WinUI-only ScrollBarHandler

src/Controls/src/Core/AppHostBuilderExtensions.cs

@@ -27,6 +27,9 @@ public static class AppHostBuilderExtensions
 			{ typeof(Layout2.Layout), typeof(LayoutHandler) },
 			{ typeof(Picker), typeof(PickerHandler) },
 			{ typeof(ProgressBar), typeof(ProgressBarHandler) },
+#if WINDOWS
+			{ typeof(ScrollView), typeof(ScrollViewHandler) },
+#endif			
 			{ typeof(SearchBar), typeof(SearchBarHandler) },
 			{ typeof(Slider), typeof(SliderHandler) },
 			{ typeof(Stepper), typeof(StepperHandler) },

src/Controls/src/Core/HandlerImpl/ScrollView.Impl.cs

@@ -0,0 +1,33 @@
+namespace Microsoft.Maui.Controls
+{
+	public partial class ScrollView : IScrollView
+	{
+		IView IScrollView.Content => Content;
+
+		double IScrollView.HorizontalOffset
+		{
+			get => ScrollX;
+			set
+			{
+				if (ScrollX != value)
+				{
+					SetScrolledPosition(value, ScrollY);
+				}
+			}
+		}
+
+		double IScrollView.VerticalOffset
+		{
+			get => ScrollY;
+			set
+			{
+				if (ScrollY != value)
+				{
+					SetScrolledPosition(ScrollX, value);
+				}
+			}
+		}
+
+		void IScrollView.ScrollFinished() => SendScrollFinished();
+	}
+}

src/Controls/src/Core/Platform/Windows/Extensions/Extensions.cs

@@ -70,15 +70,15 @@ internal static InputScope ToInputScope(this ReturnType returnType)
 			return inputScope;
 		}
 
-		internal static UwpScrollBarVisibility ToUwpScrollBarVisibility(this Maui.Controls.ScrollBarVisibility visibility)
+		internal static UwpScrollBarVisibility ToUwpScrollBarVisibility(this ScrollBarVisibility visibility)
 		{
 			switch (visibility)
 			{
-				case Maui.Controls.ScrollBarVisibility.Always:
+				case ScrollBarVisibility.Always:
 					return UwpScrollBarVisibility.Visible;
-				case Maui.Controls.ScrollBarVisibility.Default:
+				case ScrollBarVisibility.Default:
 					return UwpScrollBarVisibility.Auto;
-				case Maui.Controls.ScrollBarVisibility.Never:
+				case ScrollBarVisibility.Never:
 					return UwpScrollBarVisibility.Hidden;
 				default:
 					return UwpScrollBarVisibility.Auto;

src/Controls/src/Core/ScrollView.cs

@@ -7,7 +7,7 @@
 namespace Microsoft.Maui.Controls
 {
 	[ContentProperty(nameof(Content))]
-	public class ScrollView : Layout, IScrollViewController, IElementConfiguration<ScrollView>, IFlowDirectionController
+	public partial class ScrollView : Layout, IScrollViewController, IElementConfiguration<ScrollView>, IFlowDirectionController
 	{
 		#region IScrollViewController
 
@@ -274,7 +274,17 @@ protected override SizeRequest OnSizeRequest(double widthConstraint, double heig
 					break;
 			}
 
-			SizeRequest contentRequest = Content.Measure(widthConstraint, heightConstraint, MeasureFlags.IncludeMargins);
+			SizeRequest contentRequest;
+
+			if (Content is IFrameworkElement fe)
+			{
+				contentRequest = fe.Handler.GetDesiredSize(widthConstraint, heightConstraint);
+			}
+			else
+			{
+				contentRequest = Content.Measure(widthConstraint, heightConstraint, MeasureFlags.IncludeMargins);
+			}
+
 			contentRequest.Minimum = new Size(Math.Min(40, contentRequest.Minimum.Width), Math.Min(40, contentRequest.Minimum.Height));
 
 			return contentRequest;

src/Core/src/Core/IScrollView.cs

@@ -0,0 +1,50 @@
+using System;
+using Microsoft.Maui.Graphics;
+
+namespace Microsoft.Maui
+{
+	public interface IScrollView : IView
+	{
+		// TODO ezhart 2021-07-08 It might make sense for IPage and IScrollView to derive from (the not yet created) IContentView 
+
+		/// <summary>
+		/// Gets the view that contains the content of the ScrollView.
+		/// </summary>
+		public IView Content { get; }
+
+		/// <summary>
+		/// Gets a value indicating the visibility rules for the horizontal scroll bar.
+		/// </summary>
+		ScrollBarVisibility HorizontalScrollBarVisibility { get; }
+
+		/// <summary>
+		/// Gets a value indicating the visibility rules for the vertical scroll bar.
+		/// </summary>
+		ScrollBarVisibility VerticalScrollBarVisibility { get; }
+
+		/// <summary>
+		/// Gets a value indicating the scroll orientation of the ScrollView.
+		/// </summary>
+		ScrollOrientation Orientation { get; }
+
+		/// <summary>
+		/// Gets the size of the scrollable content in the ScrollView.
+		/// </summary>
+		Size ContentSize { get; }
+
+		/// <summary>
+		/// Gets the current scroll position of the ScrollView along the horizontal axis.
+		/// </summary>
+		double HorizontalOffset { get; set; }
+
+		/// <summary>
+		/// Gets the current scroll position of the ScrollView along the vertical axis.
+		/// </summary>
+		double VerticalOffset { get; set; }
+
+		/// <summary>
+		/// Allows the native ScrollView to inform that cross-platform code that a scroll operation has completed.
+		/// </summary>
+		void ScrollFinished();
+	}
+}

