Ruby extension to create two-column TOC layout for Asciidoctor PDF

two-col-layout.gist.rb

module TOCHelpers

  # Method to convert integers to Roman numerals
  def to_roman(num)
    romans = {
      1000 => 'M', 900 => 'CM', 500 => 'D', 400 => 'CD',
      100 => 'C', 90 => 'XC', 50 => 'L', 40 => 'XL',
      10 => 'X', 9 => 'IX', 5 => 'V', 4 => 'IV', 1 => 'I'
    }
    result = ''
    romans.each do |value, letter|
      result << letter * (num / value)
      num = num % value
    end
    result
  end

  def format_part_title(title, id, page, x_pos, y_pos, column_width)
    formatted_text_box(
      [
        { text: "#{title}", anchor: id }, # Add an anchor to the title
      ],
      at: [x_pos, y_pos],
      width: column_width,
      height: 20,
      size: 14,
      color: '000000',
      align: :left
    )

    # Create a clickable link for the page number
    link_annotation([bounds.left, y_pos, column_width, y_pos - 20], Dest: page)
    move_down 40
  end

  def format_chapter_title(title, id, page, x_pos, y_pos, column_width)
    formatted_text_box(
      [
        { text: "#{title} ........", anchor: id }, # Add an anchor to the title
        { text: page.to_s }
      ],
      at: [x_pos, y_pos],
      width: column_width,
      height: 20,
      size: 12,
      theme_font: :heading,
      color: '888888',
      align: :left
    )

    
    # Create a clickable link for the page number
    link_annotation([bounds.left, y_pos, column_width, y_pos - 20], Dest: page)
    move_down 20
    # stroke 
    stroke_horizontal_rule '00DC82', line_width: 2
    move_down 5
  end

  def format_section_title(title, id, page, x_pos, y_pos, column_width)
    formatted_text_box(
      [
        { text: "#{title} ........", anchor: id }, # Add an anchor to the title
        { text: page.to_s }
      ],
      at: [x_pos, y_pos],
      width: column_width,
      height: 20,
      size: 9,
      color: '000000',
      align: :left
    )
    # Create a clickable link for the page number
    link_annotation([bounds.left, y_pos, column_width, y_pos - 20], Dest: page)
    move_down 8
  end
end

class CustomTwoColumnTocConverter < (Asciidoctor::PDF::Converter)
  register_for 'pdf'
  include TOCHelpers

  def convert_document(doc)
    # Call the original document conversion method
    super

    warn "Page count: #{page_count}"
    toc_start_page = 3
    go_to_page(toc_start_page)
    start_new_page

    warn "Starting TOC Generation"
    # Generate the TOC PDF
    total_pages_filled = 1
      
    # Access parts
    doc.sections.each_with_index do |part, index|
      roman_number = to_roman(index + 1)
      format_part_title("#{roman_number} #{part.title}", part.id , part.attr('pdf-page-start'), 0, cursor, bounds.width) 
      
      # Access sections
      part.sections.each do |chapter|
        format_chapter_title("#{chapter.title}", chapter.id, chapter.attr('pdf-page-start'), 0, cursor, bounds.width) 
        
        # Access subsections
        toc_items = []
        chapter.sections.each do |section|
          toc_items << {
            text: section.title,
            id: section.id,
            page: "#{section.attr('pdf-page-start')}"
          }
        end

          if toc_items.empty?
            ink_prose "No sections available for this chapter", size: 10, align: :center, style: :italic, color: '888888'
            next
          end
          
          column_width = bounds.width / 2
          left_column, right_column = toc_items.each_slice((toc_items.size / 2.0).ceil).to_a
          left_column ||= [] # Ensure left_column is not nil, use empty array if nil
          right_column ||= [] # Ensure left_column is not nil, use empty array if nil

          # Render the sections in two columns
          max_items = [left_column.size, right_column.size].max # Get the maximum number of items between the two columns

          (0...max_items).each do |i|    
            y_pos = cursor          
            # Left Column - Place TOC item if available
            if left_column[i]
              format_section_title("#{left_column[i][:text]}", left_column[i][:id], left_column[i][:page], 0, y_pos, column_width)
            end

            # Left Column - Place TOC item if available
            if right_column[i]
              format_section_title("#{right_column[i][:text]}", right_column[i][:id], right_column[i][:page], column_width, y_pos, column_width)
            end
          end

        # Check if there is enough space for the item, if not, go to the next page
        if cursor < 60 # Adjust this value to control when to break the page
          start_new_page
          total_pages_filled += 1
        end
        move_down 20
        total_pages_filled
      end
      # Check if there is enough space for the item, if not, go to the next page
      if cursor < 60 # Adjust this value to control when to break the page
        start_new_page
        total_pages_filled += 1
      end
      move_down 20
      total_pages_filled
    end

    # Check if there is enough space for the item, if not, go to the next page
    if cursor < 60 # Adjust this value to control when to break the page
      start_new_page
      total_pages_filled += 1
    end

    move_down 20
    total_pages_filled
    go_to_page(toc_start_page + total_pages_filled)

    warn "TOC Generation Completed"
  end
end