shithub: plan9front

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```#include <u.h>
#include <libc.h>
#include <draw.h>
#include <event.h>

enum
{
NSTEP		= 10,		/* number of steps between throws */
RBALL		= 10,		/* radius of ball images */
Nball		= 100,
};

Image *image, **disk;
int ndisk=0;
int nhand=2;
int delay=20;			/* ms delay between steps */
int nball;
int maxhgt;
Rectangle win;

#define sub subpt
#define inset insetrect

/*
* pattern lists the heights of a repeating sequence of throws.
* At time t, hand t%nhand throws.  At that time, it must
* hold exactly one ball, unless it executes a 0 throw,
* in which case it must hold no ball.  A throw of height h
* at time t lands at time t+h in hand (t+h)%nhand.
*/
typedef struct Ball Ball;
struct Ball{
int oldhand;	/* hand that previously held the ball */
int hgt;	/* how high the throw from oldhand was */
int time;	/* time at which ball will arrive */
int hand;	/* hand in which ball will rest on arrival */
};
Ball ball[Nball];
void throw(int t, int hgt){
int hand=t%nhand;
int i, b, n;
b=n=0;
for(i=0;i!=nball;i++) if(ball[i].hand==hand && ball[i].time<=t){
n++;
b=i;
}
if(hgt==0){
if(n!=0){
print("bad zero throw at t=%d, nball=%d\n", t, n);
}
}
else if(n!=1){
print("bad ball count at t=%d, nball=%d\n", t, n);
}
else{
ball[b].oldhand=hand;
ball[b].hgt=hgt;
ball[b].time=t+hgt;
ball[b].hand=(hand+hgt)%nhand;
}
}
Point bpos(int b, int step, int t){
Ball *bp=&ball[b];
double dt=t-1+(step+1.)/NSTEP-(bp->time-bp->hgt);
double hgt=(bp->hgt*dt-dt*dt)*4./(maxhgt*maxhgt);
double alpha=(bp->oldhand+(bp->hand-bp->oldhand)*dt/bp->hgt)/(nhand-1);
return (Point){win.min.x+(win.max.x-win.min.x)*alpha,
win.max.y-1+(win.min.y-win.max.y)*hgt};
}

void move(int t){
int i, j;
for(i=0;i!=NSTEP;i++){
while(ecanmouse()) emouse();
draw(image, inset(image->r, 3), display->white, nil, ZP);
for(j=0;j!=nball;j++)
fillellipse(image, bpos(j, i, t), RBALL, RBALL, disk[j%ndisk], ZP);
draw(screen, screen->r, image, nil, image->r.min);
flushimage(display, 1);
if(delay>0)
sleep(delay);
}
}

void
{
Image *col;
disk = realloc(disk, (ndisk+1)*sizeof(Image*));
col=allocimage(display, Rect(0,0,1,1), CMAP8, 1, c);
disk[ndisk]=col;
ndisk++;
}

void
diskinit(void)
{
/* colors taken from /sys/src/cmd/stats.c */

}

void
usage(char *name)
{
fprint(2, "usage: %s [start] pattern\n", name);
exits("usage");
}

void
eresized(int new){
if(new && getwindow(display, Refnone) < 0) {
sysfatal("can't reattach to window");
}
if(image) freeimage(image);
image=allocimage(display, screen->r, screen->chan, 0, DNofill);
draw(image, image->r, display->black, nil, ZP);
win=inset(screen->r, 4+2*RBALL);
}
void
main(int argc, char *argv[]){
int sum, i, t, hgt, nstart, npattern;
char *s, *start = nil, *pattern = nil;

ARGBEGIN{
default:
usage(argv0);
case 'd':
s = ARGF();
if(s == nil)
usage(argv0);
delay = strtol(argv[0], &s, 0);
if(delay < 0 || s == argv[0] || *s != '\0')
usage(argv0);
break;
case 'h':
s = ARGF();
if(s == nil)
usage(argv0);
nhand = strtol(argv[0], &s, 0);
if(nhand <= 0 || s == argv[0] || *s != '\0')
usage(argv0);
break;
}ARGEND

switch(argc) {
case 1:
start="";
pattern=argv[0];
break;
case 2:
start=argv[0];
pattern=argv[1];
break;
default:
usage(argv0);
}
sum=0;
maxhgt=0;
for(s=pattern;*s;s++){
hgt=*s-'0';
sum+=hgt;
if(maxhgt<hgt) maxhgt=hgt;
}
npattern=s-pattern;
for(s=start;*s;s++){
hgt=*s-'0';
if(maxhgt<hgt) maxhgt=hgt;
}
if(sum%npattern){
print("%s: non-integral ball count\n",argv[0]);
exits("partial ball");
}
nball=sum/npattern;
for(i=0;i!=nball;i++){
ball[i].oldhand=(i-nball)%nhand;
if(ball[i].oldhand<0) ball[i].oldhand+=nhand;
ball[i].hgt=nball;
ball[i].time=i;
ball[i].hand=i%nhand;
}
if(initdraw(nil, nil, "juggle") < 0)
sysfatal("initdraw failed: %r");
einit(Emouse);
diskinit();
eresized(0);
if(image==0){
print("can't allocate bitmap");
exits("no space");
}
for(t=0;start[t];t++){
move(t);
throw(t, start[t]-'0');
}
nstart=t;
for(;;t++){
move(t);
throw(t, pattern[(t-nstart)%npattern]-'0');
}
}
```