src/Core/src/Handlers/ScrollView/ScrollViewHandler.Android.cs

@@ -0,0 +1,21 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+using AndroidX.Core.Widget;
+
+namespace Microsoft.Maui.Handlers
+{
+	public partial class ScrollViewHandler : ViewHandler<IScrollView, NestedScrollView>
+	{
+		protected override NestedScrollView CreateNativeView()
+		{
+			throw new NotImplementedException();
+		}
+
+		public static void MapContent(ScrollViewHandler handler, IScrollView scrollView) { }
+		public static void MapHorizontalScrollBarVisibility(ScrollViewHandler handler, IScrollView scrollView) { }
+		public static void MapVerticalScrollBarVisibility(ScrollViewHandler handler, IScrollView scrollView) { }
+		public static void MapOrientation(ScrollViewHandler handler, IScrollView scrollView) { }
+		public static void MapContentSize(ScrollViewHandler handler, IScrollView scrollView) { }
+	}
+}

src/Core/src/Handlers/ScrollView/ScrollViewHandler.Standard.cs

@@ -0,0 +1,18 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace Microsoft.Maui.Handlers
+{
+	public partial class ScrollViewHandler : ViewHandler<IScrollView, object>
+	{
+		protected override object CreateNativeView() => throw new NotImplementedException();
+
+		public static void MapContent(IViewHandler handler, IScrollView scrollView) { }
+		public static void MapHorizontalScrollBarVisibility(IViewHandler handler, IScrollView scrollView) { }
+		public static void MapVerticalScrollBarVisibility(IViewHandler handler, IScrollView scrollView) { }
+		public static void MapOrientation(IViewHandler handler, IScrollView scrollView) { }
+		public static void MapContentSize(IViewHandler handler, IScrollView scrollView) { }
+		public static void MapRequestScrollTo(ScrollViewHandler handler, IScrollView scrollView, object? args) { }
+	}
+}

src/Core/src/Handlers/ScrollView/ScrollViewHandler.Windows.cs

@@ -0,0 +1,65 @@
+#nullable enable
+using System;
+using System.Collections.Generic;
+using System.Runtime.CompilerServices;
+using System.Text;
+using Microsoft.UI.Xaml.Controls;
+
+namespace Microsoft.Maui.Handlers
+{
+	public partial class ScrollViewHandler : ViewHandler<IScrollView, ScrollViewer>
+	{
+		protected override ScrollViewer CreateNativeView()
+		{
+			return new ScrollViewer();
+		}
+
+		protected override void ConnectHandler(ScrollViewer nativeView)
+		{
+			base.ConnectHandler(nativeView);
+			nativeView.ViewChanged += ViewChanged;
+		}
+
+		protected override void DisconnectHandler(ScrollViewer nativeView)
+		{
+			base.DisconnectHandler(nativeView);
+			nativeView.ViewChanged -= ViewChanged;
+		}
+
+		public static void MapContent(ScrollViewHandler handler, IScrollView scrollView)
+		{
+			if (handler.MauiContext == null)
+			{
+				return;
+			}
+
+			handler.NativeView.Content = scrollView.Content.ToNative(handler.MauiContext);
+		}
+
+		public static void MapHorizontalScrollBarVisibility(ScrollViewHandler handler, IScrollView scrollView)
+		{
+			handler.NativeView?.UpdateScrollBarVisibility(scrollView.Orientation, scrollView.HorizontalScrollBarVisibility);
+		}
+
+		public static void MapVerticalScrollBarVisibility(ScrollViewHandler handler, IScrollView scrollView)
+		{
+			handler.NativeView.VerticalScrollBarVisibility = scrollView.VerticalScrollBarVisibility.ToWindowsScrollBarVisibility();
+		}
+
+		public static void MapOrientation(ScrollViewHandler handler, IScrollView scrollView)
+		{
+			handler.NativeView?.UpdateScrollBarVisibility(scrollView.Orientation, scrollView.HorizontalScrollBarVisibility);
+		}
+
+		void ViewChanged(object? sender, ScrollViewerViewChangedEventArgs e)
+		{
+			VirtualView.VerticalOffset = NativeView.VerticalOffset;
+			VirtualView.HorizontalOffset = NativeView.HorizontalOffset;
+
+			if (e.IsIntermediate == false)
+			{
+				VirtualView.ScrollFinished();
+			}
+		}
+	}
+}

