SUBROUTINE RVSDIAG
!   routine to test for and reverse diagonals
    USE BLK1MOD
    USE BLK2MOD
    INCLUDE 'BFILES.I90'
    
    REAL IGrDistanceLine
    dist(n1,n2)=sqrt((xusr(n1)-xusr(n2))**2+(yusr(n1)-yusr(n2))**2)
!     save current file

      IFILOUT=IACTVFIL+50
      CALL WRTFIL(IFILOUT)
	
!   fill midsides
     CALL FILM(1)
!   get elements connected to nodes table
    MIDSIDE=0
    IERR=1
    CALL NDNECON(IERR)

!   gets nodes nodes opposite
!   loop on midsides
    KCOUNT=0
    DO N=1,NP
	    IF(NECON(N,2) .EQ. 0) CYCLE
		NEL1=NECON(N,1)
		NEL2=NECON(N,2)
        WRITE(160,*) 'ELTS',NEL1,NEL2
!   test for two triangles
		IF(NCORN(NEL1) .EQ. 8  .OR.  NCORN(NEL1) .LT. 6) CYCLE
		IF(NCORN(NEL2) .EQ. 8  .OR.  NCORN(NEL2) .LT. 6) CYCLE
!   get the adjacent nodes N1 and N2
		DO K=2,6,2
		  IF(N .EQ. NOP(NEL1,K)) THEN
!   get the adjacent nodes N1 and N2
		    N1=NOP(NEL1,K-1)
		    N2=K+1
		    IF(N2 .GT. 6) N2=1
		    N2=NOP(NEL1,N2)
!   get first of two nodes facing each other  N3
		    N3=K+3
		    IF(N3 .GT. 6) N3=N3-6
		    N3=NOP(NEL1,N3)
          ENDIF
		ENDDO
!   get second of two nodes facing each other  N4
		DO K=2,6,2
		  IF(N .EQ. NOP(NEL2,K)) THEN
		    N4=K+3
		    IF(N4 .GT. 6) N4=N4-6
		    N4=NOP(NEL2,N4)
          ENDIF
        ENDDO	
        IF(WD(N1) .EQ. WD(N3)  .AND.  WD(N2) .EQ. WD(N3)) GO TO 500
        IF(WD(N1) .EQ. WD(N4)  .AND.  WD(N2) .EQ. WD(N4)) GO TO 500
        IF(WD(N1) .EQ. WD(N3)  .AND.  WD(N1) .EQ. WD(N4)) GO TO 500
        IF(WD(N2) .EQ. WD(N3)  .AND.  WD(N2) .EQ. WD(N4)) GO TO 500
        X1=XUSR(N1)
        X2=XUSR(N2)
        X3=XUSR(N3)
        X4=XUSR(N4)
        Y1=YUSR(N1)
        Y2=YUSR(N2)
        Y3=YUSR(N3)
        Y4=YUSR(N4)
        CALL IGRINTERSECTLINE(X1,Y1,X2,Y2,X3,Y3,X4,Y4,XINTER,YINTER,ISTAT)
        IF(ISTAT .NE. 5) GO TO 500
        METHOD=1
        D1=IGrDistanceLine(X1,Y1,X2,Y2,XINTER,YINTER,METHOD)
!        D2=IGrDistanceLine(X1,Y1,X2,Y2,X4,Y4,METHOD)
        D1=SQRT((X1-XINTER)**2+(Y1-YINTER)**2)
        D2=SQRT((X2-XINTER)**2+(Y2-YINTER)**2)
        D3=SQRT((X1-X2)**2+(Y1-Y2)**2)
        IF(D1 .LT. 0.05*D3) GO TO 500
        IF(D2 .LT. 0.05*D3) GO TO 500
        IF(WD(N3) .EQ. WD(N1)) THEN
          IF(ABS(WD(N4)-WD(N3)) .LT. ABS(WD(N2)-WD(N3))) THEN
            KCOUNT=KCOUNT+1
        WRITE(160,*) 'QV1',KCOUNT,NEL1,NEL2,N1,N2,N3,N4
            CALL DUMPBIN(KCOUNT,1)
            CALL REVERS(NEL1,NEL2)
            GO TO 500
          ELSE
            GO TO 500
          ENDIF
        ELSEIF(WD(N3) .EQ. WD(N2)) THEN
          IF(ABS(WD(N4)-WD(N3)) .LT. ABS(WD(N3)-WD(N2))) THEN
            KCOUNT=KCOUNT+1
        WRITE(160,*) 'QV2',KCOUNT,NEL1,NEL2,N1,N2,N3,N4
            CALL DUMPBIN(KCOUNT,1)
            CALL REVERS(NEL1,NEL2)
            GO TO 500
          ELSE
            GO TO 500
          ENDIF
        ENDIF
!   test if they are equal height
		IF(WD(N3) .EQ. WD(N4)  .or.  ABS(WD(N3) -WD(N4)) .LT. ABS(WD(N1)-WD(N2))) THEN
!   if so reverse connections
          if(dist(n1,n2)*1.5 .lt.  dist(n3,n4)) go to 500
          KCOUNT=KCOUNT+1
        WRITE(160,*) 'RV1',KCOUNT,NEL1,NEL2,N1,N2,N3,N4
		  CALL REVERS(NEL1,NEL2)
          CALL DUMPBIN(KCOUNT,1)
		  
		ELSE
!   test if N4  closer or equal to N3 than N1 or N2
		  IF(ABS(WD(N4) - WD(N3)) .LT. ABS(WD(N1) - WD(N3))  .OR.  ABS(WD(N4) - WD(N3)) .LT. ABS(WD(N2) - WD(N3))) THEN
!   if  so reverse connections
            if(dist(n1,n2)*1.5 .lt.  dist(n3,n4)) go to 500
            KCOUNT=KCOUNT+1
        WRITE(160,*) 'RV2',KCOUNT,NEL1,NEL2,N1,N2,N3,N4
		    CALL REVERS(NEL1,NEL2)
          CALL DUMPBIN(KCOUNT,1)
          ENDIF
        ENDIF
500     CONTINUE
!   end loop
	ENDDO
    RETURN
	END