fix(dragdrop): don't fire Drop if AcceptedOperation is None

src/Uno.UI.Runtime.Skia.Wpf/Extensions/WpfDragDropExtension.cs

@@ -71,7 +71,7 @@ private void OnHostDragLeave(object sender, DragEventArgs e)
 			=> e.Effects = ToDropEffects(_manager.ProcessAborted(_fakePointerId));
 
 		private void OnHostDrop(object sender, DragEventArgs e)
-			=> e.Effects = ToDropEffects(_manager.ProcessDropped(new DragEventSource(_fakePointerId, e)));
+			=> e.Effects = ToDropEffects(_manager.ProcessReleased(new DragEventSource(_fakePointerId, e)));
 
 		public void StartNativeDrag(CoreDragInfo info)
 		{
@@ -244,7 +244,7 @@ private static async Task<DataObject> ToDataObject(DataPackageView src, Cancella
 			return dst;
 		}
 
-		private class DragEventSource : IDragEventSource
+		private readonly struct DragEventSource : IDragEventSource
 		{
 			private readonly DragEventArgs _wpfArgs;
 			private static long _nextFrameId;

src/Uno.UI.Runtime.Skia.X11/X11DragDropExtension.cs

@@ -259,7 +259,7 @@ private void ProcessXdndLeave(XClientMessageEvent ev)
 	private void ProcessXdndDrop(XClientMessageEvent ev)
 	{
 		var pos = _currentSession!.Value.LastPosition!.Value;
-		var acceptedOperation = _manager.ProcessDropped(new DragEventSource((int)pos.X, (int)pos.Y));
+		var acceptedOperation = _manager.ProcessReleased(new DragEventSource((int)pos.X, (int)pos.Y));
 		_currentSession = null;
 
 		if (this.Log().IsEnabled(LogLevel.Trace))
@@ -297,7 +297,7 @@ private void ProcessXdndDrop(XClientMessageEvent ev)
 	// TODO: uno-to-outside dragging
 	public void StartNativeDrag(CoreDragInfo info) => throw new System.NotImplementedException();
 
-	private class DragEventSource(int x, int y) : IDragEventSource
+	private readonly struct DragEventSource(int x, int y) : IDragEventSource
 	{
 		private static long _nextFrameId;
 		private readonly Point _location = new Point(x, y);

src/Uno.UI.RuntimeTests/Tests/Windows_UI_Xaml/Given_UIElement.cs

@@ -1682,6 +1682,67 @@ public async Task When_ScaleTransform_HitTest(bool addClip)
 #if HAS_UNO
 		#region Drag and Drop
 
+		[TestMethod]
+		[RunsOnUIThread]
+		[UnoWorkItem("https://github.com/unoplatform/uno/issues/18770")]
+		[DataRow(true)]
+		[DataRow(false)]
+#if !HAS_INPUT_INJECTOR
+		[Ignore("InputInjector is not supported on this platform.")]
+#endif
+		public async Task When_DragDrop_AcceptedOperation_None(bool setAcceptedOperation)
+		{
+			if (TestServices.WindowHelper.IsXamlIsland)
+			{
+				Assert.Inconclusive("Drag and drop doesn't work in Uno islands.");
+			}
+
+			var injector = InputInjector.TryCreate() ?? throw new InvalidOperationException("Failed to init the InputInjector");
+			using var mouse = injector.GetMouse();
+
+			var dropCount = 0;
+			Rectangle source, target;
+			var sp = new StackPanel
+			{
+				(source = new Rectangle
+				{
+					Width = 100,
+					Height = 100,
+					Fill = new SolidColorBrush(Microsoft.UI.Colors.LightCoral),
+					CanDrag = true
+				}),
+				(target = new Rectangle
+				{
+					Width = 100,
+					Height = 100,
+					Fill = new SolidColorBrush(Microsoft.UI.Colors.LightCoral),
+					AllowDrop = true
+				})
+			};
+
+			target.Drop += (_, _) => dropCount++;
+			if (setAcceptedOperation)
+			{
+				target.DragOver += (_, e) => e.AcceptedOperation = DataPackageOperation.Copy;
+			}
+
+			await UITestHelper.Load(sp);
+
+			mouse.MoveTo(source.GetAbsoluteBoundsRect().GetCenter());
+			await TestServices.WindowHelper.WaitForIdle();
+			mouse.Press();
+			await TestServices.WindowHelper.WaitForIdle();
+			for (int i = 1; i <= 10; i++)
+			{
+				mouse.MoveBy(0, (target.GetAbsoluteBoundsRect().GetMidY() - source.GetAbsoluteBoundsRect().GetMidY()) * 0.1);
+				await TestServices.WindowHelper.WaitForIdle();
+			}
+			mouse.Release();
+			await TestServices.WindowHelper.WaitForIdle();
+
+			Assert.AreEqual(setAcceptedOperation ? 1 : 0, dropCount);
+		}
+
 		[TestMethod]
 		[RunsOnUIThread]
 		[DataRow(true)]

src/Uno.UI/UI/Xaml/DragDrop/DragDropExtension.macOS.cs

@@ -67,7 +67,7 @@ private void OnDraggingExited(NSDraggingInfo draggingInfo)
 
 		private bool OnPerformDragOperation(NSDraggingInfo draggingInfo)
 		{
-			var operation = _manager.ProcessDropped(new DragEventSource(_fakePointerId, draggingInfo, _window));
+			var operation = _manager.ProcessReleased(new DragEventSource(_fakePointerId, draggingInfo, _window));
 			return (operation != DataPackageOperation.None);
 		}
 
