Function startPage

plugins/_editor/webui/editor-preview.js:24–36

(title, level, line, start)

  let offset = 0;

  const startPage = (title, level, line, start) => {
    if (current) {
      current.end = start;
      pages.push(finalizePage(current, pages.length, source));
    }
    current = {
      title: cleanHeadingText(title) || fallbackTitle,
      level,
      lines: [line],
      start,
      end: source.length,
    };
  };

  for (const [index, line] of lines.entries()) {
    const lineStart = offset;