#include "ded.h"
#include "char.h"
#include "ter.h"

/************************************************************************
 *                                                                      *
 *                      copyright Richard Bornat 1981                   *
 *                                                                      *
 ************************************************************************/

#define TMARGIN 2
#define BMARGIN 2

split_row(arow, acol)
int *arow, *acol;
 {  register int r = *arow, c = *acol;
    register int fline = topl+r;
    int up;

    /* split strategy is
	- split down on top line
	- split up on bottom line
	- with hardware support, split down unless in bottom
	  margin and screen is blank from top margin to cursor
	- without support, split down in top margin
	   (to preserve context), elsewhere take cheaper alternative
     */

    if (r==LASTINROW) up=true;
    else
    if (r==0 || charsin(r+1,LASTINROW)==0) up=false;
    else
    if (ter.scrseq.hardscroll) /* hardsplit unlikely if this untrue */
      up = (r>LASTINROW-BMARGIN &&
		!(charsin(TMARGIN,r-1)==0 && firstcol(r)>=c));
    else
      up = (r>=TMARGIN &&
	scrollup(0,r,(char *)0)<=scrolldown(r+1,LASTINROW,(char *)0));

    /* save the row which will disappear and do the split */
    saverow(up ? 0 : LASTINROW);
    (*(c==MARGIN || c>lastcol(r) ? split0 : ter.split_row))(r,c,MARGIN,up);

    /* adjust the file rather cautiously */
    shuffile(fline+1, 1, 1);

    if (up) inc_topl();
    else *arow = ++r;
    *acol = MARGIN;

    /* adjust the marks on screen */
    retag(r-1); retag(r);
 }