1/*
2 * @(#)KernTable.cpp	1.1 04/10/13
3 *
4 * (C) Copyright IBM Corp. 2004-2007 - All Rights Reserved
5 *
6 */
7
8#include "KernTable.h"
9#include "LEFontInstance.h"
10#include "LEGlyphStorage.h"
11
12#include "LESwaps.h"
13#include "OpenTypeUtilities.h"
14
15#include <stdio.h>
16
17#define DEBUG 0
18
19U_NAMESPACE_BEGIN
20
21struct PairInfo {
22  le_uint16 left;  // left glyph of kern pair
23  le_uint16 right; // right glyph of kern pair
24  le_int16  value; // fword, kern value in funits
25};
26#define KERN_PAIRINFO_SIZE 6
27
28#define SWAP_KEY(p) (((le_uint32) SWAPW((p)->left) << 16) | SWAPW((p)->right))
29
30struct Subtable_0 {
31  le_uint16 nPairs;
32  le_uint16 searchRange;
33  le_uint16 entrySelector;
34  le_uint16 rangeShift;
35};
36#define KERN_SUBTABLE_0_HEADER_SIZE 8
37
38// Kern table version 0 only
39struct SubtableHeader {
40  le_uint16 version;
41  le_uint16 length;
42  le_uint16 coverage;
43};
44#define KERN_SUBTABLE_HEADER_SIZE 6
45
46// Version 0 only, version 1 has different layout
47struct KernTableHeader {
48  le_uint16 version;
49  le_uint16 nTables;
50};
51#define KERN_TABLE_HEADER_SIZE 4
52
53#define COVERAGE_HORIZONTAL 0x1
54#define COVERAGE_MINIMUM 0x2
55#define COVERAGE_CROSS 0x4
56#define COVERAGE_OVERRIDE 0x8
57
58/*
59 * This implementation has support for only one subtable, so if the font has
60 * multiple subtables, only the first will be used.  If this turns out to
61 * be a problem in practice we should add it.
62 *
63 * This also supports only version 0 of the kern table header, only
64 * Apple supports the latter.
65 *
66 * This implementation isn't careful about the kern table flags, and
67 * might invoke kerning when it is not supposed to.  That too I'm
68 * leaving for a bug fix.
69 *
70 * TODO: support multiple subtables
71 * TODO: respect header flags
72 */
73KernTable::KernTable(const LEFontInstance* font, const void* tableData)
74  : pairs(0), font(font)
75{
76  const KernTableHeader* header = (const KernTableHeader*)tableData;
77  if (header == 0) {
78#if DEBUG
79    fprintf(stderr, "no kern data\n");
80#endif
81    return;
82  }
83
84#if DEBUG
85  // dump first 32 bytes of header
86  for (int i = 0; i < 64; ++i) {
87    fprintf(stderr, "%0.2x ", ((const char*)tableData)[i]&0xff);
88    if (((i+1)&0xf) == 0) {
89      fprintf(stderr, "\n");
90    } else if (((i+1)&0x7) == 0) {
91      fprintf(stderr, "  ");
92    }
93  }
94#endif
95
96  if (header->version == 0 && SWAPW(header->nTables) > 0) {
97    const SubtableHeader* subhead = (const SubtableHeader*)((char*)tableData + KERN_TABLE_HEADER_SIZE);
98
99    if (subhead->version == 0) {
100      coverage = SWAPW(subhead->coverage);
101
102      if (coverage & COVERAGE_HORIZONTAL) { // only handle horizontal kerning
103        const Subtable_0* table = (const Subtable_0*)((char*)subhead + KERN_SUBTABLE_HEADER_SIZE);
104
105        nPairs        = SWAPW(table->nPairs);
106
107#if 0   // some old fonts have bad values here...
