1 /***************************************************************************/ 2 /* */ 3 /* ttkern.c */ 4 /* */ 5 /* Load the basic TrueType kerning table. This doesn't handle */ 6 /* kerning data within the GPOS table at the moment. */ 7 /* */ 8 /* Copyright 1996-2017 by */ 9 /* David Turner, Robert Wilhelm, and Werner Lemberg. */ 10 /* */ 11 /* This file is part of the FreeType project, and may only be used, */ 12 /* modified, and distributed under the terms of the FreeType project */ 13 /* license, LICENSE.TXT. By continuing to use, modify, or distribute */ 14 /* this file you indicate that you have read the license and */ 15 /* understand and accept it fully. */ 16 /* */ 17 /***************************************************************************/ 18 19 20 #include <ft2build.h> 21 #include FT_INTERNAL_DEBUG_H 22 #include FT_INTERNAL_STREAM_H 23 #include FT_TRUETYPE_TAGS_H 24 #include "ttkern.h" 25 26 #include "sferrors.h" 27 28 29 /*************************************************************************/ 30 /* */ 31 /* The macro FT_COMPONENT is used in trace mode. It is an implicit */ 32 /* parameter of the FT_TRACE() and FT_ERROR() macros, used to print/log */ 33 /* messages during execution. */ 34 /* */ 35 #undef FT_COMPONENT 36 #define FT_COMPONENT trace_ttkern 37 38 39 #undef TT_KERN_INDEX 40 #define TT_KERN_INDEX( g1, g2 ) ( ( (FT_ULong)(g1) << 16 ) | (g2) ) 41 42 43 FT_LOCAL_DEF( FT_Error ) 44 tt_face_load_kern( TT_Face face, 45 FT_Stream stream ) 46 { 47 FT_Error error; 48 FT_ULong table_size; 49 FT_Byte* p; 50 FT_Byte* p_limit; 51 FT_UInt nn, num_tables; 52 FT_UInt32 avail = 0, ordered = 0; 53 54 55 /* the kern table is optional; exit silently if it is missing */ 56 error = face->goto_table( face, TTAG_kern, stream, &table_size ); 57 if ( error ) 58 goto Exit; 59 60 if ( table_size < 4 ) /* the case of a malformed table */ 61 { 62 FT_ERROR(( "tt_face_load_kern:" 63 " kerning table is too small - ignored\n" )); 64 error = FT_THROW( Table_Missing ); 65 goto Exit; 66 } 67 68 if ( FT_FRAME_EXTRACT( table_size, face->kern_table ) ) 69 { 70 FT_ERROR(( "tt_face_load_kern:" 71 " could not extract kerning table\n" )); 72 goto Exit; 73 } 74 75 face->kern_table_size = table_size; 76 77 p = face->kern_table; 78 p_limit = p + table_size; 79 80 p += 2; /* skip version */ 81 num_tables = FT_NEXT_USHORT( p ); 82 83 if ( num_tables > 32 ) /* we only support up to 32 sub-tables */ 84 num_tables = 32; 85 86 for ( nn = 0; nn < num_tables; nn++ ) 87 { 88 FT_UInt num_pairs, length, coverage; 89 FT_Byte* p_next; 90 FT_UInt32 mask = (FT_UInt32)1UL << nn; 91 92 93 if ( p + 6 > p_limit ) 94 break; 95 96 p_next = p; 97 98 p += 2; /* skip version */ 99 length = FT_NEXT_USHORT( p ); 100 coverage = FT_NEXT_USHORT( p ); 101 102 if ( length <= 6 + 8 ) 103 break; 104 105 p_next += length; 106 107 if ( p_next > p_limit ) /* handle broken table */ 108 p_next = p_limit; 109 110 /* only use horizontal kerning tables */ 111 if ( ( coverage & ~8U ) != 0x0001 || 112 p + 8 > p_limit ) 113 goto NextTable; 114 115 num_pairs = FT_NEXT_USHORT( p ); 116 p += 6; 117 118 if ( ( p_next - p ) < 6 * (int)num_pairs ) /* handle broken count */ 119 num_pairs = (FT_UInt)( ( p_next - p ) / 6 ); 120 121 avail |= mask; 122 123 /* 124 * Now check whether the pairs in this table are ordered. 