Logo Search packages:      
Sourcecode: acm4 version File versions  Download package

DrawLine.c

#include <Alib.h>
#include <stdio.h>

void DrawLine (w, x1, y1, x2, y2, zinfo)
AWindow     *w;
int   x1, y1, x2, y2;
ZInfo *zinfo; {

      register int      t;
      register Edge     *e, *e1;

      zinfo->next = NotAnElement;

      if (ClipLine (w, &x1, &y1, &x2, &y2))
            return;

      if (y1 > y2) {
            t = x1;
            x1 = x2;
            x2 = t;
            t = y1;
            y1 = y2;
            y2 = t;
      }

      if ((x1 == x2) || (y1 == y2)) {

            if (w->EPTop >= w->EPSize - 1) {
                  fprintf (stderr, "Edge Pool Overflow\n");
                  return;
            }

            e = &(w->edgePool[(w->EPTop)++]);
            e1 = &(w->edgePool[(w->EPTop)++]);

            e->y2 = e1->y2 = y2 + 1;

#ifdef FLOAT_SLOPE
            if (x1 == x2)
                  e->x1 = e1->x1 = x1;
            else {
                  e->x1 = x1;
                  e1->x1 = x2;
            }
            e->Dx = e1->Dx = 0;
#else
            if (x1 == x2)
                  e->x1 = e1->x1 = x1 << 16;
            else {
                  e->x1 = x1 << 16;
                  e1->x1 = x2 << 16;
            }
            e->Dx = e1->Dx = 0;
#endif
            e->p = e1->p = zinfo;

            e1->nexte = w->edges[y1].head;
            e->nexte = e1;
            w->edges[y1].head = e;
      }

/*
 *  A non-trivial case.  The has a slope that is non-zero and not infinity.
 *  We will need one edge entry to hang off the line list at the strting y
 *  value of the line.  We will also pre-allocate two edge entries to be used
 *  as the line'e edges during the EdgeTableToScanLine procedure.  By our own
 *  convention, we'll place them in the two edge pool entries immediately
 *  following the line information entry. 
 */

      else {

            if (w->EPTop >= w->EPSize - 2) {
                  fprintf (stderr, "Edge Pool Overflow\n");
                  return;
            }

            e = &(w->edgePool[(w->EPTop)++]);
            w->EPTop += 2;

            e->y2 = y2;

#ifdef FLOAT_SLOPE
            e->x1 = x1;
            e->Dx = (x2 - x1) / (y2 - y1);
#else
            e->x1 = x1 << 16;
            e->Dx = ((x2 - x1) << 16) / (y2 - y1);
#endif

            e->p = (e+1)->p = (e+2)->p = zinfo;

            e->nexte = w->lines[y1].head;
            w->lines[y1].head = e;
      }

      if (y1 < w->ymin)
            w->ymin = y1;

      if (y2 > w->ymax)
            w->ymax = y2;
}

Generated by  Doxygen 1.6.0   Back to index