Method Shape

libs/drape/glyph_manager.cpp:219–257

This code is not thread safe.

    // This code is not thread safe.
    void Shape(hb_buffer_t * hbBuffer, int fontPixelSize, int fontIndex, text::TextMetrics & outMetrics)
    {
      // TODO(AB): Do not set the same font size every time.
      // TODO(AB): Use hb_font_set_scale to scale the same size font in HB instead of changing it in Freetype.
      FREETYPE_CHECK(FT_Set_Pixel_Sizes(m_fontFace, 0 /* pixel_width */, fontPixelSize /* pixel_height */));
      if (!m_harfbuzzFont)
        m_harfbuzzFont = hb_ft_font_create(m_fontFace, nullptr);
      // else
      //  Call on each font size change.
      //   hb_ft_font_changed(m_harfbuzzFont);

      // Shape!
      hb_shape(m_harfbuzzFont, hbBuffer, nullptr, 0);

      // Get the glyph and position information.
      unsigned int glyphCount;
      hb_glyph_info_t const * glyphInfo = hb_buffer_get_glyph_infos(hbBuffer, &glyphCount);
      hb_glyph_position_t const * glyphPos = hb_buffer_get_glyph_positions(hbBuffer, &glyphCount);

      for (unsigned int i = 0; i < glyphCount; ++i)
      {
        // TODO(AB): Check for missing glyph ID?
        auto const glyphId = static_cast<uint16_t>(glyphInfo[i].codepoint);

        FT_Int32 constexpr flags = FT_LOAD_DEFAULT;
        FREETYPE_CHECK(FT_Load_Glyph(m_fontFace, glyphId, flags));

        auto const & currPos = glyphPos[i];

        auto const & metrics = m_fontFace->glyph->metrics;
        auto const xOffset = static_cast<int32_t>((currPos.x_offset + metrics.horiBearingX) >> 6);
        // The original Drape code expects a bottom, not a top offset in its calculations.
        auto const yOffset = static_cast<int32_t>((currPos.y_offset + metrics.horiBearingY - metrics.height) >> 6);
        int32_t const xAdvance = currPos.x_advance >> 6;
        // yAdvance is always zero for horizontal text layouts.

        outMetrics.AddGlyphMetrics(static_cast<int16_t>(fontIndex), glyphId, xOffset, yOffset, xAdvance, fontPixelSize);
      }
    }

  private:
    ReaderPtr<Reader> m_fontReader;