class Kramdown::Converter::Html

Converts a Kramdown::Document to HTML.

You can customize the HTML converter by sub-classing it and overriding the convert_NAME methods. Each such method takes the following parameters:

el: The element of type NAME to be converted.
indent: A number representing the current amount of spaces for indent (only used for block-level elements).

The return value of such a method has to be a string containing the element el formatted as HTML element.

Constants

FOOTNOTE_BACKLINK_FMT

Attributes

indent[RW]

The amount of indentation used when nesting HTML tags.

Public Class Methods

new(root, options) click to toggle source

Initialize the HTML converter with the given Kramdown document doc.

Calls superclass method

# File lib/kramdown/converter/html.rb, line 38
def initialize(root, options)
  super
  @footnote_counter = @footnote_start = @options[:footnote_nr]
  @footnotes = []
  @footnotes_by_name = {}
  @footnote_location = nil
  @toc = []
  @toc_code = nil
  @indent = 2
  @stack = []

  # stash string representation of symbol to avoid allocations from multiple interpolations.
  @highlighter_class = " highlighter-#{options[:syntax_highlighter]}"
  @dispatcher = Hash.new {|h, k| h[k] = :"convert_#{k}" }
end

Public Instance Methods

add_syntax_highlighter_to_class_attr(attr, lang = nil) click to toggle source

Add the syntax highlighter name to the 'class' attribute of the given attribute hash. And overwrites or add a “language-LANG” part using the lang parameter if lang is not nil.

# File lib/kramdown/converter/html.rb, line 408
def add_syntax_highlighter_to_class_attr(attr, lang = nil)
  (attr['class'] = (attr['class'] || '') + @highlighter_class).lstrip!
  attr['class'].sub!(/\blanguage-\S+|(^)/) { "language-#{lang}#{$1 ? ' ' : ''}" } if lang
end

convert(el, indent = -@indent) click to toggle source

Dispatch the conversion of the element el to a convert_TYPE method using the type of the element.

# File lib/kramdown/converter/html.rb, line 56
def convert(el, indent = -@indent)
  send(@dispatcher[el.type], el, indent)
end

convert_a(el, indent) click to toggle source

# File lib/kramdown/converter/html.rb, line 271
def convert_a(el, indent)
  format_as_span_html("a", el.attr, inner(el, indent))
end

convert_abbreviation(el, _indent) click to toggle source

# File lib/kramdown/converter/html.rb, line 364
def convert_abbreviation(el, _indent)
  title = @root.options[:abbrev_defs][el.value]
  attr = @root.options[:abbrev_attr][el.value].dup
  attr['title'] = title unless title.empty?
  format_as_span_html("abbr", attr, el.value)
end

convert_blank(_el, _indent) click to toggle source

# File lib/kramdown/converter/html.rb, line 76
def convert_blank(_el, _indent)
  "\n"
end

convert_blockquote(el, indent) click to toggle source

# File lib/kramdown/converter/html.rb, line 140
def convert_blockquote(el, indent)
  format_as_indented_block_html("blockquote", el.attr, inner(el, indent), indent)
end

convert_br(_el, _indent) click to toggle source

# File lib/kramdown/converter/html.rb, line 267
def convert_br(_el, _indent)
  "<br />"
end

convert_codeblock(el, indent) click to toggle source

# File lib/kramdown/converter/html.rb, line 110
def convert_codeblock(el, indent)
  attr = el.attr.dup
  lang = extract_code_language!(attr)
  hl_opts = {}
  highlighted_code = highlight_code(el.value, el.options[:lang] || lang, :block, hl_opts)

  if highlighted_code
    add_syntax_highlighter_to_class_attr(attr, lang || hl_opts[:default_lang])
    "#{' ' * indent}<div#{html_attributes(attr)}>#{highlighted_code}#{' ' * indent}</div>\n"
  else
    result = escape_html(el.value)
    result.chomp!
    if el.attr['class'].to_s =~ /\bshow-whitespaces\b/
      result.gsub!(/(?:(^[ \t]+)|([ \t]+$)|([ \t]+))/) do |m|
        suffix = ($1 ? '-l' : ($2 ? '-r' : ''))
        m.scan(/./).map do |c|
          case c
          when "\t" then "<span class=\"ws-tab#{suffix}\">\t</span>"
          when " " then "<span class=\"ws-space#{suffix}\">&#8901;</span>"
          end
        end.join('')
      end
    end
    code_attr = {}
    code_attr['class'] = "language-#{lang}" if lang
    "#{' ' * indent}<pre#{html_attributes(attr)}>" \
      "<code#{html_attributes(code_attr)}>#{result}\n</code></pre>\n"
  end
end

