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

[Bill Haneman <bill haneman sun com>]

On Wed, 2003-03-12 at 19:16, Peter Korn wrote:
> Hi Kieran,
> 
> I'd like to just expand a bit on Bill's comments below:
> ...
Thanks Peter;

> 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).

As you and Kieran have noted (Michael as well), getting really high
performance fullscreen magnification will almost certainly require
extensions to what X normally does, and the X server will need to get
involved somewhere if we want to be competitive with Windows fullscreen
magnifiers from a performance standpoint.

However the basic functionality for fullscreen magnification is 
available now, via the somewhat unwieldly expedient of adding a second X
Display, and we are developing a "virtual screen" for Linux' XFree86 X
server without requiring the user to purchase additional hardware (we
have this for the Solaris X server already).

My feeling is that it's tolerable from a performance point of view now,
but others may have higher standards :-), certainly there is a lot of
room for improvement.  The fact that we are making this a 'service' with
a standard API should help since it should be possible to implement all
sorts of high-performance optimizations (even hardware- or
driver-specific ones) and they can just be plugged in as long as they
implement the "gnome-mag" APIs.

regards,

Bill

> 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
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-- 
Bill Haneman <bill haneman sun com>