ref: 9ec1a07af2537e5485524c8d079a07abfee6f96d
dir: /sys/src/cmd/plot/libplot/fill.c/
/*
* fill -- polygon tiler
* Updating the edgelist from scanline to scanline could be quicker if no
* edges cross: we can just merge the incoming edges. If the scan-line
* filling routine were a parameter, we could do textured
* polygons, polyblt, and other such stuff.
*/
#include "mplot.h"
typedef enum{
Odd=1,
Nonzero=~0
}Windrule;
typedef struct edge Edge;
struct edge{
Point p; /* point of crossing current scan-line */
int maxy; /* scan line at which to discard edge */
int dx; /* x increment if x fraction<1 */
int dx1; /* x increment if x fraction>=1 */
int x; /* x fraction, scaled by den */
int num; /* x fraction increment for unit y change, scaled by den */
int den; /* x fraction increment for unit x change, scaled by num */
int dwind; /* increment of winding number on passing this edge */
Edge *next; /* next edge on current scanline */
Edge *prev; /* previous edge on current scanline */
};
static void insert(Edge *ep, Edge **yp){
while(*yp && (*yp)->p.x<ep->p.x) yp=&(*yp)->next;
ep->next=*yp;
*yp=ep;
if(ep->next){
ep->prev=ep->next->prev;
ep->next->prev=ep;
if(ep->prev)
ep->prev->next=ep;
}
else
ep->prev=0;
}
static void polygon(int cnt[], double *pts[], Windrule w, int v){
Edge *edges, *ep, *nextep, **ylist, **eylist, **yp;
Point p, q, p0, p1, p10;
int i, dy, nbig, y, left, right, wind, nwind, nvert;
int *cntp;
double **ptsp, *xp;
nvert=0;
for(cntp=cnt;*cntp;cntp++) nvert+=*cntp;
edges=(Edge *)malloc(nvert*sizeof(Edge));
if(edges==0){
NoSpace:
sysfatal("polygon: no space");
}
ylist=(Edge **)malloc(Dy(screen->r)*sizeof(Edge *));
if(ylist==0) goto NoSpace;
eylist=ylist+Dy(screen->r);
for(yp=ylist;yp!=eylist;yp++) *yp=0;
ep=edges;
for(cntp=cnt,ptsp=pts;*cntp;cntp++,ptsp++){
p.x=SCX((*ptsp)[*cntp*2-2]);
p.y=SCY((*ptsp)[*cntp*2-1]);
nvert=*cntp;
for(xp=*ptsp,i=0;i!=nvert;xp+=2,i++){
q=p;
p.x=SCX(xp[0]);
p.y=SCY(xp[1]);
if(p.y==q.y) continue;
if(p.y<q.y){
p0=p;
p1=q;
ep->dwind=1;
}
else{
p0=q;
p1=p;
ep->dwind=-1;
}
if(p1.y<=screen->r.min.y) continue;
if(p0.y>=screen->r.max.y) continue;
ep->p=p0;
if(p1.y>screen->r.max.y)
ep->maxy=screen->r.max.y;
else
ep->maxy=p1.y;
p10=subpt(p1, p0);
if(p10.x>=0){
ep->dx=p10.x/p10.y;
ep->dx1=ep->dx+1;
}
else{
p10.x=-p10.x;
ep->dx=-(p10.x/p10.y); /* this nonsense rounds toward zero */
ep->dx1=ep->dx-1;
}
ep->x=0;
ep->num=p10.x%p10.y;
ep->den=p10.y;
if(ep->p.y<screen->r.min.y){
dy=screen->r.min.y-ep->p.y;
ep->x+=dy*ep->num;
nbig=ep->x/ep->den;
ep->p.x+=ep->dx1*nbig+ep->dx*(dy-nbig);
ep->x%=ep->den;
ep->p.y=screen->r.min.y;
}
insert(ep, ylist+(ep->p.y-screen->r.min.y));
ep++;
}
}
left = 0;
for(yp=ylist,y=screen->r.min.y;yp!=eylist;yp++,y++){
wind=0;
for(ep=*yp;ep;ep=nextep){
nwind=wind+ep->dwind;
if(nwind&w){ /* inside */
if(!(wind&w)){
left=ep->p.x;
if(left<screen->r.min.x) left=screen->r.min.x;
}
}
else if(wind&w){
right=ep->p.x;
if(right>=screen->r.max.x) right=screen->r.max.x;
#define BART_BUG_FIXED /* what goes on here?? -rob */
#ifdef BART_BUG_FIXED
if(right>left)
line(screen, Pt(left, y), Pt(right, y), Endsquare, Endsquare, 0, getcolor(v), ZP);
#else
if(right>left){
switch(v){
default:
segment(&screen, Pt(left, y), Pt(right, y),
~0, D&~S);
segment(&screen, Pt(left, y), Pt(right, y),
v, f);
break;
case 0:
segment(&screen, Pt(left, y), Pt(right, y),
~0, D&~S);
break;
case 3:
segment(&screen, Pt(left, y), Pt(right, y),
v, f);
break;
}
}
#endif
}
wind=nwind;
nextep=ep->next;
if(++ep->p.y!=ep->maxy){
ep->x+=ep->num;
if(ep->x>=ep->den){
ep->x-=ep->den;
ep->p.x+=ep->dx1;
}
else
ep->p.x+=ep->dx;
insert(ep, yp+1);
}
}
}
free((char *)edges);
free((char *)ylist);
}
void fill(int num[], double *ff[]){
polygon(num, ff, Odd, e1->foregr);
}