src/base/i18n/rtl.cc

// Copyright (c) 2011 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "base/i18n/rtl.h"

#include "base/file_path.h"
#include "base/logging.h"
#include "base/string_util.h"
#include "base/utf_string_conversions.h"
#include "base/sys_string_conversions.h"
#include "unicode/coll.h"
#include "unicode/locid.h"
#include "unicode/uchar.h"
#include "unicode/uscript.h"

#if defined(TOOLKIT_GTK)
#include <gtk/gtk.h>
#endif

namespace {

// Extract language, country and variant, but ignore keywords.  For example,
// en-US, ca@valencia, ca-ES@valencia.
std::string GetLocaleString(const icu::Locale& locale) {
  const char* language = locale.getLanguage();
  const char* country = locale.getCountry();
  const char* variant = locale.getVariant();

  std::string result =
      (language != NULL && *language != '\0') ? language : "und";

  if (country != NULL && *country != '\0') {
    result += '-';
    result += country;
  }

  if (variant != NULL && *variant != '\0') {
    std::string variant_str(variant);
    StringToLowerASCII(&variant_str);
    result += '@' + variant_str;
  }

  return result;
}

}  // namespace

namespace base {
namespace i18n {

// Represents the locale-specific ICU text direction.
static TextDirection g_icu_text_direction = UNKNOWN_DIRECTION;

// Convert the ICU default locale to a string.
std::string GetConfiguredLocale() {
  return GetLocaleString(icu::Locale::getDefault());
}

// Convert the ICU canonicalized locale to a string.
std::string GetCanonicalLocale(const char* locale) {
  return GetLocaleString(icu::Locale::createCanonical(locale));
}

// Convert Chrome locale name to ICU locale name
std::string ICULocaleName(const std::string& locale_string) {
  // If not Spanish, just return it.
  if (locale_string.substr(0, 2) != "es")
    return locale_string;
  // Expand es to es-ES.
  if (LowerCaseEqualsASCII(locale_string, "es"))
    return "es-ES";
  // Map es-419 (Latin American Spanish) to es-FOO depending on the system
  // locale.  If it's es-RR other than es-ES, map to es-RR. Otherwise, map
  // to es-MX (the most populous in Spanish-speaking Latin America).
  if (LowerCaseEqualsASCII(locale_string, "es-419")) {
    const icu::Locale& locale = icu::Locale::getDefault();
    std::string language = locale.getLanguage();
    const char* country = locale.getCountry();
    if (LowerCaseEqualsASCII(language, "es") &&
      !LowerCaseEqualsASCII(country, "es")) {
        language += '-';
        language += country;
        return language;
    }
    return "es-MX";
  }
  // Currently, Chrome has only "es" and "es-419", but later we may have
  // more specific "es-RR".
  return locale_string;
}

void SetICUDefaultLocale(const std::string& locale_string) {
  icu::Locale locale(ICULocaleName(locale_string).c_str());
  UErrorCode error_code = U_ZERO_ERROR;
  icu::Locale::setDefault(locale, error_code);
  // This return value is actually bogus because Locale object is
  // an ID and setDefault seems to always succeed (regardless of the
  // presence of actual locale data). However,
  // it does not hurt to have it as a sanity check.
  DCHECK(U_SUCCESS(error_code));
  g_icu_text_direction = UNKNOWN_DIRECTION;
}

bool IsRTL() {
#if defined(TOOLKIT_GTK)
  GtkTextDirection gtk_dir = gtk_widget_get_default_direction();
  return gtk_dir == GTK_TEXT_DIR_RTL;
#else
  return ICUIsRTL();
#endif
}

bool ICUIsRTL() {
  if (g_icu_text_direction == UNKNOWN_DIRECTION) {
    const icu::Locale& locale = icu::Locale::getDefault();
    g_icu_text_direction = GetTextDirectionForLocale(locale.getName());
  }
  return g_icu_text_direction == RIGHT_TO_LEFT;
}

