Class: Less::Engine

Inherits:
String
  • Object
show all
Defined in:
lib/less/engine.rb

Constant Summary collapse

COMPOUND =

Compound properties, such as ‘border: 1px solid black`

{'font' => true, 'background' => false, 'border' => false }
REGEX = 
{
  :path     => /([#.][->#.\w ]+)?( ?> ?)?/,              # #header > .title
  :selector => /[-\w #.,>*:\(\)]/,                       # .cow .milk > a
  :variable => /@([-\w]+)/,                              # @milk-white
  :property => /@[-\w]+|[-a-z]+/,                        # font-size
  :color    => /#([a-zA-Z0-9]{3,6})\b/,                  # #f0f0f0
  :number   => /\d+(?>\.\d+)?/,                          # 24.8
  :unit     => /px|em|pt|cm|mm|%/                        # em
}

Instance Method Summary collapse

Constructor Details

#initialize(s) ⇒ Engine

Returns a new instance of Engine.



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# File 'lib/less/engine.rb', line 17

def initialize s
  super
  @tree = Tree.new self.hashify
end

Instance Method Details

#compile ⇒ Object Also known as: render 



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# File 'lib/less/engine.rb', line 22

def compile     
  #
  # Parse the variables and mixins
  #
  # We use symbolic keys, such as :mixins, to store LESS-only data,
  # each branch has its own :mixins => [], and :variables => {}
  # Once a declaration has been recognised as LESS-specific, it is copied 
  # in the appropriate data structure in that branch. The declaration itself
  # can then be deleted.
  #
  @tree = @tree.traverse :leaf do |key, value, path, node|
    matched = if match = key.match( REGEX[:variable] )          
      node[:variables] ||= Tree.new
      node[:variables][ match.captures.first ] = value
    elsif value == :mixin
      node[:mixins] ||= []          
      node[:mixins] << key
    end
    node.delete key if matched # Delete the property if it's LESS-specific
  end
  
  #
  # Evaluate mixins
  #
  @tree = @tree.traverse :branch do |path, node|
    if node.include? :mixins
      node[:mixins].each do |m|
        @tree.find( :mixin, m.delete(' ').split('>') ).each {|k, v| node[ k ] = v }
      end
    end
  end
  
  # Call `evaluate` on variables, such as '@dark: @light / 2'
  @tree = @tree.traverse :branch do |path, node|
    node.vars.each do |key, value|
      evaluate key, value, path, node.vars
    end if node.vars?
  end
  
  # Call `evaluate` on css properties, such as 'font-size: @big'
  @tree = @tree.traverse :leaf do |key, value, path, node|
    evaluate key, value, path, node
  end
  
  #
  # Evaluate operations (2+2)
  #
  # Units are: 1px, 1em, 1%, #111
  @tree = @tree.traverse :leaf do |key, value, path, node|
    node[ key ] = value.gsub /(#{REGEX[:operand]}(\s?)[-+\/*](\4))+(#{REGEX[:operand]})/ do |operation|
      # Disallow operations certain compound declarations
      if COMPOUND[key]
        next value
      else
        raise CompoundOperationError, "#{key}: #{value}"
      end if COMPOUND.include? key

      if (unit = operation.scan(/#{REGEX[:numeric]}|(#)/i).flatten.compact.uniq).size <= 1
        unit = unit.join            
        operation = if unit == '#'
          evaluate = lambda do |v| 
            result = eval v
            unit + ( result.zero?? '000' : result.to_s(16) )
          end
          operation.gsub REGEX[:color] do
            hex = $1 * ( $1.size < 6 ? 6 / $1.size : 1 )
            hex.to_i(16)
          end.delete unit
        else
          evaluate = lambda {|v| eval( v ).to_s + unit }
          operation.gsub REGEX[:unit], ''
        end.to_s                
        next if operation.match /[a-z]/i
        evaluate.call operation
      else
        raise MixedUnitsError, value
      end
    end
  end
end

#evaluate(key, expression, path, node) ⇒ Object

Evaluate variables



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# File 'lib/less/engine.rb', line 107

def evaluate key, expression, path, node               
  if expression.is_a? String and expression.include? '@' # There's a var to evaluate  
    expression.scan /#{REGEX[:path]}#{REGEX[:variable]}/ do |var|
      name = var.last
      var = var.join.delete ' '
      
      value = if var.include? '>'
        @tree.find :var, var.split('>')                  # Try finding it in a specific namespace
      else            
       node.var(var) or @tree.nearest var, path          # Try local first, then nearest scope            
      end
      
      if value
        # Substitute variable with value
        node[ key ] = node[ key ].gsub /#{REGEX[:path]}@#{name}/, value
      else
        node.delete key                                  # Discard the declaration if the variable wasn't found
      end
    end    
  end
end

#hashify ⇒ Object 



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# File 'lib/less/engine.rb', line 133

def hashify
#
# Parse the LESS structure into a hash
#
###
  #   less:     color: black;
  #   hashify: "color" => "black"
  #
  hash = self.gsub(/\t+/, ' ').                                                       # Tabs
              gsub(/\r\n/, "\n").                                                     # m$
              gsub(/\/\/.*/, '').                                                     # Comments //
              gsub(/\/\*.*?\*\//m, '').                                               # Comments /*
              gsub(/"/, "'").                                                         # " => '
              gsub(/("|')(.+?)(\1)/) { $1 + CGI.escape( $2 ) + $1 }.                  # Escape string values
              gsub(/(#{REGEX[:property]}):\s*(.+?)\s*(;|(?=\}))/,'"\1"=>"\2",').      # Rules
              gsub(/\}/, "},").                                                       # Closing }
              gsub(/( *)(#{REGEX[:selector]}+?)[ \n]*(?=\{)/m, '\1"\2"=>').           # Selectors
              gsub(/([.#][->\w .#]+);/, '"\\1" => :mixin,')                           # Mixins
  eval "{" + hash + "}"                                                               # Return {hash}
end

#to_css(chain = :desc) ⇒ Object 



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# File 'lib/less/engine.rb', line 129

def to_css chain = :desc
  self.compile.to_css chain
end