1 /***************************************************************************/
5 /* Load the basic TrueType kerning table. This doesn't handle */
6 /* kerning data within the GPOS table at the moment. */
8 /* Copyright 1996-2001, 2002, 2003, 2004, 2005, 2006, 2007, 2009, 2010 by */
9 /* David Turner, Robert Wilhelm, and Werner Lemberg. */
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. */
17 /***************************************************************************/
21 #include FT_INTERNAL_DEBUG_H
22 #include FT_INTERNAL_STREAM_H
23 #include FT_TRUETYPE_TAGS_H
29 /*************************************************************************/
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. */
36 #define FT_COMPONENT trace_ttkern
40 #define TT_KERN_INDEX( g1, g2 ) ( ( (FT_ULong)(g1) << 16 ) | (g2) )
43 FT_LOCAL_DEF( FT_Error )
44 tt_face_load_kern( TT_Face face,
51 FT_UInt nn, num_tables;
52 FT_UInt32 avail = 0, ordered = 0;
55 /* the kern table is optional; exit silently if it is missing */
56 error = face->goto_table( face, TTAG_kern, stream, &table_size );
60 if ( table_size < 4 ) /* the case of a malformed table */
62 FT_ERROR(( "tt_face_load_kern:"
63 " kerning table is too small - ignored\n" ));
64 error = SFNT_Err_Table_Missing;
68 if ( FT_FRAME_EXTRACT( table_size, face->kern_table ) )
70 FT_ERROR(( "tt_face_load_kern:"
71 " could not extract kerning table\n" ));
75 face->kern_table_size = table_size;
78 p_limit = p + table_size;
80 p += 2; /* skip version */
81 num_tables = FT_NEXT_USHORT( p );
83 if ( num_tables > 32 ) /* we only support up to 32 sub-tables */
86 for ( nn = 0; nn < num_tables; nn++ )
88 FT_UInt num_pairs, length, coverage;
90 FT_UInt32 mask = (FT_UInt32)1UL << nn;
93 if ( p + 6 > p_limit )
98 p += 2; /* skip version */
99 length = FT_NEXT_USHORT( p );
100 coverage = FT_NEXT_USHORT( p );
107 if ( p_next > p_limit ) /* handle broken table */
110 /* only use horizontal kerning tables */
111 if ( ( coverage & ~8 ) != 0x0001 ||
115 num_pairs = FT_NEXT_USHORT( p );
118 if ( ( p_next - p ) < 6 * (int)num_pairs ) /* handle broken count */
119 num_pairs = (FT_UInt)( ( p_next - p ) / 6 );
124 * Now check whether the pairs in this table are ordered.
125 * We then can use binary search.
133 old_pair = FT_NEXT_ULONG( p );
136 for ( count = num_pairs - 1; count > 0; count-- )
141 cur_pair = FT_NEXT_ULONG( p );
142 if ( cur_pair <= old_pair )
157 face->num_kern_tables = nn;
158 face->kern_avail_bits = avail;
159 face->kern_order_bits = ordered;
167 tt_face_done_kern( TT_Face face )
169 FT_Stream stream = face->root.stream;
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;
180 FT_LOCAL_DEF( FT_Int )
181 tt_face_get_kerning( TT_Face face,
183 FT_UInt right_glyph )
186 FT_UInt count, mask = 1;
187 FT_Byte* p = face->kern_table;
188 FT_Byte* p_limit = p + face->kern_table_size;
194 for ( count = face->num_kern_tables;
195 count > 0 && p + 6 <= p_limit;
196 count--, mask <<= 1 )
199 FT_Byte* next = base;
200 FT_UInt version = FT_NEXT_USHORT( p );
201 FT_UInt length = FT_NEXT_USHORT( p );
202 FT_UInt coverage = FT_NEXT_USHORT( p );
206 FT_UNUSED( version );
209 next = base + length;
211 if ( next > p_limit ) /* handle broken table */
214 if ( ( face->kern_avail_bits & mask ) == 0 )
220 num_pairs = FT_NEXT_USHORT( p );
223 if ( ( next - p ) < 6 * (int)num_pairs ) /* handle broken count */
224 num_pairs = (FT_UInt)( ( next - p ) / 6 );
226 switch ( coverage >> 8 )
230 FT_ULong key0 = TT_KERN_INDEX( left_glyph, right_glyph );
233 if ( face->kern_order_bits & mask ) /* binary search */
236 FT_UInt max = num_pairs;
241 FT_UInt mid = ( min + max ) >> 1;
242 FT_Byte* q = p + 6 * mid;
246 key = FT_NEXT_ULONG( q );
250 value = FT_PEEK_SHORT( q );
259 else /* linear search */
264 for ( count2 = num_pairs; count2 > 0; count2-- )
266 FT_ULong key = FT_NEXT_ULONG( p );
271 value = FT_PEEK_SHORT( p );
281 * We don't support format 2 because we haven't seen a single font
282 * using it in real life...
292 if ( coverage & 8 ) /* override or add */