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[autofit] Speed up computation of af_reverse_character_map_new. (4/4)
With this commit, the start-up time for creating the reverse character map gets reduced from more than 300% to about 25% (as tested with `arial.ttf` version 7.00). * src/autofit/afadjust.c [FT_CONFIG_OPTION_USE_HARFBUZZ]: Include `afgsub.h`. (add_substitute): New auxiliary function to recursively add elements to the reverse cmap. (af_reverse_character_map_new): New code that replaces the old code removed in the previous commit.
This commit is contained in:
Werner Lemberg
parent
9e8b642b10
commit
6a982bde85
1 changed files with 247 additions and 22 deletions
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@ -18,6 +18,9 @@
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*/
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#include "afadjust.h"
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#ifdef FT_CONFIG_OPTION_USE_HARFBUZZ
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# include "afgsub.h"
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#endif
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#include <freetype/freetype.h>
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#include <freetype/internal/ftobjs.h>
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@ -1169,6 +1172,108 @@
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}
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#ifdef FT_CONFIG_OPTION_USE_HARFBUZZ
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static FT_Error
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add_substitute( FT_UInt glyph_idx,
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size_t value,
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FT_UInt32 codepoint,
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FT_Hash reverse_map,
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FT_Hash subst_map,
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FT_Memory memory )
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{
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FT_Error error;
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FT_UInt first_substitute = value & 0xFFFF;
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FT_UInt used = reverse_map->used;
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/*
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OpenType features like 'unic' map lowercase letter glyphs to uppercase
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forms (and vice versa), which could lead to the use of wrong entries
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in the adjustment database. For this reason we don't overwrite,
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prioritizing cmap entries.
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XXX Note, however, that this cannot cover all cases since there might
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be contradictory entries for glyphs not in the cmap. A possible
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solution might be to specially mark pairs of related lowercase and
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uppercase characters in the adjustment database that have diacritics
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on different vertical sides (for example, U+0122 'Ģ' and U+0123 'ģ').
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The auto-hinter could then perform a topological analysis to do the
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right thing.
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*/
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error = ft_hash_num_insert_no_overwrite( first_substitute, codepoint,
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reverse_map, memory );
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if ( error )
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return error;
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if ( reverse_map->used > used )
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{
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size_t* subst = ft_hash_num_lookup( first_substitute, subst_map );
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if ( subst )
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{
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error = add_substitute( first_substitute, *subst, codepoint,
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reverse_map, subst_map, memory );
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if ( error )
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return error;
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}
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}
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/* The remaining substitutes. */
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if ( value & 0xFFFF0000U )
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{
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FT_UInt num_substitutes = value >> 16;
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FT_UInt i;
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for ( i = 1; i <= num_substitutes; i++ )
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{
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size_t* substitute = ft_hash_num_lookup( glyph_idx + ( i << 16 ),
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subst_map );
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used = reverse_map->used;
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error = ft_hash_num_insert_no_overwrite( *substitute,
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codepoint,
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reverse_map,
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memory );
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if ( error )
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return error;
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if ( reverse_map->used > used )
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{
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size_t* subst = ft_hash_num_lookup( *substitute, subst_map );
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if ( subst )
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{
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error = add_substitute( *substitute, *subst, codepoint,
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reverse_map, subst_map, memory );
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if ( error )
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return error;
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}
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}
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}
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}
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return FT_Err_Ok;
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}
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#endif /* FT_CONFIG_OPTION_USE_HARFBUZZ */
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/* Construct a 'reverse cmap' (i.e., a mapping from glyph indices to */
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/* character codes) for all glyphs that an input code point could turn */
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/* into. */
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/* */
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/* If HarfBuzz support is not available, this is the direct inversion */
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/* of the cmap table, otherwise the mapping gets extended with data */
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/* from the 'GSUB' table. */
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FT_LOCAL_DEF( FT_Error )
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af_reverse_character_map_new( FT_Hash *map,
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AF_StyleMetrics metrics )
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@ -1184,19 +1289,6 @@
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FT_UInt32 codepoint;
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FT_Offset i;
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#ifdef FT_CONFIG_OPTION_USE_HARFBUZZ
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/* The next four variables are initialized to avoid compiler warnings. */
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hb_font_t *hb_font = NULL;
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hb_face_t *hb_face = NULL;
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hb_set_t *gsub_lookups = NULL;
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hb_script_t script;
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unsigned int script_count = 1;
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hb_tag_t script_tags[2] = { HB_TAG_NONE, HB_TAG_NONE };
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#endif
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FT_TRACE4(( "af_reverse_character_map_new:"
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" building reverse character map (style `%s')\n",
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@ -1219,9 +1311,69 @@
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if ( error )
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goto Exit;
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/* Initialize reverse cmap with data directly from the cmap table. */
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for ( i = 0; i < AF_ADJUSTMENT_DATABASE_LENGTH; i++ )
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{
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FT_Int cmap_glyph;
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/*
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We cannot restrict `codepoint` to character ranges; we have no
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control what data the script-specific portion of the GSUB table
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actually holds.
