var sortP = cmd.Parameters.Add("$sort", SqliteType.Integer);
+
+                foreach (var scene in scenes)
+                {
+                    var sort = 0;
+                    foreach (var config in scene.Elements.OfType<WebcamSceneConfig>())
+                    {
+                        sceneIdP.Value = scene.Id;
+                        webcamIdP.Value = config.WebcamId;
+                        visibleP.Value = config.IsVisible ? 1 : 0;
+                        xP.Value = config.X;
+                        yP.Value = config.Y;
+                        wP.Value = config.Width;
+                        hP.Value = config.Height;
+                        opacityP.Value = config.Opacity;
+                        clipP.Value = config.ClipShape.ToString();
+                        mirroredP.Value = config.IsMirrored ? 1 : 0;
+                        colorP.Value = (object?)(string.IsNullOrEmpty(config.BorderColor) ? null : config.BorderColor) ?? DBNull.Value;
+                        borderOpacityP.Value = config.BorderOpacity;
+                        borderWidthP.Value = config.BorderWidth;
+                        animationP.Value = config.BorderAnimation.ToString();
+                        rectWidthP.Value = (object?)config.RectWidth ?? DBNull.Value;
+                        rectHeightP.Value = (object?)config.RectHeight ?? DBNull.Value;
+                        sortP.Value = sort++;
+                        cmd.ExecuteNonQuery();
+                    }
+                }
+            }
+        }
+
        using (var cmd = _connection.CreateCommand())
        {
            cmd.CommandText = "DELETE FROM Asset WHERE Id NOT IN (SELECT AssetId FROM Source WHERE AssetId IS NOT NULL);";
@@ -8,14 +8,14 @@ External-facing logic: YouTube API, persistence. See
 | `YouTubeAuthService.cs` | OAuth2 via Google: loopback callback (`http://localhost:8765/oauth2/callback`), token exchange, refresh, channel fetch. Constructor takes optional `HttpClient` + `sessionChanged` callback (test seam + save hook); session persists via `Helpers/TokenStore` (DPAPI); `ClearSession()` signs out (called by `MainViewModel.StopStream` on End Livestream) |
 | `YouTubeStreamService.cs` | Broadcast/stream management via the v3 API (`enableAutoStart/Stop`). **Not yet switched to the `variable` reusable stream** |
 | `YouTubeChatService.cs` | Polls `liveChat/messages`, raises `MessageReceived`; `IDisposable` |
-| `LayoutStore.cs` | SQLite persistence (`Microsoft.Data.Sqlite`) at `%APPDATA%\ytLlive\ytLlive.db`; assets stored as BLOBs keyed by SHA-256 content hash; save/open layout files; schema `user_version` 2 (`Source.ClipShape`/`IsMirrored` — added by `ALTER TABLE` for pre-v2 DBs) |
+| `LayoutStore.cs` | SQLite persistence (`Microsoft.Data.Sqlite`) at `%APPDATA%\ytLlive\ytLlive.db`; assets stored as BLOBs keyed by SHA-256 content hash; save/open layout files; schema `user_version` 4 (`Source.ClipShape`/`IsMirrored` via `ALTER TABLE` for pre-v2 DBs; v3 = singleton `Webcam` + per-scene `WebcamSceneConfig`, migrated idempotently **without backfill** — the stale `Source.DeviceId` column remains but is no longer read/written; v4 = `WebcamSceneConfig.RectWidth`/`RectHeight`, the pre-Round rect for the round-to-rect restore) |
 | `VideoFrame.cs` | Normalized CPU frame seam (`Width`/`Height`/tightly-packed BGRA `byte[]`) — the only pixel type the rest of the app knows about; future capture sources (screen, background-removed webcam) feed the same seam |
 | `CameraDeviceInfo.cs` | `(Id, DisplayName)` for a physical capture device |
 | `ICameraEnumerator.cs` | `GetCamerasAsync()` — seam so the picker/`CameraManager` never touch WinRT (tests inject fakes) |
 | `ICameraFrameSource.cs` | `StartAsync`/`StopAsync`/`FrameAvailable(VideoFrame)` — seam for a running capture source |
 | `MediaCaptureCameraEnumerator.cs` | WinRT enumeration via `DeviceInformation.FindAllAsync(DeviceClass.VideoCapture)` |
 | `MediaCaptureFrameSource.cs` | CPU-first MediaCapture source (`MemoryPreference = Cpu`, BGRA8 via `CreateFrameReaderAsync`); frames arrive on a worker thread |
-| `CameraManager.cs` | Webcam capture ownership: refcounted by `DeviceId`, one shared `WriteableBitmap` per camera, dispatcher-coalesced ~render-rate UI updates (latest-frame drop); `PreviewBitmapChanged`/`CameraFailed` events |
+| `CameraManager.cs` | Webcam capture ownership: refcounted by `DeviceId`, one shared `WriteableBitmap` per camera, dispatcher-coalesced ~render-rate UI updates (latest-frame drop); `PreviewBitmapChanged`/`CameraFailed` events. `ReleaseAsync` decrements a ref (stops at zero); `ReleaseAllAsync` force-drops every ref + stops the source (webcam swap / layout reload) |

 Related: constructed in [`ViewModels/MainViewModel.cs`](../ViewModels/MainViewModel.cs)
 (no DI container yet). Models in [`Models/index.md`](../Models/index.md).