Fix drag/drop support (#1091)

Fix so that drag/drop support works properly with the Cocoa backend.
This PR includes these fixes:

DraggingUpdate passed the wrong coordinates. Now do the proper conversion from view coordinates to window coordinates, as expected by the Xwt client.
Get the INSDraggingInfo object in the proper way, with Runtime.GetINativeObject<INSDraggingInfo> (dragInfo, owns: false), same as we do in other code now.
Use the newer NSView.BeginDraggingSession API instead of the deprecated NSView.DragImage. This is needed so that we can provide a DraggingSource object in order to be notified when the drag/drop is over (no matter if successful or not) and call the Finished callback, as expected by Xwt client code.
Populate the pasteboard item used for the drag properly, supporting text drag/drop and internal formats (normally a serialized object where the Id is the assembly qualified type name).
To my knowledge the Android Designer is the only client that still uses this drag/drop code. All of these fixes were to make Android Designer drag/drop work properly.

Squashed commits:

* Update InitPasteboard, including all data types
* Treat as internal data
* Update INSDraggingInfo type, thanks to Sandy
* More fixes
* Fix DraggingUpdated coordinates to be widget, not window
* Serialize drag data for Cocoa backend
This more closely matches what was
done on Gtk before. It’s needed for at
least the Android Designer, supporting
drag/drop on the AndroidDesignerDragData
serializable type.
* Use BeginDraggingSession for drag/drop
This allows sending the OnDragFinished notification
when the drag/drop is complete, in turn calling
DragOperation.Finished. Calling Finished is expected
for Xwt - it did before for Gtk and this makes
the Cocoa backend behave the same.
* Update pasteboard handling
* Only use valid names for pasteboard types
* Switch to using INSDraggingSource
* Spaces -> tabs

1 files changed, 119 insertions, 23 deletions

diff --git a/Xwt.XamMac/Xwt.Mac/ViewBackend.cs b/Xwt.XamMac/Xwt.Mac/ViewBackend.cs
index 68dd61e3..05fcf8f8 100644
--- a/Xwt.XamMac/Xwt.Mac/ViewBackend.cs
+++ b/Xwt.XamMac/Xwt.Mac/ViewBackend.cs
@@ -581,18 +581,21 @@ namespace Xwt.Mac
 		
 		public void DragStart (DragStartData sdata)
 		{
-			var lo = Widget.ConvertPointToBase (new CGPoint (Widget.Bounds.X, Widget.Bounds.Y));
-			lo = Widget.Window.ConvertBaseToScreen (lo);
-			var ml = NSEvent.CurrentMouseLocation;
-			var pb = NSPasteboard.FromName (NSPasteboard.NSDragPasteboardName);
-			if (pb == null)
-				throw new InvalidOperationException ("Could not get pasteboard");
 			if (sdata.Data == null)
 				throw new ArgumentNullException ("data");
-			InitPasteboard (pb, sdata.Data);
+
+			NSPasteboardItem pasteboardItem = CreatePasteboardItem(sdata.Data);
+
+			var dragItem = new NSDraggingItem(pasteboardItem);
+
+			// Note that the hotspot (sdata.HotX, sdata.HotY) isn't currently supported here, but
+			// current users of this API don't use that anyway
 			var img = (NSImage)sdata.ImageBackend;
-			var pos = new CGPoint (ml.X - lo.X - (float)sdata.HotX, lo.Y - ml.Y - (float)sdata.HotY + img.Size.Height);
-			Widget.DragImage (img, pos, new CGSize (0, 0), NSApplication.SharedApplication.CurrentEvent, pb, Widget, true);
+			var frame = new CGRect(0, 0, img.Size.Width, img.Size.Height);
+			dragItem.SetDraggingFrame(frame, img);
+
+			var draggingSource = new DraggingSource (this);
+			Widget.BeginDraggingSession(new[] { dragItem }, NSApplication.SharedApplication.CurrentEvent, draggingSource);
 		}
 		
 		public void SetDragSource (TransferDataType[] types, DragDropAction dragAction)
@@ -602,7 +605,7 @@ namespace Xwt.Mac
 		public void SetDragTarget (TransferDataType[] types, DragDropAction dragAction)
 		{
 			SetupForDragDrop (Widget.GetType ());
-			var dtypes = types.Select (ToNSDragType).ToArray ();
+			var dtypes = types.Select (ToNSPasteboardType).ToArray ();
 			Widget.RegisterForDraggedTypes (dtypes);
 		}
 		
