Fixed Shape.AffectsGeometry.

Make sure the object on which the property changed occurred is the
correct type. Previously, e.g. the `AffectsGeometry(BoundsProperty,
StrokeThicknessProperty)` call in `Rectangle` caused *all* shapes to be
invalidated when `Bounds` changed, where it should only affect
`Rectangle.

src/Perspex.Controls/Shapes/Ellipse.cs

@@ -9,7 +9,7 @@ namespace Perspex.Controls.Shapes
     {
         static Ellipse()
         {
-            AffectsGeometry(BoundsProperty, StrokeThicknessProperty);
+            AffectsGeometry<Ellipse>(BoundsProperty, StrokeThicknessProperty);
         }
 
         protected override Geometry CreateDefiningGeometry()

src/Perspex.Controls/Shapes/Line.cs

@@ -16,7 +16,7 @@ namespace Perspex.Controls.Shapes
         static Line()
         {
             StrokeThicknessProperty.OverrideDefaultValue<Line>(1);
-            AffectsGeometry(StartPointProperty, EndPointProperty);
+            AffectsGeometry<Line>(StartPointProperty, EndPointProperty);
         }
 
         public Point StartPoint

src/Perspex.Controls/Shapes/Path.cs

@@ -13,7 +13,7 @@ namespace Perspex.Controls.Shapes
 
         static Path()
         {
-            AffectsGeometry(DataProperty);
+            AffectsGeometry<Path>(DataProperty);
         }
 
         public Geometry Data

src/Perspex.Controls/Shapes/Polygon.cs

@@ -13,7 +13,7 @@ namespace Perspex.Controls.Shapes
 
         static Polygon()
         {
-            AffectsGeometry(PointsProperty);
+            AffectsGeometry<Polygon>(PointsProperty);
         }
 
         public IList<Point> Points

src/Perspex.Controls/Shapes/Polyline.cs

@@ -14,7 +14,7 @@ namespace Perspex.Controls.Shapes
         static Polyline()
         {
             StrokeThicknessProperty.OverrideDefaultValue<Polyline>(1);
-            AffectsGeometry(PointsProperty);
+            AffectsGeometry<Polyline>(PointsProperty);
         }
 
         public IList<Point> Points

src/Perspex.Controls/Shapes/Rectangle.cs

@@ -9,7 +9,7 @@ namespace Perspex.Controls.Shapes
     {
         static Rectangle()
         {
-            AffectsGeometry(BoundsProperty, StrokeThicknessProperty);
+            AffectsGeometry<Rectangle>(BoundsProperty, StrokeThicknessProperty);
         }
 
         protected override Geometry CreateDefiningGeometry()

src/Perspex.Controls/Shapes/Shape.cs

@@ -2,6 +2,7 @@
 // Licensed under the MIT license. See licence.md file in the project root for full license information.
 
 using System;
+using System.Reflection;
 using Perspex.Collections;
 using Perspex.Controls;
 using Perspex.Media;
@@ -123,11 +124,21 @@ namespace Perspex.Controls.Shapes
         /// After a call to this method in a control's static constructor, any change to the
         /// property will cause <see cref="InvalidateGeometry"/> to be called on the element.
         /// </remarks>
-        protected static void AffectsGeometry(params PerspexProperty[] properties)
+        protected static void AffectsGeometry<TShape>(params PerspexProperty[] properties)
+            where TShape : Shape
         {
             foreach (var property in properties)
             {
-                property.Changed.Subscribe(AffectsGeometryInvalidate);
+                property.Changed.Subscribe(e =>
+                {
+                    var senderType = e.Sender.GetType().GetTypeInfo();
+                    var affectedType = typeof(TShape).GetTypeInfo();
+
+                    if (affectedType.IsAssignableFrom(senderType))
+                    {
+                        AffectsGeometryInvalidate(e);
+                    }
+                });
             }
         }