I don't fully understand this code. Please add more comments. A quite well documented routine to walk over a contour is function `FT_Outline_Decompose` in file `src/base/ftoutln.c` of the FreeType source code.
https://codereview.appspot.com/566080043/diff/560030043/lily/freetype.cc File lily/freetype.cc (right): https://codereview.appspot.com/566080043/diff/560030043/lily/freetype.cc#newcode124 lily/freetype.cc:124: else if (ctags[j] & 1) s/1/FT_CURVE_TAG_ON/ https://codereview.appspot.com/566080043/diff/560030043/lily/freetype.cc#newcode132 lily/freetype.cc:132: else if (ctags[j] & 2) s/2/FT_CURVE_TAG_CUBIC/ https://codereview.appspot.com/566080043/
