NAME

       MPCHLN - This routine is called repeatedly as boundary lines are processed by MPLNAM,
       MPLNDM, and MPLNDR.  The default version of the routine does nothing.  A user-supplied
       version may take action to change various characteristics of the lines.

SYNOPSIS

       CALL MPCHLN (IACT,ILTY,IOAL,IOAR,NPTS,PNTS)

C-BINDING SYNOPSIS

       None.

DESCRIPTION

       IACT        (an input expression of type INTEGER) specifies which of the EZMAPB routines
                   has called MPCHLN and what that routine is doing or has done with the boundary
                   line defined by the arguments NPTS and PNTS.  IACT is positive if the line is
                   about to be processed, negative if the line was just processed; its absolute
                   value is 1 if the call comes from MPLNAM (which puts lines into an area map),
                   2 if the call comes from MPLNDM (which draws lines masked by some area map),
                   and 3 if the call comes from MPLNDR (which just draws lines).

       ILTY        (an input expression of type INTEGER) specifies the type of the line: 1 => a
                   line separating land from water, 2 => a line separating one "continent" from
                   another (as, for example, Africa from Eurasia, North America from Central
                   America, or Central America from South America), 3 => a line separating one
                   country from another, 4 => a line separating one state from another, and 5 =>
                   a line separating one county from another.

       IOAL and IOAR
                   (input/output variables of type INTEGER) are the identifiers of the areas to
                   the left and right, respectively, of the line.  (Left and right are defined
                   from the standpoint of a viewer standing at point 1 of the line and looking
                   toward point 2.)  The values of IOAL and IOAR may be changed by a
                   knowledgeable user.

       NPTS        (an input/output variable of type INTEGER), on entry, is the number of points
                   defining the line.  NPTS may be zeroed by MPCHLN to suppress any use of the
                   line by the calling routine.

       PNTS        (an input/output array, dimensioned 2*NPTS, of type REAL) is an array of point
                   coordinates.  PNTS(1) and PNTS(2) are the latitude and longitude of the first
                   point, PNTS(3) and PNTS(4) the latitude and longitude of the second point, ...
                   PNTS(2*NPTS-1) and PNTS(2*NPTS) the latitude and longitude of the last point.
                   All values are in degrees.  Longitudes are all between -180 and +180; no
                   segment crosses the meridian at -180 (+180) degrees.

C-BINDING DESCRIPTION

       The C-binding argument description is the same as the FORTRAN argument description.

USAGE

       MPCHLN is called by each of the routines MPLNAM, MPLNDM, and MPLNDR just before and just
       after the processing of each boundary line read from a specified map database.  A user-
       supplied version may take action to change various characteristics of the lines.  For
       example, the area identifiers to be used for the line can be changed, the line can be
       deleted entirely, and line styles, colors, and widths can be set.

EXAMPLES

       Use the ncargex command to see the following relevant example: mpex11.

ACCESS

       To use the default version of MPCHLN, load the NCAR Graphics libraries ncarg, and
       ncarg_gks, preferably in that order.  To supply your own version, just compile it and load
       it.

SEE ALSO

       Online: ezmap, ezmap_params, mapaci, mapbla, mapblm, mapdrw, mapeod, mapfst, mapgci,
       mapgrd, mapgrm, mapgtc, mapgti, mapgtl, mapgtr, mapint, mapiq, mapiqa, mapiqd, mapiqm,
       mapit, mapita, mapitd, mapitm, maplbl, maplmb, maplot, mappos, maproj, maprs, maprst,
       mapsav, mapset, mapstc, mapsti, mapstl, mapstr, maptra, maptri, maptrn, mapusr, mapvec,
       mpfnme, mpgetc, mpgeti, mpgetl, mpgetr, mpglty, mpiaty, mpifnb, mpilnb, mpiola, mpiosa,
       mpipai, mpipan, mpipar, mpisci, mplnam, mplndm, mplndr, mplnri, mpname, mprset, mpsetc,
       mpseti, mpsetl, mpsetr, supmap, supcon, ncarg_cbind

COPYRIGHT

       Copyright (C) 1987-2009
       University Corporation for Atmospheric Research
       The use of this Software is governed by a License Agreement.