X window alpha channel and "event transparency"

[Gena Batsyan]

1) Is there a way to have an "alpha channel" in some form for an X window.
Years ago written an app that made a non-rectangular X window, however 
no partial translucency, every window pixel could be either fully 
transparent or fully opaque.

2) Is there a way for a window not to receive ANY kind of events, or 
ideally have an event mask for example to ignore anything except mouse 
movements.

The sence of the above is to have some high translucency degree "always 
on top" windows  haning over all other windows and maximally 
non-obtrusively notifying of something (for example to depict incoming 
mail or messenger messages with gnome/kde-panel in autohide mode.

any links appreciated, thx