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#include <Alib.h>
int ClipLine (w, x1, y1, x2, y2)
AWindow *w;
int *x1, *y1, *x2, *y2; {
register int dx, dy;
/*
* Top clip
*/
dx = *x2 - *x1;
dy = *y2 - *y1;
if (*y1 < w->clip.y1 || *y2 < w->clip.y1) {
if (*y1 < w->clip.y1)
if (*y2 < w->clip.y1)
return 1;
else {
*x1 = *x1 + dx * (w->clip.y1 - *y1) / dy;
*y1 = w->clip.y1;
}
else {
*x2 = *x1 + dx * (w->clip.y1 - *y1) / dy;
*y2 = w->clip.y1;
}
}
/*
* Bottom clip
*/
if (*y1 > w->clip.y2 || *y2 > w->clip.y2) {
if (*y1 > w->clip.y2)
if (*y2 > w->clip.y2)
return 1;
else {
*x1 = *x1 + dx * (w->clip.y2 - *y1) / dy;
*y1 = w->clip.y2;
}
else {
*x2 = *x1 + dx * (w->clip.y2 - *y1) / dy;
*y2 = w->clip.y2;
}
}
/*
* Left clip
*/
if (*x1 < w->clip.x1 || *x2 < w->clip.x1) {
if (*x1 < w->clip.x1)
if (*x2 < w->clip.x1)
return 1;
else {
*y1 = *y1 + dy * (w->clip.x1 - *x1) / dx;
*x1 = w->clip.x1;
}
else {
*y2 = *y1 + dy * (w->clip.x1 - *x1) / dx;
*x2 = w->clip.x1;
}
}
/*
* Right clip
*/
if (*x1 > w->clip.x2 || *x2 > w->clip.x2) {
if (*x1 > w->clip.x2)
if (*x2 > w->clip.x2)
return 1;
else {
*y1 = *y1 + dy * (w->clip.x2 - *x1) / dx;
*x1 = w->clip.x2;
}
else {
*y2 = *y1 + dy * (w->clip.x2 - *x1) / dx;
*x2 = w->clip.x2;
}
}
#ifdef DEBUG
if (*y1 < w->clip.y1 || *y1 > w->clip.y2
|| *y2 < w->clip.y1 || *y2 > w->clip.y2
|| *x1 < w->clip.x1 || *x1 > w->clip.x2
|| *x2 < w->clip.x1 || *x2 > w->clip.x2)
printf ("clip error\n");
#endif
return 0;
}
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