Date: Sun, 26 Jul 1998 12:08:33 +0300 (IDT)
From: Eli Zaretskii <eliz AT is DOT elta DOT co DOT il>
To: ALMICHVL <almichvl AT aol DOT com>
cc: djgpp AT delorie DOT com
Subject: Re: FAR POINTERS AND FP_SEG CODE IN A PROGRAM THAT LOADS A FONT
In-Reply-To: <1998072401534100.VAA13013@ladder01.news.aol.com>
Message-ID: <Pine.SUN.3.91.980726120807.26387K-100000@is>
MIME-Version: 1.0
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On 24 Jul 1998, ALMICHVL wrote:

> MOST OF THE CODE WORKS ITS JUST THE PART WHERE THE FP_SEG COMES IN. IF THERES
> ANYBODY THAT CAN HELP ME OUT WITH THIS PIECE OF IT I WOULD APPRECIATE IT

Please read Chapter 18 of the DJGPP FAQ list.  It explains how to do
many of the things this code tries (and fails) to do.

>      OldMode = _farpeekb(0x0040, 0x0049);   // save user's video mode first

This won't work.  _farpeekb needs to be called with _dos_ds as its
first argument, and 16*segment+offset (i.e. 0x449) as its second.  See
section 18.4 in the FAQ.

> 	UserFont = MK_FP(peek(0x0000,0x010e), peek(0x0000,0x010c));
> 
> 	// install our font
> 	poke(0x0000, 0x010e, FP_SEG(font));
> 	poke(0x0000, 0x010c, FP_OFF(font));
> }
> // OLDFONT								//
> // ReInstalls user's original font pointer	void OldFont()
> {
> 	poke(0x0000, 0x010e, FP_SEG(UserFont));
> 	poke(0x0000, 0x010c, FP_OFF(UserFont));
> }

There are two problems here:  First, you need to convert the calls to
peek and poke to call _farpeekw instead, and use _dos_ds in them like
explained above (and in the FAQ).

And second, to install the font, you need first to copy it to a buffer
in conventional memory, below 1MB mark, because real-mode BIOS cannot
access addresses above 1MB where your DJGPP program lives.

So you will need to use `__dpmi_allocate_dos_memory' function to
allocate a buffer in conventional memory; then call `dosmemput' to
copy the font you read from a file into that buffer; then poke the
BIOS data area with the segment and offset of that buffer.  And *then*
it will work.