Category : C Source Code
Archive   : FRASRC18.ZIP
Filename : YOURVID.C

/*

Roll-Your-Own video mode (DOTMODE 19) routines.

Even if you don't have an assembler, you can add your own video-mode
routines to FRACTINT by adding a video mode of the appropriate resolution
to FRACTINT.CFG that uses dotmode 19 (which calls these routines to
perform all the dirty work) and modifying these routines accordingly.
The four routines are:

startvideo() Do whatever you have to do to throw your adapter into
the appropriate video mode (in case it can't be accomplished
the "normal" way, with INT 10H and the AX/BX/CX/DX values
available via FRACTINT.CFG or FARVIDEO.ASM). This routine
will typically be empty (in which case the AX/BX/CX/DX values
in FRACTINT.CFG or FARVIDEO.ASM must be encoded appropriately
to accomplish the task), but some adapters like the 8514/A
and TARGA need special handling which would go here.
If you DO have to put something here, you should encode
AX = 0xFF so as to effectively convert the regular
video-switching code inside VIDEO.ASM to use
an invalid INT 10H call - "do-nothing" logic.

endvideo() do whatever you have to do to get it out of that
special video mode (in case 'setvideo(3,0,0,0)'
won't do it) - this routine will typically be empty,
but some adapters like the 8514/A and TARGA need
special handling which would go here.

writevideo(int x, int y, int color) write a pixel using color number
'color' at screen coordinates x,y (where 0,0 is the
top left corner, and sxdots,0 is the top right corner)

int readvideo(int x, int y) return the color number of pixel x,y
using the same coordinate logic as 'writevideo()'

int readvideopalette() read the contents of the adapter's video
palette into the 'BYTE dacbox[256][3]' array
(up to 256 R/G/B triplets, each with values from 0 to 63).
Set dacbox[0][0] = 255 if there is no such palette.
Return a -1 if you want the normal internal EGA/VGA
routines to handle this function.

int writevideopalette() write the contents of the adapter's video
palette from the 'BYTE dacbox[256][3]' array
(up to 256 R/G/B triplets, each with values from 0 to 63).
Return a -1 if you want the normal internal EGA/VGA
routines to handle this function.

Finally, note that, although these example routines are written in "C",
they could just as easily (or maybe more easily!) have been written
in assembler.

*/

#include
#include "port.h"
#include "prototyp.h"

/* external variables (set in the FRACTINT.CFG file, but findable here */

extern int dotmode; /* video access method (= 19) */
extern int sxdots, sydots; /* total # of dots on the screen */
extern int colors; /* maximum colors available */

/* the video-palette array (named after the VGA adapter's video-DAC) */

extern BYTE dacbox[256][3];

/* for demo purposes, these routines use VGA mode 13h - 320x200x256 */

int startvideo()
{

/* assume that the encoded values in FRACTINT.CFG or FARVIDEO.ASM
have been set to accomplish this (AX = 0x13, BX = CX = DX = 0) */

return(0); /* set flag: video started */

/* or, we could have done this instead and encoded AX = 0xFF
in FRACTINT.CFG/FARVIDEO.ASM:

union REGS regs;

regs.x.ax = 0x13;
int86(0x10,®s,®s);

*/

}

int endvideo()
{

return(0); /* set flag: video ended */

}

void writevideo(int x, int y, int color)
{

union REGS regs;

regs.h.ah = 0x0c; /* invoke INT 10H with AH = 0CH */
regs.h.al = color;
regs.x.bx = 0;
regs.x.cx = x;
regs.x.dx = y;
int86(0x10,®s,®s);

}

int readvideo(int x, int y)
{

union REGS regs;

regs.x.ax = 0x0d00; /* invoke INT 10H with AH = 0DH */
regs.x.bx = 0;
regs.x.cx = x;
regs.x.dx = y;
int86(0x10,®s,®s);

return((unsigned int)regs.h.al); /* return pixel color */

}

int readvideopalette()
{

return (-1); /* let the internal routines do it */

}

int writevideopalette()
{

return (-1); /* let the internal routines do it */

}