1PPPLCL(3NCARG) NCAR GRAPHICS PPPLCL(3NCARG)
2
6 PPPLCL - clips a polyline against a clipping rectangle. It is intended
7 that, eventually, there should be a better routine that will clip a
8 polyline against an arbitrary polygon, but that routine has not yet
9 been written.
10
12 CALL PPPLCL (XMIN,XMAX,YMIN,YMAX,XCPL,YCPL,NCPL,RWRK,LRWK,URPF,IERR)
13
15 #include <ncarg/ncargC.h>
16 void c_ppplcl(float xmin,
18 float xmax,
19 float ymin,
20 float ymax,
21 float *xcpl,
22 float *ycpl,
23 int ncpl,
24 float *rwrk,
25 int lwrk,
26 int (*urpf_)(float *xcra,
27 float *ycra,
28 int *ncra),
29 int *ierr)
30
32 XMIN (an input expression of type REAL) is the X coordinate
33 value defining the position of the left edge of the
34 clipping rectangle.
35 XMAX (an input expression of type REAL) is the X coordinate
37 value defining the position of the right edge of the
38 clipping rectangle.
39 YMIN (an input expression of type REAL) is the Y coordinate
41 value defining the position of the bottom of the clipping
42 rectangle.
43 YMAX (an input expression of type REAL) is the Y coordinate
45 value defining the position of the top of the clipping
46 rectangle.
47 XCPL (an input array of type REAL) is the X coordinate array for
49 the polyline that is to be clipped.
50 YCPL (an input array of type REAL) is the Y coordinate array for
52 the polyline that is to be clipped.
53 NCPL (an input expression of type INTEGER) is the number of
55 points defining the input polyline (the number of
56 meaningful elements in each of the arrays XCPL and YCPL).
57 RWRK (a scratch array of type REAL) is a workspace array for
59 PPPLCL to use. It is divided into halves; one half is used
60 for X coordinates and the other half for Y coordinates.
61 This array doesn't have to be too big unless it is
62 important not to break the polyline except at the edges of
63 the clipping rectangle.
64 LRWK (an input expression of type INTEGER) is the length of the
66 array RWRK.
67 URPF is the name of a user-provided routine to process the
69 fragments of the polyline resulting from the clipping
70 process. This name must appear in an EXTERNAL statement in
71 the routine that calls PPPLCL and the routine itself must
72 have the following form:
73 SUBROUTINE URPF (XCRA,YCRA,NCRA)
75 DIMENSION XCRA(NCRA),YCRA(NCRA)
76 ...(code to process a polyline)...
77 RETURN
78 END
79 Each of the arguments XCRA and YCRA is a real array,
81 dimensioned NCRA; the former holds the X coordinates, and
82 the latter the Y coordinates, of a polyline fragment.
83 IERR (an output variable of type INTEGER) is returned with the
85 value zero if no errors occurred in the execution of PPPLCL
86 or with a small positive value if an error did occur. The
87 value 1 indicates that NCPL is less than or equal to zero
88 and the value 2 indicates that LRWK is less than 4.
89
91 The C-binding argument descriptions are the same as the FORTRAN
92 argument descriptions.
93
95 The FORTRAN statement
96 CALL PPPLCL (XMIN,XMAX,YMIN,YMAX,XCPL,YCPL,NCPL,RWRK,LRWK,URPF,IERR)
98 clips a polyline against a rectangle and delivers the portions of the
100 polyline that fall within the rectangle, one by one, to the user-
101 specified polyline-fragment-processing routine URPF.
102
104 Use the ncargex command to see the following relevant examples: ppex01,
105 tppack, c_ppex01.
106
108 To use PPPLCL or c_ppplcl, load the NCAR Graphics libraries ncarg,
109 ncarg_gks, and ncarg_c, preferably in that order.
110
112 Online: polypack, ppdipo, ppditr, ppinpo, ppintr, ppppap, ppunpo,
113 ppuntr, ncarg_cbind.
114 Hardcopy: None.
116
118 Copyright (C) 1987-2009
119 University Corporation for Atmospheric Research
120 The use of this Software is governed by a License Agreement.
121UNIX March 1995 PPPLCL(3NCARG)