content/browser/font_access/font_enumeration_data_source_win.cc

// Copyright 2020 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "content/browser/font_access/font_enumeration_data_source_win.h"

#include <dwrite.h>
#include <stdint.h>
#include <wrl/client.h>

#include <optional>
#include <string>

#include "base/location.h"
#include "base/notreached.h"
#include "base/sequence_checker.h"
#include "base/threading/scoped_blocking_call.h"
#include "content/browser/font_access/font_enumeration_cache.h"
#include "third_party/blink/public/common/font_access/font_enumeration_table.pb.h"
#include "ui/gfx/win/direct_write.h"

namespace content {

namespace {

// Retrieves a DirectWrite font collection for all fonts on the system.
//
// This operation may be expensive, and its result should be cached.
//
// Returns nullptr in case of failure.
Microsoft::WRL::ComPtr<IDWriteFontCollection> GetSystemFonts() {
  base::ScopedBlockingCall scoped_blocking_call(FROM_HERE,
                                                base::BlockingType::MAY_BLOCK);
  // Returned from all code paths, to enable return value optimization.
  Microsoft::WRL::ComPtr<IDWriteFontCollection> collection = nullptr;

  Microsoft::WRL::ComPtr<IDWriteFactory> factory;
  gfx::win::CreateDWriteFactory(&factory);
  if (!factory)
    return collection;

  HRESULT hr = factory->GetSystemFontCollection(&collection);
  if (FAILED(hr))
    collection = nullptr;

  return collection;
}

// Retrieves a string from a font's information table.
//
// Returns nullptr in case of failure.
Microsoft::WRL::ComPtr<IDWriteLocalizedStrings> GetFontInformation(
    IDWriteFont* font,
    DWRITE_INFORMATIONAL_STRING_ID string_id) {
  base::ScopedBlockingCall scoped_blocking_call(FROM_HERE,
                                                base::BlockingType::MAY_BLOCK);

  // Returned from all code paths, to enable return value optimization.
  Microsoft::WRL::ComPtr<IDWriteLocalizedStrings> localized_strings;
  BOOL font_has_info;

  HRESULT hr = font->GetInformationalStrings(string_id, &localized_strings,
                                             &font_has_info);
  if (FAILED(hr) || !font_has_info)
    localized_strings = nullptr;

  return localized_strings;
}

// Retrieves a string matching a locale from a DirectWrite string collection.
//
// If a string in the given locale does not exist, falls back to retrieving the
// first string in the collection.
//
// Returns nullopt in case the string does not exist.
std::optional<std::string> GetLocalizedString(IDWriteLocalizedStrings* names,
                                              const std::string& locale) {
  std::optional<std::string> localized_name =
      gfx::win::RetrieveLocalizedString(names, locale);
  if (!localized_name.has_value()) {
    // Fall back to returning the first string in the collection.
    localized_name = gfx::win::RetrieveLocalizedString(names, std::string());
  }
  return localized_name;
}

// Retrieves a font family name that can be reported by the Fonts Access API.
//
// Returns nullopt in case of failure.
std::optional<std::string> GetFamilyName(IDWriteFontFamily* family) {
  std::optional<std::string> family_name;

  Microsoft::WRL::ComPtr<IDWriteLocalizedStrings> family_names;
  HRESULT hr = family->GetFamilyNames(&family_names);
  if (FAILED(hr))
    return family_name;

  family_name = GetLocalizedString(family_names.Get(), "en-us");
  return family_name;
}

// Retrieves a font's PostScript name, to be reported by the Fonts Access API.
//
// Returns nullopt in case of failure.
std::optional<std::string> GetFontPostScriptName(IDWriteFont* font) {
  std::optional<std::string> postscript_name;

  // DWRITE_INFORMATIONAL_STRING_POSTSCRIPT_NAME and
  // DWRITE_INFORMATIONAL_STRING_FULL_NAME are only supported on Windows 7 with
  // KB2670838 (https://support.microsoft.com/en-us/kb/2670838) installed. It is
  // possible to use a fallback as can be observed in Firefox:
  // https://bugzilla.mozilla.org/show_bug.cgi?id=947812 However, this might not
  // be worth the effort.

