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

[Peter Korn <peter korn sun com>]

Hi Kieran,

I'd like to just expand a bit on Bill's comments below:

> > At the moment I still want to persew my own little project but I will
> > contribute anything I find out or build to the gnome.  I do have some
> > questions and observations.
> > NOTE I'm not yet on the gnome-accessibility-mailing list so please send
> > mails to me directly.
> >
> > 1. It is definately curcial to have X server support for full screen
> > magnification if gmag is aver going to do full screen magnification how 
> > is it going to get around this I can't see any way other than using
> > Xlib/DGA/SVGALib/Something else I'm not awaire of yet.
> 
> Maybe I should rephrase what I said earlier: we have X server support
> for fullscreen magnification in the "X virtual screen" project and also
> it can be done without the 'virtual screen' if you have a Matrox video
> card or otherwise have two frame buffers.  Of course you only need a
> monitor attached to the magnified screen, not the unmagnified (possibly
> virtual) one!

The general approach for commercial magnification for users with low vision
is to completely image the screen at standard resolution into a memory/video
buffer somewhere, and then selective magnify portions onto the actual frame
buffer.  The X environment presents many challenges to doing this -
especially to doing this in a general purpose way and doing it with high
performance (and asking for both of those together is really asking for
trouble).

Sun is working on an "X virtual screen" which we have internally for Sun's X
server in Solaris and are in the process of proposing for XFree86.  This
creates an in-memory DISPLAY which all normal rendering would go to.  The
'gnome-mag' project provides a GNOME (Bonobo/CORBA) interface to a magnifier
process which moves pixels from one DISPLAY to another, magnifying them,
smoothing them, inverting them, etc.  This magnifier could be written using
on X calls.  The magnifier could be a modified X server that did all the
work internally.  So long as there is a gnome-mag API interface to it, it
will hook up with the gnopernicus end-user screen magnifier application,
which is strongly desired.


Regards,

Peter Korn
Sun Accessibility team