This mode uses fractional advance widths and doesn't scale glyphs
horizontally, only applying vertical scaling and hinting.
At the same time, the behaviour of the `light' auto-hinter gets
restored for backwards compatibility: Both vertical and horizontal
scaling is again based on rounded metrics values (this was changed
in a commit from 2017-03-30 as a side effect). To be more precise,
the behaviour is restored for TrueType fonts only; for other font
formats like Type 1, this is a new feature of the `light' hinting
mode.
* include/freetype/freetype.h (FT_LOAD_TARGET_SLIGHT): New macro.
(FT_RENDER_MODE_SLIGHT): New render mode.
* include/freetype/internal/ftobjs.h (FT_Size_InternalRec): Add
`autohint_mode' and `autohint_metrics' fields.
* src/autofit/afcjk.c (af_cjk_hints_init), src/autofit/aflatin.c
(af_latin_hints_init), src/autofit/aflatin2 (af_latin2_hints_init):
Updated.
* src/autofit/afloader.c (af_loader_embolden_glyph_in_slot): Use
`autohint_metrics'.
(af_loader_load_glyph): s/internal/slot_internal/.
Initialize `autohint_metrics' and `autohint_mode' depending on
current auto-hint mode.
Use `autohint_metrics'.
Updated.
* src/base/ftadvanc.c (LOAD_ADVANCE_FAST_CHECK): Updated.
* src/base/ftobjs.c (FT_Load_Glyph): Updated.
(FT_New_Size): Allocate `internal' object.
* src/pshinter/pshalgo.c (ps_hints_apply): Updated.
* src/smooth/ftsmooth.c (ft_smooth_render): Updated.
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/autofit/afhints.h (AF_SegmentRec): New member `delta'.
* src/autofit/aflatin.c (af_latin_hints_compute_segments): Compute
`delta'.
(af_latin_hints_compute_edges): Reject segments with a delta larger
than 0.5px.
Doing so allows us to link them to edges – some fonts like
`NotoSansGurmukhi-Regular' have such isolated points sitting exactly
on other outlines.
* src/autofit/aflatin.c (af_latin_hints_compute_segments): Don't
ignore one-point contours but handle them specially as one-point
segments.
(af_latin_hints_compute_edges): Append one-point segments to edges
if possible.
* src/autofit/aflatin.c (af_latin_compute_stem_width): Add argument
to pass difference between hinted and unhinted position of base
point; use this to adjust the stem width depending on the PPEM so
that it doesn't become too large under certain circumstances.
Update all callers using value 0 for this argument except...
(af_latin_align_linked_edge): Pass position delta of base point to
`af_latin_compute_stem_width'.
An example that gets better rendered is glyph `uusignTaml' (glyph
index 2286) in font `FreeSerif.ttf' (Version 0412.2263) at 22ppem.
* src/autofit/aflatin.c (af_latin_hints_compute_segments): Properly
handle segments where the last point of the first segment is
identical to the first point in the second one. This can happen for
malformed fonts or spikes. We either merge the new segment with the
previous one (both segments point into the same direction), or we
discard the shorter segment if they point into different directions.
* src/autofit/aflatin.c (af_latin_hints_compute_segments): Change
some local variable names to better differentiate between values
along a segment and values orthogonal to it.
In complex glyph shapes, the original logic was too simple to cater
for situations that would actually need something similar to PS Hint
masks. This fix should alleviate the worst cases.
* src/autofit/aflatin.c (af_latin_hint_edges): Don't allow
complete disappearance of stems.
This improves rendering of scripts like Bengali or Devanagari.
* src/autofit/afhints.c (af_axis_hints_new_edge): Add parameter to
pass top-to-bottom hinting flag. This makes the function sort edges
in descending vertical position.
* src/autofit/afhints.c: Updated.
* src/autofit/aflatin.c (af_latin_hints_compute_edges,
af_latin_hint_edges): Use `top_to_bottom_hinting' flag.
* src/autofit/afcjk.c (af_cjk_hints_compute_edges),
src/autofit/aflatin2.c (af_latin2_hints_compute_edges): Updated.
This was removed while rewriting the HarfBuzz interface.
* src/autofit/afglobal.h (AF_FaceGlobalsRec): Add `hb_buf' field to
hold internal HarfBuzz buffer, needed for feature comparison.
* src/autofit/afglobal.c (af_face_globals_new,
af_face_globals_free): Initialize and destroy `hb_buf'.
