/*
SG C Tools 1.2

(C) 1993 Steve Goldsmith
All Rights Reserved

Compiled with HI-TECH C 3.09 (CP/M-80).
*/

#include <hitech.h>
#include <vdc.h>

/* draw line using modified bresenham's algorithm */

void linevdc(int X1, int Y1, int X2, int Y2)
{
  int XInc = 1;
  int YInc = 1;
  int DX, DY, X, Y, C, R;

  DX = X2-X1;  /* delta x */
  if(DX < 0)   /* adjust for negative delta */
  {
    XInc = -1;
    DX = -DX;
  }
  DY = Y2-Y1;  /* delta y */
  if(DY < 0)   /* adjust for negative delta */
  {
    YInc = -1;
    DY = -DY;
  }
  else
    if(DY > 0)
      YInc = 1;
    else
      YInc = 0;

  X = X1;
  Y = Y1;
  setpixvdc(X,Y); /* set first point */
  if (DX > DY)    /* always draw with positive increment */
  {
    R = DX >> 1;
    for(C = 1; C <= DX; C++)
    {
      X += XInc;
      R += DY;
      if(R >= DX)
      {
        Y += YInc;
        R -= DX;
      }
      setpixvdc(X,Y);
    }
  }
  else
  {
    R = DY >> 1;
    for(C = 1; C <= DY; C++)
    {
      Y += YInc;
      R += DX;
      if(R >= DY)
      {
        X += XInc;
        R -= DY;
      }
      setpixvdc(X,Y);
    }
  }
}