Re: D-BUS based magnification API

Hi Carlos,

In two places you mention going with Metacity:

* Understanding where the masses are going with respect the
  composite extension manager.  Is it metacity, compiz, something
  else?  Where/how does gnome-mag fit in this new world?

There was a big discussion about the Metacity compositor and compiz:
and GNOME appear that will not replace Metacity by Compiz. The
discussion is quite old and things maybe changed, but I didn't saw any
other discussion about a replacement, so the path, IMHO, is metacity.

If Metacity doesn't introduce composite effects some day (something
that I doubt) we already have basic composite (let's say that the code
to track windows is there :-) being done in gnome-mag.

We must have a compositor and appear that the best path, considering
the effects cited in the other messages, is to use Metacity, since
it's still have a good architecture (thanks Sandmann) IMHO. Moreover,
in reply to Eitan (I send if the wrong e-mail, so it doesn't appear
yet in the list), I cited about an way to keep the resolution of text
and SVG images in the magnified image, that is: wrap cairo and, when
the magnifier is
activated, instead of draw (or instead of only draw) in the
application window, an SVG representation is created and the magnifier
is notified about it and about updates in this SVG. I thought in this
in something in the same layer as AT-SPI. Then when the magnifier
compose the final screen it will draw the window pixmap and render the

In this world, gnome-mag doesn't fit.

If there is no one oppositing to implement gnome-mag API inside
metacity I will start this work without further discussions (I think
that I was the only one against it in the past :-) starting with the
actual gnome-mag API, since this is the basic that we need, than we
can start to think how these interaction can be done, since they must
be carried on by the WCM.

The needs for the applications cited by Peter Korn can also be addressed here.

I would like to suggest more study of the Compiz option before making the decision to work with Metacity instead. While today it seems no desktop UNIX distro is prepared to replace Metacity with Compiz, it does appear that many (most? all?) are looking to have it as a user-available option. I continue to believe that (a) Metacity is largely in maintenance mode with new sexy development happening in Compiz; (b) we can do a lot more, and do it more naturally and easily in Compiz; and (c) if we do a great job with magnification in Compiz, we will be able to help move folks over to Compiz, either as a default user-choosable option, as a trivially user-installable option, or even as the eventual default window manager.

This is clearly something we need to socialize with the desktop folks, the Compiz folks, to determine how much of a..c above are in fact the case. But I would especially hate it to be the case that we do a lot of work to make Metacity great for magnification, only to see it slowly fade away (or have to argue for folks to keep it when their desire/tendency is to move to the new sexy thing).

Also, to the extent that Compiz isn't everywhere because of lack of video hardware... I think it is worth comparing what we can do without GL to what we can do with it; the kind of functionality in products like ZoomText (that we can most easily do with GL) that users like and use; and the cost impact of requiring what is now essentially a $50 add-on video card with GL support (and which can be found in nearly every new system being sold today) vs. the $600 software ZoomText. I personally believe that making a fantastic magnification (and reading assistance) system that requires 5-year old video hardware with a minimum of GL support & that the user install a new (and tested) window manager is a better alternative to much more limited functionality or something that is much harder to develop/maintain/etc. but which works at least somewhat with older video hardware and with the window manager that comes as a default on the desktop today.

But you are closer to the code than I am. Perhaps the downsides to going the Metacity route are more minimal than I suggest they are...


Peter Korn
Accessibility Architect,
Sun Microsystems, Inc.

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