Fixed scaling for Paths.

Will no doubt need revisiting as mentioned in the comments in
Shape.MeasureOverride.

Perspex.Controls/Shapes/Shape.cs

@@ -26,6 +26,8 @@ namespace Perspex.Controls.Shapes
 
         private Matrix transform = Matrix.Identity;
 
+        private Geometry renderedGeometry;
+
         public abstract Geometry DefiningGeometry
         {
             get;
@@ -41,15 +43,17 @@ namespace Perspex.Controls.Shapes
         {
             get
             {
-                var result = this.DefiningGeometry;
-
-                if (result != null)
+                if (this.renderedGeometry == null)
                 {
-                    result = result.Clone();
-                    result.Transform = new MatrixTransform(this.transform);
+                    if (this.DefiningGeometry != null)
+                    {
+                        this.renderedGeometry = this.DefiningGeometry.Clone();
+                        this.renderedGeometry.Transform = new MatrixTransform(this.transform);
+                    }
+
                 }
 
-                return result;
+                return this.renderedGeometry;
             }
         }
 
@@ -83,7 +87,9 @@ namespace Perspex.Controls.Shapes
 
         protected override Size MeasureOverride(Size availableSize)
         {
-            Rect shapeBounds = this.DefiningGeometry.GetRenderBounds(this.StrokeThickness);
+            // This should probably use GetRenderBounds(strokeThickness) but then the calculations 
+            // will multiply the stroke thickness as well, which isn't correct.
+            Rect shapeBounds = this.DefiningGeometry.Bounds;
             Size shapeSize = new Size(shapeBounds.Right, shapeBounds.Bottom);
             Matrix translate = Matrix.Identity;
             double width = this.Width;
@@ -111,12 +117,12 @@ namespace Perspex.Controls.Shapes
 
             if (shapeBounds.Width > 0)
             {
-                sx = desiredX / shapeBounds.Width;
+                sx = desiredX / shapeSize.Width;
             }
 
             if (shapeBounds.Height > 0)
             {
-                sy = desiredY / shapeBounds.Height;
+                sy = desiredY / shapeSize.Height;
             }
 
             if (double.IsInfinity(availableSize.Width))
@@ -154,11 +160,15 @@ namespace Perspex.Controls.Shapes
                     break;
             }
 
-            this.transform = translate * Matrix.Scaling(sx, sy);
+            var t = translate * Matrix.Scaling(sx, sy);
+
+            if (this.transform != t)
+            {
+                this.transform = t;
+                this.renderedGeometry = null;
+            }
 
-            double finalX = (width > 0) ? width : shapeSize.Width * sx;
-            double finalY = (height > 0) ? height : shapeSize.Width * sy;
-            return new Size(finalX, finalY);
+            return new Size(shapeSize.Width * sx, shapeSize.Height * sy);
         }
     }
 }

Windows/Perspex.Direct2D1.RenderTests/Shapes/PathTests.cs

@@ -65,5 +65,33 @@ namespace Perspex.Direct2D1.RenderTests.Shapes
             this.RenderToFile(target);
             this.CompareImages();
         }
+
+        [TestMethod]
+        public void Path_Expander_With_Border()
+        {
+            Decorator target = new Decorator
+            {
+                Width = 200,
+                Height = 200,
+                Content = new Border
+                {
+                    BorderBrush = Brushes.Red,
+                    BorderThickness = 1,
+                    HorizontalAlignment = HorizontalAlignment.Center,
+                    VerticalAlignment = VerticalAlignment.Center,
+                    Content = new Path
+                    {
+                        Fill = Brushes.Black,
+                        Stroke = Brushes.Black,
+                        StrokeThickness = 1,
+                        Stretch = Stretch.Uniform,
+                        Data = StreamGeometry.Parse("M 0 2 L 4 6 L 0 10 Z"),
+                    }
+                }
+            };
+
+            this.RenderToFile(target);
+            this.CompareImages();
+        }
     }
 }

Windows/Perspex.Direct2D1/Media/GeometryImpl.cs

@@ -60,6 +60,16 @@ namespace Perspex.Direct2D1.Media
             }
         }
 
-        public abstract Rect GetRenderBounds(double strokeThickness);
+        public Rect GetRenderBounds(double strokeThickness)
+        {
+            if (this.transformed != null)
+            {
+                return this.transformed.GetWidenedBounds((float)strokeThickness).ToPerspex();
+            }
+            else
+            {
+                return this.DefiningGeometry.GetWidenedBounds((float)strokeThickness).ToPerspex();
+            }
+        }
     }
 }

Windows/Perspex.Direct2D1/Media/StreamGeometryImpl.cs

@@ -44,11 +44,6 @@ namespace Perspex.Direct2D1.Media
             return new StreamGeometryImpl(result);
         }
 
-        public override Rect GetRenderBounds(double strokeThickness)
-        {
-            return this.path.GetWidenedBounds((float)strokeThickness).ToPerspex();
-        }
-
         public IStreamGeometryContextImpl Open()
         {
             return new StreamGeometryContextImpl(this.path.Open());