125 * We then can use binary search. 126 */ 127 if ( num_pairs > 0 ) 128 { 129 FT_ULong count; 130 FT_ULong old_pair; 131 132 133 old_pair = FT_NEXT_ULONG( p ); 134 p += 2; 135 136 for ( count = num_pairs - 1; count > 0; count-- ) 137 { 138 FT_UInt32 cur_pair; 139 140 141 cur_pair = FT_NEXT_ULONG( p ); 142 if ( cur_pair <= old_pair ) 143 break; 144 145 p += 2; 146 old_pair = cur_pair; 147 } 148 149 if ( count == 0 ) 150 ordered |= mask; 151 } 152 153 NextTable: 154 p = p_next; 155 } 156 157 face->num_kern_tables = nn; 158 face->kern_avail_bits = avail; 159 face->kern_order_bits = ordered; 160 161 Exit: 162 return error; 163 } 164 165 166 FT_LOCAL_DEF( void ) 167 tt_face_done_kern( TT_Face face ) 168 { 169 FT_Stream stream = face->root.stream; 170 171 172 FT_FRAME_RELEASE( face->kern_table ); 173 face->kern_table_size = 0; 174 face->num_kern_tables = 0; 175 face->kern_avail_bits = 0; 176 face->kern_order_bits = 0; 177 } 178 179 180 FT_LOCAL_DEF( FT_Int ) 181 tt_face_get_kerning( TT_Face face, 182 FT_UInt left_glyph, 183 FT_UInt right_glyph ) 184 { 185 FT_Int result = 0; 186 FT_UInt count, mask; 187 FT_Byte* p = face->kern_table; 188 FT_Byte* p_limit = p + face->kern_table_size; 189 190 191 p += 4; 192 mask = 0x0001; 193 194 for ( count = face->num_kern_tables; 195 count > 0 && p + 6 <= p_limit; 196 count--, mask <<= 1 ) 197 { 198 FT_Byte* base = p; 199 FT_Byte* next; 200 FT_UInt version = FT_NEXT_USHORT( p ); 201 FT_UInt length = FT_NEXT_USHORT( p ); 202 FT_UInt coverage = FT_NEXT_USHORT( p ); 203 FT_UInt num_pairs; 204 FT_Int value = 0; 205 206 FT_UNUSED( version ); 207 208 209 next = base + length; 210 211 if ( next > p_limit ) /* handle broken table */ 212 next = p_limit; 213 214 if ( ( face->kern_avail_bits & mask ) == 0 ) 215 goto NextTable; 216 217 if ( p + 8 > next ) 218 goto NextTable; 219 220 num_pairs = FT_NEXT_USHORT( p ); 221 p += 6; 222 223 if ( ( next - p ) < 6 * (int)num_pairs ) /* handle broken count */ 224 num_pairs = (FT_UInt)( ( next - p ) / 6 ); 225 226 switch ( coverage >> 8 ) 227 { 228 case 0: 229 { 230 FT_ULong key0 = TT_KERN_INDEX( left_glyph, right_glyph ); 231 232 233 if ( face->kern_order_bits & mask ) /* binary search */ 234 { 235 FT_UInt min = 0; 236 FT_UInt max = num_pairs; 237 238 239 while ( min < max ) 240 { 241 FT_UInt mid = ( min + max ) >> 1; 242 FT_Byte* q = p + 6 * mid; 243 FT_ULong key; 244 245 246 key = FT_NEXT_ULONG( q ); 247 248 if ( key == key0 ) 249 { 250 value = FT_PEEK_SHORT( q ); 251 goto Found; 252 } 253 if ( key < key0 ) 254 min = mid + 1; 255 else 256 max = mid; 257 } 258 } 259 else /* linear search */ 260 { 261 FT_UInt count2; 262 263 264 for ( count2 = num_pairs; count2 > 0; count2-- ) 265 { 266 FT_ULong key = FT_NEXT_ULONG( p ); 267 268 269 if ( key == key0 ) 270 { 271 value = FT_PEEK_SHORT( p ); 272 goto Found; 273 } 274 p += 2; 275 } 276 } 277 } 278 break; 279 280 /* 281 * We don't support format 2 because we haven't seen a single font 282 * using it in real life... 283 */ 284 285 default: 286 ; 287 } 288 289 goto NextTable; 290 291 Found: 292 if ( coverage & 8 ) /* override or add */ 293 result = value; 294 else 295 result += value; 296 297 NextTable: 298 p = next; 299 } 300 301 return result; 302 } 303 304 #undef TT_KERN_INDEX 305 306 /* END */ 307
