Correctly show mid markers for paths with Bezier curves

- fixes W3C example painting-marker-04-f.svg

Source/Basic Shapes/SvgMarkerElement.cs

@@ -67,8 +67,18 @@ namespace Svg
             if (this.MarkerMid != null)
             {
                 SvgMarker marker = this.OwnerDocument.GetElementById<SvgMarker>(this.MarkerMid.ToString());
+                int bezierIndex = -1;
                 for (int i = 1; i <= path.PathPoints.Length - 2; i++)
-                    marker.RenderMarker(renderer, this, path.PathPoints[i], path.PathPoints[i - 1], path.PathPoints[i], path.PathPoints[i + 1]);
+                {
+                    // for Bezier curves, the marker shall only been shown at the last point
+                    if ((path.PathTypes[i] & 7) == 3)
+                        bezierIndex = (bezierIndex + 1) % 3;
+                    else
+                        bezierIndex = -1;
+                    if (bezierIndex == -1 || bezierIndex == 2)
+                        marker.RenderMarker(renderer, this, path.PathPoints[i], path.PathPoints[i - 1], path.PathPoints[i], path.PathPoints[i + 1]);
+
+                }
             }
 
             if (this.MarkerEnd != null)

Tests/Svg.UnitTests/PassingTests.csv

@@ -48,6 +48,7 @@ painting-fill-02-t
 painting-fill-03-t
 painting-fill-05-b
 painting-marker-01-f
+painting-marker-04-f
 painting-marker-06-f
 painting-stroke-01-t
 painting-stroke-02-t

Tests/W3CTestSuite/PassingTests.txt

@@ -54,6 +54,7 @@ painting-fill-03-t.svg
 painting-fill-04-t.svg
 painting-fill-05-b.svg
 painting-marker-01-f.svg
+painting-marker-04-f.svg
 painting-marker-06-f.svg
 painting-stroke-01-t.svg
 painting-stroke-02-t.svg