fix(ComboBox): flyout placement in ios SheetPage

Co-Authored-By: Andres Pineda <pineda.andres@gmail.com>

src/Uno.UI/Extensions/UIViewExtensions.iOSmacOS.cs

@@ -384,7 +384,7 @@ public static _Controller FindViewController(this _View view)
 				// Sometimes, a view is not part of the visual tree (or doesn't have a next responder) but is part of the logical tree.
 				// Here, we substitute the view with the first logical parent that's part of the visual tree (or has a next responder).
 				view = (view as DependencyObject)
-					.GetParents()
+					?.GetParents()
 					.OfType<_View>()
 					.Where(parent => parent.NextResponder != null)
 					.FirstOrDefault();

src/Uno.UI/UI/Xaml/UIElement.Android.cs

@@ -237,7 +237,7 @@ internal static GeneralTransform TransformToVisual(View element, View visual)
 		/// Note: Offsets are only an approximation which does not take in consideration possible transformations
 		///	applied by a 'ViewGroup' between this element and its parent UIElement.
 		/// </summary>
-		private bool TryGetParentUIElementForTransformToVisual(out UIElement parentElement, ref double offsetX, ref double offsetY)
+		private bool TryGetParentUIElementForTransformToVisual(out UIElement parentElement, ref double offsetX, ref double offsetY, ref TransformToVisualContext context)
 		{
 			var parent = this.GetVisualTreeParent();
 			switch (parent)
@@ -271,7 +271,7 @@ private bool TryGetParentUIElementForTransformToVisual(out UIElement parentEleme
 					offsetY += offset.Y;
 
 					// We return the parent of the ScrollViewer, so we bypass the <Horizontal|Vertical>Offset (and the Scale) handling in shared code.
-					return sv.TryGetParentUIElementForTransformToVisual(out parentElement, ref offsetX, ref offsetY);
+					return sv.TryGetParentUIElementForTransformToVisual(out parentElement, ref offsetX, ref offsetY, ref context);
 
 				case View view: // Android.View and Android.IViewParent
 					var windowToFirstParent = new int[2];

src/Uno.UI/UI/Xaml/UIElement.cs

@@ -454,7 +454,9 @@ protected virtual void OnVisibilityChanged(Visibility oldValue, Visibility newVi
 
 		internal AutomationPeer OnCreateAutomationPeerInternal() => OnCreateAutomationPeer();
 
-		internal static Matrix3x2 GetTransform(UIElement from, UIElement to)
+		internal static Matrix3x2 GetTransform(UIElement from, UIElement to) => GetTransform(from, to, new());
+
+		private static Matrix3x2 GetTransform(UIElement from, UIElement to, TransformToVisualContext context)
 		{
 			var logInfoString = from.Log().IsEnabled(LogLevel.Debug) ? new StringBuilder() : null;
 			logInfoString?.Append($"{nameof(GetTransform)}(from: {from}, to: {to?.ToString() ?? "<null>"}) Offsets: [");
@@ -525,7 +527,7 @@ internal static Matrix3x2 GetTransform(UIElement from, UIElement to)
 #endif
 
 				logInfoString?.Append($"{elt}: ({offsetX}, {offsetY}), ");
-			} while (elt.TryGetParentUIElementForTransformToVisual(out elt, ref offsetX, ref offsetY) && elt != to); // If possible we stop as soon as we reach 'to'
+			} while (elt.TryGetParentUIElementForTransformToVisual(out elt, ref offsetX, ref offsetY, ref context) && elt != to); // If possible we stop as soon as we reach 'to'
 
 			matrix *= Matrix3x2.CreateTranslation((float)offsetX, (float)offsetY);
 
@@ -534,10 +536,20 @@ internal static Matrix3x2 GetTransform(UIElement from, UIElement to)
 				// Unfortunately we didn't find the 'to' in the parent hierarchy,
 				// so matrix == fromToRoot and we now have to compute the transform 'toToRoot'.
 				// Note: We do not propagate the 'intermediatesSelector' as cached transforms would be irrelevant
-				var toToRoot = GetTransform(to, null);
-				var rootToTo = toToRoot.Inverse();
+				var toContext = new TransformToVisualContext();
+				var toToRoot = GetTransform(to, null, toContext);
 
