Newsgroups: comp.os.msdos.djgpp
From: malyon AT netcom DOT com (Roland Acton)
Subject: Re: [q]: Getting access to BIOS font data
Message-ID: <malyonE5zvC1.Ez1@netcom.com>
Organization: Netcom On-Line Services
References: <856518100 DOT 402472 AT red DOT parallax DOT co DOT uk>
Date: Sat, 22 Feb 1997 07:55:13 GMT
Lines: 53
Sender: malyon AT netcom5 DOT netcom DOT com
To: djgpp AT delorie DOT com
DJ-Gateway: from newsgroup comp.os.msdos.djgpp

John Eccleston (johne AT parallax DOT co DOT uk) wrote:
: Hi All,

: I am trying to get the bios font data so that I can write text to my
: double buffer.  I have written a little piece of inline ASM to call
: int 10 function 11 to get the address of the font data but when I run
: the program, even though it works the data it brings back is not as
: expected.

: When I try using the data obtained the characters are all gibberish.
: On my PC even an 8x8 character set reports that it is stored as
: 16 bytes per character, and for font heights of 8, 14 and 16 they are
: all stored at the same address.

<SNIP>

  The code below is from one of my programs. It makes a copy of the
character set in order to redefine it. For some reason the copy does not
look exactly like the original, but it's usable.

--- CUT HERE ---

void set_up_graphical_pointer() {
  __dpmi_regs dpmiregs;
  unsigned int orig_font_address;

/* Duplicate the default font for the graphical mouse pointer. In text mode,
   all font definitions are 8 columns, and the 9th column behaves in a
   rather odd way. For most characters, the 9th column appears as blank, but
   for characters C0-DF the video adapter makes the 9th column a copy of the
   8th column, to allow for continuous horizontal lines. */
  font_segment_info.size = ((256 * 16) + 15) / 16;
     // 256 chars, 16 bytes each
  if (_go32_dpmi_allocate_dos_memory(&font_segment_info)) {
    printf("Couldn't allocate conventional memory for font duplication.\n");
    exit(EXIT_FAILURE);
  }
  copied_font_address = font_segment_info.rm_segment << 4;
  dpmiregs.x.ax = 0x1130;   // Get font pointer.
  dpmiregs.h.bh = 0x6;   // 8x16 font.
  __dpmi_int(VIDEO_INTERRUPT, &dpmiregs);
  orig_font_address = ((dpmiregs.x.es & 0xFFFF) << 4)
    + (dpmiregs.x.bp & 0xFFFF);
  movedata(_dos_ds, orig_font_address, _dos_ds, copied_font_address,
    256 * 16);
  dpmiregs.x.ax = 0x1100;   // Load user font patterns.
  dpmiregs.x.bx = 0x1000;   // 16 bytes per character.
  dpmiregs.x.cx = 256;   // Load 256 characters.
  dpmiregs.x.dx = 0;   // Load at character offset 0.
  dpmiregs.x.es = copied_font_address >> 4;   // Segment of font patterns.
  dpmiregs.x.bp = 0;   // Offset of font patterns.
  __dpmi_int(VIDEO_INTERRUPT, &dpmiregs);
}