Re: new frame-parameter "alpha"

[David De La Harpe Golden]

Seiji Zenitani wrote:

> Reportedly it works on "X.org (>=6.8) or XGL with composite extension".
> Is there any way to detect the capability?
> 

[Well, I think there also needs to be a compositing manager in the loop
-it's possible to have a composite extension capable X server with no
composting manager actually running, so e.g. detecting the composite
extension is no guarantee the property will take effect]

If there's a running compositing manager, it'll be owning the
"_NET_WM_CM_S{N}" X Selection(s), where {N} is screen number.

N.B. But IIRC it's also quite possible to fire up or restart a
compositing manager in the middle of an existing X session, so you
probably shouldn't conditionalise property-setting behaviour on the
presence of one, maybe just warn "No compositing manager currently
running, may have no effect." at most if one isn't detected.