@ocelot-consulting/hummus-toc/src/addTOCPages.js

An extension for HummusJS to add Table of Contents (including bookmarks).

const {verticalMax, horizontalMax, verticalMargin, leftMarginEnd, lineSpacing, fontPath} = require('../config')

const writeLine = (pageCtx, text, font, fontFactor, horizontalBegin, verticalBegin) => {
  pageCtx.BT()
    .k(0, 0, 0, 1)
    .Tf(font, fontFactor)
    .Tm(30, 0, 0, 30, horizontalBegin, verticalBegin)
    .Tj(text)
    .ET()
}

module.exports = (writer, text, customFont = null) => {
  const font = writer.getFontForFile(customFont || fontPath, 0)

  let page = writer.createPage(0, 0, horizontalMax, verticalMax)
  let pageCtx = writer.startPageContentContext(page)

  const verticalTextStart = verticalMax - verticalMargin
  writeLine(pageCtx, 'Contents', font, 1, leftMarginEnd, verticalTextStart)
  writeLine(pageCtx, 'Page', font, 0.8, 470, verticalTextStart)

  let pageSize = 0
  // Courier = .4
  // Monofur = .47
  // Monkey = .63, with heading of 1 and .8
  text.forEach(({line}, idx) => {
    const pageIndex = pageSize ? idx % pageSize : idx
    const verticalOffset = lineSpacing * (pageIndex + 1)
    const verticalLineStart = verticalTextStart - verticalOffset
    if (verticalLineStart <= verticalMargin) {
      if (!pageSize) {
        pageSize = idx + 1
      }
      writer.writePage(page)
      page = writer.createPage(0, 0, horizontalMax, verticalMax)
      pageCtx = writer.startPageContentContext(page)
      writeLine(pageCtx, line, font, 0.63, leftMarginEnd, verticalTextStart)
    } else {
      writeLine(pageCtx, line, font, 0.63, leftMarginEnd, verticalLineStart)
    }
  })

  writer.writePage(page)
  return pageSize || text.length
}