#include "\clipper\nandef.h"
#include "\clipper\extend.h"


#define VIDMODE *(unsigned char far *) 0x00449lu
#define MONOSEG 0xb0000000L
#define COLOR 	0xb8000000L
#define VIDSEG 	(unsigned char far *)((7 == VIDMODE) ? MONOSEG : COLOR )

unsigned char far *ScrPtr( int x, int y );
void RevForeAttr();

CLIPPER shadow()

{
	int 	t,l,b,r;

	t		= _parni(1);
	l		= _parni(2);
	b		= _parni(3);
	r		= _parni(4);

	t++;
	l++;
	b++;
	r++;

	if (r + 2 <= 79)
		{
		RevForeAttr((t + 1),(r + 1), b,(r + 2));

		if (b + 1 <= 24)
			{
			RevForeAttr((b + 1),(l + 2),(b + 1),(r + 2));
			}
         }
	else if (r + 1 <= 79)
        {
		RevForeAttr((t + 1),(r + 1), b,(b + 1));

		if (b + 1 <= 24)
            {
			RevForeAttr((b + 1),(l + 1),(b + 1),(r + 1));
            }
		}
	else if (b + 1 <= 24)
		{
		RevForeAttr((b + 1),(l + 1),(b + 1), r);
		}

_ret();

}


/********************************
*
* Reverse text Attribute for
* passed coordinates
*
*/


void RevForeAttr( int y, int x, int yy, int xx )

{

	register unsigned char far *scptr;
	register int	i,j;


	for (i = y; i <= yy; ++i) {
		scptr = ScrPtr( x, i );
		scptr++;
		for (j = x; j <= xx; ++j) {
			*scptr = *scptr % 8;			/* reverse the attribute */
			scptr += 2;                /* skip the character */
		}
	}
}


/* Screen pointer */

unsigned char far *ScrPtr( int col, int row )
{
	return( VIDSEG + (--row * 160) + (--col << 1) );
}