/****************************************************************************
*
* afshaper.c
*
* HarfBuzz interface for accessing OpenType features (body).
*
* Copyright (C) 2013-2023 by
* David Turner, Robert Wilhelm, and Werner Lemberg.
*
* This file is part of the FreeType project, and may only be used,
* modified, and distributed under the terms of the FreeType project
* license, LICENSE.TXT. By continuing to use, modify, or distribute
* this file you indicate that you have read the license and
* understand and accept it fully.
*
*/
#include <freetype/freetype.h>
#include <freetype/ftadvanc.h>
#include "afglobal.h"
#include "aftypes.h"
#include "afshaper.h"
#ifdef FT_CONFIG_OPTION_USE_HARFBUZZ
/**************************************************************************
*
* The macro FT_COMPONENT is used in trace mode. It is an implicit
* parameter of the FT_TRACE() and FT_ERROR() macros, used to print/log
* messages during execution.
*/
#undef FT_COMPONENT
#define FT_COMPONENT afshaper
/*
* We use `sets' (in the HarfBuzz sense, which comes quite near to the
* usual mathematical meaning) to manage both lookups and glyph indices.
*
* 1. For each coverage, collect lookup IDs in a set. Note that an
* auto-hinter `coverage' is represented by one `feature', and a
* feature consists of an arbitrary number of (font specific) `lookup's
* that actually do the mapping job. Please check the OpenType
* specification for more details on features and lookups.
*
* 2. Create glyph ID sets from the corresponding lookup sets.
*
* 3. The glyph set corresponding to AF_COVERAGE_DEFAULT is computed
* with all lookups specific to the OpenType script activated. It
* relies on the order of AF_DEFINE_STYLE_CLASS entries so that
* special coverages (like `oldstyle figures') don't get overwritten.
*
*/
/* load coverage tags */
#undef COVERAGE
#define COVERAGE( name, NAME, description, \
tag1, tag2, tag3, tag4 ) \
static const hb_tag_t name ## _coverage[] = \
{ \
HB_TAG( tag1, tag2, tag3, tag4 ), \
HB_TAG_NONE \
};
#include "afcover.h"
/* define mapping between coverage tags and AF_Coverage */
#undef COVERAGE
#define COVERAGE( name, NAME, description, \
tag1, tag2, tag3, tag4 ) \
name ## _coverage,
static const hb_tag_t* coverages[] =
{
#include "afcover.h"
NULL /* AF_COVERAGE_DEFAULT */
};
/* load HarfBuzz script tags */
#undef SCRIPT
#define SCRIPT( s, S, d, h, H, ss ) h,
static const hb_script_t scripts[] =
{
#include "afscript.h"
};
FT_Error
af_shaper_get_coverage( AF_FaceGlobals globals,
AF_StyleClass style_class,
FT_UShort* gstyles,
FT_Bool default_script )
{
hb_face_t* face;
hb_set_t* gsub_lookups = NULL; /* GSUB lookups for a given script */
hb_set_t* gsub_glyphs = NULL; /* glyphs covered by GSUB lookups */
hb_set_t* gpos_lookups = NULL; /* GPOS lookups for a given script */
hb_set_t* gpos_glyphs = NULL; /* glyphs covered by GPOS lookups */
hb_script_t script;
const hb_tag_t* coverage_tags;
hb_tag_t script_tags[] = { HB_TAG_NONE,
HB_TAG_NONE,
HB_TAG_NONE,
HB_TAG_NONE };
hb_codepoint_t idx;
#ifdef FT_DEBUG_LEVEL_TRACE
int count;
#endif
if ( !globals || !style_class || !gstyles )
return FT_THROW( Invalid_Argument );
face = hb_font_get_face( globals->hb_font );
coverage_tags = coverages[style_class->coverage];
script = scripts[style_class->script];
/* Convert a HarfBuzz script tag into the corresponding OpenType */
/* tag or tags -- some Indic scripts like Devanagari have an old */
/* and a new set of features. */
{
unsigned int tags_count = 3;
hb_tag_t tags[3];
hb_ot_tags_from_script_and_language( script,
HB_LANGUAGE_INVALID,
&tags_count,
tags,
NULL,
NULL );
script_tags[0] = tags_count > 0 ? tags[0] : HB_TAG_NONE;
script_tags[1] = tags_count > 1 ? tags[1] : HB_TAG_NONE;
script_tags[2] = tags_count > 2 ? tags[2] : HB_TAG_NONE;
}
/* If the second tag is HB_OT_TAG_DEFAULT_SCRIPT, change that to */
