fix: Use explicit XamlRoot for GetFocusedElement where possible

src/Uno.UI/Microsoft/UI/Xaml/Controls/Breadcrumb/BreadcrumbBar.cs

@@ -504,7 +504,9 @@ public partial class BreadcrumbBar : Control
 	{
 		if (m_itemsRepeater is { } itemsRepeater)
 		{
-			var focusedElem = FocusManager.GetFocusedElement();
+			var focusedElem = XamlRoot is null ?
+				FocusManager.GetFocusedElement() :
+				FocusManager.GetFocusedElement(XamlRoot);
 
 			if (focusedElem is UIElement focusedElement)
 			{

src/Uno.UI/Microsoft/UI/Xaml/Controls/RadioButtons/RadioButtons.cs

@@ -509,7 +509,7 @@ namespace Microsoft.UI.Xaml.Controls
 			var repeater = m_repeater;
 			if (repeater != null)
 			{
-				var focusedElement = FocusManager.GetFocusedElement() as UIElement;
+				var focusedElement = FocusManager.GetFocusedElement(XamlRoot) as UIElement;
 				if (focusedElement != null)
 				{
 					var focusedIndex = repeater.GetElementIndex(focusedElement);

src/Uno.UI/Microsoft/UI/Xaml/Controls/Repeater/ViewManager.cs

@@ -910,7 +910,10 @@ namespace Microsoft.UI.Xaml.Controls
 		{
 			UIElement focusedElement = null;
 
-			if (FocusManager.GetFocusedElement() is DependencyObject child)
+			var focusedObject = m_owner?.XamlRoot is null ?
+				FocusManager.GetFocusedElement() :
+				FocusManager.GetFocusedElement(m_owner.XamlRoot);
+			if (focusedObject is DependencyObject child)
 			{
 				var parent = CachedVisualTreeHelpers.GetParent(child);
 				var owner = (UIElement)m_owner;

src/Uno.UI/UI/Xaml/Controls/CalendarView/CalendarViewBaseItem.cs

@@ -280,7 +280,10 @@ namespace Windows.UI.Xaml.Controls
 			{
 				// Re-focus the currently focused item to propagate focusState (the item might be focused
 				// under a different FocusState value).
-				spItemToFocus = FocusManager.GetFocusedElement() as DependencyObject;
+				var focusedElement = XamlRoot is null ?
+					FocusManager.GetFocusedElement() :
+					FocusManager.GetFocusedElement(XamlRoot);
+				spItemToFocus = focusedElement as DependencyObject;
 			}
 			else
 			{

src/Uno.UI/UI/Xaml/Controls/CommandBar/CommandBar.Partial.cs

@@ -711,7 +711,9 @@ namespace Windows.UI.Xaml.Controls
 			}
 
 			// Only handle the up/down keys when focus is on the more/expand button.
-			var focusedElement = FocusManager.GetFocusedElement();
+			var focusedElement = XamlRoot is null ?
+				FocusManager.GetFocusedElement() :
+				FocusManager.GetFocusedElement(XamlRoot);
 			if (m_tpExpandButton == focusedElement)
 			{
 				bool isOpen = IsOpen;
@@ -756,7 +758,9 @@ namespace Windows.UI.Xaml.Controls
 
 		private void ShiftFocusVerticallyInOverflow(bool topToBottom, bool allowFocusWrap = true)
 		{
-			var focusedElement = FocusManager.GetFocusedElement();
+			var focusedElement = XamlRoot is null ?
+				FocusManager.GetFocusedElement() :
+				FocusManager.GetFocusedElement(XamlRoot);
 			DependencyObject? referenceElement = null;
 
 			if (topToBottom)
@@ -808,7 +812,9 @@ namespace Windows.UI.Xaml.Controls
 			// focus is currently on the first/last item depending on direction.
 			if (!shouldFocusLeaveOverflow)
 			{
-				var focusedElement = FocusManager.GetFocusedElement();
+				var focusedElement = XamlRoot is null ?
+					FocusManager.GetFocusedElement() :
+					FocusManager.GetFocusedElement(XamlRoot);
 				DependencyObject? referenceElement = null;
 
 				if (isShiftKeyPressed)
@@ -1033,13 +1039,14 @@ namespace Windows.UI.Xaml.Controls
 			return result;
 		}
 
-
 		private void ShiftFocusHorizontally(bool moveToRight)
 		{
 			// Determine whether we should shift focus horizontally.
 			if (m_tpContentControl is { })
 			{
-				var focusedElement = FocusManager.GetFocusedElement();
+				var focusedElement = XamlRoot is null ?
+					FocusManager.GetFocusedElement() :
+					FocusManager.GetFocusedElement(XamlRoot);
 
