third_party/ots/src/metrics.cc

   1 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "metrics.h"
   6
   7 #include "head.h"
   8 #include "maxp.h"
   9
  10 // OpenType horizontal and vertical common header format
  11 // http://www.microsoft.com/typography/otspec/hhea.htm
  12 // http://www.microsoft.com/typography/otspec/vhea.htm
  13
  14 #define TABLE_NAME "metrics" // XXX: use individual table names
  15
  16 namespace ots {
  17
  18 bool ParseMetricsHeader(Font *font, Buffer *table,
  19                         OpenTypeMetricsHeader *header) {
  20   if (!table->ReadS16(&header->ascent) ||
  21       !table->ReadS16(&header->descent) ||
  22       !table->ReadS16(&header->linegap) ||
  23       !table->ReadU16(&header->adv_width_max) ||
  24       !table->ReadS16(&header->min_sb1) ||
  25       !table->ReadS16(&header->min_sb2) ||
  26       !table->ReadS16(&header->max_extent) ||
  27       !table->ReadS16(&header->caret_slope_rise) ||
  28       !table->ReadS16(&header->caret_slope_run) ||
  29       !table->ReadS16(&header->caret_offset)) {
  30     return OTS_FAILURE_MSG("Failed to read metrics header");
  31   }
  32
  33   if (header->ascent < 0) {
  34     OTS_WARNING("bad ascent: %d", header->ascent);
  35     header->ascent = 0;
  36   }
  37   if (header->linegap < 0) {
  38     OTS_WARNING("bad linegap: %d", header->linegap);
  39     header->linegap = 0;
  40   }
  41
  42   if (!font->head) {
  43     return OTS_FAILURE_MSG("Missing head font table");
  44   }
  45
  46   // if the font is non-slanted, caret_offset should be zero.
  47   if (!(font->head->mac_style & 2) &&
  48       (header->caret_offset != 0)) {
  49     OTS_WARNING("bad caret offset: %d", header->caret_offset);
  50     header->caret_offset = 0;
  51   }
  52
  53   // skip the reserved bytes
  54   if (!table->Skip(8)) {
  55     return OTS_FAILURE_MSG("Failed to skip reserverd bytes");
  56   }
  57
  58   int16_t data_format;
  59   if (!table->ReadS16(&data_format)) {
  60     return OTS_FAILURE_MSG("Failed to read data format");
  61   }
  62   if (data_format) {
  63     return OTS_FAILURE_MSG("Bad data format %d", data_format);
  64   }
  65
  66   if (!table->ReadU16(&header->num_metrics)) {
  67     return OTS_FAILURE_MSG("Failed to read number of metrics");
  68   }
  69
  70   if (!font->maxp) {
  71     return OTS_FAILURE_MSG("Missing maxp font table");
  72   }
  73
  74   if (header->num_metrics > font->maxp->num_glyphs) {
  75     return OTS_FAILURE_MSG("Bad number of metrics %d", header->num_metrics);
  76   }
  77
  78   return true;
  79 }
  80
  81 bool SerialiseMetricsHeader(const ots::Font *font,
  82                             OTSStream *out,
  83                             const OpenTypeMetricsHeader *header) {
  84   if (!out->WriteU32(header->version) ||
  85       !out->WriteS16(header->ascent) ||
  86       !out->WriteS16(header->descent) ||
  87       !out->WriteS16(header->linegap) ||
  88       !out->WriteU16(header->adv_width_max) ||
  89       !out->WriteS16(header->min_sb1) ||
  90       !out->WriteS16(header->min_sb2) ||
  91       !out->WriteS16(header->max_extent) ||
  92       !out->WriteS16(header->caret_slope_rise) ||
  93       !out->WriteS16(header->caret_slope_run) ||
  94       !out->WriteS16(header->caret_offset) ||
  95       !out->WriteR64(0) ||  // reserved
  96       !out->WriteS16(0) ||  // metric data format
  97       !out->WriteU16(header->num_metrics)) {
  98     return OTS_FAILURE_MSG("Failed to write metrics");
  99   }
 100
 101   return true;
 102 }
 103
 104 bool ParseMetricsTable(const ots::Font *font,
 105                        Buffer *table,
 106                        const uint16_t num_glyphs,
 107                        const OpenTypeMetricsHeader *header,
 108                        OpenTypeMetricsTable *metrics) {
 109   // |num_metrics| is a uint16_t, so it's bounded < 65536. This limits that
 110   // amount of memory that we'll allocate for this to a sane amount.
