Date: Sun, 25 Jan 1998 22:21:58 -0800 (PST)
Message-Id: <199801260621.WAA01558@adit.ap.net>
Mime-Version: 1.0
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To: "David Whitlark" <witty AT itsnet DOT com>, djgpp AT delorie DOT com
From: Nate Eldredge <eldredge AT ap DOT net>
Subject: Re: Bios Font
Precedence: bulk

At 08:37  1/24/1998 -0700, David Whitlark wrote:
>how do I write a program to install a new font into the dos bios font, So
>that I change the default font of DOS?
This is a bit off-topic, but since you're here...

Snippet from Ralf Brown's Interrupt List:
INT 10 - VIDEO - TEXT-MODE CHARGEN - LOAD USER-SPECIFIED PATTERNS (PS,EGA,VGA)
        AX = 1100h
        ES:BP -> user table
        CX = count of patterns to store
        DX = character offset into map 2 block
        BL = block to load in map 2
        BH = number of bytes per character pattern
Return: nothing
Notes:  This function will cause a mode set, completely resetting
          the video environment, but without clearing the video buffer
        the current block specifiers may be determined with INT 10/AH=1Bh,
          looking at offsets 2Bh and 2Ch of the returned data (VGA only)
          (see AH=1Bh,#0037)
SeeAlso: AX=1101h,AX=1102h,AX=1103h,AX=1104h,AX=1110h,AH=1Bh,AX=CD10h

Here's the code I would use. It assumes you are using an 8x16 font, which
normally you are.

#include <sys/movedata.h>
#include <dpmi.h>
#include <go32.h>
void set_font(void *font)
{
   __dpmi_regs r;
   /* Move font to transfer buffer */
   dosmemput(font, 16 * 256, __tb & 0xfffff);
   /* Set up registers */
   r.x.ax = 0x1100;
   r.x.es = (__tb >> 4) & 0xffff;  /* segment part of transfer buffer address */
   r.x.bp = __tb & 0xf;
   r.x.cx = 256; /* Load all 256 characters... */
   r.x.dx = 0; /* ... starting with the 0th */
   r.h.bl = 0; /* block 0 */
   r.h.bh = 16; /* an 8x16 font */
   __dpmi_int(0x10, &r);
}

Note that this requires the transfer buffer to be at least 4K (it is
normally 16K but can be reduced with `stubedit' to as little as 2K).

The font is a bitmap of the font you want. 16 bytes per character,
characters in order.

Nate Eldredge
eldredge AT ap DOT net