ID2D1Geometry.Widen

Undocumented in source but is binding to Windows. You might be able to learn more by searching the web for its name.
  1. HRESULT Widen(float strokeWidth, ID2D1StrokeStyle strokeStyle, D2D1_MATRIX_3X2_F* worldTransform, ID2D1SimplifiedGeometrySink geometrySink)
  2. HRESULT Widen(float strokeWidth, ID2D1StrokeStyle strokeStyle, D2D1_MATRIX_3X2_F* worldTransform, float flatteningTolerance, ID2D1SimplifiedGeometrySink geometrySink)

Meta