C Copyright(C) 1999-2020 National Technology & Engineering Solutions
C of Sandia, LLC (NTESS).  Under the terms of Contract DE-NA0003525 with
C NTESS, the U.S. Government retains certain rights in this software.
C
C See packages/seacas/LICENSE for details

C=======================================================================
      SUBROUTINE PLTLI2(PLL,PUR,N,XV,YV,NO,XVO,YVO)
      DIMENSION PLL(2),PUR(2),XV(*),YV(*),XVO(*),YVO(*)
      DIMENSION P(2),S(2)
      CHARACTER*6 SUBNAM
      PARAMETER (SUBNAM='PLTLI2')
      LOGICAL INSIDE

      NMAX = NO
      NO = 0
      if (n .gt. 0) then
        S(1) = XV(N)
        S(2) = YV(N)
        DO 2240 I = 1,N
          P(1) = XV(I)
          P(2) = YV(I)
          INSIDE = P(1) .LE. PUR(1)
          IF (INSIDE) THEN
            INSIDE = S(1) .LE. PUR(1)
            IF (INSIDE) THEN
              NO = NO + 1
              IF (NO.GT.NMAX) THEN
                CALL PLTFLU
                CALL SIORPT(SUBNAM,
     *   'Not enough space for output vertices; polygon clip unfinished'
     *            ,2)
                RETURN

              END IF

              XVO(NO) = P(1)
              YVO(NO) = P(2)

            ELSE
              TEMP = PUR(2) - PLL(2)
              FP = - (S(1)-PUR(1))*TEMP
              FQ = - (P(1)-PUR(1))*TEMP
              XL = FQ/ (FQ-FP)
              NO = NO + 1
              IF (NO.GT.NMAX) THEN
                CALL PLTFLU
                CALL SIORPT(SUBNAM,
     *   'Not enough space for output vertices; polygon clip unfinished'
     *            ,2)
                RETURN

              END IF

              XVO(NO) = P(1) + XL* (S(1)-P(1))
              YVO(NO) = P(2) + XL* (S(2)-P(2))
              NO = NO + 1
              IF (NO.GT.NMAX) THEN
                CALL PLTFLU
                CALL SIORPT(SUBNAM,
     *   'Not enough space for output vertices; polygon clip unfinished'
     *            ,2)
                RETURN

              END IF

              XVO(NO) = P(1)
              YVO(NO) = P(2)
            END IF

          ELSE
            INSIDE = S(1) .LE. PUR(1)
            IF (INSIDE) THEN
              TEMP = PUR(2) - PLL(2)
              FP = - (S(1)-PUR(1))*TEMP
              FQ = - (P(1)-PUR(1))*TEMP
              XL = FQ/ (FQ-FP)
              NO = NO + 1
              IF (NO.GT.NMAX) THEN
                CALL PLTFLU
                CALL SIORPT(SUBNAM,
     *   'Not enough space for output vertices; polygon clip unfinished'
     *            ,2)
                RETURN

              END IF

              XVO(NO) = P(1) + XL* (S(1)-P(1))
              YVO(NO) = P(2) + XL* (S(2)-P(2))
            END IF

          END IF

          S(1) = P(1)
          S(2) = P(2)
 2240   CONTINUE
      end if
      RETURN

      END