pretty.rb   [plain text]

require 'rexml/formatters/default'

module REXML
  module Formatters
    # Pretty-prints an XML document.  This destroys whitespace in text nodes
    # and will insert carriage returns and indentations.
    #
    # TODO: Add an option to print attributes on new lines
    class Pretty < Default

      # If compact is set to true, then the formatter will attempt to use as
      # little space as possible
      attr_accessor :compact
      # The width of a page.  Used for formatting text
      attr_accessor :width

      # Create a new pretty printer.
      #
      # output::
      #   An object implementing '<<(String)', to which the output will be written.
      # indentation::
      #   An integer greater than 0.  The indentation of each level will be
      #   this number of spaces.  If this is < 1, the behavior of this object
      #   is undefined.  Defaults to 2.
      # ie_hack::
      #   If true, the printer will insert whitespace before closing empty
      #   tags, thereby allowing Internet Explorer's feeble XML parser to
      #   function. Defaults to false.
      def initialize( indentation=2, ie_hack=false )
        @indentation = indentation
        @level = 0
        @ie_hack = ie_hack
        @width = 80
      end

      protected
      def write_element(node, output)
        output << ' '*@level
        output << "<#{node.expanded_name}"

        node.attributes.each_attribute do |attr|
          output << " "
          attr.write( output )
        end unless node.attributes.empty?

        if node.children.empty?
          if @ie_hack
            output << " "
          end
          output << "/" 
        else
          output << ">"
          # If compact and all children are text, and if the formatted output
          # is less than the specified width, then try to print everything on
          # one line
          skip = false
          if compact
            if node.children.inject(true) {|s,c| s & c.kind_of?(Text)}
              string = ""
              old_level = @level
              @level = 0
              node.children.each { |child| write( child, string ) }
              @level = old_level
              if string.length < @width
                output << string
                skip = true
              end
            end
          end
          unless skip
            output << "\n"
            @level += @indentation
            node.children.each { |child|
              next if child.kind_of?(Text) and child.to_s.strip.length == 0
              write( child, output )
              output << "\n"
            }
            @level -= @indentation
            output << ' '*@level
          end
          output << "</#{node.expanded_name}"
        end
        output << ">"
      end

      def write_text( node, output )
        s = node.to_s()
        s.gsub!(/\s/,' ')
        s.squeeze!(" ")
        s = wrap(s, 80-@level)
        s = indent_text(s, @level, " ", true)
        output << (' '*@level + s)
      end

      def write_comment( node, output)
        output << ' ' * @level
        super
      end

      def write_cdata( node, output)
        output << ' ' * @level
        super
      end

      def write_document( node, output )
        # Ok, this is a bit odd.  All XML documents have an XML declaration,
        # but it may not write itself if the user didn't specifically add it,
        # either through the API or in the input document.  If it doesn't write
        # itself, then we don't need a carriage return... which makes this
        # logic more complex.
        node.children.each { |child|
          next if child == node.children[-1] and child.instance_of?(Text)
          unless child == node.children[0] or child.instance_of?(Text) or
            (child == node.children[1] and !node.children[0].writethis)
            output << "\n"
          end
          write( child, output )
        }
      end

      private
      def indent_text(string, level=1, style="\t", indentfirstline=true)
        return string if level < 0
        string.gsub(/\n/, "\n#{style*level}")
      end

      def wrap(string, width)
        # Recursively wrap string at width.
        return string if string.length <= width
        place = string.rindex(' ', width) # Position in string with last ' ' before cutoff
        return string if place.nil?
        return string[0,place] + "\n" + wrap(string[place+1..-1], width)
      end

    end
  end
end