/* pen.c ********************************************************************
* virtual plotter
* Accept pen up, down commands and x,y coordinates.  Make physical i/o
* calls only when necessary:
*     1) When pen is lifted after having been down,
*     2) When calling routine requests by setting ptype to "DATA".
*
* Not a general purpose routine.  Part of a hidden line algorithm is
* implemented here.
*****************************************/
#include "tdp.h"
void pen(NewPenState,hpos,ptype,hinc,vcum)
register short NewPenState,hpos,ptype;
register short *vcum;
{
   static short PenState = RESET, hstart = 0, hcur = -1;

   if (PenState == DOWN) {
      if (NewPenState == UP) {
         if (hstart != hcur) {
            Move(rp,hstart,TOPVERT-vcum[hstart]);
            if (PlotFile)
               fprintf(pfp,"PU %d %d;\n",1+hstart,1+TOPVERT-vcum[hstart]);
            if (To_mCAD)
               fprintf(mfp,"\n%d %d\n", hstart, vcum[hstart]);
         }
         hcur = hpos-hinc;
         Draw(rp, hcur, TOPVERT-vcum[hcur]);
         if (PlotFile)
            fprintf(pfp,"PD %d %d;\n", 1+hcur, 1+TOPVERT-vcum[hcur]);
         if (To_mCAD)
            fprintf(mfp,"%d %d\n*>\n", hcur, vcum[hcur]);
         hstart = hpos;
      }
      else if (ptype == DATA) {
         if (hstart != hcur) {
            Move(rp,hstart,TOPVERT-vcum[hstart]);
            if (PlotFile)
               fprintf(pfp,"PU %d %d;\n",1+hstart,1+TOPVERT-vcum[hstart]);
            if (To_mCAD)
               fprintf(mfp,"\n%d %d\n", hstart, vcum[hstart]);
         }
         Draw(rp, hpos, TOPVERT-vcum[hpos]);
         if (PlotFile)
            fprintf(pfp,"PD %d %d;\n", 1+hpos, 1+TOPVERT-vcum[hpos]);
         if (To_mCAD)
            fprintf(mfp,"%d %d\n", hpos, vcum[hpos]);
         hcur = hpos;
         hstart = hpos;
      }

      else if (NewPenState == RESET)
         hstart = hpos;
   }
   else if (NewPenState == DOWN) {
      if (ptype == INTERP)
         hstart = hpos-hinc;
      else if ((PenState != RESET) && (ptype == DATA)) {
         hcur = hpos-hinc;
         Move(rp, hcur, TOPVERT-vcum[hcur]);
         Draw(rp, hpos, TOPVERT-vcum[hpos]);
         if (PlotFile) {
            fprintf(pfp,"PU %d %d;\n", 1+hcur, 1+TOPVERT-vcum[hcur]);
            fprintf(pfp,"PD %d %d;\n", 1+hpos, 1+TOPVERT-vcum[hpos]);
         }
         if (To_mCAD) {
            fprintf(mfp,"\n%d %d\n", hcur, vcum[hcur]);
            fprintf(mfp,"%d %d\n", hpos, vcum[hpos]);
         }
         hstart = (hcur = hpos);
      }
   }

   else
      hstart = hpos;
      
   PenState = NewPenState;
}