gEDA-dev: Xrender support for lesstif PCB

[Peter Clifton]

On Thu, 2007-11-29 at 14:44 -0500, Stuart Brorson wrote:
> >> Yep.  Will be like using XOR in gerbv to see all layer overlaps at once,
> >> but selected according to user pref in the color choices, right?
> >
> > Gerbv.
> >
> > Oh, we *really* need this for gerbv.
> 
> Please put this into the gerb feature request tracker on SF.  If you
> remind us what fcn calls will support transparency in the feature
> request, that would be just ducky!

Cairo has opacity built in, so no need for XRender calls. ARGB, where A
is opacity. You may / may not need to set the surface up for it.

As suggested for PCB, drawing layers to spearate off-screen surfaces
(from cairo_surface_create_similar()), then compositing layer by layer
onto the main drawable might be the way forward.

I'm a bit busy at the moment, with work, and when not working, trying to
finish up some "blocking" items which will bug me if they don't make the
next gEDA release.

I can add the support for transparency in gerbv pretty painlessly. What
may require a little more thought is the configurable of colours and
opacities from an UI point of view.

Best wishes,

-- 
Peter Clifton

Electrical Engineering Division,
Engineering Department,
University of Cambridge,
9, JJ Thomson Avenue,
Cambridge
CB3 0FA

Tel: +44 (0)7729 980173 - (No signal in the lab!)