-				matrix *= rootToTo;
+#if __IOS__
+				// On iOS, the `from` and `to` may be coming different ViewController.
+				// In such case, their coordinates should not be "added" together, since they are from different coordinates space.
+				if (context?.ViewController is { } vc1 &&
+					toContext?.ViewController is { } vc2 &&
+					vc1 == vc2)
+#endif
+				{
+					var rootToTo = toToRoot.Inverse();
+					matrix *= rootToTo;
+				}
 			}
 
 			if (logInfoString != null)
@@ -553,7 +565,7 @@ internal static Matrix3x2 GetTransform(UIElement from, UIElement to)
 		/// Note: Offsets are only an approximation which does not take in consideration possible transformations
 		///	applied by a 'UIView' between this element and its parent UIElement.
 		/// </summary>
-		private bool TryGetParentUIElementForTransformToVisual(out UIElement parentElement, ref double offsetX, ref double offsetY)
+		private bool TryGetParentUIElementForTransformToVisual(out UIElement parentElement, ref double offsetX, ref double offsetY, ref TransformToVisualContext context)
 		{
 			var parent = VisualTreeHelper.GetParent(this);
 			switch (parent)
@@ -1132,5 +1144,7 @@ public UI.Input.InputCursor ProtectedCursor
 			set;
 		}
 #endif
+
+		private partial class TransformToVisualContext { }
 	}
 }

src/Uno.UI/UI/Xaml/UIElement.iOS.cs

@@ -161,7 +161,7 @@ internal Windows.Foundation.Point GetPosition(Point position, global::Windows.UI
 		/// Note: Offsets are only an approximation which does not take in consideration possible transformations
 		///	applied by a 'UIView' between this element and its parent UIElement.
 		/// </summary>
-		private bool TryGetParentUIElementForTransformToVisual(out UIElement parentElement, ref double offsetX, ref double offsetY)
+		private bool TryGetParentUIElementForTransformToVisual(out UIElement parentElement, ref double offsetX, ref double offsetY, ref TransformToVisualContext context)
 		{
 			var parent = this.GetVisualTreeParent();
 			switch (parent)
@@ -222,18 +222,28 @@ private bool TryGetParentUIElementForTransformToVisual(out UIElement parentEleme
 							case null:
 								// We reached the top of the window without any UIElement in the hierarchy,
 								// so we adjust offsets using the X/Y position of the original 'view' in the window.
-
 								offset = view.ConvertRectToView(default, null).Location;
 
 								parentElement = null;
 								offsetX += offset.X;
 								offsetY += offset.Y;
+
+								if (this.FindViewController() is { } vc)
+								{
+									context.ViewController = vc;
+								}
+
 								return false;
 						}
 					} while (true);
 			}
 		}
 
+		partial class TransformToVisualContext
+		{
+			public UIViewController ViewController { get; set; }
+		}
+
 #if DEBUG
 		public static Predicate<UIView> ViewOfInterestSelector { get; set; } = v => (v as FrameworkElement)?.Name == "TargetView";
 

src/Uno.UI/UI/Xaml/UIElement.macOS.cs

@@ -191,7 +191,7 @@ private protected override void OnNativeFlagsChanged(NSEvent evt)
 
 		private bool CheckFlagKeyDown(NSEventModifierMask flag, NSEventModifierMask newMask) => !_lastFlags.HasFlag(flag) && newMask.HasFlag(flag);
 
-		private bool TryGetParentUIElementForTransformToVisual(out UIElement parentElement, ref double offsetX, ref double offsetY)
+		private bool TryGetParentUIElementForTransformToVisual(out UIElement parentElement, ref double offsetX, ref double offsetY, ref TransformToVisualContext context)
 		{
 			var parent = this.GetVisualTreeParent();
 			switch (parent)