[Android, iOS] Fix issue using ArcSegment to create a Path

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Issue11190.xaml

@@ -0,0 +1,52 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<controls:TestContentPage
+    xmlns="http://xamarin.com/schemas/2014/forms"
+    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+    xmlns:controls="clr-namespace:Xamarin.Forms.Controls"
+    x:Class="Xamarin.Forms.Controls.Issues.Issue11190"
+    Title="Issue 11190">
+    <Grid>
+        <Grid.RowDefinitions>
+            <RowDefinition Height="Auto" />
+            <RowDefinition Height="*" />
+        </Grid.RowDefinitions>
+        <Label
+            Padding="12"
+            BackgroundColor="Black"
+            TextColor="White"
+            Text="If the Shape is rendered without problems or exceptions, the test has passed."/>
+        <Grid
+            Grid.Row="1"
+            HorizontalOptions="Start"
+            VerticalOptions="Start"
+            HeightRequest="200"
+            WidthRequest="200">
+            <Path
+                Stroke="Black"
+                HeightRequest="200"
+                WidthRequest="200">
+                <Path.Data>
+                    <PathGeometry>
+                        <PathGeometry.Figures>
+                            <PathFigureCollection>
+                                <PathFigure
+                                    StartPoint="0,0">
+                                    <PathFigure.Segments>
+                                        <PathSegmentCollection>
+                                            <ArcSegment
+                                                Size="100,100"
+                                                RotationAngle="45"
+                                                IsLargeArc="True"
+                                                SweepDirection="CounterClockwise"
+                                                Point="100,100" />
+                                        </PathSegmentCollection>
+                                    </PathFigure.Segments>
+                                </PathFigure>
+                            </PathFigureCollection>
+                        </PathGeometry.Figures>
+                    </PathGeometry>
+                </Path.Data>
+            </Path>
+        </Grid>
+    </Grid>
+</controls:TestContentPage>

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Issue11190.xaml.cs

@@ -0,0 +1,37 @@
+using Xamarin.Forms.CustomAttributes;
+using Xamarin.Forms.Internals;
+using System.Collections.Generic;
+
+#if UITEST && __ANDROID__
+using Xamarin.UITest;
+using Xamarin.UITest.Queries;
+using NUnit.Framework;
+using Xamarin.Forms.Core.UITests;
+using System.Linq;
+#endif
+
+namespace Xamarin.Forms.Controls.Issues
+{
+#if UITEST && __ANDROID__
+	[Category(UITestCategories.Shape)]
+#endif
+	[Preserve(AllMembers = true)]
+	[Issue(IssueTracker.Github, 11190, "[Bug] Shapes: ArcSegment throwing on iOS, doing nothing on Android", PlatformAffected.Android | PlatformAffected.iOS)]
+	public partial class Issue11190 : TestContentPage
+	{
+
+		public Issue11190()
+		{
+#if APP
+			Device.SetFlags(new List<string> { ExperimentalFlags.ShapesExperimental });
+			InitializeComponent();
+#endif
+		}
+
+
+		protected override void Init()
+		{
+
+		}
+	}
+}

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

@@ -1451,6 +1451,7 @@
     <Compile Include="$(MSBuildThisFileDirectory)Issue11031.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue11018.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue10940.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Issue11190.xaml.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue11050.xaml.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue9456.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue10908.xaml.cs" />
@@ -1714,6 +1715,9 @@
     <EmbeddedResource Include="$(MSBuildThisFileDirectory)Issue9555.xaml">
       <Generator>MSBuild:UpdateDesignTimeXaml</Generator>
     </EmbeddedResource>
+    <EmbeddedResource Include="$(MSBuildThisFileDirectory)Issue11190.xaml">
+      <Generator>MSBuild:UpdateDesignTimeXaml</Generator>
+    </EmbeddedResource>
     <EmbeddedResource Include="$(MSBuildThisFileDirectory)RectTest.xaml">
       <Generator>MSBuild:UpdateDesignTimeXaml</Generator>
     </EmbeddedResource>

Xamarin.Forms.Core.UITests.Shared/UITestCategories.cs

@@ -64,8 +64,8 @@ internal static class UITestCategories
 		public const string Github5000 = "Github5000";
 		public const string Github10000 = "Github10000";
 		public const string RadioButton = "RadioButton";
-		public const string Accessibility = "Accessibility";
 		public const string Shape = "Shape";
+		public const string Accessibility = "Accessibility";
 		public const string Brush = "Brush";
 	}
 }