@@ -617,10 +620,10 @@ namespace Xwt.Mac
 			if (ob == null)
 				return NSDragOperation.None;
 			var backend = ob.Backend;
-			
-			INSDraggingInfo di = (INSDraggingInfo) Runtime.GetNSObject (dragInfo);
+
+			var di = Runtime.GetINativeObject<INSDraggingInfo> (dragInfo, owns: false);
 			var types = di.DraggingPasteboard.Types.Select (ToXwtDragType).ToArray ();
-			var pos = new Point (di.DraggingLocation.X, di.DraggingLocation.Y);
+			var pos = backend.Widget.ConvertPointFromView (di.DraggingLocation, null).ToXwtPoint ();
 			
 			if ((backend.currentEvents & WidgetEvent.DragOverCheck) != 0) {
 				var args = new DragOverCheckEventArgs (pos, types, ConvertAction (di.DraggingSourceOperationMask));
@@ -663,8 +666,8 @@ namespace Xwt.Mac
 				return false;
 			
 			var backend = ob.Backend;
-			
-			INSDraggingInfo di = (INSDraggingInfo) Runtime.GetNSObject (dragInfo);
+
+			var di = Runtime.GetINativeObject<INSDraggingInfo> (dragInfo, owns: false);
 			var types = di.DraggingPasteboard.Types.Select (ToXwtDragType).ToArray ();
 			var pos = new Point (di.DraggingLocation.X, di.DraggingLocation.Y);
 			
@@ -687,7 +690,7 @@ namespace Xwt.Mac
 			
 			var backend = ob.Backend;
 			
-			INSDraggingInfo di = (INSDraggingInfo) Runtime.GetNSObject (dragInfo);
+			var di = Runtime.GetINativeObject<INSDraggingInfo> (dragInfo, owns: false);
 			var pos = new Point (di.DraggingLocation.X, di.DraggingLocation.Y);
 			
 			if ((backend.currentEvents & WidgetEvent.DragDrop) != 0) {
@@ -720,16 +723,39 @@ namespace Xwt.Mac
 				eventSink.OnDragOver (args);
 			});
 		}
-		
-		void InitPasteboard (NSPasteboard pb, TransferDataSource data)
+
+		public virtual void OnDragFinished (DragFinishedEventArgs args)
+		{
+			ApplicationContext.InvokeUserCode(delegate {
+				eventSink.OnDragFinished (args);
+			});
+		}
+
+		NSPasteboardItem CreatePasteboardItem (TransferDataSource data)
 		{
-			pb.ClearContents ();
+			var typesSupported = new List<string>();
+
 			foreach (var t in data.DataTypes) {
+				// Support dragging text internally and externally
 				if (t == TransferDataType.Text) {
-					pb.AddTypes (new string[] { NSPasteboard.NSStringType }, null);
-					pb.SetStringForType ((string)data.GetValue (t), NSPasteboard.NSStringType);
+					typesSupported.Add(NSPasteboard.NSPasteboardTypeString);
+				}
+				// For other well known types, we don't currently support dragging them
+				else if (t == TransferDataType.Uri || t == TransferDataType.Image || t == TransferDataType.Rtf || t == TransferDataType.Html) {
+					;
+				}
+				// For internal types, provided serialized data
+				else {
+					typesSupported.Add(ToNSPasteboardType(t));
 				}
 			}
+
+			var pasteboardItem = new NSPasteboardItem();
+
+			var dataProvider = new PasteboardDataProvider(data);
+			pasteboardItem.SetDataProviderForTypes(dataProvider, typesSupported.ToArray());
+
+			return pasteboardItem;
 		}
 
 		static void FillDataStore (TransferDataStore store, NSPasteboard pb, string[] types)
@@ -775,14 +801,25 @@ namespace Xwt.Mac
 			return res;
 		}
 		
