PDP-10 Archive: decus/20-0049/plttop.for from decuslib20-02

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      SUBROUTINE PLTTOP(IWIDE,IX,IY,JX,JY,NEWX,NEWY)
C
C     DONALD BARTH, CHEMISTRY DEPT., HARVARD UNIVERISTY
C
C     ROUTINE TO CALCULATE POSITION ABOVE LINE MIDPOINT
C
C     IWIDE  = DISTANCE TO BE FROM LINE
C     IX     = HORIZONTAL COORDINATE OF START OF LINE
C     IY     = VERTICAL COORDINATE OF START OF LINE
C     JX     = HORIZONTAL COORDINATE OF END OF LINE
C     JY     = VERTICAL COORDINATE OF END OF LINE
C     NEWX   = RETURNED WITH CALCULATED X COORDINATE
C     NEWY   = RETURNED WITH CALCULATED Y COORDINATE
C
C     DETERMINE OCTANT CONTAINING LINE
      IDSTX=JX-IX
      IDSTY=JY-IY
      IF(IDSTX-IDSTY)1,2,3
    1 IF(IDSTX+IDSTY)8,8,4
    2 IF(IDSTX+IDSTY)8,10,8
    3 IF(IDSTX+IDSTY)6,8,8
    4 IF(IDSTX)5,5,7
    5 MOVEX=IWIDE
      GO TO 107
    6 IF(IDSTX)7,5,5
    7 MOVEX=-IWIDE
  107 MOVEY=-(IDSTX*MOVEX)/IDSTY
      KX=IWIDE-(MOVEY/4)
      GO TO 13
    8 MOVEY=IWIDE
      MOVEX=-(IDSTY*MOVEY)/IDSTX
      IF(MOVEX)11,12,12
   10 MOVEY=IWIDE
      MOVEX=0
      GO TO 14
C
C     CORRECT WIDTH OF STRIP FOR ANGLE OF LINE
   11 KX=IWIDE+(MOVEX/4)
      GO TO 13
   12 KX=IWIDE-(MOVEX/4)
   13 MOVEY=(KX*MOVEY)/IWIDE
      MOVEX=(KX*MOVEX)/IWIDE
C
C     RETURN NEW POINT
   14 NEWX=IX+MOVEX+(IDSTX/2)
      NEWY=IY+MOVEY+(IDSTY/2)
      RETURN
      END