gistfile1.rb

    class MoveNextLineCommand < DocumentCommand
      def execute
        doc = tab.edit_view.document
        line_ix = doc.line_at_offset(doc.cursor_offset)
        if line_ix == doc.line_count - 1
          doc.cursor_offset = doc.length
        else
          doc.cursor_offset = doc.offset_at_line(line_ix + 1) - doc.delim.length
        end
        doc.ensure_visible(doc.cursor_offset)
        doc.insert(doc.cursor_offset, "\n")
      end
    end