/* HB_TAG_NONE except for the default script. */
if ( default_script )
{
if ( script_tags[0] == HB_TAG_NONE )
script_tags[0] = HB_OT_TAG_DEFAULT_SCRIPT;
else
{
if ( script_tags[1] == HB_TAG_NONE )
script_tags[1] = HB_OT_TAG_DEFAULT_SCRIPT;
else if ( script_tags[1] != HB_OT_TAG_DEFAULT_SCRIPT )
script_tags[2] = HB_OT_TAG_DEFAULT_SCRIPT;
}
}
else
{
/* we use non-standard tags like `khms' for special purposes; */
/* HarfBuzz maps them to `DFLT', which we don't want to handle here */
if ( script_tags[0] == HB_OT_TAG_DEFAULT_SCRIPT )
goto Exit;
}
gsub_lookups = hb_set_create();
hb_ot_layout_collect_lookups( face,
HB_OT_TAG_GSUB,
script_tags,
NULL,
coverage_tags,
gsub_lookups );
if ( hb_set_is_empty( gsub_lookups ) )
goto Exit; /* nothing to do */
FT_TRACE4(( "GSUB lookups (style `%s'):\n",
af_style_names[style_class->style] ));
FT_TRACE4(( " " ));
#ifdef FT_DEBUG_LEVEL_TRACE
count = 0;
#endif
gsub_glyphs = hb_set_create();
for ( idx = HB_SET_VALUE_INVALID; hb_set_next( gsub_lookups, &idx ); )
{
#ifdef FT_DEBUG_LEVEL_TRACE
FT_TRACE4(( " %d", idx ));
count++;
#endif
/* get output coverage of GSUB feature */
hb_ot_layout_lookup_collect_glyphs( face,
HB_OT_TAG_GSUB,
idx,
NULL,
NULL,
NULL,
gsub_glyphs );
}
#ifdef FT_DEBUG_LEVEL_TRACE
if ( !count )
FT_TRACE4(( " (none)" ));
FT_TRACE4(( "\n" ));
FT_TRACE4(( "\n" ));
#endif
FT_TRACE4(( "GPOS lookups (style `%s'):\n",
af_style_names[style_class->style] ));
FT_TRACE4(( " " ));
gpos_lookups = hb_set_create();
hb_ot_layout_collect_lookups( face,
HB_OT_TAG_GPOS,
script_tags,
NULL,
coverage_tags,
gpos_lookups );
#ifdef FT_DEBUG_LEVEL_TRACE
count = 0;
#endif
gpos_glyphs = hb_set_create();
for ( idx = HB_SET_VALUE_INVALID; hb_set_next( gpos_lookups, &idx ); )
{
#ifdef FT_DEBUG_LEVEL_TRACE
FT_TRACE4(( " %d", idx ));
count++;
#endif
/* get input coverage of GPOS feature */
hb_ot_layout_lookup_collect_glyphs( face,
HB_OT_TAG_GPOS,
idx,
NULL,
gpos_glyphs,
NULL,
NULL );
}
#ifdef FT_DEBUG_LEVEL_TRACE
if ( !count )
FT_TRACE4(( " (none)" ));
FT_TRACE4(( "\n" ));
FT_TRACE4(( "\n" ));
#endif
/*
* We now check whether we can construct blue zones, using glyphs
* covered by the feature only. In case there is not a single zone
* (this is, not a single character is covered), we skip this coverage.
*
*/
if ( style_class->coverage != AF_COVERAGE_DEFAULT )
{
AF_Blue_Stringset bss = style_class->blue_stringset;
const AF_Blue_StringRec* bs = &af_blue_stringsets[bss];
FT_Bool found = 0;
for ( ; bs->string != AF_BLUE_STRING_MAX; bs++ )
{
const char* p = &af_blue_strings[bs->string];
while ( *p )
{
hb_codepoint_t ch;
GET_UTF8_CHAR( ch, p );
for ( idx = HB_SET_VALUE_INVALID; hb_set_next( gsub_lookups,
&idx ); )
{
hb_codepoint_t gidx = FT_Get_Char_Index( globals->face, ch );
if ( hb_ot_layout_lookup_would_substitute( face, idx,
&gidx, 1, 1 ) )
{
found = 1;
break;
}
}
}
}
if ( !found )
{
FT_TRACE4(( " no blue characters found; style skipped\n" ));
goto Exit;
}
}
/*
* Various OpenType features might use the same glyphs at different
* vertical positions; for example, superscript and subscript glyphs
* could be the same. However, the auto-hinter is completely
* agnostic of OpenType features after the feature analysis has been
* completed: The engine then simply receives a glyph index and returns a
* hinted and usually rendered glyph.
*
* Consider the superscript feature of font `pala.ttf': Some of the
* glyphs are `real', this is, they have a zero vertical offset, but
* most of them are small caps glyphs shifted up to the superscript
* position (this is, the `sups' feature is present in both the GSUB and
* GPOS tables). The code for blue zones computation actually uses a
* feature's y offset so that the `real' glyphs get correct hints. But
* later on it is impossible to decide whether a glyph index belongs to,
* say, the small caps or superscript feature.