@@ -88,7 +88,7 @@ public void StartNativeDrag(CoreDragInfo info)
 						(NSImage image, CGPoint screenPoint, NSDragOperation operation) =>
 						{
 							// The drop was completed externally
-							_manager.ProcessDropped(new DragEventSource(info.SourceId, _window));
+							_manager.ProcessReleased(new DragEventSource(info.SourceId, _window));
 							return;
 						};
 

src/Uno.UI/UI/Xaml/DragDrop/DragDropManager.cs

@@ -86,8 +86,8 @@ public DataPackageOperation ProcessMoved(IDragEventSource src)
 		/// The last accepted operation.
 		/// Be aware that due to the async processing of dragging in UWP, this might not be the up to date.
 		/// </returns>
-		public DataPackageOperation ProcessDropped(IDragEventSource src)
-			=> FindOperation(src)?.Dropped(src) ?? DataPackageOperation.None;
+		public DataPackageOperation ProcessReleased(IDragEventSource src)
+			=> FindOperation(src)?.Released(src) ?? DataPackageOperation.None;
 
 		/// <summary>
 		/// This method is expected to be invoked when pointer involved in a drag operation
@@ -135,7 +135,7 @@ private void RegisterWindowHandlers()
 
 		private void OnPointerMoved(object snd, PointerRoutedEventArgs e) => ProcessMoved(e);
 
-		private void OnPointerReleased(object snd, PointerRoutedEventArgs e) => ProcessDropped(e);
+		private void OnPointerReleased(object snd, PointerRoutedEventArgs e) => ProcessReleased(e);
 
 		private void OnPointerCanceled(object snd, PointerRoutedEventArgs e) => ProcessAborted(e.Pointer.PointerId);
 	}

src/Uno.UI/UI/Xaml/DragDrop/DragOperation.cs

@@ -2,22 +2,20 @@
 
 using System;
 using System.Collections.Generic;
-using System.Diagnostics;
-using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
 using Uno.UI.Xaml.Core;
 using Windows.ApplicationModel.DataTransfer;
-using Windows.ApplicationModel.DataTransfer.DragDrop;
 using Windows.ApplicationModel.DataTransfer.DragDrop.Core;
-using Windows.System;
-using Windows.UI.Core;
-using Windows.UI.Input;
-using Microsoft.UI.Xaml.Input;
 using Uno.UI.Dispatching;
 
 namespace Microsoft.UI.Xaml
 {
+	/// <summary>
+	/// The state machine of a dragging operation from the initiation of a dragging event
+	/// when a pointer holds and moves to the completion of the event when the pointer
+	/// is released
+	/// </summary>
 	internal class DragOperation
 	{
 		private static readonly TimeSpan _deferralTimeout = TimeSpan.FromSeconds(30); // Random value!
@@ -35,7 +33,7 @@ internal class DragOperation
 		private State _state = State.None;
 		private uint _lastFrameId;
 		private bool _hasRequestedNativeDrag;
-		private DataPackageOperation _acceptedOperation;
+		private DataPackageOperation _acceptedOperation = DataPackageOperation.Copy | DataPackageOperation.Move | DataPackageOperation.Link;
 
 		private enum State
 		{
@@ -98,7 +96,7 @@ internal DataPackageOperation Aborted()
 			return _acceptedOperation;
 		}
 
-		internal DataPackageOperation Dropped(IDragEventSource src)
+		internal DataPackageOperation Released(IDragEventSource src)
 		{
 			// For safety, we don't validate the FrameId for the finalizing actions, we rely only on the _state
 			if (_state >= State.Completing)
@@ -107,7 +105,15 @@ internal DataPackageOperation Dropped(IDragEventSource src)
 			}
 
 			Update(src);
-			Enqueue(RaiseDrop);
+
+			if (_acceptedOperation is DataPackageOperation.None)
+			{
+				Abort();
+			}
+			else
+			{
+				Enqueue(RaiseDrop);
+			}
 
 			return _acceptedOperation;
 		}

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

@@ -1100,7 +1100,7 @@ internal bool OnPointerUp(PointerRoutedEventArgs args, BubblingContext ctx = def
 				GestureRecognizer.ProcessUpEvent(currentPoint, isOverOrCaptured && !ctx.IsCleanup);
 				if (isDragging)
 				{
-					XamlRoot.VisualTree.ContentRoot.InputManager.DragDrop.ProcessDropped(args);
+					XamlRoot.VisualTree.ContentRoot.InputManager.DragDrop.ProcessReleased(args);
 				}
 			}
 

src/Uno.UWP/ApplicationModel/DataTransfer/DragDrop/Core/CoreDragDropManager.cs

@@ -127,7 +127,7 @@ internal DataPackageOperation ProcessMoved(IDragEventSource src)
 		/// Be aware that due to the async processing of dragging in UWP, this might not be the up to date.
 		/// </returns>
 		internal DataPackageOperation ProcessDropped(IDragEventSource src)
-			=> _manager?.ProcessDropped(src) ?? DataPackageOperation.None;
+			=> _manager?.ProcessReleased(src) ?? DataPackageOperation.None;
 
 		/// <summary>
 		/// This method is expected to be invoked when pointer involved in a drag operation
@@ -169,7 +169,7 @@ internal interface IDragDropManager
 			/// The last accepted operation.
 			/// Be aware that due to the async processing of dragging in UWP, this might not be the up to date.
 			/// </returns>
-			DataPackageOperation ProcessDropped(IDragEventSource src);
+			DataPackageOperation ProcessReleased(IDragEventSource src);
 
 			/// <summary>
 			/// This method is expected to be invoked when pointer involved in a drag operation