[Linux][X11] Problème vitesse d'affichage

Bonjour,
Le programme qui suit me permet de faire défiler une balle dans une fenetre.
Le problème c'est QU ELLE VA BCP TROP VITE!!!
Pourriez vous la faire ralentir!!
Merci

#include <stdio.h>
#include <X11/Xlib.h>
#include <X11/Xutil.h>

GC gc;
Display *display;
int screen,dest_x,dest_y;
Window wina, winb, root;
unsigned long white_pixel, black_pixel;
XSetWindowAttributes attrib;
unsigned long mask_attrib;
int largf,hautf;
Drawable fenetre,src,dest;
int x,y;
unsigned int larg,haut;

int prof;
Pixmap pix;
int i;

main() {
if ((display = XOpenDisplay ("")) == NULL) {
fprintf (stderr, "Can't open Display\n");
exit (1);
}

x=10;y=10;
larg=40;
haut=40;
largf=300;
hautf=300;
gc = DefaultGC (display, screen);
screen = DefaultScreen (display);
root = RootWindow (display, screen);
white_pixel = WhitePixel (display, screen);
black_pixel = BlackPixel (display, screen);
wina = XCreateSimpleWindow (display, root,
0, 0, largf, hautf, 5, black_pixel, white_pixel);

XSelectInput (display, wina, ButtonPressMask);
XStoreName (display, wina, "gravity_S");
XMapWindow (display, wina);

winb = XCreateSimpleWindow (display, root,
0, 0, largf, hautf, 5, black_pixel, white_pixel);
XSelectInput (display, winb, ButtonPressMask);
XStoreName (display, winb, "gravity_NW");
XMapWindow (display, winb);
attrib.bit_gravity = SouthWestGravity;
mask_attrib = CWBitGravity;
XChangeWindowAttributes(display, wina, mask_attrib, &attrib);
attrib.bit_gravity = SouthWestGravity;
XChangeWindowAttributes(display, winb, mask_attrib, &attrib);

for (;;) {
XEvent ev;
XNextEvent (display, &ev);
switch (ev.type) {
case ButtonPress :
// if (ev.xbutton.window==wina)
// {
//XClearWindow (display, wina);

XFillArc(display,winb,gc,x,y,larg,haut,0,360*64);

//if (ev.xbutton.window==winb)
// {

for (i=0;i<largf;i++){
XClearWindow (display, winb);
XFillArc(display,winb,gc,i,y,larg,haut,0,360*64);
// sleep(1);
}
break;
default :
break;
}
}
}