1GFILL_AREA(3NCARG)               NCAR GRAPHICS              GFILL_AREA(3NCARG)
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NAME

6       gfill_area (Fill area) - output primitive for filling polygonal areas.
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SYNOPSIS

9       #include <ncarg/gks.h>
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11       void gfill_area(const Gpoint_list *point_list);
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DESCRIPTION

14       point_list.num_points
15                   (Gint,  Input)  - The number of points in the polygon to be
16                   filled.  Must be greater than two.
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18       point_list.points
19                   (Gpoint *, Input) - The X and Y world  coordinates  of  the
20                   polygon.
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USAGE

23       The  area  to  be  filled is delimited by the sequence of straight line
24       segments connecting  the  successive  points  ((point_list.points[0].x,
25       point_list.points[0].y),
26       ...(point_list.points[point_list.num_points-1].x,
27       point_list.points[point_list.num_points-1].y))  The  last  point in the
28       polygon is connected to the first point with a straight line segment in
29       the case that it is not the same as the first point.
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31       Given  a  polygon whose edges cross each other, it becomes ambiguous as
32       to what constitutes the "inside" of the polygon.  The algorithm used in
33       GKS is as follows: for a given point, draw a ray starting at that point
34       and going to infinity in any direction; if the number of  intersections
35       between  the  ray and the polygon is odd, the point is within the poly‐
36       gon, otherwise it is outside.  If the straight line  passes  through  a
37       polygon  vertex  tangentially,  the intersection count is not affected.
38       If a point is within the polygon, it is included  in  the  area  to  be
39       filled.
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41       Several interior styles (hollow, solid, and various hatch patterns) can
42       be  selected.   See  the  man   pages   for   gset_fill_int_style   and
43       gset_fill_style_ind for these.
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45       Note  well: By default in GKS, the interior fill style is hollow, or no
46       fill. If you call gfill_area and do not get a filled  interior  as  you
47       expected, you will probably need to call gset_fill_int_style to set the
48       fill style to something other than "hollow".
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ACCESS

51       To use the GKS C-binding  routines,  load  the  ncarg_gks  and  ncarg_c
52       libraries.
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SEE ALSO

55       Online:    gset_fill_int_style(3NCARG),    gset_fill_style_ind(3NCARG),
56       gset_colr_rep(3NCARG),                      gset_fill_colr_ind(3NCARG),
57       ginq_fill_int_style(3NCARG),  ginq_fill_style_ind(3NCARG), gks(3NCARG),
58       ncarg_gks_cbind(3NCARG)
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60       Hardcopy: User's Guide for NCAR GKS-0A Graphics; NCAR  Graphics  Funda‐
61       mentals, UNIX Version
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64       Copyright (C) 1987-2009
65       University Corporation for Atmospheric Research
66       The use of this Software is governed by a License Agreement.
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70UNIX                              March 1993                GFILL_AREA(3NCARG)
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