convert_codespan(el, _indent) click to toggle source

# File lib/kramdown/converter/html.rb, line 279
def convert_codespan(el, _indent)
  attr = el.attr.dup
  lang = extract_code_language(attr)
  hl_opts = {}
  result = highlight_code(el.value, lang, :span, hl_opts)
  if result
    add_syntax_highlighter_to_class_attr(attr, lang || hl_opts[:default_lang])
  else
    result = escape_html(el.value)
  end

  format_as_span_html('code', attr, result)
end

convert_comment(el, indent) click to toggle source

# File lib/kramdown/converter/html.rb, line 259
def convert_comment(el, indent)
  if el.options[:category] == :block
    "#{' ' * indent}<!-- #{el.value} -->\n"
  else
    "<!-- #{el.value} -->"
  end
end

convert_dd(el, indent)

Alias for: convert_li

convert_dl(el, indent) click to toggle source

# File lib/kramdown/converter/html.rb, line 173
def convert_dl(el, indent)
  format_as_indented_block_html("dl", el.attr, inner(el, indent), indent)
end

convert_dt(el, indent) click to toggle source

# File lib/kramdown/converter/html.rb, line 189
def convert_dt(el, indent)
  attr = el.attr.dup
  @stack.last.options[:ial][:refs].each do |ref|
    if ref =~ /\Aauto_ids(?:-([\w-]+))?/
      attr['id'] = "#{$1}#{basic_generate_id(el.options[:raw_text])}".lstrip
      break
    end
  end if !attr['id'] && @stack.last.options[:ial] && @stack.last.options[:ial][:refs]
  format_as_block_html("dt", attr, inner(el, indent), indent)
end

convert_em(el, indent) click to toggle source

# File lib/kramdown/converter/html.rb, line 318
def convert_em(el, indent)
  format_as_span_html(el.type, el.attr, inner(el, indent))
end

Also aliased as: convert_strong

convert_entity(el, _indent) click to toggle source

# File lib/kramdown/converter/html.rb, line 323
def convert_entity(el, _indent)
  entity_to_str(el.value, el.options[:original])
end

convert_footnote(el, _indent) click to toggle source

# File lib/kramdown/converter/html.rb, line 293
def convert_footnote(el, _indent)
  repeat = ''
  name = @options[:footnote_prefix] + el.options[:name]
  if (footnote = @footnotes_by_name[name])
    number = footnote[2]
    repeat = ":#{footnote[3] += 1}"
  else
    number = @footnote_counter
    @footnote_counter += 1
    @footnotes << [name, el.value, number, 0]
    @footnotes_by_name[name] = @footnotes.last
  end
  "<sup id=\"fnref:#{name}#{repeat}\" role=\"doc-noteref\">" \
    "<a href=\"#fn:#{name}\" class=\"footnote\" rel=\"footnote\">" \
    "#{number}</a></sup>"
end

convert_header(el, indent) click to toggle source

# File lib/kramdown/converter/html.rb, line 144
def convert_header(el, indent)
  attr = el.attr.dup
  if @options[:auto_ids] && !attr['id']
    attr['id'] = generate_id(el.options[:raw_text])
  end
  @toc << [el.options[:level], attr['id'], el.children] if attr['id'] && in_toc?(el)
  level = output_header_level(el.options[:level])
  format_as_block_html("h#{level}", attr, inner(el, indent), indent)
end

convert_hr(el, indent) click to toggle source

# File lib/kramdown/converter/html.rb, line 154
def convert_hr(el, indent)
  "#{' ' * indent}<hr#{html_attributes(el.attr)} />\n"
end

