[g-a-devel] gnome-mag, full screen magnication and composite

Carlos Eduardo Rodrigues Diógenes cerdiogenes at yahoo.com.br
Mon Jun 19 12:55:15 PDT 2006

Hi Peter,

On Tue, 2006-06-20 at 12:14 -0700, Peter Korn wrote:
> Hi Carlos Eduardo Rodrigues,
> I believe the cost of new video cards is coming down so rapidly that the 
> best place for most of our magnification investment is around 
> COMPOSITE.  Every customer I come in contact with around UNIX 
> accessibility compares what we are doing to the state of the art in 
> Windows commercial software.  And users have come to expect this level 
> of quality, and depend upon the efficiency and productivity that is 
> affords them (and are NOT willing to give that up).
> I agree that to make good use of COMPOSITE, the magnifier must know 
> about most window manager tasks.  I think the best way to do this is to 
> build magnification functionality *into* the compositing window 
> manager(s) of our desktop(s).  I don't see a lot of value to keeping the 
> magnifier separate from the window manager.

I think that compiz make something like this, isn't is?

There is anyone that is working on this type of support in metacity?
There is any documenation/discussion about magnification support in the
compositing window manager?

I have doubt if build magnification functionality *into* the compositing
window manager is really the rigth place. I think that the best, from
this scenario, is some sort of cooperation, but how? I think that
looking inside compiz could give me some answears. I don't like the idea
to merge these two kinds of applications, I think that if we could
maintaim they modular, let's maintaim, for me this is the greatest value
in keeping the magnifier separate from the window manager.

> All that said, users who don't have the resources for modern graphics 
> cards are an important group, and your idea of an OverlayWindow is an 
> interesting one.  I'm curious to see where that investigation goes!
> Regards,
> Peter Korn
> Accessibility Architect,
> Sun Microsystems, Inc.
> > Hi guys,
> >
> > I was thinking about gnome-mag and full screen magnification. The only
> > way that we can achieve this feature today is throw composite, but I
> > really doubt if we must use this technology, so I want to here what our
> > community members have in mind about this.
> >
> > If we use composite in gnome-mag we must have a window-manager like code
> > in it to manage windows that come and goes, windows overlap, so we must
> > track a lot of events and use clip lists, I don't know if the server can
> > generate clip list to us, to render only the window parts the will be
> > showed in the screen. I think that we can make a good job on this to
> > maintaim the magnifier responsive in the case that the user don't have a
> > good video card, but we still with a memory problem, because with
> > composite each window is maintained in off-screen memory. This is not a
> > big problem to new video cards, but I think that we could, and must do
> > this work in older hardware.
> >
> > Another solution that is hitting my head is that we could change a bit
> > the server, so we put the magnifier window in top of all others,
> > something like the OverlayWindow in composite, and paint the contents of
> > all windows below it in a pixmap with the same properties of the root
> > window using the same algorithm that is already used in the server.
> >
> > I think that this second solution is better, but maybe there are reasons
> > to doesn't try it there I don't realize here. I'm very motivated to try
> > this, so if there isn't any good arguments to forget this possibility I
> > will start to play.
> >
> > Thanks,
> >   
Carlos Eduardo Rodrigues Diógenes
Projeto xLupa - http://www.unioeste.br/projetos/xlupa

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