*
* For this reason, we don't assign a style to a glyph if the current
* feature covers the glyph in both the GSUB and the GPOS tables. This
* is quite a broad condition, assuming that
*
* (a) glyphs that get used in multiple features are present in a
* feature without vertical shift,
*
* and
*
* (b) a feature's GPOS data really moves the glyph vertically.
*
* Not fulfilling condition (a) makes a font larger; it would also
* reduce the number of glyphs that could be addressed directly without
* using OpenType features, so this assumption is rather strong.
*
* Condition (b) is much weaker, and there might be glyphs which get
* missed. However, the OpenType features we are going to handle are
* primarily located in GSUB, and HarfBuzz doesn't provide an API to
* directly get the necessary information from the GPOS table. A
* possible solution might be to directly parse the GPOS table to find
* out whether a glyph gets shifted vertically, but this is something I
* would like to avoid if not really necessary.
*
* Note that we don't follow this logic for the default coverage.
* Complex scripts like Devanagari have mandatory GPOS features to
* position many glyph elements, using mark-to-base or mark-to-ligature
* tables; the number of glyphs missed due to condition (b) would be far
* too large.
*
*/
if ( style_class->coverage != AF_COVERAGE_DEFAULT )
hb_set_subtract( gsub_glyphs, gpos_glyphs );
#ifdef FT_DEBUG_LEVEL_TRACE
FT_TRACE4(( " glyphs without GPOS data (`*' means already assigned)" ));
count = 0;
#endif
for ( idx = HB_SET_VALUE_INVALID; hb_set_next( gsub_glyphs, &idx ); )
{
#ifdef FT_DEBUG_LEVEL_TRACE
if ( !( count % 10 ) )
{
FT_TRACE4(( "\n" ));
FT_TRACE4(( " " ));
}
FT_TRACE4(( " %d", idx ));
count++;
#endif
/* glyph indices returned by `hb_ot_layout_lookup_collect_glyphs' */
/* can be arbitrary: some fonts use fake indices for processing */
/* internal to GSUB or GPOS, which is fully valid */
if ( idx >= (hb_codepoint_t)globals->glyph_count )
continue;
if ( gstyles[idx] == AF_STYLE_UNASSIGNED )
gstyles[idx] = (FT_UShort)style_class->style;
#ifdef FT_DEBUG_LEVEL_TRACE
else
FT_TRACE4(( "*" ));
#endif
}
#ifdef FT_DEBUG_LEVEL_TRACE
if ( !count )
{
FT_TRACE4(( "\n" ));
FT_TRACE4(( " (none)" ));
}
FT_TRACE4(( "\n" ));
FT_TRACE4(( "\n" ));
#endif
Exit:
hb_set_destroy( gsub_lookups );
hb_set_destroy( gsub_glyphs );
hb_set_destroy( gpos_lookups );
hb_set_destroy( gpos_glyphs );
return FT_Err_Ok;
}
/* construct HarfBuzz features */
#undef COVERAGE
#define COVERAGE( name, NAME, description, \
tag1, tag2, tag3, tag4 ) \
static const hb_feature_t name ## _feature[] = \
{ \
{ \
HB_TAG( tag1, tag2, tag3, tag4 ), \
1, 0, (unsigned int)-1 \
} \
};
#include "afcover.h"
/* define mapping between HarfBuzz features and AF_Coverage */
#undef COVERAGE
#define COVERAGE( name, NAME, description, \
tag1, tag2, tag3, tag4 ) \
name ## _feature,
static const hb_feature_t* features[] =
{
#include "afcover.h"
NULL /* AF_COVERAGE_DEFAULT */
};
void*
af_shaper_buf_create( FT_Face face )
{
FT_UNUSED( face );
return (void*)hb_buffer_create();
}
void
af_shaper_buf_destroy( FT_Face face,
void* buf )
{
FT_UNUSED( face );
hb_buffer_destroy( (hb_buffer_t*)buf );
}
const char*
af_shaper_get_cluster( const char* p,
AF_StyleMetrics metrics,
void* buf_,
unsigned int* count )
{
AF_StyleClass style_class;
const hb_feature_t* feature;
FT_Int upem;
const char* q;
int len;
hb_buffer_t* buf = (hb_buffer_t*)buf_;
hb_font_t* font;
hb_codepoint_t dummy;
upem = (FT_Int)metrics->globals->face->units_per_EM;
style_class = metrics->style_class;
feature = features[style_class->coverage];
font = metrics->globals->hb_font;