convert_html_element(el, indent) click to toggle source

# File lib/kramdown/converter/html.rb, line 200
def convert_html_element(el, indent)
  res = inner(el, indent)
  if el.options[:category] == :span
    "<#{el.value}#{html_attributes(el.attr)}" + \
      (res.empty? && HTML_ELEMENTS_WITHOUT_BODY.include?(el.value) ? " />" : ">#{res}</#{el.value}>")
  else
    output = +''
    if @stack.last.type != :html_element || @stack.last.options[:content_model] != :raw
      output << ' ' * indent
    end
    output << "<#{el.value}#{html_attributes(el.attr)}"
    if el.options[:is_closed] && el.options[:content_model] == :raw
      output << " />"
    elsif !res.empty? && el.options[:content_model] != :block
      output << ">#{res}</#{el.value}>"
    elsif !res.empty?
      output << ">\n#{res.chomp}\n" << ' ' * indent << "</#{el.value}>"
    elsif HTML_ELEMENTS_WITHOUT_BODY.include?(el.value)
      output << " />"
    else
      output << "></#{el.value}>"
    end
    output << "\n" if @stack.last.type != :html_element || @stack.last.options[:content_model] != :raw
    output
  end
end

convert_img(el, _indent) click to toggle source

# File lib/kramdown/converter/html.rb, line 275
def convert_img(el, _indent)
  "<img#{html_attributes(el.attr)} />"
end

convert_li(el, indent) click to toggle source

# File lib/kramdown/converter/html.rb, line 177
def convert_li(el, indent)
  output = ' ' * indent << "<#{el.type}" << html_attributes(el.attr) << ">"
  res = inner(el, indent)
  if el.children.empty? || (el.children.first.type == :p && el.children.first.options[:transparent])
    output << res << (res =~ /\n\Z/ ? ' ' * indent : '')
  else
    output << "\n" << res << ' ' * indent
  end
  output << "</#{el.type}>\n"
end

Also aliased as: convert_dd

convert_math(el, indent) click to toggle source

# File lib/kramdown/converter/html.rb, line 350
def convert_math(el, indent)
  if (result = format_math(el, indent: indent))
    result
  else
    attr = el.attr.dup
    attr['class'] = "#{attr['class']} kdmath".lstrip
    if el.options[:category] == :block
      format_as_block_html('div', attr, "$$\n#{el.value}\n$$", indent)
    else
      format_as_span_html('span', attr, "$#{el.value}$")
    end
  end
end

convert_ol(el, indent)

Alias for: convert_ul

convert_p(el, indent) click to toggle source

# File lib/kramdown/converter/html.rb, line 85
def convert_p(el, indent)
  if el.options[:transparent]
    inner(el, indent)
  elsif el.children.size == 1 && el.children.first.type == :img &&
      el.children.first.options[:ial]&.[](:refs)&.include?('standalone')
    convert_standalone_image(el, indent)
  else
    format_as_block_html("p", el.attr, inner(el, indent), indent)
  end
end

convert_raw(el, _indent) click to toggle source

# File lib/kramdown/converter/html.rb, line 310
def convert_raw(el, _indent)
  if !el.options[:type] || el.options[:type].empty? || el.options[:type].include?('html')
    el.value + (el.options[:category] == :block ? "\n" : '')
  else
    ''
  end
end

convert_root(el, indent) click to toggle source

# File lib/kramdown/converter/html.rb, line 371
def convert_root(el, indent)
  result = inner(el, indent)
  if @footnote_location
    result.sub!(/#{@footnote_location}/, footnote_content.gsub(/\\/, "\\\\\\\\"))
  else
    result << footnote_content
  end
  if @toc_code
    toc_tree = generate_toc_tree(@toc, @toc_code[0], @toc_code[1] || {})
    text = if !toc_tree.children.empty?
             convert(toc_tree, 0)
           else
             ''
           end
    result.sub!(/#{@toc_code.last}/, text.gsub(/\\/, "\\\\\\\\"))
  end
  result
end

convert_smart_quote(el, _indent) click to toggle source

# File lib/kramdown/converter/html.rb, line 346
def convert_smart_quote(el, _indent)
  entity_to_str(smart_quote_entity(el))
end

convert_standalone_image(el, indent) click to toggle source

Helper method used by convert_p to convert a paragraph that only contains a single :img element.

