Message-ID: <3842DB84.46B6E87D@interlog.com>
From: Alan Illeman <illeman AT interlog DOT com>
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Newsgroups: comp.os.msdos.djgpp
Subject: Re: Newbie tries to plot a pixel and fails :)
References: <abi04.2131$t12 DOT 95240 AT newscontent-01 DOT sprint DOT ca>
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Date: Mon, 29 Nov 1999 15:01:08 -0500
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NNTP-Posting-Date: Mon, 29 Nov 1999 14:54:11 EST
To: djgpp AT delorie DOT com
DJ-Gateway: from newsgroup comp.os.msdos.djgpp
Reply-To: djgpp AT delorie DOT com

James Migel wrote:
> 
> Hi all, I'm trying to work my way through the DJGPP tutorial on the game
> programming megasite http://perplexed.com/GPMega/ and am having trouble
> plotting a pixel. I have my code right I think... mode 13 starts and then it
> is supposed to plot at x=25 y=25 color=25 but I see nothing... I thought
> that maybe my color (25) was black but it doesn't matter what I use I still
> get a blank screen. Is it possible that I have to load a color palette
> before it knows any colors? code as follows:
[snip]

I've replied to this already, suggesting that perhaps you use Allegro but on
second thoughts, as I was new to djgpp but not to vesa, share this snippet
with you..

------------------- file: vesa.h -------------------
#ifndef VESA__H
#define VESA__H

typedef struct VESAINFO   { 
unsigned char  VESASignature[4]     __attribute__ ((packed));
unsigned short VESAVersion          __attribute__ ((packed));
unsigned long  OEMStringPtr         __attribute__ ((packed));
unsigned long  Capabilities         __attribute__ ((packed));
unsigned long  VideoModePtr         __attribute__ ((packed));
unsigned short TotalMemory          __attribute__ ((packed));
unsigned char  Reserved[236]        __attribute__ ((packed));
} VESAINFO;

typedef struct MODEINFO {
unsigned short ModeAttributes       __attribute__ ((packed));
unsigned char  WinAAttributes       __attribute__ ((packed));
unsigned char  WinBAttributes       __attribute__ ((packed));
unsigned short WinGranularity       __attribute__ ((packed));
unsigned short WinSize              __attribute__ ((packed));
unsigned short WinASegment          __attribute__ ((packed));
unsigned short WinBSegment          __attribute__ ((packed));
unsigned long  WinFuncPtr           __attribute__ ((packed));
unsigned short BytesPerScanLine     __attribute__ ((packed));
unsigned short XResolution          __attribute__ ((packed));
unsigned short YResolution          __attribute__ ((packed));
unsigned char  XCharSize            __attribute__ ((packed));
unsigned char  YCharSize            __attribute__ ((packed));
unsigned char  NumberOfPlanes       __attribute__ ((packed));
unsigned char  BitsPerPixel         __attribute__ ((packed));
unsigned char  NumberOfBanks        __attribute__ ((packed));
unsigned char  MemoryModel          __attribute__ ((packed));
unsigned char  BankSize             __attribute__ ((packed));
unsigned char  NumberOfImagePages   __attribute__ ((packed));
unsigned char  Reserved_page        __attribute__ ((packed));
unsigned char  RedMaskSize          __attribute__ ((packed));
unsigned char  RedMaskPos           __attribute__ ((packed));
unsigned char  GreenMaskSize        __attribute__ ((packed));
unsigned char  GreenMaskPos         __attribute__ ((packed));
unsigned char  BlueMaskSize         __attribute__ ((packed));
unsigned char  BlueMaskPos          __attribute__ ((packed));
unsigned char  ReservedMaskSize     __attribute__ ((packed));
unsigned char  ReservedMaskPos      __attribute__ ((packed));
unsigned char  DirectColorModeInfo  __attribute__ ((packed));
unsigned long  PhysBasePtr          __attribute__ ((packed));
unsigned long  OffScreenMemOffset   __attribute__ ((packed));
unsigned short OffScreenMemSize     __attribute__ ((packed));
unsigned char  Reserved[206]        __attribute__ ((packed));
} MODEINFO;

/* VESA 1.2 functions */
#define GET_VESA_VGA_INFO  0x4F00
#define GET_VESA_MODE_INFO 0x4F01
#define SET_VESA_MODE      0x4F02
#define GET_VESA_MODE      0x4F03
/*      not used           0x4F04  Save/Restore Super VGA state */
/*      not used           0x4F05  CPU Video Memory Window Control */
/*      not used           0x4F06  Get/Set Logical Scan Line Length */
#define SET_VESA_START     0x4F07
#define SET_VESA_DACS      0x4F08

/* VESA 2.0 functions */
#define GET_VESA_PALETTE   0x4F09  /* Get/Set Palette Data */
#define GET_VESA_PM        0x4F0A  /* Return VBE Protected Mode Interface */

#define SET_VESA_LINEAR    0x4000  /* OR with MODE in SET_VESA_MODE */

/* errors */
#define VESA_SUCCESS       0

#define VESA_ERROR            -1
#define VESA_SIGNATURE_ERROR  -2
#define VESA_VERSION_ERROR    -3
#define VESA_MODE_ERROR       -4
#define VESA_LINEAR_ERROR     -5
#define VESA_MAPPING_ERROR    -6

extern  unsigned char *video;
extern  int xres;
extern  int yres;

int SetVesaMode(unsigned short);
void ResetMode(void);

