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#include "sys-defines.h"
#include "extern.h"
/* bit fields for return value from Cohen-Sutherland clipper */
enum { ACCEPTED = 0x1, CLIPPED_FIRST = 0x2, CLIPPED_SECOND = 0x4 };
/* for internal clipper use */
enum { TOP = 0x1, BOTTOM = 0x2, RIGHT = 0x4, LEFT = 0x8 };
/* forward references */
static int _compute_outcode ____P ((double x, double y, double x_min_clip, double x_max_clip, double y_min_clip, double y_max_clip));
/* _clip_line() takes two points, the endpoints of a line segment in the
* device frame (expressed in terms of floating-point device coordinates),
* and destructively passes back two points: the endpoints of the line
* segment clipped by Cohen-Sutherland to the rectangular clipping area.
* The return value contains bitfields ACCEPTED, CLIPPED_FIRST, and
* CLIPPED_SECOND.
*/
int
#ifdef _HAVE_PROTOS
_clip_line (double *x0_p, double *y0_p, double *x1_p, double *y1_p, double x_min_clip, double x_max_clip, double y_min_clip, double y_max_clip)
#else
_clip_line (x0_p, y0_p, x1_p, y1_p, x_min_clip, x_max_clip, y_min_clip, y_max_clip)
double *x0_p, *y0_p, *x1_p, *y1_p;
double x_min_clip, x_max_clip, y_min_clip, y_max_clip;
#endif
{
double x0 = *x0_p;
double y0 = *y0_p;
double x1 = *x1_p;
double y1 = *y1_p;
int outcode0, outcode1;
bool accepted;
int clipval = 0;
outcode0 = _compute_outcode (x0, y0, x_min_clip, x_max_clip, y_min_clip, y_max_clip);
outcode1 = _compute_outcode (x1, y1, x_min_clip, x_max_clip, y_min_clip, y_max_clip);
for ( ; ; )
{
if (!(outcode0 | outcode1)) /* accept */
{
accepted = true;
break;
}
else if (outcode0 & outcode1) /* reject */
{
accepted = false;
break;
}
else
{
/* at least one endpoint is outside; choose one that is */
int outcode_out = (outcode0 ? outcode0 : outcode1);
double x, y; /* intersection with clip edge */
if (outcode_out & RIGHT)
{
x = x_max_clip;
y = y0 + (y1 - y0) * (x_max_clip - x0) / (x1 - x0);
}
else if (outcode_out & LEFT)
{
x = x_min_clip;
y = y0 + (y1 - y0) * (x_min_clip - x0) / (x1 - x0);
}
else if (outcode_out & TOP)
{
x = x0 + (x1 - x0) * (y_max_clip - y0) / (y1 - y0);
y = y_max_clip;
}
else
{
x = x0 + (x1 - x0) * (y_min_clip - y0) / (y1 - y0);
y = y_min_clip;
}
if (outcode_out == outcode0)
{
x0 = x;
y0 = y;
outcode0 = _compute_outcode (x0, y0, x_min_clip, x_max_clip, y_min_clip, y_max_clip);
}
else
{
x1 = x;
y1 = y;
outcode1 = _compute_outcode (x1, y1, x_min_clip, x_max_clip, y_min_clip, y_max_clip);
}
}
}
if (accepted)
{
clipval |= ACCEPTED;
if ((x0 != *x0_p) || (y0 != *y0_p))
clipval |= CLIPPED_FIRST;
if ((x1 != *x1_p) || (y1 != *y1_p))
clipval |= CLIPPED_SECOND;
*x0_p = x0;
*y0_p = y0;
*x1_p = x1;
*y1_p = y1;
}
return clipval;
}
static int
#ifdef _HAVE_PROTOS
_compute_outcode (double x, double y, double x_min_clip, double x_max_clip, double y_min_clip, double y_max_clip)
#else
_compute_outcode (x, y, x_min_clip, x_max_clip, y_min_clip, y_max_clip)
double x, y, x_min_clip, x_max_clip, y_min_clip, y_max_clip;
#endif
{
int code = 0;
if (x > x_max_clip)
code |= RIGHT;
else if (x < x_min_clip)
code |= LEFT;
if (y > y_max_clip)
code |= TOP;
else if (y < y_min_clip)
code |= BOTTOM;
return code;
}
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