RE: Does child-frame not support alpha frame param?

[Drew Adams]

> It's a limitation of the window manager.  For example, it doesn't work
> with Debian stable's xfwm4 here and it doesn't work with Windows XP
> either.  That's the main reason why I don't show eldoc info with child
> frames but use classic tooltip frames instead.  But ISTR that alpha for
> child frames works with Windows 10 and there might also exist
> compositing window managers for GNU/Linux that can handle it.  So YMMV.

Dunno how important this info is, or whether this
is already done.  But if it's not yet done, could
such info be added to some doc somewhere?  (Thanks
for considering it.)