Unify SHAPE_ARC clockwise calc.

We don't really need the extra angle calculations

libs/kimath/include/geometry/shape_arc.h

@@ -150,8 +150,6 @@ public:
      */
     int Intersect( const SHAPE_ARC& aArc, std::vector<VECTOR2I>* aIpsBuffer ) const;
 
-    bool IsClockwise() const;
-
     void SetWidth( int aWidth )
     {
         m_width = aWidth;
@@ -250,13 +248,23 @@ public:
     void TransformToPolygon( SHAPE_POLY_SET& aBuffer, int aError,
                              ERROR_LOC aErrorLoc ) const override;
 
-private:
-    bool ccw( const VECTOR2I& aA, const VECTOR2I& aB, const VECTOR2I& aC ) const
+    /**
+     * @return true if the arc is counter-clockwise.
+     */
+    bool IsCCW() const
     {
-        return ( ecoord{ aC.y } - aA.y ) * ( ecoord{ aB.x } - aA.x ) >
-               ( ecoord{ aB.y } - aA.y ) * ( ecoord{ aC.x } - aA.x );
+        VECTOR2I v1 = m_end - m_mid;
+        VECTOR2I v2 = m_start - m_mid;
+
+        return v1.Cross( v2 ) > 0;
     }
 
+    bool IsClockwise() const
+    {
+    return !IsCCW();
+}
+
+private:
     void update_values();
 
     bool sliceContainsPoint( const VECTOR2I& p ) const;

libs/kimath/src/geometry/shape_arc.cpp

@@ -396,12 +396,6 @@ const BOX2I SHAPE_ARC::BBox( int aClearance ) const
 }
 
 
-bool SHAPE_ARC::IsClockwise() const
-{
-    return GetCentralAngle() < ANGLE_0;
-}
-
-
 VECTOR2I SHAPE_ARC::NearestPoint( const VECTOR2I& aP ) const
 {
     const static int s_epsilon = 8;