Added ArcTo implementation based on Bezier curves

src/Gtk/Perspex.Cairo/Media/StreamGeometryContextImpl.cs

@@ -5,6 +5,7 @@ using System;
 using System.Collections.Generic;
 using Perspex.Media;
 using Perspex.Platform;
+using Perspex.RenderHelpers;
 
 namespace Perspex.Cairo.Media
 {
@@ -12,6 +13,7 @@ namespace Perspex.Cairo.Media
 
     public class StreamGeometryContextImpl : IStreamGeometryContextImpl
     {
+        private Point _currentPoint;
 		public StreamGeometryContextImpl(Cairo.Path path = null)
         {
 
@@ -27,24 +29,44 @@ namespace Perspex.Cairo.Media
 
         public void ArcTo(Point point, Size size, double rotationAngle, bool isLargeArc, SweepDirection sweepDirection)
         {
+            ArcToHelper.ArcTo(this, _currentPoint, point, size, rotationAngle, isLargeArc, sweepDirection);
+            _currentPoint = point;
         }
 
         public void BeginFigure(Point startPoint, bool isFilled)
         {
-			if (this.Path == null)
+            if (this.Path == null)
-            	_context.MoveTo(startPoint.ToCairo());
+            {
+                _context.MoveTo(startPoint.ToCairo());
+                _currentPoint = startPoint;
+            }
         }
 
         public void BezierTo(Point point1, Point point2, Point point3)
         {
-			if (this.Path == null)
+            if (this.Path == null)
-            	_context.CurveTo(point1.ToCairo(), point2.ToCairo(), point3.ToCairo());
+            {
+                _context.CurveTo(point1.ToCairo(), point2.ToCairo(), point3.ToCairo());
+                _currentPoint = point3;
+            }
+        }
+
+        public void QuadTo(Point control, Point endPoint)
+        {
+            if (this.Path == null)
+            {
+                QuadBezierHelper.QuadTo(this, _currentPoint, control, endPoint);
+                _currentPoint = endPoint;
+            }
         }
 
         public void LineTo(Point point)
         {
-			if (this.Path == null)
+            if (this.Path == null)
-            	_context.LineTo(point.ToCairo());
+            {
+                _context.LineTo(point.ToCairo());
+                _currentPoint = point;
+            }
         }
 
         private readonly Cairo.Context _context;

src/Perspex.SceneGraph/Platform/IStreamGeometryContextImpl.cs

@@ -38,6 +38,13 @@ namespace Perspex.Platform
         /// <param name="point3">The destination point for the end of the curve.</param>
         void BezierTo(Point point1, Point point2, Point point3);
 
+        /// <summary>
+        /// Draws a quadratic Bezier curve to the specified point
+        /// </summary>
+        /// <param name="control">Control point</param>
+        /// <param name="endPoint">DestinationPoint</param>
+        void QuadTo(Point control, Point endPoint);
+
         /// <summary>
         /// Draws a line to the specified point.
         /// </summary>

src/Perspex.SceneGraph/Point.cs

@@ -128,6 +128,30 @@ namespace Perspex
             return new Point(a._x - b.X, a._y - b.Y);
         }
 
+        /// <summary>
+        /// Multiplies a point by a factor coordinate-wise
+        /// </summary>
+        /// <param name="p">Point to multiply</param>
+        /// <param name="k">Factor</param>
+        /// <returns>Points having its coordinates multiplied</returns>
+        public static Point operator *(Point p, double k) => new Point(p.X*k, p.Y*k);
+
+        /// <summary>
+        /// Multiplies a point by a factor coordinate-wise
+        /// </summary>
+        /// <param name="p">Point to multiply</param>
+        /// <param name="k">Factor</param>
+        /// <returns>Points having its coordinates multiplied</returns>
+        public static Point operator *(double k, Point p) => new Point(p.X*k, p.Y*k);
+
+        /// <summary>
+        /// Divides a point by a factor coordinate-wise
+        /// </summary>
+        /// <param name="p">Point to divide by</param>
+        /// <param name="k">Factor</param>
+        /// <returns>Points having its coordinates divided</returns>
+        public static Point operator /(Point p, double k) => new Point(p.X/k, p.Y/k);
+         
         /// <summary>
         /// Applies a matrix to a point.
         /// </summary>

src/Perspex.SceneGraph/Vector.cs

@@ -3,6 +3,7 @@
 
 using System;
 using System.Globalization;
+using System.Xml.Linq;
 
 namespace Perspex
 {
@@ -51,6 +52,24 @@ namespace Perspex
             return new Point(a._x, a._y);
         }
 
+        
+
+        /// <summary>
+        /// Calculates the dot product of two vectors
+        /// </summary>
+        /// <param name="a">First vector</param>
+        /// <param name="b">Second vector</param>
+        /// <returns>The dot product</returns>
+        public static double operator *(Vector a, Vector b)
+        {
+            return a.X*b.X + a.Y*b.Y;
+        }
+
+        /// <summary>
+        /// Length of the vector
+        /// </summary>
+        public double Length => Math.Sqrt(X*X + Y*Y);
+
         /// <summary>
         /// Negates a vector.
         /// </summary>

src/Shared/RenderHelpers/QuadBezierHelper.cs

@@ -0,0 +1,13 @@
+using Perspex.Platform;
+
+namespace Perspex.RenderHelpers
+{
+    static class QuadBezierHelper
+    {
+        public static void QuadTo(IStreamGeometryContextImpl context, Point current, Point controlPoint, Point endPoint)
+        {
+            //(s, (s + 2c)/ 3, (e + 2c)/ 3, e)
+            context.BezierTo((current + 2*controlPoint)/3, (endPoint + 2*controlPoint)/3, endPoint);
+        }
+    }
+}

src/Shared/RenderHelpers/RenderHelpers.projitems

@@ -9,6 +9,8 @@
     <Import_RootNamespace>Perspex.RenderHelpers</Import_RootNamespace>
   </PropertyGroup>
   <ItemGroup>
+    <Compile Include="$(MSBuildThisFileDirectory)ArcToHelper.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)QuadBezierHelper.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)TileBrushImplHelper.cs" />
   </ItemGroup>
 </Project>

src/Windows/Perspex.Direct2D1/Media/StreamGeometryContextImpl.cs

@@ -47,6 +47,15 @@ namespace Perspex.Direct2D1.Media
             });
         }
 
+        public void QuadTo(Point control, Point dest)
+        {
+            _sink.AddQuadraticBezier(new QuadraticBezierSegment
+            {
+                Point1 = control.ToSharpDX(),
+                Point2 = dest.ToSharpDX()
+            });
+        }
+
         public void LineTo(Point point)
         {
             _sink.AddLine(point.ToSharpDX());