# File lib/kramdown/converter/html.rb, line 98
def convert_standalone_image(el, indent)
  figure_attr = el.attr.dup
  image_attr = el.children.first.attr.dup

  figure_attr['class'] = image_attr.delete('class') if image_attr.key?('class') and not figure_attr.key?('class')
  figure_attr['id'] = image_attr.delete('id') if image_attr.key?('id') and not figure_attr.key?('id')

  body = "#{' ' * (indent + @indent)}<img#{html_attributes(image_attr)} />\n" \
    "#{' ' * (indent + @indent)}<figcaption>#{image_attr['alt']}</figcaption>\n"
  format_as_indented_block_html("figure", figure_attr, body, indent)
end

convert_strong(el, indent)

Alias for: convert_em

convert_table(el, indent) click to toggle source

# File lib/kramdown/converter/html.rb, line 237
def convert_table(el, indent)
  format_as_indented_block_html(el.type, el.attr, inner(el, indent), indent)
end

Also aliased as: convert_thead, convert_tbody, convert_tfoot, convert_tr

convert_tbody(el, indent)

Alias for: convert_table

convert_td(el, indent) click to toggle source

# File lib/kramdown/converter/html.rb, line 247
def convert_td(el, indent)
  res = inner(el, indent)
  type = (@stack[-2].type == :thead ? :th : :td)
  attr = el.attr
  alignment = @stack[-3].options[:alignment][@stack.last.children.index(el)]
  if alignment != :default
    attr = el.attr.dup
    attr['style'] = (attr.key?('style') ? "#{attr['style']}; " : '') + "text-align: #{alignment}"
  end
  format_as_block_html(type, attr, res.empty? ? entity_to_str(ENTITY_NBSP) : res, indent)
end

convert_text(el, _indent) click to toggle source

# File lib/kramdown/converter/html.rb, line 80
def convert_text(el, _indent)
  escaped = escape_html(el.value, :text)
  @options[:remove_line_breaks_for_cjk] ? fix_cjk_line_break(escaped) : escaped
end

convert_tfoot(el, indent)

Alias for: convert_table

convert_thead(el, indent)

Alias for: convert_table

convert_tr(el, indent)

Alias for: convert_table

convert_typographic_sym(el, _indent) click to toggle source

# File lib/kramdown/converter/html.rb, line 338
def convert_typographic_sym(el, _indent)
  if (result = @options[:typographic_symbols][el.value])
    escape_html(result, :text)
  else
    TYPOGRAPHIC_SYMS[el.value].map {|e| entity_to_str(e) }.join('')
  end
end

convert_ul(el, indent) click to toggle source

# File lib/kramdown/converter/html.rb, line 161
def convert_ul(el, indent)
  if !@toc_code && el.options.dig(:ial, :refs)&.include?('toc')
    @toc_code = [el.type, el.attr, ZERO_TO_ONETWENTYEIGHT.map { rand(36).to_s(36) }.join]
    @toc_code.last
  elsif !@footnote_location && el.options.dig(:ial, :refs)&.include?('footnotes')
    @footnote_location = ZERO_TO_ONETWENTYEIGHT.map { rand(36).to_s(36) }.join
  else
    format_as_indented_block_html(el.type, el.attr, inner(el, indent), indent)
  end
end

Also aliased as: convert_ol

convert_xml_comment(el, indent) click to toggle source

# File lib/kramdown/converter/html.rb, line 227
def convert_xml_comment(el, indent)
  if el.options[:category] == :block &&
      (@stack.last.type != :html_element || @stack.last.options[:content_model] != :raw)
    ' ' * indent << el.value << "\n"
  else
    el.value
  end
end

Also aliased as: convert_xml_pi

convert_xml_pi(el, indent)

Alias for: convert_xml_comment

fix_for_toc_entry(elements) click to toggle source

Fixes the elements for use in a TOC entry.

# File lib/kramdown/converter/html.rb, line 452
def fix_for_toc_entry(elements)
  remove_footnotes(elements)
  unwrap_links(elements)
  elements
end

footnote_content() click to toggle source

Return an HTML ordered list with the footnote content for the used footnotes.

# File lib/kramdown/converter/html.rb, line 487
def footnote_content
  ol = Element.new(:ol)
  ol.attr['start'] = @footnote_start if @footnote_start != 1
  i = 0
  backlink_text = escape_html(@options[:footnote_backlink], :text)
  while i < @footnotes.length
    name, data, _, repeat = *@footnotes[i]
    li = Element.new(:li, nil, 'id' => "fn:#{name}", 'role' => 'doc-endnote')
    li.children = Marshal.load(Marshal.dump(data.children))

    para = nil
    if li.children.last.type == :p || @options[:footnote_backlink_inline]
      parent = li
      while !parent.children.empty? && ![:p, :header].include?(parent.children.last.type)
        parent = parent.children.last
      end
      para = parent.children.last
      insert_space = true
    end

    unless para
      li.children << (para = Element.new(:p))
      insert_space = false
    end

