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// Copyright 2019 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "pdf/pdfium/pdfium_font_linux.h"
#include <stddef.h>
#include <stdint.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include <algorithm>
#include <limits>
#include <memory>
#include <string>
#include "base/check_op.h"
#include "base/files/file.h"
#include "base/i18n/encoding_detection.h"
#include "base/i18n/icu_string_conversions.h"
#include "base/no_destructor.h"
#include "base/numerics/safe_conversions.h"
#include "base/posix/eintr_wrapper.h"
#include "base/sequence_checker.h"
#include "base/strings/string_util.h"
#include "base/sys_byteorder.h"
#include "components/services/font/public/cpp/font_loader.h"
#include "pdf/pdfium/pdfium_engine.h"
#include "third_party/blink/public/platform/web_font_description.h"
#include "third_party/pdfium/public/fpdf_sysfontinfo.h"
namespace chrome_pdf {
namespace {
// GetFontTable loads a specified font table from an open SFNT file.
// fd: a file descriptor to the SFNT file. The position doesn't matter.
// table_tag: the table tag in *big-endian* format, or 0 for the entire font.
// output: a buffer of size output_length that gets the data. can be 0, in
// which case output_length will be set to the required size in bytes.
// output_length: size of output, if it's not 0.
// returns: true on success.
// TODO(drott): This should be should be replaced with using FreeType for the
// purpose instead of reimplementing table parsing.
bool GetFontTable(int fd,
uint32_t table_tag,
uint8_t* output,
size_t* output_length) {
size_t data_length = 0; // the length of the file data.
off_t data_offset = 0; // the offset of the data in the file.
if (table_tag == 0) {
// Get the entire font file.
struct stat st;
if (fstat(fd, &st) < 0) {
return false;
data_length = base::checked_cast<size_t>(st.st_size);
} else {
// Get a font table. Read the header to find its offset in the file.
uint16_t num_tables;
ssize_t n = HANDLE_EINTR(
pread(fd, &num_tables, sizeof(num_tables), 4 /* skip the font type */));
if (n != sizeof(num_tables)) {
return false;
// Font data is stored in net (big-endian) order.
num_tables = base::NetToHost16(num_tables);
// Read the table directory.
static const size_t kTableEntrySize = 16;
const size_t directory_size = num_tables * kTableEntrySize;
std::unique_ptr<uint8_t[]> table_entries(new uint8_t[directory_size]);
n = HANDLE_EINTR(pread(fd, table_entries.get(), directory_size,
12 /* skip the SFNT header */));
if (n != base::checked_cast<ssize_t>(directory_size)) {
return false;
for (uint16_t i = 0; i < num_tables; ++i) {
uint8_t* entry = table_entries.get() + i * kTableEntrySize;
uint32_t tag = *reinterpret_cast<uint32_t*>(entry);
if (tag == table_tag) {
// Font data is stored in net (big-endian) order.
data_offset =
base::NetToHost32(*reinterpret_cast<uint32_t*>(entry + 8));
data_length =
base::NetToHost32(*reinterpret_cast<uint32_t*>(entry + 12));
if (!data_length) {
return false;
if (output) {
// 'output_length' holds the maximum amount of data the caller can accept.
data_length = std::min(data_length, *output_length);
ssize_t n = HANDLE_EINTR(pread(fd, output, data_length, data_offset));
if (n != base::checked_cast<ssize_t>(data_length)) {
return false;
*output_length = data_length;
return true;
// Maps font description and charset to `FontId` as requested by PDFium, with
// `FontId` as an opaque type that PDFium works with. Based on the `FontId`,
// PDFium can read from the font files using GetFontData(). Properly frees the
// underlying resource type when PDFium is done with the mapped font.
class BlinkFontMapper {
// Defined as the type most convenient for use with PDFium's
// `FPDF_SYSFONTINFO` functions.
using FontId = void*;
BlinkFontMapper() = default;
~BlinkFontMapper() = delete;
// Returns a handle to the font mapped based on `desc` and `charset`, for use
// as the `font_id` in GetFontData() and DeleteFont() below. Returns nullptr
// on failure.
// TODO(thestig): Document how this handles TTC files.
