XComposite related question

Alexei Babich a.babich at rez.ru
Fri Apr 24 00:06:54 PDT 2009

Hello everybody.

I met the difficulties trying to understand XComposite behaviour in the following case.
I need to use alpha-channel with my windows although I know the core protocol can't provide that. So it's needed to use XRenderComposite() manually. This means to put pictures of windows on a picture produced for the root window just the same way as xcompmgr does.
When trying XCompositeRedirectSubwindows(display, root_win, CompositeRedirectManual) for the root window, the hierarchy of windows is redirected to off-screen storage.
Then I create a picture for every window separately and a one for the root window as well.
Then I try to perform a sequence of XRenderComposite() calls keeping dst picture == root picture.
Here the thing turnes out that if trying to display the hierarchy of windows (e.g. root -> w1 -> w2) w1 contains the image of w2. So there's no right way for the problem in consecutive calls of XRenderComposite(). Probably it could be solved in the case of windows being independent pixmaps.

So how should I display the hierarchy using alpha channel?
Thanks a lot.
Alexei Babich, circuit design engineer, Rezonans plc., Chelyabinsk, Russia
Jabber ID: impatt at jabber.ru

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