1 files changed, 21 insertions, 25 deletions

diff --git a/include/cru/platform/graphics/Geometry.h b/include/cru/platform/graphics/Geometry.h
index d1045b59..112c95e6 100644
--- a/include/cru/platform/graphics/Geometry.h
+++ b/include/cru/platform/graphics/Geometry.h
@@ -17,49 +17,45 @@ struct CRU_PLATFORM_GRAPHICS_API IGeometry : virtual IGraphicsResource {
   virtual std::unique_ptr<IGeometry> CreateStrokeGeometry(float width) = 0;
 };
 
+/**
+ * \remarks We always run into platform porting problems. When I designed this
+ * interface, I thought every platform would support GetCurrentPosition.
+ * However, this is not actually true.
+ * For web canvas, it turns out that it can't get current position. So I have to
+ * not implement or use it, which disables every relative actions because they
+ * depend on it. But luckily, the web canvas path can be constructed from svg
+ * path (see https://developer.mozilla.org/en-US/docs/Web/API/Path2D/Path2D). So
+ * I come up with a new idea that first create a geometry describe itself in
+ * svg, and then construct path from it. And all relative methods should become
+ * virtual so it can override them.
+ */
 struct CRU_PLATFORM_GRAPHICS_API IGeometryBuilder : virtual IGraphicsResource {
   virtual Point GetCurrentPosition() = 0;
 
   virtual void MoveTo(const Point& point) = 0;
-  void RelativeMoveTo(const Point& offset) {
-    MoveTo(GetCurrentPosition() + offset);
-  }
+  virtual void RelativeMoveTo(const Point& offset);
 
   virtual void LineTo(const Point& point) = 0;
   void LineTo(float x, float y) { LineTo(Point(x, y)); }
-  void RelativeLineTo(const Point& offset) {
-    LineTo(GetCurrentPosition() + offset);
-  }
+  virtual void RelativeLineTo(const Point& offset);
   void RelativeLineTo(float x, float y) { RelativeLineTo(Point(x, y)); }
 
   virtual void CubicBezierTo(const Point& start_control_point,
                              const Point& end_control_point,
                              const Point& end_point) = 0;
-  void RelativeCubicBezierTo(const Point& start_control_offset,
-                             const Point& end_control_offset,
-                             const Point& end_offset) {
-    auto current_position = GetCurrentPosition();
-    CubicBezierTo(current_position + start_control_offset,
-                  current_position + end_control_offset,
-                  current_position + end_offset);
-  }
+  virtual void RelativeCubicBezierTo(const Point& start_control_offset,
+                                     const Point& end_control_offset,
+                                     const Point& end_offset);
 
   virtual void QuadraticBezierTo(const Point& control_point,
                                  const Point& end_point) = 0;
-  void RelativeQuadraticBezierTo(const Point& control_offset,
-                                 const Point& end_offset) {
-    auto current_position = GetCurrentPosition();
-    QuadraticBezierTo(current_position + control_offset,
-                      current_position + end_offset);
-  }
+  virtual void RelativeQuadraticBezierTo(const Point& control_offset,
+                                 const Point& end_offset);
 
   virtual void ArcTo(const Point& radius, float angle, bool is_large_arc,
                      bool is_clockwise, const Point& end_point);
-  void RelativeArcTo(const Point& radius, float angle, bool is_large_arc,
-                     bool is_clockwise, const Point& end_offset) {
-    ArcTo(radius, angle, is_large_arc, is_clockwise,
-          GetCurrentPosition() + end_offset);
-  }
+  virtual void RelativeArcTo(const Point& radius, float angle, bool is_large_arc,
+                     bool is_clockwise, const Point& end_offset);
 
   virtual void CloseFigure(bool close) = 0;