Category : C Source Code
Archive   : WTWG12B.ZIP
Filename : W50LINE.C

/* w50line.c - control EGA/VGA display in text modes to 43/50 line
*
* USAGE: w50line ( ON_OFF );
* PARAMETER: ON_OFF = if 0, restore to 25 line mode
* non-0, set to 50/43 line
* RETURNS: int is50 = 0 if in 25 line mode,
* non-0 if in 50/43 line mode
* ALSO: changes winymax to 42,49, or 24 as needed.
* changes the size of wfullscreen, the initial fullscreen window.
* moves the cursor to within a 25-line window if needed.
* changes parameters governing multiple video pages.
* allows for 2 top protected lines if pulldown menus are installed.
*
* WARNINGS: When switching back to 25-line mode, this function
* does not check any currently open windows
* to make sure they are inside the 25-line screen.
*
* This function has no effect in graphics modes or on HERCULES cards.
*
* ACKNOWLEDGEMENT: The logic for switching to 43/50 line mode comes
* from DOS POWER TOOLS by Somerson.
*
*/
#include "wsys.h"


static void clear50(void); /* prototype for atexit func */
static char exit_installed =0;

static char is50 =0;

#define BIOS_CURSOR_EMULATION *( (unsigned char far *) 0x0487L )

#define BIOS_PAGE_SIZE *( (int far *) 0x044CL )

int w50line ( int want50 )
{
int nlines;
unsigned char save_BIOS_CURSOR;

PSEUDOREGS


if (
( wmonitor == 'E' || wmonitor == 'V' )
#ifndef TEXTONLY
/* do nothing if in a graphics mode */
&& ( wmode == 'T' )
#endif /* TEXTONLY */
)
{
if ( want50 )
{
if ( !exit_installed )
{
/* install exit function only once per program
*/
exit_installed = ON;
atexit (clear50);
}

/*set 8-byte font
*/
_BX = 0; /* load font */
_AX = 0x1112;
INTERRUPT ( 0x10 );


wcurscanln = 0x0607;

/* force EGA cursor to correct size
* A fairly complex situation here.
* with 'cursor emulation' ON,
* EGA card converts row 6 to row 12 (for CGA compat.)
* so have to turn OFF cursor emulation, then set cur. row
*
*/
save_BIOS_CURSOR = BIOS_CURSOR_EMULATION;
BIOS_CURSOR_EMULATION |= 0x01; /* turn OFF emulation*/
_CX = 0x0600; /* cursor size request */
_AH = 1;
INTERRUPT ( 0x10 );
BIOS_CURSOR_EMULATION = save_BIOS_CURSOR; /* restore emul. */
outport ( 0x03B4, 0x0714 );


/* set number of screen lines
* dividing BIOS_PAGE_SIZE by 80 (=#columns) doesn't work
* for some reason in VGA BIOS page size is 64 bytes too big.
*/
nlines = ( wmonitor == 'V' ) ? 50 : 43;

/* setup windows globals
*/
wyabsmax = nlines -1;

/* adjust size of wfullscreen to allow for top menu
*/
wfullscreen->winymax = nlines-1 - (wfullscreen->wintop);

/* clear lower half of screen to fullscreen color
*/
wdefine ( 0, 25, wxabsmax+1, nlines-25, 0, 0, 0);
wsetattr ( wfullscreen-> winattr );
wclear ();
wabandon();

/* setup multiple pages if this is a 'paging' program
*/
if ( wlastpage )
{
/* have to change the PAGE size to reflect smaller chars.
* also, for reasons totally unclear to me,
* the pages in 50-line mode are 32 chars =64 bytes longer.
* ie, 64 bytes are unused in VGA RAM at end of each page.
* and the pages in 43-line mode are something else.
*
* Therefore, get the page size form the BIOS storage area.
*/
wlastpage = 3; /* pages 0, 1, 2, 3 = 4 total */
wpage_size = BIOS_PAGE_SIZE;
}
is50 = ON;
}
else
{
/* don't want50 */
#if 0
/* OLD-FASHIONED WAY TO SET 25 LINE MODE
*/
/*set BIOS to 25 line mode
*/
_BX = 0;
_AX = 0x1111;
INTERRUPT (0x10);

wcurscanln = 0x0C0D; /* cursor scan lines */

/* force EGA/VGA cursor to correct size
*/
_CX = 0x0C0D; /* cursor size request */
_AX = 1;
INTERRUPT ( 0x10 );
outport ( 0x03B4, 0x0D14 );
#endif /* 0 */
/* NEW, easier way to restore 25-line mode
*/
/* revert video using BIOS mode select
* MODE=3, bit 7 of AL =1 means save video contents
*/
_AX = 0x0083;
INTERRUPT ( 0x10 );

nlines = 25;
wyabsmax = 24;

/* wfullscreen may have been shrunk by 2 lines by wpulldown()
*/
wfullscreen->winymax = 24 - (wfullscreen-> wintop);
if ( w0 -> winy > 24 )
{
/* make sure cursor is inside 24-line boundary
*/
wgoto ( -1, 24 );
}
if ( w0 != wfullscreen )
{
/* make sure wfullscreen is also inside 24-line boundary
*/
if (wfullscreen-> winy > (wfullscreen->winymax) )
{
wfullscreen-> winy = (wfullscreen->winymax);
}
}

/* reset multiple pages if this is a 'paging' program
*/
if ( wlastpage )
{
wlastpage = 7; /* pages 0..7 = 8 total */
wpage_size = 4096;
}
is50 = OFF;
}

/* the cursor was turned 'ON' during the above manipulation.
* if the cursor was 'OFF' prior to calling this routine,
* it should be turned 'OFF' again.
*/
if ( (w0-> winflag & WFL_CURSOR) == 0 )
{
wcursor (OFF);
}

/* change mouse mvt limits to match nlines.
*/
if ( wmouse.wms_present )
{
_DX = (nlines*8)-1;
_CX = 0;
_AX = 0x08;
INTERRUPT ( 0x33 );
}

} /* end if wmonitor== 'E' or 'V' and wmode=='T' */

return (is50); /* w50line() */
}

static void clear50 (void)
{
if ( is50 )
{
w50line ( OFF );
}
return; /* clear50() - called only atexit */
}