Date: Tue, 5 Dec 1995 10:30:32 -0500
To: djgpp AT sun DOT soe DOT clarkson DOT edu
From: wroberts AT aug DOT com
Subject: Re: Graphics in V2

>What address is the VGA buffer mapped to in V2 ?
>
>I've tried writing to 0xD0000000, 0xD1000000, and 0xA0000000 - all 
>the r/w video address mentioned in the docs.
>
Here's a snippet of code that uses the _farpokeb() function to plot a pixel:


#include <stdio.h>
#include <go32.h>
#include <dpmi.h>
#include <sys/farptr.h>

int main(void)
{
        __dpmi_regs dr;
        unsigned long offset;   /* offset of video mem. */
        unsigned char color;    /* color of pixel to plot. */
        unsigned short _d_selectr;   /*dos mem selector. */     

        dr.x.ax = 0x0013;        /*320X200X256 mode 13h*/
        __dpmi_int(0x10, &dr);   /*init mode 13h */
        
        _d_selectr = _dos_ds;    /*set up the dos mem selector */

        offset = 0xa0000;        /*point offset to start of vid mem.*/
        color = 2;               /*color to plot*/
        
        _farpokeb (_d_selectr,offset,color) /*plot a pixel in u/l corner
of screen.*/

        while (!kbhit());      /*allow time to view artwork.*/

        dr.x.ax = 0x0003;      /*init 80X25 text mode*/
        __dpmi_int (0x10,&dr);

        return 1;               /*Bye-Bye*/

}

NOTE: please forgive any typos. :)

        
>The graphics do work in DPMI now, don't they ?  (GRX2.0 works)
>

The routine above is DPMI compliant.  I don't know about GRX2.0, I don't use it.



>Also, are the pixel routines more complex in V2 - or is a slower 
>addressing method done ?
>

I don't know about that either. :)


>Lee Braiden  (lee_b AT celestia DOT dnet DOT co DOT uk)
><Celestia>
>



If you want to know how to speed up the plotting of pixels and copying
buffers to the VGA screen, etc.., just drop me some e-mail.  


Hope I've been of some help to ya!

Later,
Wayne