TextDirection GetTextDirectionForLocale(const char* locale_name) {
#if defined(__LB_SHELL__) || defined(OS_STARBOARD)
  // lbshell does not have the icu tables needed to determine RTL-ness.
  // Rather than beef up our icu tables, hard-code the list of RTL languages
  // that Chrome supports.  RTL layout is implemented by other components,
  // so this does not affect our ability to do RTL layout nor RTL text.
  return (!strncmp(locale_name, "he", 2) ||
          !strncmp(locale_name, "ar", 2) ||
          !strncmp(locale_name, "iw", 2) ||
          !strncmp(locale_name, "fa", 2) ||
          !strncmp(locale_name, "ur", 2))
         ? RIGHT_TO_LEFT : LEFT_TO_RIGHT;
#else
  UErrorCode status = U_ZERO_ERROR;
  ULayoutType layout_dir = uloc_getCharacterOrientation(locale_name, &status);
  DCHECK(U_SUCCESS(status));
  // Treat anything other than RTL as LTR.
  return (layout_dir != ULOC_LAYOUT_RTL) ? LEFT_TO_RIGHT : RIGHT_TO_LEFT;
#endif
}

TextDirection GetFirstStrongCharacterDirection(const string16& text) {
  const UChar* string = text.c_str();
  size_t length = text.length();
  size_t position = 0;
  while (position < length) {
    UChar32 character;
    size_t next_position = position;
    U16_NEXT(string, next_position, length, character);

    // Now that we have the character, we use ICU in order to query for the
    // appropriate Unicode BiDi character type.
    int32_t property = u_getIntPropertyValue(character, UCHAR_BIDI_CLASS);
    if ((property == U_RIGHT_TO_LEFT) ||
        (property == U_RIGHT_TO_LEFT_ARABIC) ||
        (property == U_RIGHT_TO_LEFT_EMBEDDING) ||
        (property == U_RIGHT_TO_LEFT_OVERRIDE)) {
      return RIGHT_TO_LEFT;
    } else if ((property == U_LEFT_TO_RIGHT) ||
               (property == U_LEFT_TO_RIGHT_EMBEDDING) ||
               (property == U_LEFT_TO_RIGHT_OVERRIDE)) {
      return LEFT_TO_RIGHT;
    }

    position = next_position;
  }

  return LEFT_TO_RIGHT;
}

#if defined(OS_WIN)
bool AdjustStringForLocaleDirection(string16* text) {
  if (!IsRTL() || text->empty())
    return false;

  // Marking the string as LTR if the locale is RTL and the string does not
  // contain strong RTL characters. Otherwise, mark the string as RTL.
  bool has_rtl_chars = StringContainsStrongRTLChars(*text);
  if (!has_rtl_chars)
    WrapStringWithLTRFormatting(text);
  else
    WrapStringWithRTLFormatting(text);

  return true;
}

bool UnadjustStringForLocaleDirection(string16* text) {
  if (!IsRTL() || text->empty())
    return false;

  *text = StripWrappingBidiControlCharacters(*text);
  return true;
}
#else
bool AdjustStringForLocaleDirection(string16* text) {
  // On OS X & GTK the directionality of a label is determined by the first
  // strongly directional character.
  // However, we want to make sure that in an LTR-language-UI all strings are
  // left aligned and vice versa.
  // A problem can arise if we display a string which starts with user input.
  // User input may be of the opposite directionality to the UI. So the whole
  // string will be displayed in the opposite directionality, e.g. if we want to
  // display in an LTR UI [such as US English]:
  //
  // EMAN_NOISNETXE is now installed.
  //
  // Since EXTENSION_NAME begins with a strong RTL char, the label's
  // directionality will be set to RTL and the string will be displayed visually
  // as:
  //
  // .is now installed EMAN_NOISNETXE
  //
  // In order to solve this issue, we prepend an LRM to the string. An LRM is a
  // strongly directional LTR char.
  // We also append an LRM at the end, which ensures that we're in an LTR
  // context.

  // Unlike Windows, Linux and OS X can correctly display RTL glyphs out of the
  // box so there is no issue with displaying zero-width bidi control characters
  // on any system.  Thus no need for the !IsRTL() check here.
  if (text->empty())
    return false;

  bool ui_direction_is_rtl = IsRTL();

  bool has_rtl_chars = StringContainsStrongRTLChars(*text);
  if (!ui_direction_is_rtl && has_rtl_chars) {
    WrapStringWithRTLFormatting(text);
    text->insert(0U, 1U, kLeftToRightMark);
    text->push_back(kLeftToRightMark);
  } else if (ui_direction_is_rtl && has_rtl_chars) {
    WrapStringWithRTLFormatting(text);
    text->insert(0U, 1U, kRightToLeftMark);
    text->push_back(kRightToLeftMark);
  } else if (ui_direction_is_rtl) {
    WrapStringWithLTRFormatting(text);
    text->insert(0U, 1U, kRightToLeftMark);
    text->push_back(kRightToLeftMark);
  } else {
    return false;
  }

