Rapier 24  Double-buffer Patch 57 v1.0    
                                     October 1993

This software adds an extra mode to the Rapier 24
CONFIG program.  This extra mode provides a PAL
resolution that is double-buffered.  This is
useful for smooth animations for programs that use 
the TIGA interface.  Microsoft Windows cannot make 
use of the double-buffer feature.


1.  Install Rapier 24 software in the normal way.

2.  The new RAPIER.CL file should be copied to the 
\RAPIER directory, replacing the previous copy.

3.  Run CONFIG and select "Standard TV line rate"
for the monitor option and 768x512 @50Hz for the
resolution.  Save with F10 in the normal way.

4. Dual-monitor mode must be used, i.e. a VGA monitor
attached to the VGA card and a TV monitor attached to
Rapier 24.

5.  To use the double-buffer, the program must
send TIGA commands to flip between pages 0 and 1;
one for drawing, and one for displaying.

Some example TIGA commands:
                          
get_config()
;returns hardware and current mode info including num_pages.

page_flip(display, draw) 
;only flips at end of field.

page_busy()
returns non-zero while a page_flip is outstanding.


A typical module:

int a =0; b = 1;

do
{
/* flip the page and wait till actioned */ 
page_flip(a, b);
while (page_busy());

/* copy from display buffer to new (scrolled) 
position in drawing buff */  
bitblt(...);

/* draw next 'slice' of scrolled info */ 
host2gsp() ?
text_out() ?

a ^= 1;
b ^= 1;
} while (1);

