void clip(double x0, double y0, double x1, double y1)
{
outcode outcode0, outcode1, outcodeOut;
int accept = FALSE, done = FALSE;
outcode0 = CompOutCode(x0, y0);
outcode1 = CompOutCode(x1, y1);
do
{
if (!(outcode0 | outcode1))
{
accept = TRUE;
done = TRUE;
}
else if (outcode0 & outcode1)
done = TRUE;
else
{
double x, y;
outcodeOut = outcode0 ? outcode0 : outcode1;
if (outcodeOut & TOP)
{
x = x0 + (x1 - x0) * (ymax - y0) / (y1 - y0);
y = ymax;
}
else if (outcodeOut & BOTTOM)
{
x = x0 + (x1 - x0) * (ymin - y0) / (y1 - y0);
y = ymin;
}
else if (outcodeOut & RIGHT)
{
y = y0 + (y1 - y0) * (xmax - x0) / (x1 - x0);
x = xmax;
}
else
{
y = y0 + (y1 - y0) * (xmin - x0) / (x1 - x0);
x = xmin;
}
if (outcodeOut == outcode0)
{
x0 = x;
y0 = y;
outcode0 = CompOutCode(x0, y0);
}
else
{
x1 = x;
y1 = y;
outcode1 = CompOutCode(x1, y1);
}
}
} while (done == FALSE);
if (accept)
line(x0, y0, x1, y1);
rectangle(xmin, ymin, xmax, ymax);
}
ClipResult cohen_sutherland_line_clip_d (double *x0, double *y0, double *x1, double *y1,
double xmin_, double xmax_, double ymin_, double ymax_)
{
/* Cohen-Sutherland clipping algorithm for line P0=(x1,y0) to P1=(x1,y1)
and clip rectangle with diagonal from (xmin,ymin) to (xmax,ymax).*/
struct LOC_cohen_sutherland_line_clip V;
int accept = CFALSE, done = CFALSE;
ClipResult clip = Visible;
outcode outcode0, outcode1, outcodeOut;
/*Outcodes for P0,P1, and whichever point lies outside the clip rectangle*/
double x=0., y=0.;
V.xmin = xmin_;
V.xmax = xmax_;
V.ymin = ymin_;
V.ymax = ymax_;
CompOutCode(*x0, *y0, &outcode0, &V);
CompOutCode(*x1, *y1, &outcode1, &V);
do {
if (outcode0 == 0 && outcode1 == 0) { /*Trivial accept and exit*/
accept = CTRUE;
done = CTRUE;
} else if ((outcode0 & outcode1) != 0) {
clip = Invisible;
done = CTRUE;
}
/*Logical intersection is true, so trivial reject and exit.*/
else {
clip = Visible;
/*Failed both tests, so calculate the line segment to clip;
from an outside point to an intersection with clip edge.*/
/*At least one endpoint is outside the clip rectangle; pick it.*/
if (outcode0 != 0)
outcodeOut = outcode0;
else
outcodeOut = outcode1;
/*Now find intersection point;
use formulas y=y0+slope*(x-x0),x=x0+(1/slope)*(y-y0).*/
if (((1L << ((long)TOP)) & outcodeOut) != 0) {
/*Divide line at top of clip rectangle*/
x = *x0 + (*x1 - *x0) * (V.ymax - *y0) / (*y1 - *y0);
y = V.ymax;
} else if (((1L << ((long)BOTTOM)) & outcodeOut) != 0) {
/*Divide line at bottom of clip rectangle*/
x = *x0 + (*x1 - *x0) * (V.ymin - *y0) / (*y1 - *y0);
y = V.ymin;
} else if (((1L << ((long)RIGHT)) & outcodeOut) != 0) {
/*Divide line at right edge of clip rectangle*/
y = *y0 + (*y1 - *y0) * (V.xmax - *x0) / (*x1 - *x0);
x = V.xmax;
} else if (((1L << ((long)LEFT)) & outcodeOut) != 0) {
/*Divide line at left edge of clip rectangle*/
y = *y0 + (*y1 - *y0) * (V.xmin - *x0) / (*x1 - *x0);
x = V.xmin;
}
/*Now we move outside point to intersection point to clip,
and get ready for next pass.*/
if (outcodeOut == outcode0) {
*x0 = x;
*y0 = y;
CompOutCode(*x0, *y0, &outcode0, &V);
} else {
*x1 = x;
*y1 = y;
CompOutCode(*x1, *y1, &outcode1, &V);
}
}
} while (!done);
return clip;
}
