tfill.c - plan9port - [fork] Plan 9 from user space
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tfill.c (4097B)
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1 /*
2 * fill -- polygon tiler
3 * Updating the edgelist from scanline to scanline could be quicker if no
4 * edges cross: we can just merge the incoming edges. If the scan-line
5 * filling routine were a parameter, we could do textured
6 * polygons, polyblt, and other such stuff.
7 */
8 #include "mplot.h"
9 typedef enum{
10 Odd=1,
11 Nonzero=~0
12 }Windrule;
13 typedef struct edge Edge;
14 struct edge{
15 Point p; /* point of crossing current scan-line */
16 int maxy; /* scan line at which to discard edge */
17 int dx; /* x increment if x fraction<1 */
18 int dx1; /* x increment if x fraction>=1 */
19 int x; /* x fraction, scaled by den */
20 int num; /* x fraction increment for unit y change, scaled by den */
21 int den; /* x fraction increment for unit x change, scaled by num */
22 int dwind; /* increment of winding number on passing this edge */
23 Edge *next; /* next edge on current scanline */
24 Edge *prev; /* previous edge on current scanline */
25 };
26 static void insert(Edge *ep, Edge **yp){
27 while(*yp && (*yp)->p.x<ep->p.x) yp=&(*yp)->next;
28 ep->next=*yp;
29 *yp=ep;
30 if(ep->next){
31 ep->prev=ep->next->prev;
32 ep->next->prev=ep;
33 if(ep->prev)
34 ep->prev->next=ep;
35 }
36 else
37 ep->prev=0;
38 }
39 static void polygon(int cnt[], double *pts[], Windrule w, int v){
40 Edge *edges, *ep, *nextep, **ylist, **eylist, **yp;
41 Point p, q, p0, p1, p10;
42 int i, dy, nbig, y, left, right, wind, nwind, nvert;
43 int *cntp;
44 double **ptsp, *xp;
45 nvert=0;
46 for(cntp=cnt;*cntp;cntp++) nvert+=*cntp;
47 edges=(Edge *)malloc(nvert*sizeof(Edge));
48 if(edges==0){
49 NoSpace:
50 fprintf(stderr, "polygon: no space\n");
51 exits("malloc failed");
52 }
53 ylist=(Edge **)malloc(Dy(screen->r)*sizeof(Edge *));
54 if(ylist==0) goto NoSpace;
55 eylist=ylist+Dy(screen->r);
56 for(yp=ylist;yp!=eylist;yp++) *yp=0;
57 ep=edges;
58 for(cntp=cnt,ptsp=pts;*cntp;cntp++,ptsp++){
59 p.x=SCX((*ptsp)[*cntp*2-2]);
60 p.y=SCY((*ptsp)[*cntp*2-1]);
61 nvert=*cntp;
62 for(xp=*ptsp,i=0;i!=nvert;xp+=2,i++){
63 q=p;
64 p.x=SCX(xp[0]);
65 p.y=SCY(xp[1]);
66 if(p.y==q.y) continue;
67 if(p.y<q.y){
68 p0=p;
69 p1=q;
70 ep->dwind=1;
71 }
72 else{
73 p0=q;
74 p1=p;
75 ep->dwind=-1;
76 }
77 if(p1.y<=screen->r.min.y) continue;
78 if(p0.y>=screen->r.max.y) continue;
79 ep->p=p0;
80 if(p1.y>screen->r.max.y)
81 ep->maxy=screen->r.max.y;
82 else
83 ep->maxy=p1.y;
84 p10=subpt(p1, p0);
85 if(p10.x>=0){
86 ep->dx=p10.x/p10.y;
87 ep->dx1=ep->dx+1;
88 }
89 else{
90 p10.x=-p10.x;
91 ep->dx=-(p10.x/p10.y); /* this nonsense rounds toward zero */
92 ep->dx1=ep->dx-1;
93 }
94 ep->x=0;
95 ep->num=p10.x%p10.y;
96 ep->den=p10.y;
97 if(ep->p.y<screen->r.min.y){
98 dy=screen->r.min.y-ep->p.y;
99 ep->x+=dy*ep->num;
100 nbig=ep->x/ep->den;
101 ep->p.x+=ep->dx1*nbig+ep->dx*(dy-nbig);
102 ep->x%=ep->den;
103 ep->p.y=screen->r.min.y;
104 }
105 insert(ep, ylist+(ep->p.y-screen->r.min.y));
106 ep++;
107 }
108 }
109 left = 0;
110 for(yp=ylist,y=screen->r.min.y;yp!=eylist;yp++,y++){
111 wind=0;
112 for(ep=*yp;ep;ep=nextep){
113 nwind=wind+ep->dwind;
114 if(nwind&w){ /* inside */
115 if(!(wind&w)){
116 left=ep->p.x;
117 if(left<screen->r.min.x) left=screen->r.min.x;
118 }
119 }
120 else if(wind&w){
121 right=ep->p.x;
122 if(right>=screen->r.max.x) right=screen->r.max.x;
123 #define BART_BUG_FIXED /* what goes on here?? -rob */
124 #ifdef BART_BUG_FIXED
125 if(right>left)
126 line(screen, Pt(left, y), Pt(right, y), Endsquare, Endsquare, 0, getcolor(v), ZP);
127 #else
128 if(right>left){
129 switch(v){
130 default:
131 segment(&screen, Pt(left, y), Pt(right, y),
132 ~0, D&~S);
133 segment(&screen, Pt(left, y), Pt(right, y),
134 v, f);
135 break;
136 case 0:
137 segment(&screen, Pt(left, y), Pt(right, y),
138 ~0, D&~S);
139 break;
140 case 3:
141 segment(&screen, Pt(left, y), Pt(right, y),
142 v, f);
143 break;
144 }
145 }
146 #endif
147 }
148 wind=nwind;
149 nextep=ep->next;
150 if(++ep->p.y!=ep->maxy){
151 ep->x+=ep->num;
152 if(ep->x>=ep->den){
153 ep->x-=ep->den;
154 ep->p.x+=ep->dx1;
155 }
156 else
157 ep->p.x+=ep->dx;
158 insert(ep, yp+1);
159 }
160 }
161 }
162 free((char *)edges);
163 free((char *)ylist);
164 }
165 void fill(int num[], double *ff[]){
166 polygon(num, ff, Odd, e1->foregr);
167 }