FontId MapFont(const blink::WebFontDescription& desc, int charset) {
// If there was never a SkFontConfigInterface::SetGlobal() call, then `fci`
// defaults to the direct interface, which is not suitable, as it does not
// provide MatchFontWithFallback(). This only happens in unit tests, so just
// refuse to map fonts there.
sk_sp<SkFontConfigInterface> fci = SkFontConfigInterface::RefGlobal();
if (fci.get() == SkFontConfigInterface::GetSingletonDirectInterface())
return nullptr;
auto font_file = std::make_unique<base::File>();
// In RendererBlinkPlatform, SkFontConfigInterface::SetGlobal() only ever
// sets the global to a FontLoader. Thus it is safe to assume the returned
// result is just that.
auto* font_loader = reinterpret_cast<font_service::FontLoader*>(fci.get());
desc.weight >= blink::WebFontDescription::kWeightBold, desc.italic,
charset, desc.generic_family, font_file.get());
if (!font_file->IsValid())
return nullptr;
// Release to PDFium. PDFium will free `font_file` in DeleteFont() below.
return font_file.release();
// Releases the font file that `font_id` points to.
void DeleteFont(FontId font_id) {
delete FileFromFontId(font_id);
// Reads data from the `font_id` handle for `table` into a `buffer` of
// `buf_size`. Returns the amount of data read on success, or 0 on failure.
// If `buffer` is null, then just return the required size for the buffer.
// See content::GetFontTable() for information on the `table_tag` parameter.
unsigned long GetFontData(FontId font_id,
unsigned int table_tag,
unsigned char* buffer,
unsigned long buf_size) const {
// TODO(thestig): cache?
base::PlatformFile platform_file =
size_t size = buf_size;
if (!GetFontTable(platform_file, table_tag, buffer, &size)) {
return 0;
return size;
static base::File* FileFromFontId(FontId font_id) {
return reinterpret_cast<base::File*>(font_id);
BlinkFontMapper& GetBlinkFontMapper() {
static base::NoDestructor<BlinkFontMapper> mapper;
return *mapper;
blink::WebFontDescription::Weight WeightToBlinkWeight(int weight) {
static_assert(blink::WebFontDescription::kWeight100 == 0, "Blink Weight min");
static_assert(blink::WebFontDescription::kWeight900 == 8, "Blink Weight max");
constexpr int kMinimumWeight = 100;
constexpr int kMaximumWeight = 900;
int normalized_weight = std::clamp(weight, kMinimumWeight, kMaximumWeight);
normalized_weight = (normalized_weight / 100) - 1;
return static_cast<blink::WebFontDescription::Weight>(normalized_weight);
// This list is for CPWL_FontMap::GetDefaultFontByCharset().
// We pretend to have these font natively and let the browser (or underlying
// fontconfig) pick the proper font on the system.
void EnumFonts(FPDF_SYSFONTINFO* sysfontinfo, void* mapper) {
FPDF_AddInstalledFont(mapper, "Arial", FXFONT_DEFAULT_CHARSET);
const FPDF_CharsetFontMap* font_map = FPDF_GetDefaultTTFMap();
for (; font_map->charset != -1; ++font_map) {
FPDF_AddInstalledFont(mapper, font_map->fontname, font_map->charset);
int weight,
int italic,
int charset,
int pitch_family,
const char* face,
int* exact) {
// The code below is Blink-specific, return early in non-Blink mode to avoid
// crashing.
if (PDFiumEngine::GetFontMappingMode() != FontMappingMode::kBlink) {
DCHECK_EQ(PDFiumEngine::GetFontMappingMode(), FontMappingMode::kNoMapping);
return nullptr;
// Pretend the system does not have the Symbol font to force a fallback to
// the built in Symbol font in CFX_FontMapper::FindSubstFont().