#endif

------------------ file: vesa.c ----------------------

#include <dpmi.h>
#include <go32.h>
#include <sys/farptr.h>
#include <sys/nearptr.h>
#include "vesa.h"

static VESAINFO vesainfo;
static MODEINFO modeinfo;
static char oldmode;

unsigned char *video;
int  xres;
int  yres;

static int GetVESAINFO(void)
{
    __dpmi_regs r;
    long dosbuf;
    int i;

    /* use the memory transfer buffer */
    dosbuf = __tb & 0xFFFFF;

    /* initialize the buffer to zero */
    for (i=0; i<sizeof(VESAINFO); i++)
       _farpokeb(_dos_ds, dosbuf+i, 0);

    /* call the VESA function */
    r.x.ax = GET_VESA_VGA_INFO;
    r.x.di = dosbuf & 0xF;
    r.x.es = (dosbuf>>4) & 0xFFFF;
    __dpmi_int(0x10, &r);

    if (r.d.eax == -1)
        return VESA_ERROR;

    /* copy data into structure */
    dosmemget(dosbuf, sizeof(VESAINFO), &vesainfo);

    if (strncmp(vesainfo.VESASignature, "VESA", 4) != 0)
        return VESA_SIGNATURE_ERROR;
    if(vesainfo.VESAVersion < 0x200)
        return VESA_VERSION_ERROR;
      
    return VESA_SUCCESS;
}

static int GetMODEINFO(unsigned short mode)
{
    __dpmi_regs r;
    long dosbuf;
    int i;

    /* use the memory transfer buffer */
    dosbuf = __tb & 0xFFFFF;

    /* initialize the buffer to zero */
    for (i=0; i<sizeof(MODEINFO); i++)
       _farpokeb(_dos_ds, dosbuf+i, 0);

    /* call the VESA function */
    r.x.ax = GET_VESA_MODE_INFO;
    r.x.cx = mode;
    r.x.di = dosbuf & 0xF;
    r.x.es = (dosbuf>>4) & 0xFFFF;
    __dpmi_int(0x10, &r);

    if (r.d.eax == -1)
        return VESA_ERROR;

    /* copy data into structure */
    dosmemget(dosbuf, sizeof(MODEINFO), &modeinfo);
     
    return VESA_SUCCESS;
}


static int GetModeInfo(unsigned short mode)
{
    long modeptr;
    int i, error;
    __dpmi_meminfo mapping;

    if((error=GetVESAINFO()) != VESA_SUCCESS)
        return error;

    /* convert the mode list pointer from seg:offset to a linear address */
    modeptr = ((vesainfo.VideoModePtr & 0xFFFF0000) >> 12) + 
               (vesainfo.VideoModePtr & 0xFFFF);

    for(i=0; ;i++) {
        if(_farpeekw(_dos_ds, modeptr) == 0xFFFF)
            return VESA_MODE_ERROR;
        if(_farpeekw(_dos_ds, modeptr) == mode)
            break;
        modeptr += 2;  /* next WORD */
    }

    if((error=GetMODEINFO(mode)) != VESA_SUCCESS)
        return error;

    /* check for linear frame buffer capability */
    if(!(modeinfo.ModeAttributes & 0x0080))
 	return VESA_LINEAR_ERROR;

    /* create direct pointer to video memory */
    if (!__djgpp_nearptr_enable())
        return VESA_MAPPING_ERROR; /* not really */

    /* map into linear memory */
    mapping.address = modeinfo.PhysBasePtr;
    mapping.size = vesainfo.TotalMemory << 16;
    if (__dpmi_physical_address_mapping(&mapping) != 0)
        return VESA_MAPPING_ERROR; 

    video = (unsigned char *)(mapping.address + __djgpp_conventional_base);
    xres  = modeinfo.XResolution;
    yres  = modeinfo.YResolution;
    return VESA_SUCCESS;
}

int SetVesaMode(unsigned short mode)
{
    __dpmi_regs r;
    int error;

    if((error=GetModeInfo(mode)) != VESA_SUCCESS)
        return error;

    /* get current video mode */
    oldmode = _farpeekb(_dos_ds, 0x449);  /* byte at 40:49h */

    /* call the VESA function */
    r.x.ax = SET_VESA_MODE;
    r.x.bx = mode | SET_VESA_LINEAR;
    __dpmi_int(0x10, &r);

    if (r.d.eax == -1)
        return VESA_ERROR;

    return VESA_SUCCESS;
}

void ResetMode(void)
{
    __dpmi_regs r;

    if(oldmode != _farpeekb(_dos_ds, 0x449)) {
	    r.h.ah = 0;
	    r.h.al = oldmode;
	    __dpmi_int(0x10, &r);
    }
}


-----------------  file: vesa1.c --------------------------

#include <stdio.h>
#include "vesa.h"

int main(void)
{
    int i, j, error;
    unsigned short mode;

    /*--------------------------------------------
      Test VESA mode 0x105 1024x768, 256 colors
      for Matrox Mystique 2Mb video card
    --------------------------------------------*/
    mode = 0x105;

    if((error=SetVesaMode(mode)) != VESA_SUCCESS)
         return -error;

    /* clear video memory */
    memset(video, 0x3F, xres*yres);  /* sort of pink color */

    for(i=0,j=0; i<yres-1; i++,j+=xres)
         video[i+j] = 0xFF;	/* black */

    getch();
    ResetMode();
    printf("\nVesa test of mode 0x%3.3X was successful\n", mode);
    return 0;
}


regards,  Alan