| /***************************************************************************/ |
| /* */ |
| /* ttkern.c */ |
| /* */ |
| /* Load the basic TrueType kerning table. This doesn't handle */ |
| /* kerning data within the GPOS table at the moment. */ |
| /* */ |
| /* Copyright 1996-2015 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 <ft2build.h> |
| #include FT_INTERNAL_DEBUG_H |
| #include FT_INTERNAL_STREAM_H |
| #include FT_TRUETYPE_TAGS_H |
| #include "ttkern.h" |
| |
| #include "sferrors.h" |
| |
| |
| /*************************************************************************/ |
| /* */ |
| /* 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 trace_ttkern |
| |
| |
| #undef TT_KERN_INDEX |
| #define TT_KERN_INDEX( g1, g2 ) ( ( (FT_ULong)(g1) << 16 ) | (g2) ) |
| |
| |
| FT_LOCAL_DEF( FT_Error ) |
| tt_face_load_kern( TT_Face face, |
| FT_Stream stream ) |
| { |
| FT_Error error; |
| FT_ULong table_size; |
| FT_Byte* p; |
| FT_Byte* p_limit; |
| FT_UInt nn, num_tables; |
| FT_UInt32 avail = 0, ordered = 0; |
| |
| |
| /* the kern table is optional; exit silently if it is missing */ |
| error = face->goto_table( face, TTAG_kern, stream, &table_size ); |
| if ( error ) |
| goto Exit; |
| |
| if ( table_size < 4 ) /* the case of a malformed table */ |
| { |
| FT_ERROR(( "tt_face_load_kern:" |
| " kerning table is too small - ignored\n" )); |
| error = FT_THROW( Table_Missing ); |
| goto Exit; |
| } |
| |
| if ( FT_FRAME_EXTRACT( table_size, face->kern_table ) ) |
| { |
| FT_ERROR(( "tt_face_load_kern:" |
| " could not extract kerning table\n" )); |
| goto Exit; |
| } |
| |
| face->kern_table_size = table_size; |
| |
| p = face->kern_table; |
| p_limit = p + table_size; |
| |
| p += 2; /* skip version */ |
| num_tables = FT_NEXT_USHORT( p ); |
| |
| if ( num_tables > 32 ) /* we only support up to 32 sub-tables */ |
| num_tables = 32; |
| |
| for ( nn = 0; nn < num_tables; nn++ ) |
| { |
| FT_UInt num_pairs, length, coverage; |
| FT_Byte* p_next; |
| FT_UInt32 mask = (FT_UInt32)1UL << nn; |
| |
| |
| if ( p + 6 > p_limit ) |
| break; |
| |
| p_next = p; |
| |
| p += 2; /* skip version */ |
| length = FT_NEXT_USHORT( p ); |
| coverage = FT_NEXT_USHORT( p ); |
| |
| if ( length <= 6 + 8 ) |
| break; |
| |
| p_next += length; |
| |
| if ( p_next > p_limit ) /* handle broken table */ |
| p_next = p_limit; |
| |
| /* only use horizontal kerning tables */ |
| if ( ( coverage & ~8U ) != 0x0001 || |
| p + 8 > p_limit ) |
| goto NextTable; |
| |
| num_pairs = FT_NEXT_USHORT( p ); |
| p += 6; |
| |
| if ( ( p_next - p ) < 6 * (int)num_pairs ) /* handle broken count */ |
| num_pairs = (FT_UInt)( ( p_next - p ) / 6 ); |
| |
| avail |= mask; |
| |
| /* |
| * Now check whether the pairs in this table are ordered. |
| * We then can use binary search. |
| */ |
| if ( num_pairs > 0 ) |
| { |
| FT_ULong count; |
| FT_ULong old_pair; |
| |
| |
| old_pair = FT_NEXT_ULONG( p ); |
| p += 2; |
| |
| for ( count = num_pairs - 1; count > 0; count-- ) |
| { |
| FT_UInt32 cur_pair; |
