    # File lib/prawn/font/afm.rb, line 25
          def initialize(document, name, options={})
            unless BUILT_INS.include?(name)
              raise Prawn::Errors::UnknownFont, "#{name} is not a known font."
            end

            super

            @attributes     = {}
            @glyph_widths   = {}
            @bounding_boxes = {}
            @kern_pairs     = {}

            file_name = @name.dup
            file_name << ".afm" unless file_name =~ /\.afm$/
            file_name = file_name[0] == ?/ ? file_name : find_font(file_name)

            parse_afm(file_name)

            @ascender  = @attributes["ascender"].to_i
            @descender = @attributes["descender"].to_i
            @line_gap  = Float(bbox[3] - bbox[1]) - (@ascender - @descender)
          end