Add ability to set up native control when subclassing NativeControlHost

src/Eto.Gtk/Forms/Controls/NativeControlHandler.cs

@@ -16,27 +16,40 @@ public NativeControlHandler()
 		{
 		}
 
-		public void Create(object controlObject)
+		protected override Gtk.Widget CreateControl()
 		{
-			if (controlObject == null)
+			if (Widget is NativeControlHost host && Callback is NativeControlHost.ICallback callback)
 			{
-				Control = _eventBox;
+				var args = new CreateNativeControlArgs();
+				callback.OnCreateNativeControl(host, args);
+				return CreateHost(args.NativeControl);
 			}
-			else if (controlObject is Gtk.Widget widget)
+			return base.CreateControl();
+		}
+
+		public void Create(object nativeControl) => CreateHost(nativeControl);
+
+		Gtk.Widget CreateHost(object nativeControl)
+		{
+			if (nativeControl == null)
+			{
+				return _eventBox;
+			}
+			else if (nativeControl is Gtk.Widget widget)
 			{
-				Control = widget;
 				_eventBox.Child = widget;
+				return _eventBox;
 			}
-			else if (controlObject is IntPtr handle)
+			else if (nativeControl is IntPtr handle)
 			{
 				widget = GLib.Object.GetObject(handle) as Gtk.Widget;
 				if (widget == null)
 					throw new InvalidOperationException("Could not convert handle to Gtk.Widget");
-				Control = widget;
 				_eventBox.Child = widget;
+				return _eventBox;
 			}
 			else
-				throw new NotSupportedException($"controlObject of type {controlObject.GetType()} is not supported by this platform");
+				throw new NotSupportedException($"Native control of type {nativeControl.GetType()} is not supported by this platform");
 		}
 	}
 }

src/Eto.Gtk/GtkHelpers.cs

@@ -46,7 +46,7 @@ public static Control ToEto(this Gtk.Widget nativeWidget)
 		{
 			if (nativeWidget == null)
 				return null;
-			return new Control(new NativeControlHandler(nativeWidget));
+			return new NativeControlHost(nativeWidget);
 		}
 
 		/// <summary>

src/Eto.Mac/Forms/Controls/NativeControlHandler.cs

@@ -13,9 +13,20 @@ public NativeControlHandler()
 		{
 		}
 
+		protected override NSView CreateControl()
+		{
+			if (Widget is NativeControlHost host && Callback is NativeControlHost.ICallback callback)
+			{
+				var args = new CreateNativeControlArgs();
+				callback.OnCreateNativeControl(host, args);
+				return CreateHost(args.NativeControl);
+			}
+			return base.CreateControl();
+		}
+
 		public override SizeF GetPreferredSize(SizeF availableSize)
 		{
-			return Control.FittingSize.ToEto();
+			return Control?.FittingSize.ToEto() ?? SizeF.Empty;
 		}
 
 		public NativeControlHandler(NSViewController nativeControl)
@@ -26,25 +37,35 @@ public NativeControlHandler(NSViewController nativeControl)
 
 		public override NSView ContainerControl { get { return Control; } }
 
-		public void Create(object controlObject)
+		public void Create(object nativeControl)
 		{
-			if (controlObject == null)
+			Control = CreateHost(nativeControl);
+		}
+
+		NSView CreateHost(object nativeControl)
+		{
+			if (nativeControl == null)
+			{
+				return new NSView();
+			}
+			else if (nativeControl is NSView view)
 			{
-				Control = new NSView();
+				return view;
 			}
-			else if (controlObject is NSView view)
+			else if (nativeControl is NSViewController viewController)
 			{
-				Control = view;
+				controller = viewController;
+				return controller.View;
 			}
-			else if (controlObject is IntPtr handle)
+			else if (nativeControl is IntPtr handle)
 			{
 				view = Runtime.GetNSObject(handle) as NSView;
 				if (view == null)
 					throw new InvalidOperationException("supplied handle is invalid or does not refer to an object derived from NSView");
-				Control = view;
+				return view;
 			}
 			else
-				throw new NotSupportedException($"controlObject of type {controlObject.GetType()} is not supported by this platform");
+				throw new NotSupportedException($"Native control of type {nativeControl.GetType()} is not supported by this platform");
 		}
 	}
 }

src/Eto.Mac/MacHelpers.cs

@@ -66,7 +66,7 @@ public static Control ToEto(this NSView view)
 		{
 			if (view == null)
 				return null;
-			return new Control(new NativeControlHandler(view));
+			return new NativeControlHost(view);
 		}
 
 		/// <summary>
@@ -78,7 +78,7 @@ public static Control ToEto(this NSViewController viewController)
 		{
 			if (viewController == null)
 				return null;
-			return new Control(new NativeControlHandler(viewController));
+			return new NativeControlHost(viewController);
 		}
 
 		/// <summary>

src/Eto.WinForms/Forms/Controls/NativeControlHandler.cs

@@ -14,42 +14,58 @@ public NativeControlHandler()
 		{
 		}
 
+		protected override swf.Control CreateControl()
+		{
+			if (Widget is NativeControlHost host && Callback is NativeControlHost.ICallback callback)
+			{
+				var args = new CreateNativeControlArgs();
+				callback.OnCreateNativeControl(host, args);
+				return CreateHost(args.NativeControl);
+			}
+			return base.CreateControl();
+		}
+
 
