tree 02accbb76dfdc47c4cc8fe32c7da7f9ff77b28b8
parent cc3333902bbfe5d8c16cf84c4e85016533ab2ee0
author Werner Lemberg <wl@gnu.org> 1529846530 +0200
committer Werner Lemberg <wl@gnu.org> 1529846530 +0200

[truetype] Increase precision while applying VF deltas.

It turned out that we incorrectly round CVT and glyph point deltas
before accumulation, leading to severe positioning errors if there
are many delta values to sum up.

Problem reported by Akiem Helmling <akiem@underware.nl> and analyzed
by Behdad.

* src/truetype/ttgxvar.c (ft_var_readpackeddelta): Return deltas in
16.16 format.
(tt_face_var_cvt): Collect deltas in `cvt_deltas', which is a 16.16
format array, and add the accumulated values to the CVT at the end
of the function.
(TT_Vary_Apply_Glyph_Deltas): Store data in `points_org' and
`points_out' in 16.16 format.
Collect deltas in `point_deltas_x' and `point_deltas_y', which are
16.16 format arrays, and add the accumulated values to the glyph
coordinates at the end of the function.