if (strcmp(face, "Symbol") == 0)
return nullptr;
blink::WebFontDescription desc;
if (pitch_family & FXFONT_FF_FIXEDPITCH) {
desc.generic_family = blink::WebFontDescription::kGenericFamilyMonospace;
} else if (pitch_family & FXFONT_FF_ROMAN) {
desc.generic_family = blink::WebFontDescription::kGenericFamilySerif;
} else {
desc.generic_family = blink::WebFontDescription::kGenericFamilyStandard;
static const struct {
const char* pdf_name;
const char* face;
bool bold;
bool italic;
} kPdfFontSubstitutions[] = {
{"Courier", "Courier New", false, false},
{"Courier-Bold", "Courier New", true, false},
{"Courier-BoldOblique", "Courier New", true, true},
{"Courier-Oblique", "Courier New", false, true},
{"Helvetica", "Arial", false, false},
{"Helvetica-Bold", "Arial", true, false},
{"Helvetica-BoldOblique", "Arial", true, true},
{"Helvetica-Oblique", "Arial", false, true},
{"Times-Roman", "Times New Roman", false, false},
{"Times-Bold", "Times New Roman", true, false},
{"Times-BoldItalic", "Times New Roman", true, true},
{"Times-Italic", "Times New Roman", false, true},
// MS P?(Mincho|Gothic) are the most notable fonts in Japanese PDF files
// without embedding the glyphs. Sometimes the font names are encoded
// in Japanese Windows's locale (CP932/Shift_JIS) without space.
// Most Linux systems don't have the exact font, but for outsourcing
// fontconfig to find substitutable font in the system, we pass ASCII
// font names to it.
{"MS-PGothic", "MS PGothic", false, false},
{"MS-Gothic", "MS Gothic", false, false},
{"MS-PMincho", "MS PMincho", false, false},
{"MS-Mincho", "MS Mincho", false, false},
// MS PGothic in Shift_JIS encoding.
{"\x82\x6C\x82\x72\x82\x6F\x83\x53\x83\x56\x83\x62\x83\x4E", "MS PGothic",
false, false},
// MS Gothic in Shift_JIS encoding.
{"\x82\x6C\x82\x72\x83\x53\x83\x56\x83\x62\x83\x4E", "MS Gothic", false,
// MS PMincho in Shift_JIS encoding.
{"\x82\x6C\x82\x72\x82\x6F\x96\xBE\x92\xA9", "MS PMincho", false, false},
// MS Mincho in Shift_JIS encoding.
{"\x82\x6C\x82\x72\x96\xBE\x92\xA9", "MS Mincho", false, false},
// Similar logic exists in PDFium's CFX_FolderFontInfo::FindFont().
if (charset == FXFONT_ANSI_CHARSET && (pitch_family & FXFONT_FF_FIXEDPITCH))
face = "Courier New";
// Map from the standard PDF fonts to TrueType font names.
size_t i;
for (i = 0; i < std::size(kPdfFontSubstitutions); ++i) {
if (strcmp(face, kPdfFontSubstitutions[i].pdf_name) == 0) { = blink::WebString::FromUTF8(kPdfFontSubstitutions[i].face);
if (kPdfFontSubstitutions[i].bold)
desc.weight = blink::WebFontDescription::kWeightBold;
if (kPdfFontSubstitutions[i].italic)
desc.italic = true;
if (i == std::size(kPdfFontSubstitutions)) {
// Convert to UTF-8 and make sure it is valid.
std::string face_utf8;
if (base::IsStringUTF8(face)) {
face_utf8 = face;
} else {
std::string encoding;
if (base::DetectEncoding(face, &encoding)) {
// ConvertToUtf8AndNormalize() clears `face_utf8` on failure.
base::ConvertToUtf8AndNormalize(face, encoding, &face_utf8);
if (face_utf8.empty())
return nullptr; = blink::WebString::FromUTF8(face_utf8);
desc.weight = WeightToBlinkWeight(weight);
desc.italic = italic > 0;
return GetBlinkFontMapper().MapFont(desc, charset);
unsigned long GetFontData(FPDF_SYSFONTINFO*,
void* font_id,
unsigned int table,
unsigned char* buffer,
unsigned long buf_size) {
DCHECK_EQ(PDFiumEngine::GetFontMappingMode(), FontMappingMode::kBlink);
return GetBlinkFontMapper().GetFontData(font_id, table, buffer, buf_size);
void DeleteFont(FPDF_SYSFONTINFO*, void* font_id) {
DCHECK_EQ(PDFiumEngine::GetFontMappingMode(), FontMappingMode::kBlink);
FPDF_SYSFONTINFO g_font_info = {1, 0, EnumFonts, MapFont, 0,
GetFontData, 0, 0, DeleteFont};
} // namespace
void InitializeLinuxFontMapper() {
} // namespace chrome_pdf