| |
| |
| cur_pair = FT_NEXT_ULONG( p ); |
| if ( cur_pair <= old_pair ) |
| break; |
| |
| p += 2; |
| old_pair = cur_pair; |
| } |
| |
| if ( count == 0 ) |
| ordered |= mask; |
| } |
| |
| NextTable: |
| p = p_next; |
| } |
| |
| face->num_kern_tables = nn; |
| face->kern_avail_bits = avail; |
| face->kern_order_bits = ordered; |
| |
| Exit: |
| return error; |
| } |
| |
| |
| FT_LOCAL_DEF( void ) |
| tt_face_done_kern( TT_Face face ) |
| { |
| FT_Stream stream = face->root.stream; |
| |
| |
| FT_FRAME_RELEASE( face->kern_table ); |
| face->kern_table_size = 0; |
| face->num_kern_tables = 0; |
| face->kern_avail_bits = 0; |
| face->kern_order_bits = 0; |
| } |
| |
| |
| FT_LOCAL_DEF( FT_Int ) |
| tt_face_get_kerning( TT_Face face, |
| FT_UInt left_glyph, |
| FT_UInt right_glyph ) |
| { |
| FT_Int result = 0; |
| FT_UInt count, mask; |
| FT_Byte* p = face->kern_table; |
| FT_Byte* p_limit = p + face->kern_table_size; |
| |
| |
| p += 4; |
| mask = 0x0001; |
| |
| for ( count = face->num_kern_tables; |
| count > 0 && p + 6 <= p_limit; |
| count--, mask <<= 1 ) |
| { |
| FT_Byte* base = p; |
| FT_Byte* next; |
| FT_UInt version = FT_NEXT_USHORT( p ); |
| FT_UInt length = FT_NEXT_USHORT( p ); |
| FT_UInt coverage = FT_NEXT_USHORT( p ); |
| FT_UInt num_pairs; |
| FT_Int value = 0; |
| |
| FT_UNUSED( version ); |
| |
| |
| next = base + length; |
| |
| if ( next > p_limit ) /* handle broken table */ |
| next = p_limit; |
| |
| if ( ( face->kern_avail_bits & mask ) == 0 ) |
| goto NextTable; |
| |
| if ( p + 8 > next ) |
| goto NextTable; |
| |
| num_pairs = FT_NEXT_USHORT( p ); |
| p += 6; |
| |
| if ( ( next - p ) < 6 * (int)num_pairs ) /* handle broken count */ |
| num_pairs = (FT_UInt)( ( next - p ) / 6 ); |
| |
| switch ( coverage >> 8 ) |
| { |
| case 0: |
| { |
| FT_ULong key0 = TT_KERN_INDEX( left_glyph, right_glyph ); |
| |
| |
| if ( face->kern_order_bits & mask ) /* binary search */ |
| { |
| FT_UInt min = 0; |
| FT_UInt max = num_pairs; |
| |
| |
| while ( min < max ) |
| { |
| FT_UInt mid = ( min + max ) >> 1; |
| FT_Byte* q = p + 6 * mid; |
| FT_ULong key; |
| |
| |
| key = FT_NEXT_ULONG( q ); |
| |
| if ( key == key0 ) |
| { |
| value = FT_PEEK_SHORT( q ); |
| goto Found; |
| } |
| if ( key < key0 ) |
| min = mid + 1; |
| else |
| max = mid; |
| } |
| } |
| else /* linear search */ |
| { |
| FT_UInt count2; |
| |
| |
| for ( count2 = num_pairs; count2 > 0; count2-- ) |
| { |
| FT_ULong key = FT_NEXT_ULONG( p ); |
| |
| |
| if ( key == key0 ) |
| { |
| value = FT_PEEK_SHORT( p ); |
| goto Found; |
| } |
| p += 2; |
| } |
| } |
| } |
| break; |
| |
| /* |
| * We don't support format 2 because we haven't seen a single font |
| * using it in real life... |
| */ |
| |
| default: |
| ; |
| } |
| |
| goto NextTable; |
| |
| Found: |
| if ( coverage & 8 ) /* override or add */ |
| result = value; |
| else |
| result += value; |
| |
| NextTable: |
| p = next; |
| } |
| |
| return result; |
| } |
| |
| #undef TT_KERN_INDEX |
| |
| /* END */ |