Rakefile

require 'slippery'
require 'fileutils'
require 'tempfile'
require_relative 'watch_task'

namespace :slippery do
  extend Slippery::ProcessorHelpers::ClassMethods

  NAME = 'learn_to_learn'

  desc 'watch the presentation and theme for changes and rebuild'
  watch ["#{NAME}.md", 'stylesheets/stylesheet.css', 'images', 'javascripts'] do
    dest = Tempfile.new("#{NAME}.html")
    File.open("#{NAME}.html") { |src| FileUtils.copy_stream(src, dest) }
    dest.close
    Rake::Task['slippery:build'].execute
    puts "="*80
    print `diff -u #{dest.path} #{NAME}.html` if File.exist? "#{NAME}.html"
  end

  task :profile do
    require 'perftools'
    PerfTools::CpuProfiler.start("/tmp/slippery_profile") do
      Rake::Task['slippery:build'].execute
    end
  end

  task :benchmark do
    require 'benchmark'
    10.times do
      puts Benchmark.measure {
        Rake::Task['slippery:build'].execute
      }
    end
  end

  desc 'build the presentation html'
  task :build do
    Dir["#{NAME}.md"].each do |infile|
      doc = markdown_to_doc(infile)
      File.write(infile.sub(/md$/, 'html'), doc.to_html)
    end
  end

  task :toc do
    doc = markdown_to_doc('presentation.md').select('.heading') do |heading|
      puts "- #{heading.text.strip}"
    end
  end

  def markdown_to_doc(infile)
    include Slippery::Processors

    doc = Slippery::Document.new(File.read(infile))
    doc = Slippery::Presentation.new(doc,
      type: :reveal_js,
      theme: 'beige',
      controls: false,
      backgroundTransition: 'slide',
      history: true,
      plugins: [:notes]
    )

    doc.process(
      GraphvizDot.new('.language-dot'),
      add_custom_assets,
      init_highlighting,
      set_prettyprint_classes,
      set_heading_background_color,
      split_subsection_slides,
      split_bigsection_slides,
      override_svg_font,
      notes,
      SelfContained
    )
  end

  processor :set_prettyprint_classes, '[class~=language-ruby] code' do |code|
    code.add_class('prettyprint ruby')
  end

  processor :set_heading_background_color, '.heading' do |section|
    section.attr('data-background-color',"#4d7e65")
  end

  processor :split_subsection_slides, '.subsections' do |section|
    section.add_class('fragmented').map_children.with_index do |ch, idx|
      (ch.tag == :p && idx > 1) ? ch.add_class('fragment') : ch
    end
  end

  processor :notes, '.language-notes' do |notes|
    notes.set_tag(:aside).add_class('notes').set_children(notes.text.split("\n").flat_map{|n| [n, H[:br]]})
  end

  processor :split_bigsection_slides, '.bigsections p' do |para|
    H[:section, para].add_class(:big)
  end

  processor :override_svg_font, 'svg text[font-family]' do |text|
    text.attr('font-family', 'Lato')
  end

  processor :add_custom_assets, 'head' do |h|
    h <<= H[:title, "Learn to Learn"]
    h <<= H[:link, rel: 'stylesheet', href: file_uri_relative('stylesheets/stylesheet.css')]
    h <<= H[:link, rel: 'stylesheet', href: file_uri_relative('stylesheets/highlight.css')]
    h <<= H[:script, src: 'http://code.jquery.com/jquery-1.10.1.min.js']
    h <<= H[:script, src: file_uri_relative('javascripts/impress_js_addons.js')]
    h <<= H[:script, src: file_uri_relative('javascripts/highlight.pack.js')]
    h <<= H[:script, 'hljs.initHighlightingOnLoad();']
  end

  processor :init_highlighting, 'body' do |body|
    body.add_child(H[:script, '$("code").each(function(i,e){hljs.highlightBlock(e);});'])
  end

  def file_uri_relative(path)
    "file://#{File.expand_path(File.join('..', path), __FILE__)}"
  end
end

watch_task.rb

require 'rb-inotify'

class WatchTask
  def initialize(name, files, &block)
    Rake::Task.define_task name do
      Array(files).each do |pattern|
        notifier.watch(pattern, :modify, &block)
      end
      at_exit do
        block.call
        notifier.run
      end
    end
  end

  def notifier
    @notifier ||= INotify::Notifier.new
  end
end

def watch(files, name = :watch, &block)
  WatchTask.new(name, files, &block)
end