Re: fullscreen magnification

[Peter Korn <Peter Korn Sun COM>]

Hi Krister,

A more general/note comment on magnification...

Unlike Windows, we aren't replacing/chaining video drivers in X.  One of the 
key design goals of the GNOME Accessibility Project was that all AT would be 
fully supported by the underlying platform.  Where necessary functionality 
wasn't present, we would build it.

Not all of the necessary support for magnification was present when we began. 
 Things we've fixed so far including tracking the mouse cursor changes and 
getting the mouse pixels (XFIXES extension to X), and tracking pixel changes 
to the screen (DAMAGE extension to X).  To do full screen magnification we at 
a minimum need to have the unmagnified pixels rendered to an off-screen 
bitmap, so that the magnifier can then copy them appropriately to the real 
display.  We discovered the existing dummy driver in Linux, and created the 
Virtual Frame Buffer (VFB) for Solaris.

Note, though, that we aren't done.  For magnification to be highly performant 
(similar to what you experience with ZoomText version 8.x on Windows for 
example), we need to ensure that the process of taking the unmagnified pixels 
and moving them (while we magnify them) to the physical frame buffer display 
is fast.  Doing this full-screen 30-60 times/second is often not possible on 
many system architectures (especially at 1280x1024 24 bit resolution).

So the next step is to move to the COMPOSITE X extension, which allows us to 
allocate unmagnified pixel maps on the video card (rather than in system 
memory), and will do so on a window-by-window basis if we want (in fact, that 
is the default behavior).  Then we can direct the video card processor (the 
GPU) to do the copying, magnifying, etc. for us.  This should get us fast 
magnification, and the ability to support functionality as you experience in 
ZoomText 8.x.


So, this is really all just a long-winded way of saying "things will get better".


Regards,

Peter Korn
Sun Accessibility team


Bill Haneman wrote:
> Hi Krister:
>
> You'll need a very recent gnome-mag, version 0.11.13.  0.11.14 is a 
> little better, because it allows the source display to be smaller than 
> the target.  Configuring fullscreen magnification to work is a little 
> tricky still.
>
> Once you've got a recent gnome-mag, you can enable the 'dummy screen' 
> which is mentioned in George Kraft's notes on magnification (the uri 
> which was previously posted).  This URI has lots of info, not all of 
> which is relevant for your needs.  The part you need is called "Virtual 
> Screen Buffer"  / "Off Screen Configuration".
> Also, there is one additional line that should go into the dummy 
> "Device" section:
>
> > Section "Device"
> >     Identifier "dummy"
> >     Driver     "dummy"
> >     VendorName "dummy"
> >     BoardName  "dummy"
> >
> >        videoram 10000
> >
> > EndSection
> Once you have done this, the steps for getting a usable fullscreen login 
> are a little tricky, because you now have one "display" that isn't 
> connected to any physical monitor, and you can paint yourself into a 
> corner.
>
> The suggested XOrg.conf file (or XF86Config file should work also) puts 
> the 'virtual' display on "screen 1".
> The way I do it is this:
>
> (1) start gnopernicus with the halfscreen magnification option (default 
> magnification settings).
> (2) from gnopernicus magnifier preferences, choose the 'default' zoomer 
> and edit it to change the 'source' from ":0.0" to ":0.1".
> (3) you will now need to exit gnopernicus from the unmagnified view 
> (sorry).  Turning speech on may help.
> (4) restart gnopernicus from the command line, but tell it to use the 
> second display instead of the first:
> "gnopernicus --display=:0.1"  You should now see the gnopernicus UI in 
> the magnified section of your screen again.
> (5) from gnopernicus magnifier preferences, choose 'default' zoomer and 
> change the left bounds of the region to '0', and 'Apply'.  You should 
> now have fullscreen magnification.
>
>  From this point, as long as your mouse pointer is in the right hand 
> side of the screen (if so, it will be magnified), the applications you 
> launch from the panel or nautilus should display in the 'virtual' screen 
> and get magnified to the fullscreen window on 'screen 0'.
>
> It is a little annoying that the mouse pointer can go back into the 
> 'wrong' screen if you move too far left, we are still working out the 
> kinks in fullscreen magnification, so please bear with us.  In my 
> experience this works pretty well up to zoom factors of about 5, but 
> above that you may see some odd behavior which we are still working to fix.
>
> It should be possible to make 'gnopernicus' launch in display :0.1 
> everytime (as a startup application), if you want to do that please let 
> us know and we'll try to send directions.  Until then, starting 
> gnopernicus from a terminal with the "--display=0.1" parameter should do 
> the trick.
>
> If you just want mouse-centered magnification and don't need 
> focus-tracking, you can get it without using gnopernicus, by running 
> gnome-mag directly with the following command:
>
> "magnifier -s:0.1 -m -f"
>
> (-f==fullscreen; -m==keep mouse centered; -s==source display).
>
> You can add "-z4", etc. to get higher magnification (zoom) factors, the 
> default is just 2.0.
>
> best regards,
>
> Bill
>
> > Hello, I need to get the fullscreen magnification to work. What do i 
> > have to change in the XF86Config file? I am using Ubuntu linux.
> >
> > Krister
> >
> >
> >  
>
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