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