From b86b6bb601623372264dabfc99842cc2c80e3119 Mon Sep 17 00:00:00 2001
From: gramps <gramps@llamachile.shop>
Date: Tue, 27 Oct 2026 09:12:59 -0700
Subject: [PATCH] Transitions: Wipe (left-to-right reveal), added to the App
 Settings picker

Test: WipeTransitionTests. Not pushed.
---
 Controls/OverlayHost.xaml           |  1 +
 Services/TransitionService.cs       | 26 +++++++++++++++++++++++++-
 TASKS.md                            |  2 +-
 ytLive.Tests/WipeTransitionTests.cs | 25 +++++++++++++++++++++++++
 4 files changed, 52 insertions(+), 2 deletions(-)
 create mode 100644 ytLive.Tests/WipeTransitionTests.cs

diff --git a/Controls/OverlayHost.xaml b/Controls/OverlayHost.xaml
index a66718d..50ec09d 100644
--- a/Controls/OverlayHost.xaml
+++ b/Controls/OverlayHost.xaml
@@ -61,6 +61,7 @@
                             <ComboBoxItem Content="Cut" Tag="{x:Static services:TransitionType.Cut}"/>
                             <ComboBoxItem Content="Fade" Tag="{x:Static services:TransitionType.Fade}"/>
                             <ComboBoxItem Content="Move" Tag="{x:Static services:TransitionType.Move}"/>
+                            <ComboBoxItem Content="Wipe" Tag="{x:Static services:TransitionType.Wipe}"/>
                         </ComboBox>
                         <TextBlock Style="{StaticResource YtLabel}" Margin="0,8,0,4">
                             <Run Text="Transition length: "/><Run Text="{Binding TransitionDurationMs, StringFormat={}{0:0} ms}"/>
diff --git a/Services/TransitionService.cs b/Services/TransitionService.cs
index df2e0d7..06089f0 100644
--- a/Services/TransitionService.cs
+++ b/Services/TransitionService.cs
@@ -10,7 +10,8 @@ public enum TransitionType
 {
     Cut,
     Fade,
-    Move
+    Move,
+    Wipe
 }
 
 /// <summary>
@@ -102,10 +103,33 @@ public sealed class TransitionService
         {
             TransitionType.Fade => BlendFade(FromFrame, toFrame, t),
             TransitionType.Move => BlendMove(FromFrame, toFrame, t),
+            TransitionType.Wipe => BlendWipe(FromFrame, toFrame, t),
             _ => toFrame
         };
     }
 
+    /// <summary>Left-to-right reveal: the new scene sweeps in across the frame.</summary>
+    private static VideoFrame BlendWipe(VideoFrame from, VideoFrame to, float t)
+    {
+        var w = from.Width;
+        var h = from.Height;
+        var output = new byte[w * h * 4];
+        var edge = (int)Math.Round(Math.Clamp(t, 0f, 1f) * w);
+        for (var y = 0; y < h; y++)
+        {
+            for (var x = 0; x < w; x++)
+            {
+                var src = x < edge ? to.BgraPixels : from.BgraPixels;
+                var i = (y * w + x) * 4;
+                output[i] = src[i];
+                output[i + 1] = src[i + 1];
+                output[i + 2] = src[i + 2];
+                output[i + 3] = src[i + 3];
+            }
+        }
+        return new VideoFrame(w, h, output);
+    }
+
     private static VideoFrame BlendFade(VideoFrame from, VideoFrame to, float t)
     {
         var w = from.Width;
diff --git a/TASKS.md b/TASKS.md
index c8edc59..eb74c5c 100644
--- a/TASKS.md
+++ b/TASKS.md
@@ -456,7 +456,7 @@ These were explicitly ruled out:
 
 - ✅ **Fade fix** — swaps fade from the outgoing picture (`TransitionFadeTests`). On-screen check pending.
 - ✅ **Transition picker** in App Settings (type + duration), saved with the layout (`TransitionPickerTests`).
-- ☐ **Wipe** — CPU blend, direction setting.
+- ✅ **Wipe** — CPU blend, left-to-right reveal (`WipeTransitionTests`). Direction setting not yet added.
 - ☐ **Move** — persistent layers (per-layer "carry across scenes" flag), per-scene placement, fixed z band.
 - ☐ **Brand logo** — permanent "Brand logo" layer above background in every scene; file in App Settings
   (imported to the asset table); per-scene eye toggle; top-left default.
diff --git a/ytLive.Tests/WipeTransitionTests.cs b/ytLive.Tests/WipeTransitionTests.cs
new file mode 100644
index 0000000..e0d4669
--- /dev/null
+++ b/ytLive.Tests/WipeTransitionTests.cs
@@ -0,0 +1,25 @@
+using System.Linq;
+using Xunit;
+using ytLive.Services;
+
+namespace ytLive.Tests;
+
+public class WipeTransitionTests
+{
+    [Fact]
+    public void Wipe_At_Half_Reveals_The_New_Scene_On_The_Left_Half()
+    {
+        var transition = new TransitionService();
+        var to = new VideoFrame(4, 1, Enumerable.Repeat((byte)255, 16).ToArray());
+        var from = new VideoFrame(4, 1, new byte[16]);
+
+        transition.Start(TransitionType.Wipe, 300, from);
+        transition.Tick(150);
+        var blended = transition.BlendFrame(to);
+
+        Assert.Equal((byte)255, blended.BgraPixels[0]);
+        Assert.Equal((byte)255, blended.BgraPixels[4]);
+        Assert.Equal((byte)0, blended.BgraPixels[8]);
+        Assert.Equal((byte)0, blended.BgraPixels[12]);
+    }
+}