X Zoom Extension: Ideas and Suggestions!

Keith Packard keithp at keithp.com
Wed Apr 27 08:39:58 PDT 2005

On Wed, 2005-04-27 at 12:00 -0300, Carlos Eduardo Rodrigues Diógenes
> Hi,
> How the accessibility list is dead, I decide to post it here.
> I have an idea of an extension, the X Zoom Extension. I'm posting it 
> here, because sometimes someone have some good ideas and have thinked in 
> this problem.

Have you seen my demonstration application 'diopter'?  It's in xapps CVS
at freedesktop.org and presents a full-screen magnified view which can
trivially be modified to display any combination of normal and magnified
presentation.  The missing piece in this puzzle is mouse-position
remapping and work on that piece is on-going.  That can be
kludged-around by drawing the mouse to the magnified screen by hand
while replacing the 'real' sprite with an empty image.

> Other thing that I think that is very interesting to this type of 
> solution is the fonts of X Window System use SVG, because this way we do 
> not have problem in magnifying text, we can maintain the quality. Cairo 
> can give some help with this???

Yes, a few people have started thinking about how we might present the
application with information about the complete transformation of the
window so that the application could construct a target-pixel based
representation of its contents.  We should start looking into this once
we have a more complete implementation of magnification working.

> If someone have something to say about this, have some tips of what I 
> can study to solve the problems that I apresented or if I say somethings 
> that are very stupid, share, I will be very thankful.

I think we have nearly completed the required extensions for this kind
of application; please feel free to explore 'diopter' and see whether
that does what you need.

Given basic magnification, I'd also like to explore different resampling
algorithms which can improve the appearance of existing applications.
I've seen some interesting algorithmic pixel selection mechanisms which
smooth the image while retaining sharp edges of glyphs.  I'm wondering
if we can't achieve this in hardware by using pixel shaders.  Exploring
this using the 'luminocity' framework would prove whether it was
feasible before we have a completed X server architecture which can get
at this kind of hardware.


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