 111   const unsigned num_metrics = header->num_metrics;
 112
 113   if (num_metrics > num_glyphs) {
 114     return OTS_FAILURE_MSG("Bad number of metrics %d", num_metrics);
 115   }
 116   if (!num_metrics) {
 117     return OTS_FAILURE_MSG("No metrics!");
 118   }
 119   const unsigned num_sbs = num_glyphs - num_metrics;
 120
 121   metrics->entries.reserve(num_metrics);
 122   for (unsigned i = 0; i < num_metrics; ++i) {
 123     uint16_t adv = 0;
 124     int16_t sb = 0;
 125     if (!table->ReadU16(&adv) || !table->ReadS16(&sb)) {
 126       return OTS_FAILURE_MSG("Failed to read metric %d", i);
 127     }
 128
 129     // This check is bogus, see https://github.com/khaledhosny/ots/issues/36
 130 #if 0
 131     // Since so many fonts don't have proper value on |adv| and |sb|,
 132     // we should not call ots_failure() here. For example, about 20% of fonts
 133     // in http://www.princexml.com/fonts/ (200+ fonts) fails these tests.
 134     if (adv > header->adv_width_max) {
 135       OTS_WARNING("bad adv: %u > %u", adv, header->adv_width_max);
 136       adv = header->adv_width_max;
 137     }
 138
 139     if (sb < header->min_sb1) {
 140       OTS_WARNING("bad sb: %d < %d", sb, header->min_sb1);
 141       sb = header->min_sb1;
 142     }
 143 #endif
 144
 145     metrics->entries.push_back(std::make_pair(adv, sb));
 146   }
 147
 148   metrics->sbs.reserve(num_sbs);
 149   for (unsigned i = 0; i < num_sbs; ++i) {
 150     int16_t sb;
 151     if (!table->ReadS16(&sb)) {
 152       // Some Japanese fonts (e.g., mona.ttf) fail this test.
 153       return OTS_FAILURE_MSG("Failed to read side bearing %d", i + num_metrics);
 154     }
 155
 156     // This check is bogus, see https://github.com/khaledhosny/ots/issues/36
 157 #if 0
 158     if (sb < header->min_sb1) {
 159       // The same as above. Three fonts in http://www.fontsquirrel.com/fontface
 160       // (e.g., Notice2Std.otf) have weird lsb values.
 161       OTS_WARNING("bad lsb: %d < %d", sb, header->min_sb1);
 162       sb = header->min_sb1;
 163     }
 164 #endif
 165
 166     metrics->sbs.push_back(sb);
 167   }
 168
 169   return true;
 170 }
 171
 172 bool SerialiseMetricsTable(const ots::Font *font,
 173                            OTSStream *out,
 174                            const OpenTypeMetricsTable *metrics) {
 175   for (unsigned i = 0; i < metrics->entries.size(); ++i) {
 176     if (!out->WriteU16(metrics->entries[i].first) ||
 177         !out->WriteS16(metrics->entries[i].second)) {
 178       return OTS_FAILURE_MSG("Failed to write metric %d", i);
 179     }
 180   }
 181
 182   for (unsigned i = 0; i < metrics->sbs.size(); ++i) {
 183     if (!out->WriteS16(metrics->sbs[i])) {
 184       return OTS_FAILURE_MSG("Failed to write side bearing %ld", i + metrics->entries.size());
 185     }
 186   }
 187
 188   return true;
 189 }
 190
 191 }  // namespace ots
 192
 193 #undef TABLE_NAME