-		public void Create(object controlObject)
+		public void Create(object nativeControl)
+		{
+			Control = CreateHost(nativeControl);
+		}
+		swf.Control CreateHost(object nativeControl)
 		{
-			if (controlObject == null)
+			if (nativeControl == null)
 			{
-				Control = new swf.UserControl();
+				return new swf.UserControl();
 			}
-			else if (controlObject is swf.Control control)
+			else if (nativeControl is swf.Control control)
 			{
-				Control = control;
+				return control;
 			}
-			else if (controlObject is IntPtr handle)
+			else if (nativeControl is IntPtr handle)
 			{
-				CreateWithHandle(handle);
+				return CreateWithHandle(handle);
 			}
-			else if (controlObject is swf.IWin32Window win32Window)
+			else if (nativeControl is swf.IWin32Window win32Window)
 			{
 				// keep a reference so it doesn't get GC'd
 				_win32Window = win32Window;
-				CreateWithHandle(win32Window.Handle);
+				return CreateWithHandle(win32Window.Handle);
 			}
 			else
-				throw new NotSupportedException($"controlObject of type {controlObject.GetType()} is not supported by this platform");
+				throw new NotSupportedException($"Native control of type {nativeControl.GetType()} is not supported by this platform");
 		}
 
-		private void CreateWithHandle(IntPtr handle)
+		private swf.Control CreateWithHandle(IntPtr handle)
 		{
-			Control = new swf.Control();
+			var control = new swf.Control();
 			Win32.GetWindowRect(handle, out var rect);
-			Win32.SetParent(handle, Control.Handle);
-			Control.Size = rect.ToSD().Size;
+			Win32.SetParent(handle, control.Handle);
+			control.Size = rect.ToSD().Size;
 			Widget.SizeChanged += (sender, e) =>
 			{
-				var size = Control.Size;
+				var size = control.Size;
 				Win32.SetWindowPos(handle, IntPtr.Zero, 0, 0, size.Width, size.Height, Win32.SWP.NOZORDER);
 			};
+			return control;
 		}
 	}
 }

src/Eto.WinForms/WinFormsHelpers.cs

@@ -48,7 +48,7 @@ public static Control ToEto(this swf.Control nativeControl)
 		{
 			if (nativeControl == null)
 				return null;
-			return new Control(new NativeControlHandler(nativeControl));
+			return new NativeControlHost(nativeControl);
 		}
 
 		/// <summary>

src/Eto.Wpf/Forms/Controls/NativeControlHandler.cs

@@ -25,44 +25,60 @@ public NativeControlHandler(sw.FrameworkElement nativeControl)
 		Control = nativeControl;
 	}
 
+	protected override sw.FrameworkElement CreateControl()
+	{
+		if (Widget is NativeControlHost host && Callback is NativeControlHost.ICallback callback)
+		{
+			var args = new CreateNativeControlArgs();
+			callback.OnCreateNativeControl(host, args);
+			return CreateHost(args.NativeControl);
+		}
+		return base.CreateControl();
+	}
+
 	public override Color BackgroundColor
 	{
 		get => throw new NotSupportedException("You cannot get this property for native controls");
 		set => throw new NotSupportedException("You cannot set this property for native controls");
 	}
 
-	public void Create(object controlObject)
+	public void Create(object nativeControl)
+	{
+		Control = CreateHost(nativeControl);
+	}
+
+	public sw.FrameworkElement CreateHost(object nativeControl)
 	{
-		if (controlObject == null)
+		if (nativeControl == null)
 		{
 			var host = new EtoHwndHost(null);
 			host.GetPreferredSize += () => Size.Round(UserPreferredSize.ToEto() * (Widget.ParentWindow?.Screen?.LogicalPixelSize ?? 1));
-			Control = host;
+			return host;
 		}
-		else if (controlObject is sw.FrameworkElement element)
+		else if (nativeControl is sw.FrameworkElement element)
 		{
-			Control = element;
+			return element;
 		}
-		else if (controlObject is IntPtr handle)
+		else if (nativeControl is IntPtr handle)
 		{
-			Control = new EtoHwndHost(new HandleRef(this, handle));
+			return new EtoHwndHost(new HandleRef(this, handle));
 		}
-		else if (controlObject is IWin32WindowWinForms win32Window)
+		else if (nativeControl is IWin32WindowWinForms win32Window)
 		{
 			// keep a reference to the win32window object
 			var host = new EtoHwndHost(new HandleRef(win32Window, win32Window.Handle));
 			host.GetPreferredSize += () => Size.Round(UserPreferredSize.ToEto() * (Widget.ParentWindow?.Screen?.LogicalPixelSize ?? 1));
-			Control = host;
+			return host;
 		}
-		else if (controlObject is IWin32WindowInterop win32WindowWpf)
+		else if (nativeControl is IWin32WindowInterop win32WindowWpf)
 		{
 			// keep a reference to the win32window object
 			var host = new EtoHwndHost(new HandleRef(win32WindowWpf, win32WindowWpf.Handle));
 			host.GetPreferredSize += () => Size.Round(UserPreferredSize.ToEto() * (Widget.ParentWindow?.Screen?.LogicalPixelSize ?? 1));
-			Control = host;
+			return host;
 		}
 		else
-			throw new NotSupportedException($"controlObject of type {controlObject.GetType()} is not supported by this platform");
+			throw new NotSupportedException($"Native control of type {nativeControl.GetType()} is not supported by this platform");
 	}
 }