[Win32] Drag & drop indicator position

src/SamplesApp/UITests.Shared/Windows_UI_Xaml/DragAndDrop/DragDrop_Files.xaml.cs

@@ -18,7 +18,10 @@ namespace UITests.Windows_UI_Xaml.DragAndDrop
 {
 	[Sample(
 		Description =
-			"This test showcases the common scenario of dragging files and/or folders from another window (usually a file explorer) into a specific rectangle that accepts the drop. The files that were dragged and dropped should be seen as a list.",
+		"""
+		- This test showcases the common scenario of dragging files and/or folders from another window (usually a file explorer) into a specific rectangle that accepts the drop. The files that were dragged and dropped should be seen as a list.
+		- If you have non-100% scaling of your screen, the drag indicator should always render above your mouse cursor, irrespective of where in the app's window you move it.
+		""",
 		IsManualTest = true,
 		IgnoreInSnapshotTests = true)]
 	public sealed partial class DragDrop_Files : UserControl

src/Uno.UI.Runtime.Skia.Win32/ApplicationMode/DataTransfer/DragDrop/Win32DragDropExtension.cs

@@ -61,6 +61,12 @@ public unsafe Win32DragDropExtension(DragDropManager manager)
 		_dropTarget.Dispose();
 	}
 
+	private Point GetScaledPosition(float x, float y)
+	{
+		var xamlRoot = _manager.ContentRoot.GetOrCreateXamlRoot();
+		return new Point(x / xamlRoot.RasterizationScale, y / xamlRoot.RasterizationScale);
+	}
+
 	unsafe HRESULT IDropTarget.Interface.DragEnter(IDataObject* dataObject, MODIFIERKEYS_FLAGS grfKeyState, POINTL pt, DROPEFFECT* pdwEffect)
 	{
 		Debug.Assert(_manager is not null && _coreDragDropManager is not null);
@@ -87,9 +93,12 @@ unsafe HRESULT IDropTarget.Interface.DragEnter(IDataObject* dataObject, MODIFIER
 		}
 
 		var position = new System.Drawing.Point(pt.x, pt.y);
+
 		var success = PInvoke.ScreenToClient(_hwnd, ref position);
 		if (!success) { this.LogError()?.Error($"{nameof(PInvoke.ScreenToClient)} failed: {Win32Helper.GetErrorMessage()}"); }
-		var src = new DragEventSource(position.X, position.Y, grfKeyState);
+		var scaledPosition = GetScaledPosition(position.X, position.Y);
+
+		var src = new DragEventSource(scaledPosition, grfKeyState);
 
 		var formats = new Span<FORMATETC>(formatBuffer, (int)fetchedFormatCount);
 		if (this.Log().IsEnabled(LogLevel.Trace))
@@ -154,7 +163,8 @@ unsafe HRESULT IDropTarget.Interface.DragOver(MODIFIERKEYS_FLAGS grfKeyState, PO
 		var position = new System.Drawing.Point(pt.x, pt.y);
 		var success = PInvoke.ScreenToClient(_hwnd, ref position);
 		if (!success) { this.LogError()?.Error($"{nameof(PInvoke.ScreenToClient)} failed: {Win32Helper.GetErrorMessage()}"); }
-		var src = new DragEventSource(position.X, position.Y, grfKeyState);
+		var scaledPosition = GetScaledPosition(position.X, position.Y);
+		var src = new DragEventSource(scaledPosition, grfKeyState);
 
 		this.LogTrace()?.Trace($"{nameof(IDropTarget.Interface.DragOver)} @ {position}");
 
@@ -177,7 +187,8 @@ unsafe HRESULT IDropTarget.Interface.Drop(IDataObject* dataObject, MODIFIERKEYS_
 		var position = new System.Drawing.Point(pt.x, pt.y);
 		var success = PInvoke.ScreenToClient(_hwnd, ref position);
 		if (!success) { this.LogError()?.Error($"{nameof(PInvoke.ScreenToClient)} failed: {Win32Helper.GetErrorMessage()}"); }
-		var src = new DragEventSource(position.X, position.Y, grfKeyState);
+		var scaledPosition = GetScaledPosition(position.X, position.Y);
+		var src = new DragEventSource(scaledPosition, grfKeyState);
 
 		this.LogTrace()?.Trace($"{nameof(IDropTarget.Interface.Drop)} @ {position}");
 
@@ -188,10 +199,10 @@ unsafe HRESULT IDropTarget.Interface.Drop(IDataObject* dataObject, MODIFIERKEYS_
 
 	public void StartNativeDrag(CoreDragInfo info, Action<DataPackageOperation> action) => throw new System.NotImplementedException();
 
-	private readonly struct DragEventSource(int x, int y, MODIFIERKEYS_FLAGS modifierFlags) : IDragEventSource
+	private readonly struct DragEventSource(Point point, MODIFIERKEYS_FLAGS modifierFlags) : IDragEventSource
 	{
 		private static long _nextFrameId;
-		private readonly Point _location = new(x, y);
+		private readonly Point _location = point;
 
 		public long Id => _fakePointerId;