Re: [JOS-Kernel] decaf updates

[Ranieri Argentini]

>>cool, do you read the fonts from the vid-mem? the start
routine
>>clears unforunately the hole vid-mem, so no fonts after the stop
routine
>>are available (yet).
>
>well, I just copy the font from Linux and store in byte array. and
draw it
>pixel on the screen. I think that would be much more easy to do
it.
>hm, What's vid-mem ?  :o, I remember that font are stored in
VGA.
>But I forget how to retrieve it from VGA. is there any Doc?

This is the way to retrieve it using the BIOS. This might prove to be a
bit problematic in OS design, but solving this problem is left as an
excersize for the reader ;-D

This info has been extracted from Ralf Brown's interrupt list, file
inter60a.zip available through ftpsearch.lycos.com ....

Hope it helps someone somewhere ...

Ranieri

--------V-101130-----------------------------
INT 10 - VIDEO - GET FONT INFORMATION (EGA, MCGA, VGA)
        AX =
1130h
        BH =
pointer specifier
           
00h INT 1Fh pointer
           
01h INT 43h pointer
           
02h ROM 8x14 character font pointer
           
03h ROM 8x8 double dot font pointer
           
04h ROM 8x8 double dot font (high 128 characters)
           
05h ROM alpha alternate (9 by 14) pointer (EGA,VGA)
           
06h ROM 8x16 font (MCGA, VGA)
           
07h ROM alternate 9x16 font (VGA only) (see #00021)
           
11h (UltraVision v2+) 8x20 font (VGA) or 8x19 font (autosync EGA)
           
12h (UltraVision v2+) 8x10 font (VGA) or 8x11 font (autosync EGA)
Return: ES:BP = specified pointer
        CX   
= bytes/character of on-screen font (not the requested font!)
        DL   
= highest character row on screen
Note:   for UltraVision v2+, the 9xN
alternate fonts follow the corresponding
          8xN
font at ES:BP+256N
BUG:    the IBM EGA and some other EGA
cards return in DL the number of rows on
         
screen rather than the highest row number (which is one less).
SeeAlso: AX=1100h,AX=1103h,AX=1120h,INT 1F"SYSTEM DATA",INT
43"VIDEO DATA"

Format of alternate font table [array]:
Offset  Size    Description     (Table
00021)
 00h    BYTE    character
to be replaced (00h = end of table)
 01h  N BYTEs   graphics data for
character, one byte per scan line
--------V-101130BX4D4F-----------------------






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