ncl_mpchln - Man Page
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)
(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).
(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.
(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.
(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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