* src/autofit/afshaper.c (af_shaper_get_cluster): Compare character
(cluster) with and without applied feature.
* src/autofit/aflatin.c (af_latin_metrics_init_blues): Fix tracing
message.
This feature is mainly for Khmer: The idea is to avoid a clash
between the top of subscript glyphs and the bottom of normal
baseline glyphs.
This only works for character clusters mapped to multiple glyphs.
* src/autofit/afblue.dat: Add subscript top blue zone for Khmer.
* src/autofit/afblue.hin (AF_BLUE_PROPERTY_LATIN_SUB_TOP): New
macro.
* src/autofit/afblue.c, src/autofit/afblue.h: Regenerated.
* src/autofit/aflatin.h (AF_LATIN_IS_SUB_TOP_BLUE,
AF_LATIN_BLUE_SUB_TOP): New macros.
* src/autofit/aflatin.c (af_latin_metrics_init_blues): Handle new
blue zone property.
Update tracing messages.
(af_latin_metrics_scale_dim): Handle new blue zone property.
(af_latin_hints_compute_blue_edges): Updated.
Scripts like Khmer have blue zones that can't be directly
represented by Unicode characters. Instead, it is necessary to let
HarfBuzz convert character clusters into proper glyph representation
forms, then deriving the blue zone information from the resulting
glyphs.
* src/autofit/hbshim.c, src/autofit/hbshim.h: Replaced by...
* src/autofit/afshaper.c, src/autofit/afshaper.h: ... these two new
files, providing a new API to access HarfBuzz.
The new API manages a HarfBuzz buffer with `af_shaper_buf_create'
and `af_shaper_buf_destroy'. The buffer receives a UTF8 encoded
string with function `af_shaper_get_cluster', and the resulting
glyph data (indices, advance widths, vertical offsets) can be
iteratively accessed with function `af_shaper_get_elem'.
* src/autofit/afcjk.c (af_cjk_metrics_init_widths,
af_cjk_metrics_init_blues, af_cjk_metrics_check_digits): Updated.
* src/autofit/aflatin.c (af_latin_metrics_init_widths,
af_latin_metrics_init_blues, af_latin_metrics_check_digits):
Updated.
* include/freetype/internal/fttrace.h: s/afharfbuzz/afshaper/.
* src/autofit/afglobal.c: s/hbshim.h/afshaper.h/.
(af_face_globals_compute_style_coverage): Updated.
* src/autofit/afglocal.h: s/hbshim.h/afshaper.h/.
* src/autofit/autofit.c: s/hbshim.c/afshaper.c/.
* src/autofit/Jamfile, src/autofit/rules.mk (AUTOF_DRV_SRC):
Updated.
This is more flexible; additionally, it would allow character
clusters.
* src/autofit/aftypes.h (SCRIPT, AF_DEFINE_SCRIPT_CLASS): Updated.
(AF_ScriptClassRec): Replace `standard_char[123]' with
`standard_charstring'.
* src/autofit/afscript.h: Replace last three character arguments
of the `SCRIPT' calls with a string parameter, holding the standard
characters (in UTF-8 encoding) separated with spaces.
* src/autofit/afglobal.c, src/autofit/afglobal.h,
src/autofit/afpic.c, src/autofit/afranges.c, src/autofit/hbshim.c
(SCRIPT): Updated.
* src/autofit/afcjk.c (af_cjk_metrics_init_widths),
src/autofit/aflatin.c (af_latin_metrics_init_widths): Updated.
* src/autofit/aflatin.h (AF_LatinBlueRec): Add `ascender' and
`descender' fields.
* src/autofit/aflatin.c (af_latin_metrics_init_blues): Collect
ascender and descender data for blue zones.
(af_latin_metrics_scale_dim): Reject vertical scaling values that
change the result by more than two pixels.
We need the computed standard horizontal and vertical widths for the
emboldening calculation. This method provides a convenient way to
extract it from writing-system-specific metrics structures, which
all script definitions must implement.
* src/autofit/aftypes.h (AF_WritingSystem_GetStdWidthsFunc): New
function type.
(AF_WritingSystemClassRec): New member `style_metrics_getstdw'.
(AF_DEFINE_WRITING_SYSTEM_CLASS): Updated.
* src/autofit/afcjk.c (af_cjk_get_standard_width): New function.
(af_cjk_writing_system_class): Updated.
* src/autofit/afdummy.c (af_dummy_writing_system_class): Updated.
* src/autofit/afindic.c (af_cjk_get_standard_width): New function.
