Re: [g-a-devel]Re: [blindpng sdf lonestar org: Full Screen Magnification for X Windows] (fwd)

[Bill Haneman <bill haneman sun com>]

Hi Kieran!

As Michael said, we have some support for the kind of magnification you
are asking for, in 'gnome-mag'.  The gnopernicus project
(http://www.baum.ro/gnopernicus.html) is developing an integrated
screenreader-magnifier that uses the GNOME-2 framework and gnome-mag.

There are some inherent problem with doing fullscreen magnification in
X, because of the XServer architecture.  Basically, anything displayed
on the screen must go through the X server to a specific X
"display/screen" combination.  The only reasonable way to do fullscreen
magnification in X is to make the magnified image and the "source" image
two separate X "screens".  Up until now the only way to get truly
separate X screens [*] is to have two 'framebuffers', which means either
a high-end graphics case like Matrox, or two graphics cards.

On Solaris we now have a capability called the "X Virtual Display" which
allows you to have an unmagnified display that's not attached to a
physical framebuffer, and so with this extension you can do fullscreen
magnification in X.  We hope to provide this for Linux as well in the
near future.

best regards,

Bill

[* "Xvfb", the X Virtual Frame Buffer, gives you a passive virtual
screen but it can't be used for interactive programs so it does not meet
our needs in this case]

On Wed, 2003-03-12 at 12:33, Michael Meeks wrote:
> Hi Kieran,
> 
> 	Osvaldo forwarded me your mail:
> 
> 	As you notice, it is almost crucial to have Xserver support to do fast
> magnification - particularly for the scaling.
> 
> 	However - we already have a working project using Gnome a11y
> infrastructure - which lets us do some very nice things (well beyond
> following the mouse), which is fairly powerful already.
> 
> 	It's called 'gnome-mag', it's in Gnome CVS (see
> http://developer.gnome.org/). Of course - it requires a fairly recent
> Gnome [ 2.2 should do nicely ], and works best in conjunction with
> gnopernicus, also from CVS there.
> 
> 	It'd be great to have you working with us, improving this.
> 
> 	Best regards,
> 
> 		Michael.
> 
> On Tue, 2003-03-11 at 16:28, Osvaldo La Rosa wrote:
> > ----- Forwarded message from Kieran O'Sullivan <blindpng sdf lonestar org> -----
> > Date: Mon, 10 Mar 2003 11:45:06 +0000 (UTC)
> > From: "Kieran O'Sullivan" <blindpng sdf lonestar org>
> > Subject: Full Screen Magnification for X Windows
> > To: debian-accessibility lists debian org
> > 
> > BlindPenguin - X Windows Accessability Project
> > http://www.blindpenguin.org
> > kieran osullivan blindpenguin org
> > SDF Public Access UNIX System - http://sdf.lonestar.org
> > 
> > I am writing an Xlib (written in c) based screen magnification program for
> > X Windows called BlindPenguin (http://www.blindpenguin.org).  I am posting
> > to this group to get ideas on a technical issue with the program.  The
> > issue is this any X magnification program that I have seen draws the
> > magnified area on a window I DO NOT WANT TO DO THIS.  I want to write a
> > program, which zooms in like a video camera on a particular part of the
> > screen what will happen is that the magnified area of the screen will
> > fill the entire screen, in simple terms the magnified area will be re-drawn
> > with more pixels to fill the screen.  However the X server and clients
> > shouldn't care about this in-fact they shouldn't know.  Basically there
> > are 2 screens 1 is the screen that the X server creates and the other is
> > the screen that the user sees.  As I move the mouse around the X server
> > moves it on the real screen but the user sees the magnified screen moving.
> >   To use the video camera analogy again imagine a person walking around a
> > room using the view finder of a video camera turned up to full zoom to see.
> >  Their coordinates would change relative to the objects in the room but they
> > would see things much larger than they are.
> > 
> > WHAT I AM LOOKING FOR
> > 
> > I am looking for ideas or code that will help me do this Especially DGA
> > code.  Also anyone who
> > has knowledge of how programs like ZoomText or Lunar do this in Windows
> > I would like to hear of it, I know that ZoomText doesn't work in X but
> > the ideas may inspire me.
> > 
> > THIS PROGRMA WILL BE RELEASED UNDER GPL
-- 
Bill Haneman <bill haneman sun com>