From 162dee578f19ef3e2f159c94ce240dce45b9c8d3 Mon Sep 17 00:00:00 2001
From: David Oliver <david.oliver@nventive.com>
Date: Thu, 28 Oct 2021 10:47:56 -0400
Subject: [PATCH] fix(transformtovisual): [iOS] Fix TransformToVisual inside
 ListView

Fix regression introduced by https://github.com/unoplatform/uno/pull/5944 . TransformToVisual() is now calculated correctly for elements within the hierarchy of a ListView, accounting for the presence of intermediate native elements.

(cherry picked from commit b3c0a7bdabb4d11d967906c9bad28f3e68ce8719)
---
 .../Given_UIElement.TransformToVisual.cs      | 55 ++++++++++++++++++-
 .../ListViewBase/ListViewBaseSource.iOS.cs    |  3 +-
 src/Uno.UI/UI/Xaml/FrameworkElement.iOS.cs    |  6 +-
 src/Uno.UI/UI/Xaml/UIElement.iOS.cs           |  6 ++
 4 files changed, 67 insertions(+), 3 deletions(-)

diff --git a/src/Uno.UI.RuntimeTests/Tests/Windows_UI_Xaml/Given_UIElement.TransformToVisual.cs b/src/Uno.UI.RuntimeTests/Tests/Windows_UI_Xaml/Given_UIElement.TransformToVisual.cs
index 933cb9feb597..2d09a1bae9ab 100644
--- a/src/Uno.UI.RuntimeTests/Tests/Windows_UI_Xaml/Given_UIElement.TransformToVisual.cs
+++ b/src/Uno.UI.RuntimeTests/Tests/Windows_UI_Xaml/Given_UIElement.TransformToVisual.cs
@@ -16,13 +16,15 @@
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 using Private.Infrastructure;
 using Uno.Extensions;
-using Uno.UI.Extensions;
 using DependencyObjectExtensions = Uno.UI.Extensions.DependencyObjectExtensions;
 using static Private.Infrastructure.TestServices.WindowHelper;
 using Windows.UI.Xaml.Shapes;
+using Uno.UI.RuntimeTests.Helpers;
 
 #if __IOS__
 using UIKit;
+#else
+using Uno.UI.Extensions;
 #endif
 
 namespace Uno.UI.RuntimeTests.Tests.Windows_UI_Xaml
@@ -146,6 +148,57 @@ void AssertItem(int index)
 			}
 		}
 #endif
+		[TestMethod]
+		[RunsOnUIThread]
+		public async Task When_TransformToVisual_Through_ListView_Scrolled()
+		{
+			var listView = new ListView
+			{
+				ItemContainerStyle = TestsResourceHelper.GetResource<Style>("NoExtraSpaceListViewContainerStyle"),
+				ItemTemplate = TestsResourceHelper.GetResource<DataTemplate>("FixedSizeItemTemplate"),
+				ItemsSource = Enumerable.Range(0, 20).ToArray(),
+				Height = 120
+			};
+			var sut = new Grid
+			{
+				Height = 300,
+				Width = 200,
+				Children = { listView }
+			};
+
+			WindowContent = sut;
+			await WaitForLoaded(listView);
+
+			AssertItem(0, 0);
+			AssertItem(1, 29);
+
+			var sv = listView.FindFirstChild<ScrollViewer>();
+			Assert.IsNotNull(sv);
+			sv.ChangeView(null, 10, null);
+			await WaitForEqual(10, () => sv.VerticalOffset);
+
+			AssertItem(0, -10);
+			AssertItem(1, 19);
+
+			sv.ChangeView(null, 40, null);
+
+			await WaitForEqual(40, () => sv.VerticalOffset);
+
+			AssertItem(1, -11);
+
+			void AssertItem(int index, double expectedY)
+			{
+				const double defaultTolerance = 1.5;
+				var tolerance = defaultTolerance * Math.Min(index + 1, 3);
+
+				var container = listView.ContainerFromIndex(index) as ContentControl
+					?? throw new NullReferenceException($"Cannot find the container of item {index}");
+
+				var containerToListView = container.TransformToVisual(listView).TransformBounds(new Rect(0, 0, 42, 42));
+
+				Assert.AreEqual(expectedY, containerToListView.Y, tolerance);
+			}
+		}
 
