Method render

lib/Epub/Epub/blocks/TextBlock.cpp:10–74

#include <cstring>

void TextBlock::render(const GfxRenderer& renderer, const int fontId, const int x, const int y) const {
  // Focus annotations are optional: empty vectors mean no word in this block has a split.
  // When present, they must be sized in lockstep with words[].
  const bool hasFocus = !wordFocusBoundary.empty();
  if (words.size() != wordXpos.size() || words.size() != wordStyles.size() ||
      (hasFocus && (words.size() != wordFocusBoundary.size() || words.size() != wordFocusSuffixX.size()))) {
    LOG_ERR("TXB", "Render skipped: size mismatch (words=%u, xpos=%u, styles=%u, boundary=%u, suffixX=%u)\n",
            (uint32_t)words.size(), (uint32_t)wordXpos.size(), (uint32_t)wordStyles.size(),
            (uint32_t)wordFocusBoundary.size(), (uint32_t)wordFocusSuffixX.size());
    return;
  }

  const bool scanning = renderer.isFontCacheScanning();
  const int ascender = renderer.getFontAscenderSize(fontId);
  for (size_t i = 0; i < words.size(); i++) {
    const int wordX = wordXpos[i] + x;
    const EpdFontFamily::Style currentStyle = wordStyles[i];
    const auto baseDir = static_cast<BidiUtils::BidiBaseDir>(
        BidiUtils::detectParagraphLevel(words[i].c_str(), blockStyle.isRtl ? 1 : 0));
    const uint8_t boundary = hasFocus ? wordFocusBoundary[i] : 0;

    // SUP/SUB shift the baseline passed to drawText; the glyph is also scaled 50% inside
    // drawText, so these offsets are chosen relative to the full-size ascender:
    //   SUP: raise by 40% of ascender — sits clearly above the cap-height
    //   SUB: lower by 25% of ascender — descends below baseline without clashing with ascenders below
    int wordY = y;
    if ((currentStyle & EpdFontFamily::SUP) != 0) {
      wordY -= ascender * 2 / 5;
    } else if ((currentStyle & EpdFontFamily::SUB) != 0) {
      wordY += ascender / 4;
    }

    if (boundary > 0) {
      // Focus split: draw bold prefix, then the regular suffix at a pre-computed x offset.
      // The bold prefix is bounded to 9 codepoints by the clamp on targetBoldChars in
      // ParsedText::addWord; 9 UTF-8 codepoints occupy at most 9 * 4 = 36 bytes, +1 for null = 37.
      // suffixX is computed at cache-creation time to avoid font metric lookups at render time.
      static constexpr size_t MAX_FOCUS_PREFIX_BYTES = 9 * 4 + 1;
      char boldBuf[40];
      static_assert(sizeof(boldBuf) >= MAX_FOCUS_PREFIX_BYTES,
                    "boldBuf too small for max focus prefix (9 codepoints * 4 UTF-8 bytes + null)");
      const auto boldStyle = static_cast<EpdFontFamily::Style>(currentStyle | EpdFontFamily::BOLD);
      const size_t boldLen = std::min<size_t>({static_cast<size_t>(boundary), words[i].size(), sizeof(boldBuf) - 1});
      memcpy(boldBuf, words[i].c_str(), boldLen);
      boldBuf[boldLen] = '\0';
      renderer.drawText(fontId, wordX, wordY, boldBuf, true, boldStyle, baseDir);
      const int suffixX = wordX + wordFocusSuffixX[i];
      renderer.drawText(fontId, suffixX, wordY, words[i].c_str() + boldLen, true, currentStyle, baseDir);
    } else {
      renderer.drawText(fontId, wordX, wordY, words[i].c_str(), true, currentStyle, baseDir);
    }

    if (!scanning && (currentStyle & EpdFontFamily::UNDERLINE) != 0) {
      const std::string& w = words[i];
      int underlineWidth = renderer.getTextWidth(fontId, w.c_str(), currentStyle, baseDir);
      const int underlineY = wordY + ascender + 2;

      if ((currentStyle & (EpdFontFamily::SUP | EpdFontFamily::SUB)) != 0) {