  return true;
}

bool UnadjustStringForLocaleDirection(string16* text) {
  if (text->empty())
    return false;

  size_t begin_index = 0;
  char16 begin = text->at(begin_index);
  if (begin == kLeftToRightMark ||
      begin == kRightToLeftMark) {
    ++begin_index;
  }

  size_t end_index = text->length() - 1;
  char16 end = text->at(end_index);
  if (end == kLeftToRightMark ||
      end == kRightToLeftMark) {
    --end_index;
  }

  string16 unmarked_text =
      text->substr(begin_index, end_index - begin_index + 1);
  *text = StripWrappingBidiControlCharacters(unmarked_text);
  return true;
}

#endif  // !OS_WIN

bool StringContainsStrongRTLChars(const string16& text) {
  const UChar* string = text.c_str();
  size_t length = text.length();
  size_t position = 0;
  while (position < length) {
    UChar32 character;
    size_t next_position = position;
    U16_NEXT(string, next_position, length, character);

    // Now that we have the character, we use ICU in order to query for the
    // appropriate Unicode BiDi character type.
    int32_t property = u_getIntPropertyValue(character, UCHAR_BIDI_CLASS);
    if ((property == U_RIGHT_TO_LEFT) || (property == U_RIGHT_TO_LEFT_ARABIC))
      return true;

    position = next_position;
  }

  return false;
}

void WrapStringWithLTRFormatting(string16* text) {
  if (text->empty())
    return;

  // Inserting an LRE (Left-To-Right Embedding) mark as the first character.
  text->insert(0U, 1U, kLeftToRightEmbeddingMark);

  // Inserting a PDF (Pop Directional Formatting) mark as the last character.
  text->push_back(kPopDirectionalFormatting);
}

void WrapStringWithRTLFormatting(string16* text) {
  if (text->empty())
    return;

  // Inserting an RLE (Right-To-Left Embedding) mark as the first character.
  text->insert(0U, 1U, kRightToLeftEmbeddingMark);

  // Inserting a PDF (Pop Directional Formatting) mark as the last character.
  text->push_back(kPopDirectionalFormatting);
}

void WrapPathWithLTRFormatting(const FilePath& path,
                               string16* rtl_safe_path) {
  // Wrap the overall path with LRE-PDF pair which essentialy marks the
  // string as a Left-To-Right string.
  // Inserting an LRE (Left-To-Right Embedding) mark as the first character.
  rtl_safe_path->push_back(kLeftToRightEmbeddingMark);
#if defined(OS_MACOSX)
    rtl_safe_path->append(UTF8ToUTF16(path.value()));
#elif defined(OS_WIN)
    rtl_safe_path->append(path.value());
#else  // defined(OS_POSIX) && !defined(OS_MACOSX)
    std::wstring wide_path = base::SysNativeMBToWide(path.value());
    rtl_safe_path->append(WideToUTF16(wide_path));
#endif
  // Inserting a PDF (Pop Directional Formatting) mark as the last character.
  rtl_safe_path->push_back(kPopDirectionalFormatting);
}

string16 GetDisplayStringInLTRDirectionality(const string16& text) {
  // Always wrap the string in RTL UI (it may be appended to RTL string).
  // Also wrap strings with an RTL first strong character direction in LTR UI.
  if (IsRTL() || GetFirstStrongCharacterDirection(text) == RIGHT_TO_LEFT) {
    string16 text_mutable(text);
    WrapStringWithLTRFormatting(&text_mutable);
    return text_mutable;
  }
  return text;
}

string16 StripWrappingBidiControlCharacters(const string16& text) {
  if (text.empty())
    return text;
  size_t begin_index = 0;
  char16 begin = text[begin_index];
  if (begin == kLeftToRightEmbeddingMark ||
      begin == kRightToLeftEmbeddingMark ||
      begin == kLeftToRightOverride ||
      begin == kRightToLeftOverride)
    ++begin_index;
  size_t end_index = text.length() - 1;
  if (text[end_index] == kPopDirectionalFormatting)
    --end_index;
  return text.substr(begin_index, end_index - begin_index + 1);
}

}  // namespace i18n
}  // namespace base