 		[TestMethod]
 		[RunsOnUIThread]
diff --git a/src/Uno.UI/UI/Xaml/Controls/ListViewBase/ListViewBaseSource.iOS.cs b/src/Uno.UI/UI/Xaml/Controls/ListViewBase/ListViewBaseSource.iOS.cs
index 044fe06b3da8..d1a2cdaeaa31 100644
--- a/src/Uno.UI/UI/Xaml/Controls/ListViewBase/ListViewBaseSource.iOS.cs
+++ b/src/Uno.UI/UI/Xaml/Controls/ListViewBase/ListViewBaseSource.iOS.cs
@@ -21,6 +21,7 @@
 using Uno.Logging;
 using Uno.UI.Extensions;
 using Microsoft.Extensions.Logging;
+using Uno.UI.UI.Xaml.Controls.Layouter;
 
 #if XAMARIN_IOS_UNIFIED
 using Foundation;
@@ -655,7 +656,7 @@ private NSString GetReusableCellIdentifier(NSIndexPath indexPath)
 	/// <summary>
 	/// A hidden root item that allows the reuse of ContentControl features.
 	/// </summary>
-	internal class ListViewBaseInternalContainer : UICollectionViewCell
+	internal class ListViewBaseInternalContainer : UICollectionViewCell, ISetLayoutSlots
 	{
 		/// <summary>
 		/// Native constructor, do not use explicitly.
diff --git a/src/Uno.UI/UI/Xaml/FrameworkElement.iOS.cs b/src/Uno.UI/UI/Xaml/FrameworkElement.iOS.cs
index f58495c67a5a..4e4cdae2c30e 100644
--- a/src/Uno.UI/UI/Xaml/FrameworkElement.iOS.cs
+++ b/src/Uno.UI/UI/Xaml/FrameworkElement.iOS.cs
@@ -64,7 +64,11 @@ public override void LayoutSubviews()
 
 					Rect finalRect;
 					var parent = Superview;
-					if (parent is UIElement || parent is ISetLayoutSlots)
+					if (parent is UIElement
+						|| parent is ISetLayoutSlots
+						// In the case of ListViewItem inside native list, its parent's parent is ListViewBaseInternalContainer
+						|| parent?.Superview is ISetLayoutSlots
+					)
 					{
 						finalRect = LayoutSlotWithMarginsAndAlignments;
 					}
diff --git a/src/Uno.UI/UI/Xaml/UIElement.iOS.cs b/src/Uno.UI/UI/Xaml/UIElement.iOS.cs
index f939814fe1c7..4ab6a8fbaf8f 100644
--- a/src/Uno.UI/UI/Xaml/UIElement.iOS.cs
+++ b/src/Uno.UI/UI/Xaml/UIElement.iOS.cs
@@ -162,6 +162,12 @@ private bool TryGetParentUIElementForTransformToVisual(out UIElement parentEleme
 
 						switch (parent)
 						{
+							case ListViewBaseInternalContainer listViewBaseInternalContainer:
+								// In the case of ListViewBaseInternalContainer, the first managed parent is normally ItemsPresenter. We omit
+								// the offset since it's incorporated separately via the layout slot propagated to ListViewItem + the scroll offset.
+								parentElement = listViewBaseInternalContainer.FindFirstParent<UIElement>();
+								return true;
+
 							case UIElement eltParent:
 								// We found a UIElement in the parent hierarchy, we compute the X/Y offset between the
 								// first parent 'view' and this 'elt', and return it.