 				// Don't do it if focus is in the custom content area.
 				var isChildOfContentControl = m_tpContentControl.IsAncestorOf(focusedElement as DependencyObject);

src/Uno.UI/UI/Xaml/Controls/ListViewBase/ListViewBase.cs

@@ -90,7 +90,10 @@ namespace Windows.UI.Xaml.Controls
 				return false;
 			}
 
-			var focusedContainer = FocusManager.GetFocusedElement() as SelectorItem;
+			var focusedElement = XamlRoot is null ?
+				FocusManager.GetFocusedElement() :
+				FocusManager.GetFocusedElement(XamlRoot);
+			var focusedContainer = focusedElement as SelectorItem;
 
 			if (args.Key == VirtualKey.Enter ||
 				args.Key == VirtualKey.Space)
@@ -150,7 +153,10 @@ namespace Windows.UI.Xaml.Controls
 
 		private int GetFocusedItemIndex()
 		{
-			var focusedItem = FocusManager.GetFocusedElement() as SelectorItem;
+			var focusedElement = XamlRoot is null ?
+				FocusManager.GetFocusedElement() :
+				FocusManager.GetFocusedElement(XamlRoot);
+			var focusedItem = focusedElement as SelectorItem;
 			if (focusedItem != null)
 			{
 				return IndexFromContainer(focusedItem);

src/Uno.UI/UI/Xaml/Controls/MenuFlyout/MenuFlyoutPresenter.cs

@@ -802,7 +802,9 @@ namespace Windows.UI.Xaml.Controls
 			{
 				// A child element got focus, so make sure we keep m_iFocusedIndex in sync
 				// with it.
-				var focusedElement = FocusManager.GetFocusedElement() as DependencyObject;
+				var focusedElement = (XamlRoot is null ?
+					FocusManager.GetFocusedElement() :
+					FocusManager.GetFocusedElement(XamlRoot)) as DependencyObject;
 
 				// Since GotFocus is an async event, the focused element could be null if we got it
 				// after the popup closes, which clears focus.
@@ -823,7 +825,9 @@ namespace Windows.UI.Xaml.Controls
 		{
 			if (m_iFocusedIndex == -1)
 			{
-				var focusedElement = FocusManager.GetFocusedElement();
+				var focusedElement = XamlRoot is null ?
+					FocusManager.GetFocusedElement() :
+					FocusManager.GetFocusedElement(XamlRoot);
 
 				if (this != focusedElement)
 				{

src/Uno.UI/UI/Xaml/Controls/Popup/Popup.WithPopupRoot.cs

@@ -86,7 +86,7 @@ public partial class Popup
 			{
 #if !HAS_UNO_WINUI
 				// In UWP, XamlRoot is set automatically to CoreWindow XamlRoot if not set beforehand.
-				if (XamlRoot is null && Child?.XamlRoot is null)
+				if (XamlRoot is null && Child?.XamlRoot is null && CoreServices.Instance.InitializationType != InitializationType.IslandsOnly)
 				{
 					XamlRoot = CoreServices.Instance.ContentRootCoordinator.CoreWindowContentRoot.XamlRoot;
 				}

src/Uno.UI/UI/Xaml/Internal/RootVisual.cs

@@ -152,7 +152,7 @@ namespace Uno.UI.Xaml.Core
 		}
 #endif
 
-		internal static void ProcessPointerUp(PointerRoutedEventArgs args, bool isAfterHandledUp = false)
+		internal void ProcessPointerUp(PointerRoutedEventArgs args, bool isAfterHandledUp = false)
 		{
 			// We don't want handled events raised on RootVisual,
 			// instead we wait for the element that handled it to directly forward it to us,
@@ -183,11 +183,14 @@ namespace Uno.UI.Xaml.Core
 			// Uno specific: To ensure focus is properly lost when clicking "outside" app's content,
 			// we set focus here. In case UWP, focus is set to the root ScrollViewer instead,
 			// but Uno does not have it on all targets yet.
+			var focusedElement = XamlRoot is null ?
+				FocusManager.GetFocusedElement() :
+				FocusManager.GetFocusedElement(XamlRoot);
 			if (!isHandled // so isAfterHandledUp is false!
 				&& _canUnFocusOnNextLeftPointerRelease
 				&& args.GetCurrentPoint(null).Properties.PointerUpdateKind is PointerUpdateKind.LeftButtonReleased
 				&& !PointerCapture.TryGet(args.Pointer, out _)
-				&& FocusManager.GetFocusedElement() is UIElement uiElement)
+				&& focusedElement is UIElement uiElement)
 			{
 				uiElement.Unfocus();
 				args.Handled = true;