feat(text): composite shared text rasters in output

Raster static text on UI-thread changes and reuse the same transparent BGRA frame in preview and all compositor paths. Cache text frame identity in the frame-pump signature and invalidate static bakes on edits. Follow OBS text-source conventions: https://obsproject.com/kb/text-sources

ViewModels/MainViewModel.Scenes.cs

@@ -281,6 +281,7 @@ public partial class MainViewModel
                 UnwireScene(scene);
         OnPropertyChanged(nameof(MissingScenes));
         OnPropertyChanged(nameof(ShowAddScene));
+        RetainTextOverlaySubscriptions();
         ScheduleSave();
     }
 
@@ -306,12 +307,29 @@ public partial class MainViewModel
 
     private void OnElementsChanged(object? sender, NotifyCollectionChangedEventArgs e)
     {
-        if (e.NewItems != null)
-            foreach (SceneElement element in e.NewItems)
-                element.PropertyChanged += OnElementPropertyChanged;
-        if (e.OldItems != null)
-            foreach (SceneElement element in e.OldItems)
-                element.PropertyChanged -= OnElementPropertyChanged;
+        if (e.Action != NotifyCollectionChangedAction.Move)
+        {
+            if (e.NewItems != null)
+                foreach (SceneElement element in e.NewItems)
+                {
+                    if (element is Source { Type: SourceType.TextOverlay } text)
+                    {
+                        WireTextOverlaySource(text);
+                        UpdateTextOverlayPreview(text);
+                    }
+                    else
+                        element.PropertyChanged += OnElementPropertyChanged;
+                }
+            if (e.OldItems != null)
+                foreach (SceneElement element in e.OldItems)
+                {
+                    if (element is Source { Type: SourceType.TextOverlay } text)
+                        RemoveTextOverlayPreview(text);
+                    else
+                        element.PropertyChanged -= OnElementPropertyChanged;
+                }
+        }
+        RetainTextOverlaySubscriptions();
         OnPropertyChanged(nameof(CanAddWebcam));
         OnPropertyChanged(nameof(CanAddYouTubeChat));
         OnPropertyChanged(nameof(CanAddTicker));
@@ -320,6 +338,9 @@ public partial class MainViewModel
 
     private void OnElementPropertyChanged(object? sender, PropertyChangedEventArgs e)
     {
+        if (sender is Source { Type: SourceType.TextOverlay } text)
+            OnTextOverlayPropertyChanged(text, e.PropertyName);
+
         if (sender is WebcamSceneConfig && e.PropertyName == nameof(SceneElement.IsVisible))
             OnPropertyChanged(nameof(CanShowWebcamInStagedScene));
 
@@ -330,7 +351,10 @@ public partial class MainViewModel
             var bakedSurface = e.PropertyName is nameof(SceneElement.X) or nameof(SceneElement.Y)
                 or nameof(SceneElement.Width) or nameof(SceneElement.Height)
                 or nameof(SceneElement.Opacity) or nameof(SceneElement.IsVisible)
-                or nameof(SceneElement.ClipShape) or nameof(SceneElement.IsMirrored);
+                or nameof(SceneElement.ClipShape) or nameof(SceneElement.IsMirrored)
+                or nameof(Source.TextContent) or nameof(Source.TextFontFamily)
+                or nameof(Source.TextFontSize) or nameof(Source.TextColor) or nameof(Source.TextBold)
+                or nameof(Source.TextItalic) or nameof(Source.TextUnderline) or nameof(Source.TextAlignment);
             if (bakedSurface)
             {
                 var containingScene = Scenes.FirstOrDefault(s => s.Elements.Contains(el));

ViewModels/MainViewModel.TextOverlay.cs

@@ -0,0 +1,61 @@
+using System.Collections.Generic;
+using System.Linq;
+using ytLive.Models;
+using ytLive.Services;
+
+namespace ytLive.ViewModels;
+
+public partial class MainViewModel
+{
+    private readonly TextOverlayRenderer _textOverlayRenderer = new();
+    private readonly HashSet<Source> _wiredTextOverlays = new();
+
+    private void UpdateConfiguredTextOverlays()
+    {
+        var sources = Scenes.SelectMany(scene => scene.Elements).OfType<Source>()
+            .Where(source => source.Type == SourceType.TextOverlay).ToArray();
+        RetainTextOverlaySubscriptions();
+        _textOverlayRenderer.Retain(sources);
+        foreach (var source in sources)
+        {
+            if (source.Width <= 0) source.Width = 900;
+            if (source.Height <= 0) source.Height = 140;
+            WireTextOverlaySource(source);
+            _textOverlayRenderer.UpdatePreview(source);
+        }
+    }
+
+    private void WireTextOverlaySource(Source source)
+    {
+        if (_wiredTextOverlays.Add(source))
+            source.PropertyChanged += OnElementPropertyChanged;
+    }
+
+    private void UpdateTextOverlayPreview(Source source) => _textOverlayRenderer.UpdatePreview(source);
+
+    private void RemoveTextOverlayPreview(Source source)
+    {
+        if (_wiredTextOverlays.Remove(source))
+            source.PropertyChanged -= OnElementPropertyChanged;
+        _textOverlayRenderer.Remove(source);
+    }
+
+    private void RetainTextOverlaySubscriptions()
+    {
+        var active = Scenes.SelectMany(scene => scene.Elements).OfType<Source>()
+            .Where(source => source.Type == SourceType.TextOverlay).ToHashSet();
+        foreach (var source in _wiredTextOverlays.ToArray())
+            if (!active.Contains(source))
+                RemoveTextOverlayPreview(source);
+    }
+
+    private void OnTextOverlayPropertyChanged(Source source, string? propertyName)
+    {
+        if (propertyName is nameof(Source.TextContent) or nameof(Source.TextFontFamily)
+            or nameof(Source.TextFontSize) or nameof(Source.TextColor) or nameof(Source.TextBold)
+            or nameof(Source.TextItalic) or nameof(Source.TextUnderline) or nameof(Source.TextAlignment)
+            or nameof(Source.Width) or nameof(Source.Height))
+            UpdateTextOverlayPreview(source);
+    }
+
+}

