From: zmbenhal@isis.cs.du.edu (Zeyd M. Ben-Halim) Subject: Re: Linux & VGA graphics: state of play? Date: 1 May 1992 06:12:56 GMT
eonu24@castle.ed.ac.uk (I Reid) writes:
>Just a quick question.....
>What's the state of play with respect to Linux and VGA graphics (say 800x600
>even tho' it's not strictly VGA). I had a play about with the graphics mode
>changing code on tsx-11 but didn't really get anywhere so I was wondering what
>others are working on and how far they've got. If anyone has enough code
>working to allow me to change into 800x600 and some kind of put_pixel routine
>it would be very very usefull (i.e. I could do with it for next week!).
I've been playing around with the vga code. Switching to graphics modes seems
to work. Unfortunately, screen access in 16-color mode is complicated and
requires user-level access to ports. Also there is no bank-switching routine.
Access to screen in 256-colors modes is straight-forward, but I couldn't get
the mode switching to work.
If it were possible to use int10 and int33 (for the mouse) like djgpp does,
a lot of this would be simplified. Otherwise register-level mode setting will
remain a black-art.
Support for graphics in linux requires:
mode switching via int10 or register manipulation.
bank switching for modes requiring more than 64K.
screen read/write functions for 16-color modes.
screen read/write functions for 256-colors modes. (very easy)
The first two functions are video-card dependant.
Any volunteers?
Zeyd