[Android] Remove extra scrolling when ScrollOrientation is Both (#1294)

* Repro of 60774

* Remove extra Y-direction scrolling when bidirectional scrolling is on

* Add tests for horizontal and diagonal scrolling
Fix horizontal scroll speed, restore diagonal scrolling and fix speed

* Add test instructions

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Bugzilla60774.cs

@@ -0,0 +1,84 @@
+using Xamarin.Forms.CustomAttributes;
+using Xamarin.Forms.Internals;
+
+namespace Xamarin.Forms.Controls.Issues
+{
+	// Manual test to verify that ScrollOrientation.Both scrolls at the correct speed vertically
+	[Preserve(AllMembers = true)]
+	[Issue(IssueTracker.Bugzilla, 60774, "[Android] ScrollOrientation.Both doubles the distance of scrolling", 
+		PlatformAffected.Android)]
+	public class Bugzilla60774 : TestContentPage
+	{
+		ScrollOrientation _currentOrientation;
+		Grid _host;
+		Label _labelOrientation;
+
+		protected override void Init()
+		{
+			Title = "ScrollOrientation Vertical/Both";
+
+			var grid = new Grid
+			{
+				RowDefinitions = new RowDefinitionCollection
+				{
+					new RowDefinition { Height = GridLength.Auto },
+					new RowDefinition()
+				}
+			};
+
+			var layout = new StackLayout();
+
+			var instructions = new Label
+			{
+				Text = "Scroll the text vertically. Tap 'Change Orientation' to change the ScrollView orientation " 
+						+ "to 'Both'. Scroll the text vertically again - the text should scroll at the same rate. " 
+						+ "If the text scrolls more quickly in one orientation, the test has failed."
+			};
+
+			var button = new Button { Text = "Change Orientation" };
+			button.Clicked += (sender, args) => ChangeOrientation();
+
+			_labelOrientation = new Label { Text = "" };
+
+			layout.Children.Add(instructions);
+			layout.Children.Add(button);
+			layout.Children.Add(_labelOrientation);
+
+			_host = new Grid();
+			Grid.SetRow(_host, 1);
+
+			grid.Children.Add(layout);
+			grid.Children.Add(_host);
+
+			Content = grid;
+
+			_currentOrientation = ScrollOrientation.Both;
+			ChangeOrientation();
+		}
+
+		void ChangeOrientation()
+		{
+			_host.Children.Clear();
+			_currentOrientation = _currentOrientation == ScrollOrientation.Vertical
+				? ScrollOrientation.Both
+				: ScrollOrientation.Vertical;
+
+			var al = new AbsoluteLayout();
+			for (var i = 0; i < 100; i++)
+			{
+				var label = new Label { Text = "label " + i };
+				AbsoluteLayout.SetLayoutBounds(label, new Rectangle(0, i * 50, 100, 30));
+				al.Children.Add(label);
+			}
+
+			var sv = new ScrollView
+			{
+				Orientation = _currentOrientation,
+				Content = al
+			};
+
+			_host.Children.Add(sv);
+			_labelOrientation.Text = "Current orientation is: " + _currentOrientation;
+		}
+	}
+}

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Bugzilla60774_1.cs

@@ -0,0 +1,85 @@
+using Xamarin.Forms.CustomAttributes;
+using Xamarin.Forms.Internals;
+
+namespace Xamarin.Forms.Controls.Issues
+{
+	// Manual test to verify that ScrollOrientation.Both scrolls at the correct speed horizontally
+
+	[Preserve(AllMembers = true)]
+	[Issue(IssueTracker.Bugzilla, 60774, "[Android] ScrollOrientation.Both doubles the distance of scrolling", 
+		PlatformAffected.Android, issueTestNumber: 1)]
+	public class Bugzilla60774_1 : TestContentPage
+	{
+		ScrollOrientation _currentOrientation;
+		Grid _host;
+		Label _labelOrientation;
+
+		protected override void Init()
+		{
+			Title = "ScrollOrientation Horizontal/Both";
+
+			var grid = new Grid
+			{
+				RowDefinitions = new RowDefinitionCollection
+				{
+					new RowDefinition { Height = GridLength.Auto },
+					new RowDefinition()
+				}
+			};
+
+			var layout = new StackLayout();
+
+			var instructions = new Label
+			{
+				Text = "Scroll the text horizontally. Tap 'Change Orientation' to change the ScrollView orientation " 
+						+ "to 'Both'. Scroll the text horizontally again - the text should scroll at the same rate. " 
+						+ "If the text scrolls more quickly in one orientation, the test has failed."
+			};
+
+			var button = new Button { Text = "Change Orientation" };
+			button.Clicked += (sender, args) => ChangeOrientation();
+
+			_labelOrientation = new Label { Text = "" };
+
+			layout.Children.Add(instructions);
+			layout.Children.Add(button);
+			layout.Children.Add(_labelOrientation);
+
+			_host = new Grid();
+			Grid.SetRow(_host, 1);
+
+			grid.Children.Add(layout);
+			grid.Children.Add(_host);
+
+			Content = grid;
+
+			_currentOrientation = ScrollOrientation.Both;
+			ChangeOrientation();
+		}
+
+		void ChangeOrientation()
+		{
+			_host.Children.Clear();
+			_currentOrientation = _currentOrientation == ScrollOrientation.Horizontal
+				? ScrollOrientation.Both
+				: ScrollOrientation.Horizontal;
+
+			var al = new AbsoluteLayout();
+			for (var i = 0; i < 100; i++)
+			{
+				var label = new Label { Text = $"{i} label", Margin = 10 };
+				AbsoluteLayout.SetLayoutBounds(label, new Rectangle(i * 50, 50, 30, 200));
+				al.Children.Add(label);
+			}
+
+			var sv = new ScrollView
+			{
+				Orientation = _currentOrientation,
+				Content = al
+			};
+
+			_host.Children.Add(sv);
+			_labelOrientation.Text = "Current orientation is: " + _currentOrientation;
+		}
+	}
+}

