Add Sector shape

src/Avalonia.Base/Utilities/MathUtilities.cs

@@ -324,6 +324,41 @@ namespace Avalonia.Utilities
             return angle * 2 * Math.PI;
         }
 
+        /// <summary>
+        /// Calculates the point of an angle on an ellipse.
+        /// </summary>
+        /// <param name="centre">The centre point of the ellipse.</param>
+        /// <param name="radiusX">The x radius of the ellipse.</param>
+        /// <param name="radiusY">The y radius of the ellipse.</param>
+        /// <param name="angle">The angle in radians.</param>
+        /// <returns>A point on the ellipse.</returns>
+        public static Point GetEllipsePoint(Point centre, double radiusX, double radiusY, double angle)
+        {
+            return new Point(radiusX * Math.Cos(angle) + centre.X, radiusY * Math.Sin(angle) + centre.Y);
+        }
+
+        /// <summary>
+        /// Gets the minimum and maximum from the specified numbers.
+        /// </summary>
+        /// <param name="a">The first number.</param>
+        /// <param name="b">The second number.</param>
+        /// <returns>A tuple containing the minimum and maximum of the two specified numbers.</returns>
+        public static (double min, double max) GetMinMax(double a, double b)
+        {
+            return a < b ? (a, b) : (b, a);
+        }
+
+        /// <summary>
+        /// Gets the minimum and maximum from the specified number and the difference with that number.
+        /// </summary>
+        /// <param name="initialValue">The initial value to use.</param>
+        /// <param name="delta">The difference for <paramref name="initialValue"/>.</param>
+        /// <returns>A tuple containing the minimum and maximum of the specified number and the difference with that number.</returns>
+        public static (double min, double max) GetMinMaxFromDelta(double initialValue, double delta)
+        {
+            return GetMinMax(initialValue, initialValue + delta);
+        }
+
         private static void ThrowCannotBeGreaterThanException<T>(T min, T max)
         {
             throw new ArgumentException($"{min} cannot be greater than {max}.");

src/Avalonia.Controls/Shapes/Sector.cs

@@ -0,0 +1,65 @@
+using System;
+using Avalonia.Media;
+using Avalonia.Utilities;
+
+namespace Avalonia.Controls.Shapes
+{
+    public class Sector : Shape
+    {
+        public static readonly StyledProperty<double> StartAngleProperty = AvaloniaProperty.Register<Sector, double>(nameof(StartAngle), 0.0d);
+        public static readonly StyledProperty<double> AngleProperty = AvaloniaProperty.Register<Sector, double>(nameof(Angle), 0.0d);
+
+        public double StartAngle
+        {
+            get => GetValue(StartAngleProperty);
+            set => SetValue(StartAngleProperty, value);
+        }
+
+        public double Angle
+        {
+            get => GetValue(AngleProperty);
+            set => SetValue(AngleProperty, value);
+        }
+
+        static Sector()
+        {
+            StrokeThicknessProperty.OverrideDefaultValue<Sector>(1.0d);
+            AffectsGeometry<Sector>(BoundsProperty, StrokeThicknessProperty, StartAngleProperty, AngleProperty);
+        }
+
+        protected override Geometry? CreateDefiningGeometry()
+        {
+            Rect rect = new Rect(Bounds.Size);
+            Rect deflatedRect = rect.Deflate(StrokeThickness * 0.5d);
+
+            if (Angle >= 360.0d || Angle <= -360.0d)
+            {
+                return new EllipseGeometry(deflatedRect);
+            }
+
+            if (Angle == 0.0d)
+            {
+                return new StreamGeometry();
+            }
+
+            (double startAngle, double endAngle) = MathUtilities.GetMinMaxFromDelta(MathUtilities.Deg2Rad(StartAngle), MathUtilities.Deg2Rad(Angle));
+
+            Point centre = new Point(rect.Width * 0.5d, rect.Height * 0.5d);
+            double radiusX = deflatedRect.Width * 0.5d;
+            double radiusY = deflatedRect.Height * 0.5d;
+            Point startCurvePoint = MathUtilities.GetEllipsePoint(centre, radiusX, radiusY, startAngle);
+            Point endCurvePoint = MathUtilities.GetEllipsePoint(centre, radiusX, radiusY, endAngle);
+            Size size = new Size(radiusX, radiusY);
+
+            StreamGeometry streamGeometry = new StreamGeometry();
+            using StreamGeometryContext streamGeometryContext = streamGeometry.Open();
+
+            streamGeometryContext.BeginFigure(startCurvePoint, false);
+            streamGeometryContext.ArcTo(endCurvePoint, size, 0.0d, Math.Abs(Angle) > 180.0d, SweepDirection.Clockwise);
+            streamGeometryContext.LineTo(centre);
+            streamGeometryContext.EndFigure(true);
+
+            return streamGeometry;
+        }
+    }
+}