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An example is `arial.ttf` version 7.00; in this font, there are
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lookups for Cyrillic (lookup 43), Greek (lookup 44), and Latin
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(lookup 45) that map capital letter glyphs to small capital glyphs.
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It is tempting to expect that script-specific versions of the 'c2sc'
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feature only use script-specific lookups. However, this is not the
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case in this font: the feature uses all three lookups regardless of
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the script.
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The auto-hinter, while assigning glyphs to styles, uses the first
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coverage result it encounters for a particular glyph. For example,
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if the coverage for Cyrillic is tested before Latin (as is currently
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the case), glyphs without a cmap entry that are covered in 'c2sc'
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are treated as Cyrillic.
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If we now look at glyph 3498, which is a small-caps version of the
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Latin character 'A grave' (U+00C0, glyph 172), we can see that it is
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registered as belonging to a Cyrillic style due to the algorithm
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just described. As a result, checking only for characters from the
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Latin range would miss this glyph; we thus have to test all
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character codes in the database.
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*/
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codepoint = adjustment_database[i].codepoint;
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cmap_glyph = FT_Get_Char_Index( face, codepoint );
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if ( cmap_glyph == 0 )
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continue;
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error = ft_hash_num_insert( cmap_glyph, codepoint, *map, memory );
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if ( error )
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goto Exit;
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}
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#ifdef FT_CONFIG_OPTION_USE_HARFBUZZ
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{
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hb_font_t *hb_font;
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hb_face_t *hb_face;
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hb_set_t *gsub_lookups;
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hb_script_t script;
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unsigned int script_count = 1;
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hb_tag_t script_tags[2] = { HB_TAG_NONE, HB_TAG_NONE };
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FT_Hash subst_map = NULL;
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hb_codepoint_t idx;
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FT_UInt hash_idx;
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FT_Int glyph_idx;
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size_t value;
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/* No need to check whether HarfBuzz has allocation issues; */
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/* it continues to work in such cases and simply returns */
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/* 'empty' objects that do nothing. */
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@ -1245,8 +1397,7 @@
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#ifdef FT_DEBUG_LEVEL_TRACE
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{
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hb_codepoint_t idx;
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FT_Bool have_idx = FALSE;
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FT_Bool have_idx = FALSE;
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FT_TRACE4(( " GSUB lookups to check:\n" ));
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@ -1267,17 +1418,91 @@
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}
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#endif
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if ( FT_QNEW( subst_map ) )
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goto Exit_HarfBuzz;
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error = ft_hash_num_init( subst_map, memory );
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if ( error )
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goto Exit_HarfBuzz;
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idx = HB_SET_VALUE_INVALID;
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while ( hb( set_next )( gsub_lookups, &idx ) )
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{
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FT_UInt32 offset = globals->gsub_lookups_single_alternate[idx];
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/* Put all substitutions into a single hash table. Note that */
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/* the hash values usually contain more than a single character */
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/* code; this can happen if different 'SingleSubst' subtables */
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/* map a given glyph index to different substitutions, or if */
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/* 'AlternateSubst' subtable entries are present. */
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if ( offset )
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af_map_lookup( globals, subst_map, offset );
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}
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/*
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Now iterate over the collected substitution data in `subst_map`
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(using recursion to resolve one-to-many mappings) and insert the
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data into the reverse cmap.
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As an example, suppose we have the following cmap and substitution
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data:
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cmap: X -> a
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Y -> b
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Z -> c
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substitutions: a -> b
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b -> c, d
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d -> e
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The reverse map now becomes as follows.
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a -> X
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b -> Y
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c -> Z (via cmap, ignoring mapping from 'b')
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d -> Y (via 'b')
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e -> Y (via 'b' and 'd')
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*/
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hash_idx = 0;
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while ( ft_hash_num_iterator( &hash_idx,
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&glyph_idx,
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&value,
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subst_map ) )
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{
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size_t* val;
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/* Ignore keys that do not point to the first substitute. */
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if ( glyph_idx & 0xFFFF0000 )
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continue;
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/* Ignore glyph indices that are not related to accents. */
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val = ft_hash_num_lookup( glyph_idx, *map );
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if ( !val )
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continue;
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codepoint = *val;
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error = add_substitute( glyph_idx, value, codepoint,
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*map, subst_map, memory );
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if ( error )
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break;
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}
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Exit_HarfBuzz:
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hb( set_destroy )( gsub_lookups );
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ft_hash_num_free( subst_map, memory );
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FT_FREE( subst_map );
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if ( error )
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goto Exit;
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}
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#endif /* FT_CONFIG_OPTION_USE_HARFBUZZ */
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#ifdef FT_CONFIG_OPTION_USE_HARFBUZZ
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if ( hb( version_atleast )( 7, 2, 0 ) )
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{
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hb( set_destroy )( gsub_lookups );
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}
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#endif
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FT_TRACE4(( " reverse character map built successfully"
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" with %d entries\n", ( *map )->used ));
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