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1.1 root 1: .ds ZZ DEVELOPMENT PACKAGE
2: .TH POLYGON 3L "630 MTG"
3: .XE "polyf()"
4: .XE "ptinpoly()"
5: .SH NAME
6: polygon: polyf, ptinpoly \- polygon routines
7: .SH SYNOPSIS
8: .ft B
9: #include <dmd.h>
10: .sp
11: int polyf (bp, poly, np, t, f)
12: .sp
13: int ptinpoly (pt, poly, np)
14: .sp
15: Bitmap \(**bp;
16: .br
17: Point poly[ ];
18: .br
19: short np;
20: .br
21: Texture16 \(**t;
22: .br
23: Code f;
24: .br
25: Point pt;
26: .SH DESCRIPTION
27: The
28: .I polyf
29: function
30: is used to fill a closed polygon defined by the
31: .I np
32: Points in the array of Points
33: .IR poly .
34: The Points are absolute with respect to the Bitmap
35: .I bp.
36: The polygon is filled with the Texture16
37: .I t
38: using Code
39: .I f.
40: The
41: .I polyf
42: call
43: returns 0 if the polygon is filled and -1 if a memory allocation
44: error occurred during processing, in which case the polygon
45: is not filled.
46: .PP
47: The
48: .I ptinpoly
49: call
50: determines whether the Point
51: .I pt
52: is contained in the polygon defined by
53: .I poly
54: and
55: .I np.
56: The
57: .I ptinpoly
58: function
59: returns 1 if the Point is inside the polygon,
60: 0 if the Point is not inside the polygon,
61: and -1 if a memory allocation error occurs.
62: .PP
63: The polygon can consist of an arbitrary number of filled and unfilled
64: regions.
65: For example, a doughnut shape could be formed
66: without filling
67: the portion of the Bitmap corresponding to the hole of the doughnut.
68: This permits a preservation of any background information previously
69: placed in the Bitmap.
70: Each region, filled or unfilled, is delimited
71: by a Point whose x-coordinate has a value of
72: .I \s-1POLY_F\s+1
73: (defined in \f3dmd.h\f1).
74: This Point in
75: .I poly
76: is ignored and merely serves as a flag indicating
77: the start of a new region.
78: There is always an assumed line connecting the first and last Point
79: of each region.
80: .SH EXAMPLE
81: The following code permits interactive drawing of
82: a polygon with interior regions, fills it, and then
83: uses \f2ptinpoly\f1 to determine if the mouse is inside the polygon.
84: Button 1 is used to draw the points, and button 2 sets a point to \f2POLY_F\f1. After the polygon fills, clicking button 1 with the mouse inside the polygon will ring the terminal bell. Clicking button 3 will exit
85: the drawing and exit the program.
86: .bp
87: .PP
88: .RS 3
89: .nf
90: \s-1
91: .ft CM
92: #include <dmd.h>
93:
94: Point npoly[1000];
95:
96: main()
97: {
98: register int i, j;
99: register char c;
100:
101: request (MOUSE|KBD);
102:
103: i = 0;
104: for (;;)
105: {
106: while (i < 1000){
107: wait (MOUSE);
108: if( button1 () ){
109: npoly[i++] = mouse.xy;
110: point (&display, mouse.xy,
111: F_STORE);
112: sleep (10);
113: continue;
114: }
115: if( button2 () ){
116: npoly[i++].x = POLY_F;
117: continue;
118: }
119: if( button3 () ) break;
120: }
121: polyf (&display, npoly, i, &T_black,
122: F_STORE);
123:
124: wait(MOUSE);
125:
126: while( !button3() ){
127: wait (MOUSE);
128: if( button1() && ptinpoly
129: (mouse.xy, npoly, i) )
130: ringbell();
131:
132: }
133: break;
134: }
135: }
136: \fR
137: .fi
138: .RE
139: \s+1
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