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Bugzilla60774_2.cs

@@ -0,0 +1,60 @@
+using Xamarin.Forms.CustomAttributes;
+using Xamarin.Forms.Internals;
+
+namespace Xamarin.Forms.Controls.Issues
+{
+	// Manual test to make sure diagonal scrolling works at the correct speed 
+
+	[Preserve(AllMembers = true)]
+	[Issue(IssueTracker.Bugzilla, 60774, "[Android] ScrollOrientation.Both doubles the distance of scrolling", 
+		PlatformAffected.Android, issueTestNumber: 2)]
+	public class Bugzilla60774_2 : TestContentPage
+	{
+		protected override void Init()
+		{
+			Title = "ScrollOrientation Both";
+
+			var grid = new Grid
+			{
+				RowDefinitions = new RowDefinitionCollection
+				{
+					new RowDefinition { Height = GridLength.Auto },
+					new RowDefinition()
+				}
+			};
+
+			var layout = new StackLayout();
+
+			var instructions = new Label
+			{
+				Text = "Move the label around. It should be able to move in any direction, with uniform speed. " 
+						+ "If it moves twice as fast vertically as horizontally or vice versa, the test has failed. " 
+						+ "If the label cannot move diagonally, the test has failed."
+			};
+
+			layout.Children.Add(instructions);
+			grid.Children.Add(layout);
+			
+			var host = new Grid();
+			Grid.SetRow(host, 1);
+			
+			grid.Children.Add(host);
+
+			Content = grid;
+
+			var al = new AbsoluteLayout();
+			
+			var label = new Label { Text = "Move this label around", FontSize = 72, Margin = 300 };
+			AbsoluteLayout.SetLayoutBounds(label, new Rectangle(0, 0, 2000, 2000));
+			al.Children.Add(label);
+
+			var sv = new ScrollView
+			{
+				Orientation = ScrollOrientation.Both,
+				Content = al
+			};
+
+			host.Children.Add(sv);
+		}
+	}
+}

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Xamarin.Forms.Controls.Issues.Shared.projitems

@@ -238,6 +238,9 @@
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla59863_1.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla59863_2.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla60563.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Bugzilla60774.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Bugzilla60774_1.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Bugzilla60774_2.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)ButtonBackgroundColorTest.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)CarouselAsync.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla34561.cs" />

Xamarin.Forms.Platform.Android/Renderers/AHorizontalScrollView.cs

@@ -46,15 +46,15 @@ namespace Xamarin.Forms.Platform.Android
 			// on the initial direction of movement (i.e., horizontal/vertical).
 			if (IsBidirectional)
 			{
-				float dX = _renderer.LastX - ev.RawX;
 				float dY = _renderer.LastY - ev.RawY;
+
 				_renderer.LastY = ev.RawY;
 				_renderer.LastX = ev.RawX;
 				if (ev.Action == MotionEventActions.Move)
 				{
 					var parent = (global::Android.Widget.ScrollView)Parent;
 					parent.ScrollBy(0, (int)dY);
-					ScrollBy((int)dX, 0);
+					// Fall through to base.OnTouchEvent, it'll take care of the X scrolling 					
 				}
 			}
 

Xamarin.Forms.Platform.Android/Renderers/ScrollViewRenderer.cs

@@ -153,19 +153,20 @@ namespace Xamarin.Forms.Platform.Android
 			if (_isBidirectional && !Element.InputTransparent)
 			{
 				float dX = LastX - ev.RawX;
-				float dY = LastY - ev.RawY;
+
 				LastY = ev.RawY;
 				LastX = ev.RawX;
 				if (ev.Action == MotionEventActions.Move)
 				{
-					ScrollBy(0, (int)dY);
 					foreach (AHorizontalScrollView child in this.GetChildrenOfType<AHorizontalScrollView>())
 					{
 						child.ScrollBy((int)dX, 0);
 						break;
 					}
+					// Fall through to base.OnTouchEvent, it'll take care of the Y scrolling				
 				}
 			}
+
 			return base.OnTouchEvent(ev);
 		}