-		static string ToNSDragType (TransferDataType type)
+		public static string ToNSPasteboardType (TransferDataType type)
 		{
 			if (type == TransferDataType.Text) return NSPasteboard.NSStringType;
 			if (type == TransferDataType.Uri) return NSPasteboard.NSFilenamesType;
 			if (type == TransferDataType.Image) return NSPasteboard.NSPictType;
 			if (type == TransferDataType.Rtf) return NSPasteboard.NSRtfType;
 			if (type == TransferDataType.Html) return NSPasteboard.NSHtmlType;
-			return type.Id;
+
+			// Internal types often use an assembly qualified name for the id, which
+			// apparently isn't valid for the pasteboard typename. In that case,
+			// remove everything after the ", " so that just the class full name
+			// forms the pasteboard type name (alphanumeric + periods, no spaces).
+			string pasteboardType = type.Id;
+			int delimiterIndex = pasteboardType.IndexOf(", ");
+			if (delimiterIndex != -1 && delimiterIndex > 0) {
+				pasteboardType = pasteboardType.Substring(0, delimiterIndex);
+			}
+
+			return pasteboardType;
 		}
 		
 		static TransferDataType ToXwtDragType (string type)
@@ -883,5 +920,64 @@ namespace Xwt.Mac
 			child.Frame = new CGRect ((nfloat)cx, (nfloat)cy, (nfloat)cwidth, (nfloat)cheight);
 		}
 	}
+
+	class DraggingSource : NSObject, INSDraggingSource
+	{
+		WeakReference<ViewBackend> weakViewBackend;
+
+		public DraggingSource(ViewBackend viewBackend)
+		{
+			weakViewBackend = new WeakReference<ViewBackend>(viewBackend);
+		}
+		
+		[Export("draggingSession:willBeginAtPoint:")]
+		public void DraggingSessionWillBeginAtPoint(NSDraggingSession session, CGPoint screenPoint)
+		{
+		}
+
+		[Export("draggingSession:endedAtPoint:operation:")]
+		public void DraggingSessionEndedAtPoint(NSDraggingSession session, CGPoint screenPoint, NSDragOperation operation)
+		{
+			if (weakViewBackend.TryGetTarget(out var viewBackend))
+			{
+				bool deleteSource = operation == NSDragOperation.Move || operation == NSDragOperation.Delete;
+				var args = new DragFinishedEventArgs(deleteSource);
+
+				viewBackend.OnDragFinished(args);
+			}
+		}
+	}
+
+	public class PasteboardDataProvider : NSObject, INSPasteboardItemDataProvider
+	{
+		TransferDataSource dataSource;
+
+		public PasteboardDataProvider(TransferDataSource dataSource)
+		{
+			this.dataSource = dataSource;
+		}
+
+		public void ProvideDataForType (NSPasteboard pasteboard, NSPasteboardItem item, string type)
+		{
+			foreach (TransferDataType transferDataType in dataSource.DataTypes) {
+				string currentPasteboardType = ViewBackend.ToNSPasteboardType (transferDataType);
+				if (currentPasteboardType == type) {
+					if (transferDataType == TransferDataType.Text) {
+						pasteboard.SetStringForType((string)dataSource.GetValue(transferDataType), NSPasteboard.NSPasteboardTypeString);
+					}
+					else {
+						// For internal types, provided serialized data
+						object value = dataSource.GetValue(transferDataType);
+						NSData serializedData = NSData.FromArray(TransferDataSource.SerializeValue(value));
+						pasteboard.SetDataForType(serializedData, type);
+					}
+				}
+			}
+		}
+
+		public void FinishedWithDataProvider (NSPasteboard pasteboard)
+		{
+		}
+	}
 }