customized gantt_start_compare for Redmine

gantt_start_compare

      def gantt_start_compare(x, y)
        def cmp(a, b)
          if a != nil && b != nil
            a <=> b
          else
            0
          end
        end

        def effective_date(x)
          if (x.class == Version)
            return x.effective_date
          else
            return x.fixed_version.effective_date if x.fixed_version != nil
          end
          nil
        end

        def fixed_version(x)
          if (x.class == Version)
            return x.id
          else
            return x.fixed_version.id if x.fixed_version != nil
          end
          nil
        end

        def due_date(x)
          if x.due_date != nil
            return x.due_date
          else
            return x.fixed_version.effective_date if x.fixed_version != nil
          end
          nil
        end

        if x.start_date.nil?
          -1
        elsif y.start_date.nil?
          1
        else
          # sort by project                                                                                                  
          r = cmp(x.project_id, y.project_id)
          return r if r != 0

          # sort by version                                                                                                  
          r = cmp(effective_date(x), effective_date(y))
          return r if r != 0

          r = cmp(fixed_version(x), fixed_version(y))
          return r if r != 0

          # sort by start date                                                                                               
          r = x.start_date <=> y.start_date
          return r if r != 0

          # sort by end date                                                                                                 
          r = cmp(due_date(x), due_date(y))
          return r if r != 0

          x.id <=> y.id
        end
      end