ViewModels/MainViewModel.cs

@@ -47,6 +47,7 @@ public partial class MainViewModel : ViewModelBase
     // born yet (startup crash regression from TASK 31, 2026-09-01; headless RealApp
     // tests never ran it, so it waited for the first native launch).
     private SceneGraph _sceneGraph = new();
+    internal SceneGraph SceneGraphForTests => _sceneGraph;
 
     /// <summary>Alert audio plays on the default device (creator ruling 2026-11-01): the WASAPI
     /// loopback then picks it up, so it is audible AND visible in the desktop sound bar.</summary>
@@ -497,6 +498,7 @@ public partial class MainViewModel : ViewModelBase
         }
         ClearPreviewHistory();
         StagedScene = Scenes.FirstOrDefault(s => SceneCatalog.Is(s.Name, SceneCatalog.Starting)) ?? Scenes.FirstOrDefault();
+        UpdateConfiguredTextOverlays();
         UpdateActiveBackground();
         UpdateActiveChatBoxPreviews();
         UpdateActiveAlertBoxPreviews();
@@ -585,7 +587,7 @@ public partial class MainViewModel : ViewModelBase
     // Scene-element → latest frame, for the live compositor. The map mirrors the
     // preview: webcam by DeviceId, live captures (the background) by CaptureKey,
     // images/background by AssetId. A null frame leaves the element transparent.
-    private VideoFrame? ResolveOutputFrame(SceneElement element)
+    internal VideoFrame? ResolveOutputFrame(SceneElement element)
     {
         var frame = ResolveOutputFrameCore(element);
         // Output-side eyes (2026-09-01): preview showed the webcam but the recording
@@ -644,6 +646,7 @@ public partial class MainViewModel : ViewModelBase
             // (caught by the resolver logging, 2026-09-01 take two).
             WebcamSceneConfig webcam => _cameraManager.GetLatestFrame(DeviceKeyForWebcam(webcam.WebcamId), EffectKeyFor(webcam)),
             Source { IsLiveCapture: true, CaptureKey: not null } live => _screenCaptureManager.GetLatestFrame(live.CaptureKey),
+            Source { Type: SourceType.TextOverlay } text => _textOverlayRenderer.RenderFrame(text),
             Source { Type: SourceType.ChatBox } chatBox => RenderChatBox(chatBox),
             Source { Type: SourceType.Ticker } ticker => _alertLayer.RenderSceneTicker(ticker),
             Source { Type: SourceType.Scoreboard } => _scoreboardPresenter?.Frame,

ViewModels/index.md

@@ -8,7 +8,7 @@ areas' docs in their own rows keeps this index small to read.
 
