/ OPTIONS PROCESSING
/ strip IDs the same way revealjs does (remove when hakimel/reveal.js#1230 is fixed)
- _id = id.gsub(/[^a-zA-Z0-9\-\_\:\.]/, '')

/ hide slides on %conceal, %notitle and named "!"
- titleless = (title = self.title) == '!'
- hide_title = (titleless || (option? :notitle) || (option? :conceal))

- vertical_slides = find_by(context: :section) {|section| section.level == 2 }

/ extracting block image attributes to find an image to use as a
/ background_image attribute
- data_background_image, data_background_size, data_background_repeat,
  data_background_transition = nil

/ process the first image block in the current section that acts as a background
- section_images = blocks.map do |block|
  - if (ctx = block.context) == :image
    - ['background', 'canvas'].include?(block.attr 1) ? block : []
  - elsif ctx == :section
    - []
  - else
    - block.find_by(context: :image) {|image| ['background', 'canvas'].include?(image.attr 1) } || []
- if (bg_image = section_images.flatten.first)
  - data_background_image = image_uri(bg_image.attr 'target')
  / make sure no crash on nil and default values make sense
  - data_background_size = bg_image.attr 'size'
  - data_background_repeat = bg_image.attr 'repeat'
  - data_background_transition = bg_image.attr 'transition'

/ background-image section attribute overrides the image one
- if attr? 'background-image'
  - data_background_image = image_uri(attr 'background-image')

- if attr? 'background-color'
  - data_background_color = attr 'background-color'

/ RENDERING
/ render parent section of vertical slides set
- if @level == 1 && !vertical_slides.empty?
  section
    / TODO: try to get rid of duplication w/ standalone slide section
    section(id=(titleless ? nil : _id)
      class=roles
      data-transition=(attr 'transition')
      data-transition-speed=(attr 'transition-speed')
      data-background-color=data_background_color
      data-background-image=data_background_image
      data-background-size=(data_background_size || attr('background-size'))
      data-background-repeat=(data_background_repeat || attr('background-repeat'))
      data-background-transition=(data_background_transition || attr('background-transition'))
      data-background-iframe=(attr "background-iframe")
      data-background-video=(attr "background-video")
      data-background-video-loop=((attr? 'background-video-loop') || (option? 'loop'))
      data-background-video-muted=((attr? 'background-video-muted') || (option? 'muted'))
      data-state=(attr 'state'))

      - unless hide_title
        h2=title
      - (blocks - vertical_slides).each do |block|
        =block.convert
    - vertical_slides.each do |subsection|
      =subsection.convert

/ render standalone slides (or vertical slide subsection)
- else
  - if @level >= 3
    / dynamic tags which maps <hX> with level
    *{tag: %(h#{@level})} =title
    =content.chomp
  - else
    section(id=(titleless ? nil : _id)
      class=roles
      data-transition=(attr 'transition')
      data-transition-speed=(attr 'transition-speed')
      data-background-color=data_background_color
      data-background-image=data_background_image
      data-background-size=(data_background_size || attr('background-size'))
      data-background-repeat=(data_background_repeat || attr('background-repeat'))
      data-background-transition=(data_background_transition || attr('background-transition'))
      data-background-iframe=(attr "background-iframe")
      data-background-video=(attr "background-video")
      data-background-video-loop=((attr? 'background-video-loop') || (option? 'loop'))
      data-background-video-muted=((attr? 'background-video-muted') || (option? 'muted'))
      data-state=(attr 'state'))

      - unless hide_title
        h2=title
      =content.chomp