Problem reported as
https://github.com/google/fonts/issues/632
The font in question (Nunito) has values 705 and 713 for the
reference and overshoot values, respectively, of the first blue
zone. Blue zone 2, however, has value 710 for both the reference
and overshoot. At 12ppem, reference and overshoot of blue zone 0
becomes 8px, while blue zone 2 becomes 9px.
A peculiarity of this font is that the tops of isolated vertical
stems like `N' have a slight overshoot also. The auto-hinter tries
to find the nearest blue zone using the *original* coordinates. For
vertical stems, this is value 713. For normal horizontal tops like
in character `E', this is value 710. Since value 713 is mapped to
8px but value 710 to 9px, `N' and similar characters are one pixel
higher than `E', which looks very bad.
This commit sanitizes blue zones to avoid such a behaviour.
* src/autofit/aflatin.c (af_latin_sort_blue): New function.
(af_latin_metrics_init_blues): Sort blue values and remove overlaps.
* src/truetype/ttgxvar.h (GX_HVarTable): Renamed to...
(GX_HVVarTable): ...This.
(GX_Blend): Add fields for `VVAR' table handling.
Other minor updates.
* src/truetype/ttgxvar.c (ft_var_load_hvar): Renamed to...
(ft_var_load_hvvar): ...This.
Handle VVAR loading also (controlled by an additional parameter).
(tt_hadvance_adjust): Renamed to...
(tt_hvadvance_adjust): ...This.
Handle application of advance height also (controlled by an
additional parameter).
(tt_hadvance_adjust, tt_vadvance_adjust): Wrappers for
`tt_hvadvance_adjust'.
* src/truetype/ttdriver.c (tt_service_metrics_variations): Updated.
The number of lowercase characters for computing the top flat blue
zone value was too small (in most cases only `x' and `z'). If one
of the two characters has a large serif, say, it can happen that
FreeType must select between two different values, having a 50%
chance to use the wrong one. As a result, rendering at larger PPEM
values could yield uneven lowercase glyph heights.
Problem reported by Christoph Koeberlin <christoph@koe.berlin>.
* src/autofit/afblue.dat (AF_BLUE_STRING_LATIN_SMALL): Replaced
with...
(AF_BLUE_STRING_LATIN_SMALL_TOP, AF_BLUE_STRING_LATIN_SMALL_BOTTOM):
... New, extended sets.
(AF_BLUE_STRINGSET_LATN): Updated.
* src/autofit/afblue.c, scr/autofit/afblue.h: Regenerated.
Only now I've got an OTF with an HVAR table for testing...
The code in `ftmm.c' uses `FT_FACE_LOOKUP_SERVICE' to get the
metrics variations interface. However, this didn't work with
`FT_FACE_FIND_GLOBAL_SERVICE' used in `sfnt_init_face'.
* src/cff/cffdrivr.c: Include FT_SERVICE_METRICS_VARIATIONS_H.
(cff_hadvance_adjust, cff_metrics_adjust): Wrapper functions for
metric service functions from the `truetype' module.
(cff_service_metrics_variations): New service.
(cff_services): Updated.
* src/cff/cffpic.h (CFF_SERVICE_METRICS_VAR_GET): New macro.
[FT_CONFIG_OPTION_PIC]: Synchronize code.
* src/sfnt/sfobjs.c (sfnt_init_face): Replace call to
FT_FACE_FIND_GLOBAL_SERVICE with `ft_module_get_service' to always
load the service from the `truetype' module.
* include/freetype/internal/tttypes.h (TT_LangTagRec): New
structure.
(TT_NameTableRec): Add fields `numLangTagRecords' and `langTags'.
* src/sfnt/ttload.c (tt_face_load_name): Add support for language
tags.
Reduce array size of name strings in case of invalid entries.
(tt_face_free_name): Updated.
* docs/CHANGES: Updated.
* src/truetype/ttgxvar.h (GX_MVarTable): `axisCount' has been
removed frem the specification; it is now reserved.
* src/truetype/ttgxvar.c (ft_var_load_mvar): Updated.
(GX_FVar_Head): Remove `countSizePairs'; the corresponding data
field in the `MVAR' table is now reserved.
(fvar_fields): Updated.
Show more macros in the reference: TT_MAC_LANGID_XXX, TT_MS_LANGID_XXX,
TT_NAME_ID_XXX, TT_UCR_XXX.
This commit is viewed best with
git diff --color-words='[^*/ ]+'
* src/base/ftmm.c: Include FT_SERVICE_METRICS_VARIATIONS_H.
(ft_face_get_mvar_service): New auxiliary function to look up
metrics variation service.
(FT_Set_Var_Design_Coordinates, FT_Set_MM_Blend_Coordinates,
FT_Set_Var_Blend_Coordinates): Call metrics variation service.
* src/truetype/ttobjs.c (tt_face_init): Use metrics variations for
named instances.
Werner Lemberg