  Microsoft::WRL::ComPtr<IDWriteLocalizedStrings> postscript_names =
      GetFontInformation(font, DWRITE_INFORMATIONAL_STRING_POSTSCRIPT_NAME);
  if (!postscript_names)
    return postscript_name;

  postscript_name = GetLocalizedString(postscript_names.Get(), "en-us");
  return postscript_name;
}

// Retrieves a font's full name, to be reported by the Fonts Access API.
//
// Returns nullopt in case of failure.
std::optional<std::string> GetFontFullName(IDWriteFont* font,
                                           const std::string& locale) {
  std::optional<std::string> full_name;

  Microsoft::WRL::ComPtr<IDWriteLocalizedStrings> full_names =
      GetFontInformation(font, DWRITE_INFORMATIONAL_STRING_FULL_NAME);
  if (!full_names)
    return full_name;

  full_name = GetLocalizedString(full_names.Get(), locale);
  return full_name;
}

// Returns a font's style name, to be reported by the Fonts Access API.
//
// Returns nullopt in case of failure.
std::optional<std::string> GetFontStyleName(IDWriteFont* font) {
  std::optional<std::string> style_name;

  // All fonts should have a subfamily name compatible with Windows GDI,
  // available as the string DWRITE_INFORMATIONAL_STRING_WIN32_SUBFAMILY_NAMES.
  //
  // In some cases, the family / sub-family names preferred by designer wouldn't
  // be compatible with Windows GDI, and the desiner. In these cases, the
  // designer-preferred subfamily name is availabe as the string
  // DWRITE_INFORMATIONAL_STRING_PREFERRED_SUBFAMILY_NAMES.
  //
  // More details at
  // https://docs.microsoft.com/en-us/windows/win32/api/dwrite/ne-dwrite-dwrite_informational_string_id

  Microsoft::WRL::ComPtr<IDWriteLocalizedStrings> style_names =
      GetFontInformation(font,
                         DWRITE_INFORMATIONAL_STRING_PREFERRED_SUBFAMILY_NAMES);
  if (!style_names) {
    style_names = GetFontInformation(
        font, DWRITE_INFORMATIONAL_STRING_WIN32_SUBFAMILY_NAMES);
    if (!style_names)
      return style_name;
  }

  style_name = GetLocalizedString(style_names.Get(), "en-us");
  return style_name;
}

}  // namespace

FontEnumerationDataSourceWin::FontEnumerationDataSourceWin() {
  DETACH_FROM_SEQUENCE(sequence_checker_);
}

FontEnumerationDataSourceWin::~FontEnumerationDataSourceWin() {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
}

blink::FontEnumerationTable FontEnumerationDataSourceWin::GetFonts(
    const std::string& locale) {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);

  blink::FontEnumerationTable font_enumeration_table;

  Microsoft::WRL::ComPtr<IDWriteFontCollection> collection = GetSystemFonts();
  uint32_t family_count;
  {
    base::ScopedBlockingCall scoped_blocking_call(
        FROM_HERE, base::BlockingType::MAY_BLOCK);

    family_count = collection->GetFontFamilyCount();
  }

  // Used to filter duplicates.
  std::set<std::string> fonts_seen;

  for (uint32_t family_index = 0; family_index < family_count; ++family_index) {
    Microsoft::WRL::ComPtr<IDWriteFontFamily> family;
    HRESULT hr = collection->GetFontFamily(family_index, &family);
    if (FAILED(hr))
      continue;

    std::optional<std::string> family_name = GetFamilyName(family.Get());

    uint32_t font_count = family->GetFontCount();
    for (uint32_t font_index = 0; font_index < font_count; ++font_index) {
      Microsoft::WRL::ComPtr<IDWriteFont> font;
      {
        base::ScopedBlockingCall scoped_blocking_call(
            FROM_HERE, base::BlockingType::MAY_BLOCK);
        hr = family->GetFont(font_index, &font);
      }

      if (FAILED(hr))
        continue;

      // Skip this font if it's a simulation.
      if (font->GetSimulations() != DWRITE_FONT_SIMULATIONS_NONE)
        continue;

      std::optional<std::string> postscript_name =
          GetFontPostScriptName(font.Get());
      if (!postscript_name)
        continue;

      auto it_and_success = fonts_seen.emplace(postscript_name.value());
      if (!it_and_success.second) {
        // Skip duplicates.
        continue;
      }

      std::optional<std::string> localized_full_name =
          GetFontFullName(font.Get(), locale);
      if (!localized_full_name)
        localized_full_name = postscript_name;

      std::optional<std::string> style_name = GetFontStyleName(font.Get());
      if (!style_name)
        continue;

      blink::FontEnumerationTable_FontData* data =
          font_enumeration_table.add_fonts();
      data->set_postscript_name(std::move(postscript_name).value());
      data->set_full_name(std::move(localized_full_name).value());
      data->set_family(family_name.value());
      data->set_style(style_name ? std::move(style_name.value())
                                 : std::string());
    }
  }

  return font_enumeration_table;
}

}  // namespace content