Re: Full screen magnifier: howto?

[Peter Korn <Peter Korn Sun COM>]

Hi Enzo,

To do fullscreen magnification with Gnopernicus, or with anything based on 
stock X today, is a system with two frame buffers - one for the source (or 
unmagnified) view, and another for the display (or magnified) view.  You can 
do this by installing two video cards, or by using a video card with two 
frame buffers on it (I've used both the Matrox G550 and Nvidia FX5200 cards 
in this configuration).  Another alternative is to go with a virtual frame 
buffer for your X system.  This virtual frame buffer is essentially a hunk 
of RAM that acts as a video card in your system.  I've been playing with the 
"dummy driver" (dummy_drv.o) developed by Egbert Eich for this purpose. 
Note: in both cases you need to properly configure your X server to be aware 
of and use the two frame buffers.  Specifically in the "ServerLayout" 
section of your /etc/X11/XF86Config file you need two "Screen" lines (one 
would be 0 and the other 1).  Once this is done you need to be sure that the 
gnome-mag service is using the correct source and destination screens (some 
recent changes to gnome-mag and gnopernicus help with this - be sure you 
have the *very* latest code).

There are a number of subtle issues that still need to be worked out before 
full-screen magnification is really ready for prime time.  These include 
restricting the mouse cursor to the source view, automatically engaging the 
second frame buffer (and re-starting the X server) at login time, and a 
bunch of general magnification service improvements that are dependent on 
some new X extensions (to obtain the mouse cursor pixels and notification 
when the mouse cursor shape changes, and to get dirty region notification so 
the magnifier doesn't need to poll for updates).


Regards,

Peter Korn
Sun Accessibility team


Enzo wrote:
> Hello,
> I am new to this list.
>
> I am an italian developer and I have a friend who has low vision abilities.
> For that reason I developed in my spare time a magnified terminal (based on
> rxvt code) to let him explore things in linux.
>
> You can view it at   http://www.gupix.it/projects/magterm/
>
> Obviously this project is not the solution. The solution is the fullscreen
> magnifier for X. Searching in the web I found this:
>
> http://mail.gnome.org/archives/gnome-accessibility-list/2004-February/msg00045.html
>
> It will be wonderful if I could setup something like that. Expecially because
> my friend is also a great programmer and he could give you some feedbacks and
> maybe write some code for the community.
>
> What I need to setup a fullscreen magnifier with gnopenicus? Can someone help me?
> I have a debian Sid: the sid version of gnopernicus is able to do this?
> Or I have to get the cvs version and compile it?
> What kind of graphic card if necessary to make it work?
>
> Thanks much for the support.
>
> Enzo
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