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.
CALL MPCHLN (IACT,ILTY,IOAL,IOAR,NPTS,PNTS)
- 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.
The C-binding argument description is the same as the FORTRAN
argument description.
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.
Use the ncargex command to see the following relevant example:
mpex11.
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.
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