while (pcurrentline != NULL)
    {
      // Skip the root line when encountered
      if (pcurrentline == prootline) {
        pcurrentline = pcurrentline->pnextlineseg;
      } else  {
        nx = pvertexlist[prootline->startvertex].y -
                pvertexlist[prootline->endvertex].y;
        ny = -(pvertexlist[prootline->startvertex].x -
                pvertexlist[prootline->endvertex].x);
        // Calculate the dot products we'll need for line intersection
        // and spatial relationship
        numer = (nx * (pvertexlist[pcurrentline->startvertex].x -
                 pvertexlist[prootline->startvertex].x)) +
                (ny * (pvertexlist[pcurrentline->startvertex].y -
                 pvertexlist[prootline->startvertex].y));
        denom = ((-nx) * (pvertexlist[pcurrentline->endvertex].x -
                 pvertexlist[pcurrentline->startvertex].x)) +
                (-(ny) * (pvertexlist[pcurrentline->endvertex].y -
                 pvertexlist[pcurrentline->startvertex].y));
        // Figure out if the infinite lines of the current line and
        // the root intersect; if so, figure out if the current line
        // segment is actually split, split if so, and add front/back
        // polygons as appropriate
        if (denom == 0.0) {
            // No intersection, because lines are parallel; just add
            // to appropriate list
            pnextlineseg = pcurrentline->pnextlineseg;
            if (numer < 0.0) {
                // Current line is in front of root line; link into
                // front list
                pcurrentline->pnextlineseg = pfrontlines;
                pfrontlines = pcurrentline;
            } else {
                // Current line behind root line; link into back list
                pcurrentline->pnextlineseg = pbacklines;
                pbacklines = pcurrentline;
            }
            pcurrentline = pnextlineseg;
        } else {
            // Infinite lines intersect; figure out whether the actual
            // line segment intersects the infinite line of the root,
            // and split if so
            t =  numer / denom;
            if ((t > pcurrentline->tstart) &&
                    (t < pcurrentline->tend)) {
                // The line segment must be split; add one split
                // segment to each list
                if (NumCompiledLinesegs > (MAX_NUM_LINESEGS - 1)) {
                    DisplayMessageBox("Out of space for line segs;"
                                 "increase MAX_NUM_LINESEGS");
                    return NULL;
                }
                // Make a new line entry for the split part of line
                psplitline = &pCompiledLinesegs[NumCompiledLinesegs];
                NumCompiledLinesegs++;
                *psplitline = *pcurrentline;
                psplitline->tstart = t;
                pcurrentline->tend = t;

                pnextlineseg = pcurrentline->pnextlineseg;
                if (numer < 0.0) {
                    // Presplit part is in front of root line; link
                    // into front list and put postsplit part in back
                    // list
                    pcurrentline->pnextlineseg = pfrontlines;
                    pfrontlines = pcurrentline;
                    psplitline->pnextlineseg = pbacklines;
                    pbacklines = psplitline;
                } else {
                    // Presplit part is in back of root line; link
                    // into back list and put postsplit part in front
                    // list
                    psplitline->pnextlineseg = pfrontlines;
                    pfrontlines = psplitline;
                    pcurrentline->pnextlineseg = pbacklines;
                    pbacklines = pcurrentline;
                }
                pcurrentline = pnextlineseg;
            } else {
                // Intersection outside segment limits, so no need to
                // split; just add to proper list
                pnextlineseg = pcurrentline->pnextlineseg;
                Done = 0;
                while (!Done) {
                    if (numer < -MATCH_TOLERANCE) {
                        // Current line is in front of root line;
                        // link into front list
                        pcurrentline->pnextlineseg = pfrontlines;
                        pfrontlines = pcurrentline;
                        Done = 1;
                    } else if (numer > MATCH_TOLERANCE) {
                        // Current line is behind root line; link
                        // into back list
                        pcurrentline->pnextlineseg = pbacklines;
                        pbacklines = pcurrentline;
                        Done = 1;
                    } else {
                        // The point on the current line we picked to
                        // do front/back evaluation happens to be
                        // collinear with the root, so use the other
                        // end of the current line and try again
                        numer =
                            (nx *
                             (pvertexlist[pcurrentline->endvertex].x -
                              pvertexlist[prootline->startvertex].x))+
                            (ny *
                             (pvertexlist[pcurrentline->endvertex].y -
                              pvertexlist[prootline->startvertex].y));
                    }
                }
                pcurrentline = pnextlineseg;
            }
        }
      }
    }