Category : C Source Code
Archive   : WTWG12B.ZIP
Filename : WCLEAR.C

/*! wclear
* clear an area of screen to current background
*
*/
#include "wscreen.h"
#include "wsys.h"



void wclear ( void )
{
wclearabs ( w0->winleft, w0->wintop,
w0->winleft + w0->winxmax, w0->wintop + w0->winymax
);
wgoto ( 0,0 );
return;
}

void wclearline ( void )
{
wclearabs ( w0->winleft + w0->winx, w0->wintop + w0->winy,
w0->winleft + w0->winxmax, w0->wintop + w0->winy
);
return;
}



void wclearabs ( int l, int t, int r, int b )
{
unsigned char far *p, far *s; /* to video ram */
int col; /* column counter */


struct _CHATTR
{
unsigned char c;
unsigned char a;
}
chattr;
typedef struct _CHATTR far *CHATTR; /*ptr to a far ch/attr pair*/





#ifndef TEXTONLY

unsigned char a; /* background attribute */
unsigned int hn; /* hercules bank offset */
unsigned char far *base; /* base of each row */
unsigned char far *colptr; /* pointer to column */

unsigned char latch;
#endif /* TEXTONLY - end graphics-mode declarations */



if ( l < 0 || r > wxabsmax || t < 0 || b > wyabsmax )
{
return;
}




if ( wmode == 'T' )
{
s = wpage_ram + 2*80*t + 2*l;

chattr.c =' ';
chattr.a = wgetattr();



for ( ; t <= b; ++t, s += 2*80 )
/* s pts to start of each line */
{
for ( col = l, p = s; col <= r; ++col )
{
*((CHATTR) p) = chattr;
p += 2;
}
}
/* end text mode absolute clear */

return;
} /* end text mode */


#ifndef TEXTONLY
/* graphics mode wclearabs */



a = ( wgetattr() ) >> 4; /* background color */



switch ( wmonitor )
{
case ( 'H'):
/* NOTE addressing hercules graphics ram:
* l, t are 'text-mode' addresses.
* 720 pixels/row, wpxchar pixels per 'x' increment
* so 1st factor = wxabsmax = chars per row
* divide wpychar by 4(=# herc banks) =
* gives #of sets of banks (4 pixel rows each)
* wpxchar/8 =1 always, included only for clarity.
*
* because charsizes are mults of 4, whbank starts at 0;
*/
base = wpage_ram
+ ( (720/wpxchar)*(wpychar/4)*t ) + l;

/* in hercules, 'dither' blue and green bits
* note this line changes 'a' from attr to bitmask.
* and sets 8 adjacent bits on screen
*/
a = (a & 0x03) ? 0xff : 0x00;

/* convert to pixel co-ords only for counting rows */
t *= wpychar;
b = (b+1) * wpychar; /* includes last pixel row */


for ( hn = 0; t < b; ++t, hn += 0x2000 )
{
/* loop iterates once per row
*/
if ( hn == 0x8000 )
{
/* finished one set of 4 banks,
* move up to next tier.
*/
hn = 0;
base += 90;
}
for ( col = l, colptr = base;
col <=r;
++col, ++colptr)
{
/* once per column within each row */
*( colptr + hn ) = a;
}
}
break; /* end hercules mode */

case ( 'E' ):
case ( 'V' ):

base = wpage_ram + ( wegarowsize * wpychar * t ) + l;

/* convert to pixel co-ords to count rows
*/
t *= wpychar;
b = (b+1)* wpychar; /* last pixel row in last char row*/

EGA_OUT (1, EGA_ENABLE);
EGA_BITPLANE (0x0f);


EGA_OUT (3, 0x00); /* OVERWRITE */
/* write attribute to 8 bits */
EGA_OUT (0, a);
EGA_OUT (8, 0xFF);


for ( ; /* loop once per row */
t < b;
++t, base += 640/wpxchar )
{
for ( col = l, colptr =base ;
col <= r;
++col, ++colptr)
{

*(colptr) = 0xff;

}
} /* end for each rows */

/* reset EGA */
EGA_OUT (0,0); /* BLACK */


break;
} /* end switch (wgdriver) */

#endif /* TEXTONLY - end graphics mode wclearabs */
return; /* wclearabs */


}


/*---------------------- end of WCLEAR.C -----------------------------*/