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#include <stdlib.h>

#include "spacewar.h"

//************************************************************

// externals

//

extern volatile int xinit, yinit;

extern void set_xy(int, int);

// ************************************************************

//

// cline

//

//  continue line draw

//

/* Description:

Draws short lines based on fixed size increments so longer lines have more

points.  First calculates the delta x and delta y.  Finds the larger.  Scales

the larger by dividing by 2 until delta is less that fixed_inc.  Scales the

other increment at the same time.  Also generates the loop counter for # of

increments to draw the line.  Finally the function draws the line with points.

*/

void cline(int xfin, int yfin)

{

int delta_x, delta_y, delta_adj;

int i = 1;

  delta_x = (xfin - xinit);

  delta_y = (yfin - yinit);

  // find larger delta_x or delta_y - use the larger to scale

  delta_adj = (abs(delta_y) <= abs(delta_x)) ? abs(delta_x) : abs(delta_y);

  // calc the delta inc

  while(fixed_inc < delta_adj) {

    i += i; ;                     // double loop counter

    delta_x = delta_x >> 1;       // 1/2 inc size x

    delta_y = delta_y >> 1;       // 1/2 inc size y

    delta_adj = delta_adj >> 1;

  }

  // draw the line with dots

  while(i--) {

    set_xy(xinit, yinit);         // move dot 

    xinit += delta_x;

    yinit += delta_y;

  }

}