Xamarin.Forms.Core.UnitTests/GeometryTests.cs

@@ -0,0 +1,71 @@
+using System.Collections.Generic;
+using NUnit.Framework;
+using Xamarin.Forms.Shapes;
+
+namespace Xamarin.Forms.Core.UnitTests
+{
+	[TestFixture]
+	public class GeometryTests : BaseTestFixture
+	{
+		[SetUp]
+		public override void Setup()
+		{
+			base.Setup();
+
+			Device.SetFlags(new[] { ExperimentalFlags.ShapesExperimental });
+		}
+
+		[TestCase(0, true)]
+		[TestCase(0, false)]
+		[TestCase(45, true)]
+		[TestCase(45, false)]
+		[TestCase(180, true)]
+		[TestCase(180, false)]
+		[TestCase(270, true)]
+		[TestCase(270, false)]
+		public void FlattenArcTest(double angle, bool isLargeArc)
+		{
+			var path = new Path
+			{
+				HeightRequest = 200,
+				WidthRequest = 200,
+				Stroke = Brush.Black
+			};
+
+			PathFigure figure = new PathFigure();
+
+			ArcSegment arcSegment = new ArcSegment
+			{
+				Point = new Point(10, 100),
+				Size = new Size(100, 50),
+				RotationAngle = angle,
+				IsLargeArc = isLargeArc
+			};
+
+			figure.Segments.Add(arcSegment);
+
+			path.Data = new PathGeometry
+			{
+				Figures = new PathFigureCollection
+				{
+					figure
+				}
+			};
+
+			List<Point> points = new List<Point>();
+
+			GeometryHelper.FlattenArc(
+				points,
+				Point.Zero,
+				arcSegment.Point,
+				arcSegment.Size.Width,
+				arcSegment.Size.Height,
+				arcSegment.RotationAngle,
+				arcSegment.IsLargeArc,
+				arcSegment.SweepDirection == SweepDirection.CounterClockwise,
+				1);
+
+			Assert.AreNotEqual(0, points.Count);
+		}
+	}
+}

Xamarin.Forms.Core.UnitTests/Xamarin.Forms.Core.UnitTests.csproj

@@ -253,6 +253,7 @@
     <Compile Include="PolylineTests.cs" />
     <Compile Include="RectangleTests.cs" />
     <Compile Include="LineTests.cs" />
+    <Compile Include="GeometryTests.cs" />
     <Compile Include="RectUnitTests.cs" />
     <Compile Include="BrushUnitTests.cs" />
     <Compile Include="LinearGradientBrushTests.cs" />

Xamarin.Forms.Core/Shapes/GeometryHelper.cs

@@ -196,14 +196,19 @@ public static void FlattenGeometry(PathGeometry pathGeoDst, Geometry geoSrc, dou
                         else if (segSrc is ArcSegment)
                         {
                             ArcSegment arcSeg = segSrc as ArcSegment;
+
                             Points.Clear();
 
-                            FlattenArc(Points, ptLast, arcSeg.Point,
-                                       arcSeg.Size.Width, arcSeg.Size.Height,
-                                       arcSeg.RotationAngle,
-                                       arcSeg.IsLargeArc,
-                                       arcSeg.SweepDirection == SweepDirection.CounterClockwise,
-                                       tolerance);
+                            FlattenArc(
+                                Points,
+                                ptLast,
+                                arcSeg.Point,
+                                arcSeg.Size.Width,
+                                arcSeg.Size.Height,
+                                arcSeg.RotationAngle,
+                                arcSeg.IsLargeArc,
+                                arcSeg.SweepDirection == SweepDirection.CounterClockwise,
+                                tolerance);
 
                             // Set ptLast while transferring points
                             for (int i = 1; i < Points.Count; i++)
@@ -260,6 +265,7 @@ public static void FlattenQuadraticBezier(List<Point> points, Point ptStart, Poi
             }
         }
 
+        // More information: http://www.charlespetzold.com/blog/2008/01/Mathematics-of-ArcSegment.html
         public static void FlattenArc(List<Point> points, Point pt1, Point pt2, double radiusX, double radiusY, double angleRotation,
             bool isLargeArc, bool isCounterclockwise, double tolerance)
         {
@@ -285,8 +291,8 @@ public static void FlattenArc(List<Point> points, Point pt1, Point pt2, double r
 
             vectRotated = vectRotated.Normalized;
 
-            // Distance from chord to center 
-            double centerDistance = Math.Sqrt(radiusY * radiusY - halfChord * halfChord);
+            // Distance from chord to center
+            double centerDistance = Math.Sqrt(Math.Abs((radiusY * radiusY) - (halfChord * halfChord)));
 
             // Calculate center point
             Point center = midPoint + centerDistance * vectRotated;

Xamarin.Forms.Platform.Android/Extensions/GeometryExtensions.cs

@@ -162,7 +162,8 @@ public static APath ToAPath(this Geometry geometry, Context context)
 
                             List<Point> points = new List<Point>();
 
-                            GeometryHelper.FlattenArc(points,
+                            GeometryHelper.FlattenArc(
+                                points,
                                 lastPoint,
                                 arcSegment.Point,
                                 arcSegment.Size.Width,

Xamarin.Forms.Platform.iOS/Extensions/GeometryExtensions.cs

@@ -162,7 +162,8 @@ public static PathData ToCGPath(this Geometry geometry, Transform renderTransfor
 
                             List<Point> points = new List<Point>();
 
-                            GeometryHelper.FlattenArc(points,
+                            GeometryHelper.FlattenArc(
+                                points,
                                 lastPoint,
                                 arcSegment.Point,
                                 arcSegment.Size.Width,
@@ -179,7 +180,7 @@ public static PathData ToCGPath(this Geometry geometry, Transform renderTransfor
 
                             pathData.Data.AddLines(cgpoints);
 
-                            lastPoint = points[points.Count - 1];
+                            lastPoint = points.Count > 0 ? points[points.Count - 1] : Point.Zero;
                         }
                     }