nsPangoBreaker.cpp

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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

/* This Source Code Form is subject to the terms of the Mozilla Public

 * License, v. 2.0. If a copy of the MPL was not distributed with this

 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "nsComplexBreaker.h"

#include <pango/pango-break.h>

#include "nsUTF8Utils.h"

#include "nsString.h"

#include "nsTArray.h"

void NS_GetComplexLineBreaks(const char16_t* aText, uint32_t aLength,

                             uint8_t* aBreakBefore) {

  NS_ASSERTION(aText, "aText shouldn't be null");

  memset(aBreakBefore, uint8_t(false), aLength * sizeof(uint8_t));

  AutoTArray<PangoLogAttr, 2000> attrBuffer;

  // XXX(Bug 1631371) Check if this should use a fallible operation as it

  // pretended earlier.

  attrBuffer.AppendElements(aLength + 1);

  // `PangoLogAttr` doesn't have a default constructor (it is a C struct), so

  // we need to manually initialize the new elements.  See bug 1808182.

  memset(attrBuffer.Elements(), 0, attrBuffer.Length() * sizeof(PangoLogAttr));

  NS_ConvertUTF16toUTF8 aUTF8(aText, aLength);

  const gchar* p = aUTF8.Data();

  const gchar* end = p + aUTF8.Length();

  uint32_t u16Offset = 0;

  static PangoLanguage* language = pango_language_from_string("en");

  while (p < end) {

    PangoLogAttr* attr = attrBuffer.Elements();

    pango_get_log_attrs(p, end - p, -1, language, attr, attrBuffer.Length());

    while (p < end) {

      aBreakBefore[u16Offset] = attr->is_line_break;

      if (NS_IS_LOW_SURROGATE(aText[u16Offset]))

        aBreakBefore[++u16Offset] = false;  // Skip high surrogate

      ++u16Offset;

      // We're iterating over text obtained from NS_ConvertUTF16toUTF8,

      // so we know we have valid UTF-8 and don't need to check for

      // errors.

      uint32_t ch = UTF8CharEnumerator::NextChar(&p, end);

      ++attr;

      if (!ch) {

        // pango_break (pango 1.16.2) only analyses text before the

        // first NUL (but sets one extra attr). Workaround loop to call

        // pango_break again to analyse after the NUL is done somewhere else

        // (gfx/thebes/gfxFontconfigFonts.cpp: SetupClusterBoundaries()).

        // So, we do the same here for pango_get_log_attrs.

        break;