RDoc::Markup parses plain text documents and attempts to decompose them into their constituent parts. Some of these parts are high-level: paragraphs, chunks of verbatim text, list entries and the like. Other parts happen at the character level: a piece of bold text, a word in code font. This markup is similar in spirit to that used on WikiWiki webs, where folks create web pages using a simple set of formatting rules.

RDoc::Markup itself does no output formatting: this is left to a different set of classes.

RDoc::Markup is extendable at runtime: you can add new markup elements to be recognised in the documents that RDoc::Markup parses.

RDoc::Markup is intended to be the basis for a family of tools which share the common requirement that simple, plain-text should be rendered in a variety of different output formats and media. It is envisaged that RDoc::Markup could be the basis for formating RDoc style comment blocks, Wiki entries, and online FAQs.

Basic Formatting

• RDoc::Markup looks for a document‘s natural left margin. This is used as the initial margin for the document.
• Consecutive lines starting at this margin are considered to be a paragraph.
• If a paragraph starts with a "*", "-", or with "<digit>.", then it is taken to be the start of a list. The margin in increased to be the first non-space following the list start flag. Subsequent lines should be indented to this new margin until the list ends. For example:

     * this is a list with three paragraphs in
       the first item.  This is the first paragraph.
  
       And this is the second paragraph.
  
       1. This is an indented, numbered list.
       2. This is the second item in that list
  
       This is the third conventional paragraph in the
       first list item.
  
     * This is the second item in the original list
  

• You can also construct labeled lists, sometimes called description or definition lists. Do this by putting the label in square brackets and indenting the list body:

      [cat]  a small furry mammal
             that seems to sleep a lot
  
      [ant]  a little insect that is known
             to enjoy picnics
  

  A minor variation on labeled lists uses two colons to separate the label from the list body:

      cat::  a small furry mammal
             that seems to sleep a lot
  
      ant::  a little insect that is known
             to enjoy picnics
  

  This latter style guarantees that the list bodies’ left margins are aligned: think of them as a two column table.

• Any line that starts to the right of the current margin is treated as verbatim text. This is useful for code listings. The example of a list above is also verbatim text.
• A line starting with an equals sign (=) is treated as a heading. Level one headings have one equals sign, level two headings have two,and so on.
• A line starting with three or more hyphens (at the current indent) generates a horizontal rule. The more hyphens, the thicker the rule (within reason, and if supported by the output device)
• You can use markup within text (except verbatim) to change the appearance of parts of that text. Out of the box, RDoc::Markup supports word-based and general markup.

  Word-based markup uses flag characters around individual words:

  *word*

  displays word in a bold font

  _word_

  displays word in an emphasized font

  +word+

  displays word in a code font

  General markup affects text between a start delimiter and and end delimiter. Not surprisingly, these delimiters look like HTML markup.

  <b>text…</b>

  displays word in a bold font

  <em>text…</em>

  displays word in an emphasized font

  <i>text…</i>

  displays word in an emphasized font

  <tt>text…</tt>

  displays word in a code font

  Unlike conventional Wiki markup, general markup can cross line boundaries. You can turn off the interpretation of markup by preceding the first character with a backslash, so \<b>bold text</b> and \*bold* produce <b>bold text</b> and *bold* respectively.

• Hyperlinks to the web starting http:, mailto:, ftp:, or www. are recognized. An HTTP url that references an external image file is converted into an inline <IMG..>. Hyperlinks starting ‘link:’ are assumed to refer to local files whose path is relative to the —op directory.

  Hyperlinks can also be of the form label[url], in which case the label is used in the displayed text, and url is used as the target. If label contains multiple words, put it in braces: {multi word label}[url].

Synopsis

This code converts input_string to HTML. The conversion takes place in the convert method, so you can use the same RDoc::Markup converter to convert multiple input strings.

  require 'rdoc/markup/to_html'

  h = RDoc::Markup::ToHtml.new

  puts h.convert(input_string)

You can extend the RDoc::Markup parser to recognise new markup sequences, and to add special processing for text that matches a regular epxression. Here we make WikiWords significant to the parser, and also make the sequences {word} and <no>text…</no> signify strike-through text. When then subclass the HTML output class to deal with these:

  require 'rdoc/markup'
  require 'rdoc/markup/to_html'

  class WikiHtml < RDoc::Markup::ToHtml
    def handle_special_WIKIWORD(special)
      "<font color=red>" + special.text + "</font>"
    end
  end

  m = RDoc::Markup.new
  m.add_word_pair("{", "}", :STRIKE)
  m.add_html("no", :STRIKE)

  m.add_special(/\b([A-Z][a-z]+[A-Z]\w+)/, :WIKIWORD)

  wh = WikiHtml.new
  wh.add_tag(:STRIKE, "<strike>", "</strike>")

  puts "<body>#{wh.convert ARGF.read}</body>"