/* we shape at a size of units per EM; this means font units */
hb_font_set_scale( font, upem, upem );
while ( *p == ' ' )
p++;
/* count bytes up to next space (or end of buffer) */
q = p;
while ( !( *q == ' ' || *q == '\0' ) )
GET_UTF8_CHAR( dummy, q );
len = (int)( q - p );
/* feed character(s) to the HarfBuzz buffer */
hb_buffer_clear_contents( buf );
hb_buffer_add_utf8( buf, p, len, 0, len );
/* we let HarfBuzz guess the script and writing direction */
hb_buffer_guess_segment_properties( buf );
/* shape buffer, which means conversion from character codes to */
/* glyph indices, possibly applying a feature */
hb_shape( font, buf, feature, feature ? 1 : 0 );
if ( feature )
{
hb_buffer_t* hb_buf = metrics->globals->hb_buf;
unsigned int gcount;
hb_glyph_info_t* ginfo;
unsigned int hb_gcount;
hb_glyph_info_t* hb_ginfo;
/* we have to check whether applying a feature does actually change */
/* glyph indices; otherwise the affected glyph or glyphs aren't */
/* available at all in the feature */
hb_buffer_clear_contents( hb_buf );
hb_buffer_add_utf8( hb_buf, p, len, 0, len );
hb_buffer_guess_segment_properties( hb_buf );
hb_shape( font, hb_buf, NULL, 0 );
ginfo = hb_buffer_get_glyph_infos( buf, &gcount );
hb_ginfo = hb_buffer_get_glyph_infos( hb_buf, &hb_gcount );
if ( gcount == hb_gcount )
{
unsigned int i;
for (i = 0; i < gcount; i++ )
if ( ginfo[i].codepoint != hb_ginfo[i].codepoint )
break;
if ( i == gcount )
{
/* both buffers have identical glyph indices */
hb_buffer_clear_contents( buf );
}
}
}
*count = hb_buffer_get_length( buf );
#ifdef FT_DEBUG_LEVEL_TRACE
if ( feature && *count > 1 )
FT_TRACE1(( "af_shaper_get_cluster:"
" input character mapped to multiple glyphs\n" ));
#endif
return q;
}
FT_ULong
af_shaper_get_elem( AF_StyleMetrics metrics,
void* buf_,
unsigned int idx,
FT_Long* advance,
FT_Long* y_offset )
{
hb_buffer_t* buf = (hb_buffer_t*)buf_;
hb_glyph_info_t* ginfo;
hb_glyph_position_t* gpos;
unsigned int gcount;
FT_UNUSED( metrics );
ginfo = hb_buffer_get_glyph_infos( buf, &gcount );
gpos = hb_buffer_get_glyph_positions( buf, &gcount );
if ( idx >= gcount )
return 0;
if ( advance )
*advance = gpos[idx].x_advance;
if ( y_offset )
*y_offset = gpos[idx].y_offset;
return ginfo[idx].codepoint;
}
#else /* !FT_CONFIG_OPTION_USE_HARFBUZZ */
FT_Error
af_shaper_get_coverage( AF_FaceGlobals globals,
AF_StyleClass style_class,
FT_UShort* gstyles,
FT_Bool default_script )
{
FT_UNUSED( globals );
FT_UNUSED( style_class );
FT_UNUSED( gstyles );
FT_UNUSED( default_script );
return FT_Err_Ok;
}
void*
af_shaper_buf_create( FT_Face face )
{
FT_UNUSED( face );
return NULL;
}
void
af_shaper_buf_destroy( FT_Face face,
void* buf )
{
FT_UNUSED( face );
FT_UNUSED( buf );
}
const char*
af_shaper_get_cluster( const char* p,
AF_StyleMetrics metrics,
void* buf_,
unsigned int* count )
{
FT_Face face = metrics->globals->face;
FT_ULong ch, dummy = 0;
FT_ULong* buf = (FT_ULong*)buf_;
while ( *p == ' ' )
p++;
GET_UTF8_CHAR( ch, p );
/* since we don't have an engine to handle clusters, */
/* we scan the characters but return zero */
while ( !( *p == ' ' || *p == '\0' ) )
GET_UTF8_CHAR( dummy, p );
if ( dummy )
{
*buf = 0;
*count = 0;
}
else
{
*buf = FT_Get_Char_Index( face, ch );
*count = 1;
}
return p;
}
FT_ULong
af_shaper_get_elem( AF_StyleMetrics metrics,
void* buf_,
unsigned int idx,
FT_Long* advance,
FT_Long* y_offset )
{
FT_Face face = metrics->globals->face;
FT_ULong glyph_index = *(FT_ULong*)buf_;
FT_UNUSED( idx );
if ( advance )
FT_Get_Advance( face,
glyph_index,
FT_LOAD_NO_SCALE |
FT_LOAD_NO_HINTING |
FT_LOAD_IGNORE_TRANSFORM,
advance );
if ( y_offset )
*y_offset = 0;
return glyph_index;
}
#endif /* !FT_CONFIG_OPTION_USE_HARFBUZZ */
/* END */