108        searchRange   = SWAPW(table->searchRange);
109        entrySelector = SWAPW(table->entrySelector);
110        rangeShift    = SWAPW(table->rangeShift);
111#else
112        entrySelector = OpenTypeUtilities::highBit(nPairs);
113        searchRange   = (1 << entrySelector) * KERN_PAIRINFO_SIZE;
114        rangeShift    = (nPairs * KERN_PAIRINFO_SIZE) - searchRange;
115#endif
116
117        pairs         = (const PairInfo*)((char*)table + KERN_SUBTABLE_0_HEADER_SIZE);
118
119#if DEBUG
120        fprintf(stderr, "coverage: %0.4x nPairs: %d pairs 0x%x\n", coverage, nPairs, pairs);
121        fprintf(stderr, "  searchRange: %d entrySelector: %d rangeShift: %d\n", searchRange, entrySelector, rangeShift);
122
123        {
124          // dump part of the pair list
125          char ids[256];
126
127          for (int i = 256; --i >= 0;) {
128            LEGlyphID id = font->mapCharToGlyph(i);
129
130            if (id < 256) {
131              ids[id] = (char)i;
132            }
133          }
134
135          const PairInfo* p = pairs;
136
137          for (i = 0; i < nPairs; ++i, p = (const PairInfo*)((char*)p+KERN_PAIRINFO_SIZE)) {
138            le_uint16 left = p->left;
139            le_uint16 right = p->right;
140
141            if (left < 256 && right < 256) {
142              char c = ids[left];
143
144              if (c > 0x20 && c < 0x7f) {
145                fprintf(stderr, "%c/", c & 0xff);
146              } else {
147                printf(stderr, "%0.2x/", c & 0xff);
148              }
149
150              c = ids[right];
151              if (c > 0x20 && c < 0x7f) {
152                fprintf(stderr, "%c ", c & 0xff);
153              } else {
154                fprintf(stderr, "%0.2x ", c & 0xff);
155              }
156            }
157          }
158        }
159#endif
160      }
161    }
162  }
163}
164
165
166/*
167 * Process the glyph positions.  The positions array has two floats for each
168 * glyph, plus a trailing pair to mark the end of the last glyph.
169 */
170void KernTable::process(LEGlyphStorage& storage)
171{
172  if (pairs) {
173    LEErrorCode success = LE_NO_ERROR;
174
175    le_uint32 key = storage[0]; // no need to mask off high bits
176    float adjust = 0;
177
178    for (int i = 1, e = storage.getGlyphCount(); i < e; ++i) {
179      key = key << 16 | (storage[i] & 0xffff);
180
181      // argh, to do a binary search, we need to have the pair list in sorted order
182      // but it is not in sorted order on win32 platforms because of the endianness difference
183      // so either I have to swap the element each time I examine it, or I have to swap
184      // all the elements ahead of time and store them in the font
185
186      const PairInfo* p = pairs;
187      const PairInfo* tp = (const PairInfo*)((char*)p + rangeShift);
188
189      if (key > SWAP_KEY(tp)) {
190        p = tp;
191      }
192
193#if DEBUG
194      fprintf(stderr, "binary search for %0.8x\n", key);
195#endif
196
197      le_uint32 probe = searchRange;
198
199      while (probe > KERN_PAIRINFO_SIZE) {
200        probe >>= 1;
201        tp = (const PairInfo*)((char*)p + probe);
202
203        le_uint32 tkey = SWAP_KEY(tp);
204#if DEBUG
205        fprintf(stdout, "   %.3d (%0.8x)\n", ((char*)tp - (char*)pairs)/KERN_PAIRINFO_SIZE, tkey);
206#endif
207        if (tkey <= key) {
208          if (tkey == key) {
209            le_int16 value = SWAPW(tp->value);
210#if DEBUG
211            fprintf(stdout, "binary found kerning pair %x:%x at %d, value: 0x%x (%g)\n",
212              storage[i-1], storage[i], i, value & 0xffff, font->xUnitsToPoints(value));
213            fflush(stdout);
214#endif
215            adjust += font->xUnitsToPoints(value);
216            break;
217          }
218
219          p = tp;
220        }
221      }
222
223      storage.adjustPosition(i, adjust, 0, success);
224    }
225
226    storage.adjustPosition(storage.getGlyphCount(), adjust, 0, success);
227  }
228}
229
230U_NAMESPACE_END
231
232