    unless @options[:footnote_backlink].empty?
      nbsp = entity_to_str(ENTITY_NBSP)
      value = sprintf(FOOTNOTE_BACKLINK_FMT, (insert_space ? nbsp : ''), name, backlink_text)
      para.children << Element.new(:raw, value)
      (1..repeat).each do |index|
        value = sprintf(FOOTNOTE_BACKLINK_FMT, nbsp, "#{name}:#{index}",
                        "#{backlink_text}<sup>#{index + 1}</sup>")
        para.children << Element.new(:raw, value)
      end
    end

    ol.children << Element.new(:raw, convert(li, 4))
    i += 1
  end
  if ol.children.empty?
    ''
  else
    format_as_indented_block_html('div', {class: "footnotes", role: "doc-endnotes"}, convert(ol, 2), 0)
  end
end

format_as_block_html(name, attr, body, indent) click to toggle source

Format the given element as block HTML.

# File lib/kramdown/converter/html.rb, line 396
def format_as_block_html(name, attr, body, indent)
  "#{' ' * indent}<#{name}#{html_attributes(attr)}>#{body}</#{name}>\n"
end

format_as_indented_block_html(name, attr, body, indent) click to toggle source

Format the given element as block HTML with a newline after the start tag and indentation before the end tag.

# File lib/kramdown/converter/html.rb, line 402
def format_as_indented_block_html(name, attr, body, indent)
  "#{' ' * indent}<#{name}#{html_attributes(attr)}>\n#{body}#{' ' * indent}</#{name}>\n"
end

format_as_span_html(name, attr, body) click to toggle source

Format the given element as span HTML.

# File lib/kramdown/converter/html.rb, line 391
def format_as_span_html(name, attr, body)
  "<#{name}#{html_attributes(attr)}>#{body}</#{name}>"
end

generate_toc_tree(toc, type, attr) click to toggle source

Generate and return an element tree for the table of contents.

# File lib/kramdown/converter/html.rb, line 414
def generate_toc_tree(toc, type, attr)
  sections = Element.new(type, nil, attr.dup)
  sections.attr['id'] ||= 'markdown-toc'
  stack = []
  toc.each do |level, id, children|
    li = Element.new(:li, nil, nil, level: level)
    li.children << Element.new(:p, nil, nil, transparent: true)
    a = Element.new(:a, nil)
    a.attr['href'] = "##{id}"
    a.attr['id'] = "#{sections.attr['id']}-#{id}"
    a.children.concat(fix_for_toc_entry(Marshal.load(Marshal.dump(children))))
    li.children.last.children << a
    li.children << Element.new(type)

    success = false
    until success
      if stack.empty?
        sections.children << li
        stack << li
        success = true
      elsif stack.last.options[:level] < li.options[:level]
        stack.last.children.last.children << li
        stack << li
        success = true
      else
        item = stack.pop
        item.children.pop if item.children.last.children.empty?
      end
    end
  end
  until stack.empty?
    item = stack.pop
    item.children.pop if item.children.last.children.empty?
  end
  sections
end

inner(el, indent) click to toggle source

Return the converted content of the children of el as a string. The parameter indent has to be the amount of indentation used for the element el.

Pushes el onto the @stack before converting the child elements and pops it from the stack afterwards.

# File lib/kramdown/converter/html.rb, line 65
def inner(el, indent)
  result = +''
  indent += @indent
  @stack.push(el)
  el.children.each do |inner_el|
    result << send(@dispatcher[inner_el.type], inner_el, indent)
  end
  @stack.pop
  result
end

obfuscate(text) click to toggle source

Obfuscate the text by using HTML entities.

# File lib/kramdown/converter/html.rb, line 475
def obfuscate(text)
  result = +''
  text.each_byte do |b|
    result << (b > 128 ? b.chr : sprintf("&#%03d;", b))
  end
  result.force_encoding(text.encoding)
  result
end

remove_footnotes(elements) click to toggle source

Remove all footnotes from the given elements.

# File lib/kramdown/converter/html.rb, line 467
def remove_footnotes(elements)
  elements.delete_if do |c|
    remove_footnotes(c.children)
    c.type == :footnote
  end
end

unwrap_links(elements) click to toggle source

Remove all link elements by unwrapping them.

# File lib/kramdown/converter/html.rb, line 459
def unwrap_links(elements)
  elements.map! do |c|
    unwrap_links(c.children)
    c.type == :a ? c.children : c
  end.flatten!
end