feat(alerts): add scene-local recent ticker

Model the AlertBox and standalone ticker with shared settings; scene tickers render the in-memory active and queued events without saving history. Keep AlertBox content active-event-only.

Ref: https://obsproject.com/kb/obs-studio-overview

ViewModels/MainViewModel.AlertTicker.cs

@@ -1,3 +1,5 @@
+using System.Linq;
+using ytLive.Models;
 using ytLive.Services;
 
 namespace ytLive.ViewModels;
@@ -44,8 +46,15 @@ public partial class MainViewModel
     /// Reuses one <see cref="System.Windows.Media.Imaging.WriteableBitmap"/> and
     /// overwrites its back buffer — a fresh bitmap every tick would churn the
     /// render cache for no reason.</summary>
-    internal void PublishAlertTickerPreview(VideoFrame? frame)
+    internal void PublishAlertTickerPreview(VideoFrame? incomingFrame)
     {
+        var frame = incomingFrame;
+        var previewScene = IsEditMode ? StagedScene : LiveScene ?? StagedScene;
+        var alertBox = previewScene?.Elements.OfType<Source>()
+            .FirstOrDefault(source => source.Type == SourceType.AlertBox && source.IsVisible);
+        if (_alertLayer.IsPlaying)
+            frame = _alertLayer.AlertBoxTickerFrame(alertBox);
+
         if (frame == null)
         {
             if (_alertTickerBitmap != null)

ViewModels/MainViewModel.Chat.cs

@@ -44,6 +44,11 @@ public partial class MainViewModel : ViewModelBase
         => StagedScene != null
            && !Scenes.Any(s => s.Elements.OfType<Source>().Any(e => e.Type == SourceType.AlertBox));
 
+    /// <summary>A recent-alert ticker is an independent layer, one per scene.</summary>
+    public bool CanAddTicker
+        => StagedScene != null
+           && !StagedScene.Elements.OfType<Source>().Any(e => e.Type == SourceType.Ticker);
+
     /// <summary>Privacy blur is a Live-scene tool only (creator ruling 2026-11-01) — every other
     /// scene's art is authored, and there is no desktop there to hide.</summary>
     public bool CanAddBlur

ViewModels/MainViewModel.Scenes.cs

@@ -55,6 +55,7 @@ public partial class MainViewModel
                 OnPropertyChanged(nameof(CanChangeBackground));
                 OnPropertyChanged(nameof(CanAddWebcam));
                 OnPropertyChanged(nameof(CanAddYouTubeChat));
+                OnPropertyChanged(nameof(CanAddTicker));
                 OnPropertyChanged(nameof(CanShowWebcamInStagedScene));
                 OnPropertyChanged(nameof(WebcamAddToolTip));
                 OnPropertyChanged(nameof(IsCountdownAvailable));
@@ -313,6 +314,7 @@ public partial class MainViewModel
                 element.PropertyChanged -= OnElementPropertyChanged;
         OnPropertyChanged(nameof(CanAddWebcam));
         OnPropertyChanged(nameof(CanAddYouTubeChat));
+        OnPropertyChanged(nameof(CanAddTicker));
         ScheduleSave();
     }
 
@@ -356,4 +358,4 @@ public partial class MainViewModel
         Scenes.Add(scene);
         StagedScene = scene;
     }
-}
+}

ViewModels/MainViewModel.Sources.cs

@@ -38,6 +38,7 @@ public partial class MainViewModel
             SourceType.WebSource => "Web Resource",
             SourceType.ChatBox => "YouTube Chat",
             SourceType.AlertBox => "Stream Alerts",
+            SourceType.Ticker => "Ticker",
             SourceType.Scoreboard => "Scoreboard",
             _ => "Layer",
         };
@@ -45,11 +46,12 @@ public partial class MainViewModel
         // The (+) menu only adds regular layers. The Background is a locked
         // per-screen layer managed by EnsureBackground/NormalizeBackgrounds —
         // never user-created, never deleted. YouTube Chat and Stream Alerts
-        // are one-per-layout.
+        // are one-per-layout; a ticker is one-per-scene.
         if (sourceType is SourceType.DisplayCapture or SourceType.WindowCapture or SourceType.Background)
             return;
         if ((sourceType == SourceType.ChatBox && !CanAddYouTubeChat)
-            || (sourceType == SourceType.AlertBox && !CanAddAlerts))
+            || (sourceType == SourceType.AlertBox && !CanAddAlerts)
+            || (sourceType == SourceType.Ticker && !CanAddTicker))
             return;
 
         // Web resources use "Web Resource-N" naming (0-indexed per scene)
@@ -73,11 +75,13 @@ public partial class MainViewModel
                 : sourceType == SourceType.ChatBox ? 500
                 : sourceType == SourceType.AlertBox ? 680
                 : sourceType == SourceType.Scoreboard ? 1920
+                : sourceType == SourceType.Ticker ? 1920
                 : sourceType == SourceType.Blur ? 240 : 0,
             Height = sourceType == SourceType.WebSource ? 480
                 : sourceType == SourceType.ChatBox ? 648
                 : sourceType == SourceType.AlertBox ? 200
                 : sourceType == SourceType.Scoreboard ? 56
+                : sourceType == SourceType.Ticker ? 48
                 : sourceType == SourceType.Blur ? 160 : 0,
         };
 

ViewModels/MainViewModel.cs

@@ -405,7 +405,8 @@ public partial class MainViewModel : ViewModelBase
             encoderFactory: () => new FfmpegEncoder(new FfmpegLocator()),
             log: message => AppLog.Write(message),
             socialBar: () => (_socialBarFrame, _socials?.BarPosition ?? SocialBarPosition.Bottom),
-            alertTicker: () => _alertLayer.AlertTickerFrame,
+            alertTicker: scene => _alertLayer.AlertBoxTickerFrame(
+                scene.Elements.OfType<Source>().FirstOrDefault(source => source.Type == SourceType.AlertBox && source.IsVisible)),
             brandFlash: BrandFlashFrame,
             transition: _transition,
             sceneGraph: _sceneGraph);
@@ -639,6 +640,7 @@ public partial class MainViewModel : ViewModelBase
             WebcamSceneConfig webcam => _cameraManager.GetLatestFrame(DeviceKeyForWebcam(webcam.WebcamId), EffectKeyFor(webcam)),
             Source { IsLiveCapture: true, CaptureKey: not null } live => _screenCaptureManager.GetLatestFrame(live.CaptureKey),
             Source { Type: SourceType.ChatBox } chatBox => RenderChatBox(chatBox),
+            Source { Type: SourceType.Ticker } ticker => _alertLayer.RenderSceneTicker(ticker),
             Source { Type: SourceType.Scoreboard } => _scoreboardPresenter?.Frame,
             Source { Type: SourceType.AlertBox } alertBox => RenderAlertBox(alertBox),
             Source { Type: SourceType.WebSource } web => _webView2Manager?.GetLatestFrame(web.Id),

ViewModels/index.md

@@ -28,6 +28,9 @@ areas' docs in their own rows keeps this index small to read.
 | `MicPickerViewModel.cs` | Select Microphone dialog (voice source): async mic list (loading / has / none states), `UseRequested(MicrophoneDeviceInfo)`/`CancelRequested` |
 | `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. |
+| `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)
 for what the ViewModels drive; base class in [`Helpers/ViewModelBase.cs`](../Helpers/ViewModelBase.cs).