[sdf] Impliment deviation based splitting for bezier curves.

* src/sdf/ftsdf.c (split_sdf_cubic, split_sdf_shape): Added checks
  to figure out the deviation of bezier curves and stop splitting
  if the curve is flat enough.

* src/sdf/ftsdfcommon.h (ONE_PIXEL): Added macro for unit pixel size
  in 26.6 fixed point representation.
2 files changed