(af_indic_writing_system_class): Updated.
* src/autofit/aflatin.c (af_latin_get_standard_width): New function.
(af_indic_writing_system_class): Updated.
* src/autofit/aflatin.c (af_latin_get_standard_width): New function.
(af_indic_writing_system_class): Updated.
This commit adds two fallback scripts (`latb', `latp') and
implements support for the no-base character ranges introduced in
the previous commit.
* src/autofit/aftypes.h (AF_ScriptClassRec): Add
`script_uni_nobase_ranges' field.
(AF_DEFINE_SCRIPT_CLASS): Updated.
* src/autofit/afscript.h, src/autofit/afstyles.h: Add `latb' and
`latp' fallback scripts.
* src/autofit/afblue.dat: Add blue zones for Latin subscript and
superscript fallback scripts.
* src/autofit/afblue.c, src/autofit/afblue.h: Regenerated.
* src/autofit/afglobal.h (AF_NOBASE): New style flag for no-base
characters.
(AF_STYLE_MASK): Updated.
* src/autofit/afglobal.c (SCRIPT): Updated.
(af_face_globals_compute_style_coverage): Handle new style flag.
* src/autofit/aflatin.c (af_latin_hints_apply): Handle new style
flag.
* src/autofit/afranges.h (SCRIPT): Use it to export no-base ranges.
Lower the flatness threshold from upem/8 to upem/14, making the
auto-hinter accept shorter elements.
Synchronize flat/round stem selection algorithm with blue zone code.
* src/autofit/aflatin.c (FLAT_THRESHOLD): New macro.
(af_latin_metrics_init_blues): Use it.
(af_latin_hints_compute_segments): Collect information on maximum
and minimum coordinates of `on' points; use this to add a constraint
for the flat/round decision similar to
`af_latin_metrics_init_blues'.
This code replaces the debugging hook from the previous commit with
a better, more generic solution.
* include/ftautoh.h: Document it.
* src/autofit/afmodule.h (AF_ModuleRec)
[AF_CONFIG_OPTION_USE_WARPER]: Add `warping' field.
* src/autofit/afmodule.c (_af_debug_disable_warper): Remove.
(af_property_set, af_property_get, af_autofitter_init)
[AF_CONFIG_OPTION_USE_WARPER]: Handle `warping' option.
* src/autofit/afhints.h (AF_HINTS_DO_WARP): Remove use of the no
longer existing `_af_debug_disable_warper'.
* src/autofit/afcjk.c (af_cjk_hints_init), src/autofit/aflatin.c
(af_latin_hints_init), src/autofit/aflatin2.c (af_latin2_hints_init)
[AF_CONFIG_OPTION_USE_WARPER]: Add `AF_SCALER_FLAG_NO_WARPER' to the
scaler flags if warping is off.
* src/autofit/aftypes.h: Updated.
* src/autofit/afmodule.c (_af_debug_disable_warper)
[FT_DEBUG_AUTOFIT]: New global variable.
* src/autofit/aftypes.h: Updated.
(AF_SCALER_FLAG_NO_WARPER): New macro (not actively used yet).
* src/autofit/afhints.h (AF_HINTS_DO_WARP): New macro.
* src/autofi/aflatin.c (af_latin_hints_apply)
[AF_CONFIG_OPTION_USE_WARPER]: Use `AF_HINTS_DO_WARP' to control use
of warper.
* src/autofit/afcjk.c (af_cjk_hints_init, af_cjk_hints_apply)
[AF_CONFIG_OPTION_USE_WARPER]: Synchronize with `aflatin.c'.
* src/autofit/aflatin2.c (af_latin2_hints_apply)
[AF_CONFIG_OPTION_USE_WARPER]: Synchronize with `aflatin.c'.
This harmonizes with other code in FreeType (and reduces the number
of necessary casts to avoid compiler warnings).
* src/autofit/afblue.hin: Make flag macros unsigned.
* src/autofit/afblue.h: Regenerated.
* src/autofit/afcjk.h: Replace flag enumeration with macros.
* src/autofit/afcjk.c: Updated.
* src/autofit/afhints.h (AF_Flags, AF_Edge_Flags): Replace with
macros.
* src/autofit/afhints.c: Updated.
* src/autofit/aflatin.h: Replace flag enumerations with macros.
* src/autofit/aflatin.c, src/autofit/aflatin2.c: Updated.
* src/autofit/aftypes.h (AF_ScalerFlags): Replace with macros.
Werner Lemberg