1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/gfx/ots/src/kern.cc Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,202 @@
1.4 +// Copyright (c) 2009 The Chromium Authors. All rights reserved.
1.5 +// Use of this source code is governed by a BSD-style license that can be
1.6 +// found in the LICENSE file.
1.7 +
1.8 +#include "kern.h"
1.9 +
1.10 +// kern - Kerning
1.11 +// http://www.microsoft.com/typography/otspec/kern.htm
1.12 +
1.13 +#define TABLE_NAME "kern"
1.14 +
1.15 +#define DROP_THIS_TABLE \
1.16 + do { \
1.17 + delete file->kern; \
1.18 + file->kern = 0; \
1.19 + OTS_FAILURE_MSG("Table discarded"); \
1.20 + } while (0)
1.21 +
1.22 +namespace ots {
1.23 +
1.24 +bool ots_kern_parse(OpenTypeFile *file, const uint8_t *data, size_t length) {
1.25 + Buffer table(data, length);
1.26 +
1.27 + OpenTypeKERN *kern = new OpenTypeKERN;
1.28 + file->kern = kern;
1.29 +
1.30 + uint16_t num_tables = 0;
1.31 + if (!table.ReadU16(&kern->version) ||
1.32 + !table.ReadU16(&num_tables)) {
1.33 + return OTS_FAILURE_MSG("Failed to read kern header");
1.34 + }
1.35 +
1.36 + if (kern->version > 0) {
1.37 + DROP_THIS_TABLE;
1.38 + return true;
1.39 + }
1.40 +
1.41 + if (num_tables == 0) {
1.42 + OTS_WARNING("num_tables is zero");
1.43 + DROP_THIS_TABLE;
1.44 + return true;
1.45 + }
1.46 +
1.47 + kern->subtables.reserve(num_tables);
1.48 + for (unsigned i = 0; i < num_tables; ++i) {
1.49 + OpenTypeKERNFormat0 subtable;
1.50 + uint16_t sub_length = 0;
1.51 +
1.52 + if (!table.ReadU16(&subtable.version) ||
1.53 + !table.ReadU16(&sub_length)) {
1.54 + return OTS_FAILURE_MSG("Failed to read kern subtable %d header", i);
1.55 + }
1.56 +
1.57 + if (subtable.version > 0) {
1.58 + OTS_WARNING("Bad subtable version: %d", subtable.version);
1.59 + continue;
1.60 + }
1.61 +
1.62 + const size_t current_offset = table.offset();
1.63 + if (current_offset - 4 + sub_length > length) {
1.64 + return OTS_FAILURE_MSG("Bad kern subtable %d offset %ld", i, current_offset);
1.65 + }
1.66 +
1.67 + if (!table.ReadU16(&subtable.coverage)) {
1.68 + return OTS_FAILURE_MSG("Cailed to read kern subtable %d coverage", i);
1.69 + }
1.70 +
1.71 + if (!(subtable.coverage & 0x1)) {
1.72 + OTS_WARNING(
1.73 + "We don't support vertical data as the renderer doesn't support it.");
1.74 + continue;
1.75 + }
1.76 + if (subtable.coverage & 0xF0) {
1.77 + OTS_WARNING("Reserved fields should zero-filled.");
1.78 + DROP_THIS_TABLE;
1.79 + return true;
1.80 + }
1.81 + const uint32_t format = (subtable.coverage & 0xFF00) >> 8;
1.82 + if (format != 0) {
1.83 + OTS_WARNING("Format %d is not supported.", format);
1.84 + continue;
1.85 + }
1.86 +
1.87 + // Parse the format 0 field.
1.88 + uint16_t num_pairs = 0;
1.89 + if (!table.ReadU16(&num_pairs) ||
1.90 + !table.ReadU16(&subtable.search_range) ||
1.91 + !table.ReadU16(&subtable.entry_selector) ||
1.92 + !table.ReadU16(&subtable.range_shift)) {
1.93 + return OTS_FAILURE_MSG("Failed to read kern subtable %d format 0 fields", i);
1.94 + }
1.95 +
1.96 + if (!num_pairs) {
1.97 + OTS_WARNING("Zero length subtable is found.");
1.98 + DROP_THIS_TABLE;
1.99 + return true;
1.100 + }
1.101 +
1.102 + // Sanity checks for search_range, entry_selector, and range_shift. See the
1.103 + // comment in ots.cc for details.
1.104 + const size_t kFormat0PairSize = 6; // left, right, and value. 2 bytes each.
1.105 + if (num_pairs > (65536 / kFormat0PairSize)) {
1.106 + // Some fonts (e.g. calibri.ttf, pykes_peak_zero.ttf) have pairs >= 10923.