 | File | Purpose |
 |------|---------|
-| `MainViewModel.cs` | Core. `public partial class MainViewModel : ViewModelBase`. **Source commands + element rows:** scenes are pure selection rows; sources carry edit/visibility/trash (`EditElementCommand` sets `element.IsEditing`, `ToggleElementVisibilityCommand` flips `IsVisible`, `RemoveSourceCommand`; Backdrop trash slot reserved via `HiddenBoolToVisibilityConverter` — TASK 13); shared `NextSourceName` (Image, Image2, Image3… no-space increment from actual names — used by `AddSource` + `AddReusedImage`), `AddImageCommand`. **Lifecycle/ctor wiring:** fields + ctor wiring (all command assignments, mixer/camera/chat/hotkey/subscription hookups), `Shutdown`/`SaveLayoutNow`/`ScheduleSave`/`LoadLayout`, `CreateBrush` + shared `BarOnBrush`/`BarOffBrush` (referenced by Audio/Trax/Socials partials), window-geometry pass-through, `SelectedElement`/`OnSelectedElementPropertyChanged` (the selection change also raises `CanToggleClipShape` — TASK 57), `ShowPreviewPlaceholder`, `BrandFlash*`, WebView2 hosting (`InitWebView2`/`RegisterLoadedWebSources`/`OnWebView2PreviewBitmapChanged`), frame-pump wiring (construction + `_rtmpUrlProvider` seam + `Dispose`, plus `ResolveOutputFrame` → `RenderChatBox`/`RenderAlertBox` for chat + alert layers) — the pump's stream-state consumers live in the Streaming partial. |
+| `MainViewModel.cs` | Core. `public partial class MainViewModel : ViewModelBase`. **Source commands + element rows:** scenes are pure selection rows; sources carry edit/visibility/trash (`EditElementCommand` sets `element.IsEditing`, `ToggleElementVisibilityCommand` flips `IsVisible`, `RemoveSourceCommand`; Backdrop trash slot reserved via `HiddenBoolToVisibilityConverter` — TASK 13); shared `NextSourceName` (Image, Image2, Image3… no-space increment from actual names — used by `AddSource` + `AddReusedImage`), `AddImageCommand`. **Lifecycle/ctor wiring:** fields + ctor wiring (all command assignments, mixer/camera/chat/hotkey/subscription hookups), `Shutdown`/`SaveLayoutNow`/`ScheduleSave`/`LoadLayout`, `CreateBrush` + shared `BarOnBrush`/`BarOffBrush` (referenced by Audio/Trax/Socials partials), window-geometry pass-through, `SelectedElement`/`OnSelectedElementPropertyChanged` (the selection change also raises `CanToggleClipShape` — TASK 57), `ShowPreviewPlaceholder`, `BrandFlash*`, WebView2 hosting (`InitWebView2`/`RegisterLoadedWebSources`/`OnWebView2PreviewBitmapChanged`), frame-pump wiring (construction + `_rtmpUrlProvider` seam + `Dispose`, plus `ResolveOutputFrame` → cached TextOverlay frame / `RenderChatBox` / `RenderAlertBox` for text, chat, and alert layers) — the pump's stream-state consumers live in the Streaming partial. |
 | `MainViewModel.Account.cs` | Session + connected account: `LoadSavedSessionAsync` (DPAPI restore at startup), `SignInAsync`/`ChangeAccountAsync`/`SignOutYouTubeAsync`, `IsConnected`/`AccountAvatarUrl`/`AccountDisplayName`/`AccountStatusLightToolTip` via `SyncConnectedAccount` (cleared on End). |
 | `MainViewModel.License.cs` | Polar license (freemium): `LicenseKey`/`LicenseMessage`/`IsLicenseValidating`/`IsLicenseEntryOpen`/`IsHubVisible`/`IsPremium`, `OfflineGracePeriod`, `ValidateLicenseAtStartupAsync`/`ActivateLicenseAsync`. |
 | `MainViewModel.Scenes.cs` | Five-scene catalog: `Scenes` + `StagedScene`/`LiveScene`/`IsEditMode`, `AddScene` (canonical names only), `MissingScenes`/`ShowAddScene`/`AddSceneCommand`; scene wiring `OnScenesChanged`/`WireScene`/`UnwireScene`; transitions `SelectedTransitionType`/`TransitionDurationMs`/`TransitionToScene`/`ApplyTransitionToLive`; global hotkeys `HandleHotkey`/`OpenHotkeyConfig`/`RefreshHotkeyLabels`; scene-gating hints (`CanChangeBackground`). |
@@ -30,6 +30,7 @@ areas' docs in their own rows keeps this index small to read.
 | `SocialsDialogViewModel.cs` | Social Media Site Promotion dialog (six fixed slots, `SocialSlotViewModel`): row 0 = YouTube sign-in gate (sign-in provider fills the channel, delete = sign-out); rows 1-5 validated entries / empty / freemium locks 2-5 (`isPremium` seam); `DetectService` → `ISocialValidator` on confirm (input snaps to text + real logo on success, red do-not + stays editable on failure); `CanSave` blocked while any slot edits/validates/errors; `BarEnabled` switch; commit via `CommittedEntries` + `BuildSocialsConfig()` (YouTube first) + `SaveRequested`/`CancelRequested`. WPF-free — the window owns the dialogs (delete confirm, sign-in gate) and calls `StartEdit`/`ConfirmEdit`/`DeleteSlotAsync`. |
 
 | `MainViewModel.Sources.cs` | Source creation/removal; `AddSource` creates the standalone ticker layer with one-per-scene gating and its 1920×48 default geometry; TextOverlay starts as a visible 900×140 draggable text layer. |
+| `MainViewModel.TextOverlay.cs` | Raster-on-change TextOverlay preview hookup and settings/dimension invalidation; output resolution reads its immutable cached frame. |
 | `MainViewModel.AlertTicker.cs` | AlertBox ticker preview routing: selects the preview scene's AlertBox settings and publishes the positioned box-sized frame to PreviewPane. |
 
 Related: [`Models/index.md`](../Models/index.md) for the data; [`Services/index.md`](../Services/index.md)