src/Core/src/Handlers/ScrollView/ScrollViewHandler.cs

@@ -0,0 +1,21 @@
+#nullable enable
+using System;
+
+namespace Microsoft.Maui.Handlers
+{
+	public partial class ScrollViewHandler
+	{
+		public static PropertyMapper<IScrollView, ScrollViewHandler> ScrollViewMapper = new(ViewMapper)
+		{
+			[nameof(IScrollView.Content)] = MapContent,
+			[nameof(IScrollView.HorizontalScrollBarVisibility)] = MapHorizontalScrollBarVisibility,
+			[nameof(IScrollView.VerticalScrollBarVisibility)] = MapVerticalScrollBarVisibility,
+			[nameof(IScrollView.Orientation)] = MapOrientation,
+		};
+
+		public ScrollViewHandler() : base(ScrollViewMapper)
+		{
+
+		}
+	}
+}

src/Core/src/Handlers/ScrollView/ScrollViewHandler.iOS.cs

@@ -0,0 +1,25 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+using UIKit;
+
+namespace Microsoft.Maui.Handlers
+{
+	public partial class ScrollViewHandler : ViewHandler<IScrollView, UIScrollView>
+	{
+		public ScrollViewHandler(PropertyMapper mapper) : base(mapper)
+		{
+		}
+
+		protected override UIScrollView CreateNativeView()
+		{
+			throw new NotImplementedException();
+		}
+
+		public static void MapContent(ScrollViewHandler handler, IScrollView scrollView) { }
+		public static void MapHorizontalScrollBarVisibility(ScrollViewHandler handler, IScrollView scrollView) { }
+		public static void MapVerticalScrollBarVisibility(ScrollViewHandler handler, IScrollView scrollView) { }
+		public static void MapOrientation(ScrollViewHandler handler, IScrollView scrollView) { }
+		public static void MapContentSize(ScrollViewHandler handler, IScrollView scrollView) { }
+	}
+}

src/Core/src/Hosting/AppHostBuilderExtensions.cs

@@ -27,6 +27,9 @@ public static partial class AppHostBuilderExtensions
 			{ typeof(ILayout), typeof(LayoutHandler) },
 			{ typeof(IPicker), typeof(PickerHandler) },
 			{ typeof(IProgress), typeof(ProgressBarHandler) },
+#if WINDOWS
+			{ typeof(IScrollView), typeof(ScrollViewHandler) },
+#endif			
 			{ typeof(ISearchBar), typeof(SearchBarHandler) },
 			{ typeof(IShapeView), typeof(ShapeViewHandler) },
 			{ typeof(ISlider), typeof(SliderHandler) },

src/Core/src/Platform/Windows/ScrollViewerExtensions.cs

@@ -0,0 +1,53 @@
+using Microsoft.UI.Xaml.Controls;
+using WScrollBarVisibility = Microsoft.UI.Xaml.Controls.ScrollBarVisibility;
+
+namespace Microsoft.Maui
+{
+	public static class ScrollViewerExtensions
+	{
+		public static WScrollBarVisibility ToWindowsScrollBarVisibility(this ScrollBarVisibility visibility)
+		{
+			return visibility switch
+			{
+				ScrollBarVisibility.Always => WScrollBarVisibility.Visible,
+				ScrollBarVisibility.Default => WScrollBarVisibility.Auto,
+				ScrollBarVisibility.Never => WScrollBarVisibility.Hidden,
+				_ => WScrollBarVisibility.Auto,
+			};
+		}
+
+		public static void UpdateScrollBarVisibility(this ScrollViewer scrollViewer, ScrollOrientation orientation,
+			ScrollBarVisibility horizontalScrollBarVisibility)
+		{
+			if (horizontalScrollBarVisibility == ScrollBarVisibility.Default)
+			{
+				// If the user has not explicitly set a horizontal scroll bar visibility, then the orientation will
+				// determine what the horizontal scroll bar does
+
+				scrollViewer.HorizontalScrollBarVisibility = orientation switch
+				{
+					ScrollOrientation.Horizontal or ScrollOrientation.Both => WScrollBarVisibility.Auto,
+					_ => WScrollBarVisibility.Disabled,
+				};
+
+				return;
+			}
+
+			// If the user _has_ set a horizontal scroll bar visibility preference, then convert that preference to the native equivalent
+			// if the orientation allows for it
+
+			scrollViewer.HorizontalScrollBarVisibility = orientation switch
+			{
+				ScrollOrientation.Horizontal or ScrollOrientation.Both => horizontalScrollBarVisibility.ToWindowsScrollBarVisibility(),
+				_ => WScrollBarVisibility.Disabled,
+			};
+
+			// TODO ezhart 2021-07-08 RE: the note below - do we actually need to be accounting for Neither in the measurement code?
+			// Could we just disable the scroll bars entirely?
+			// Accounting for Neither in the xplat measurement code is a leftover from Forms, it may be easier to do that on the native side here.
+
+			// Note that the Orientation setting of "Neither" is covered by the measurement code (the size of the content is limited
+			// so that no scrolling is possible) and the xplat scrolling code (the ScrollTo methods are disabled when Orientation=Neither)
+		}
+	}
+}