1.107 + OTS_WARNING("Too large subtable.");
1.108 + DROP_THIS_TABLE;
1.109 + return true;
1.110 + }
1.111 + unsigned max_pow2 = 0;
1.112 + while (1u << (max_pow2 + 1) <= num_pairs) {
1.113 + ++max_pow2;
1.114 + }
1.115 + const uint16_t expected_search_range = (1u << max_pow2) * kFormat0PairSize;
1.116 + if (subtable.search_range != expected_search_range) {
1.117 + OTS_WARNING("bad search range");
1.118 + subtable.search_range = expected_search_range;
1.119 + }
1.120 + if (subtable.entry_selector != max_pow2) {
1.121 + return OTS_FAILURE_MSG("Bad subtable %d entry selector %d", i, subtable.entry_selector);
1.122 + }
1.123 + const uint32_t expected_range_shift
1.124 + = kFormat0PairSize * num_pairs - subtable.search_range;
1.125 + if (subtable.range_shift != expected_range_shift) {
1.126 + OTS_WARNING("bad range shift");
1.127 + subtable.range_shift = expected_range_shift;
1.128 + }
1.129 +
1.130 + // Read kerning pairs.
1.131 + subtable.pairs.reserve(num_pairs);
1.132 + uint32_t last_pair = 0;
1.133 + for (unsigned j = 0; j < num_pairs; ++j) {
1.134 + OpenTypeKERNFormat0Pair kerning_pair;
1.135 + if (!table.ReadU16(&kerning_pair.left) ||
1.136 + !table.ReadU16(&kerning_pair.right) ||
1.137 + !table.ReadS16(&kerning_pair.value)) {
1.138 + return OTS_FAILURE_MSG("Failed to read subtable %d kerning pair %d", i, j);
1.139 + }
1.140 + const uint32_t current_pair
1.141 + = (kerning_pair.left << 16) + kerning_pair.right;
1.142 + if (j != 0 && current_pair <= last_pair) {
1.143 + OTS_WARNING("Kerning pairs are not sorted.");
1.144 + // Many free fonts don't follow this rule, so we don't call OTS_FAILURE
1.145 + // in order to support these fonts.
1.146 + DROP_THIS_TABLE;
1.147 + return true;
1.148 + }
1.149 + last_pair = current_pair;
1.150 + subtable.pairs.push_back(kerning_pair);
1.151 + }
1.152 +
1.153 + kern->subtables.push_back(subtable);
1.154 + }
1.155 +
1.156 + if (!kern->subtables.size()) {
1.157 + OTS_WARNING("All subtables are removed.");
1.158 + DROP_THIS_TABLE;
1.159 + return true;
1.160 + }
1.161 +
1.162 + return true;
1.163 +}
1.164 +
1.165 +bool ots_kern_should_serialise(OpenTypeFile *file) {
1.166 + if (!file->glyf) return false; // this table is not for CFF fonts.
1.167 + return file->kern != NULL;
1.168 +}
1.169 +
1.170 +bool ots_kern_serialise(OTSStream *out, OpenTypeFile *file) {
1.171 + const OpenTypeKERN *kern = file->kern;
1.172 +
1.173 + if (!out->WriteU16(kern->version) ||
1.174 + !out->WriteU16(kern->subtables.size())) {
1.175 + return OTS_FAILURE_MSG("Can't write kern table header");
1.176 + }
1.177 +
1.178 + for (unsigned i = 0; i < kern->subtables.size(); ++i) {
1.179 + const uint16_t length = 14 + (6 * kern->subtables[i].pairs.size());
1.180 + if (!out->WriteU16(kern->subtables[i].version) ||
1.181 + !out->WriteU16(length) ||
1.182 + !out->WriteU16(kern->subtables[i].coverage) ||
1.183 + !out->WriteU16(kern->subtables[i].pairs.size()) ||
1.184 + !out->WriteU16(kern->subtables[i].search_range) ||
1.185 + !out->WriteU16(kern->subtables[i].entry_selector) ||
1.186 + !out->WriteU16(kern->subtables[i].range_shift)) {
1.187 + return OTS_FAILURE_MSG("Failed to write kern subtable %d", i);
1.188 + }
1.189 + for (unsigned j = 0; j < kern->subtables[i].pairs.size(); ++j) {
1.190 + if (!out->WriteU16(kern->subtables[i].pairs[j].left) ||
1.191 + !out->WriteU16(kern->subtables[i].pairs[j].right) ||
1.192 + !out->WriteS16(kern->subtables[i].pairs[j].value)) {
1.193 + return OTS_FAILURE_MSG("Failed to write kern pair %d for subtable %d", j, i);
1.194 + }
1.195 + }
1.196 + }
1.197 +
1.198 + return true;
1.199 +}
1.200 +
1.201 +void ots_kern_free(OpenTypeFile *file) {
1.202 + delete file->kern;
1.203 +}
1.204 +
1.205 +} // namespace ots
