I’ve been trying for a couple of days to figure out why a shaped window in Compiz doesn’t have a shadow. After looking through the Emerald and GTK+ decorators’ code, it seems that they only apply a shadow if the window has a titlebar decoration. This seems quite silly and limiting. Does anybody know of a way around this, or why we’re limited in such a way? Is this something that could be fixed?
Love,
Christian
ChipLog 
Maybe it’s been done that way to subtly discourage the use of shaped windows. Shaped windows are horrible.
Shaped windows are absolutely essential for our case. If you look at one of my more recent posts, you can probably guess why.
I also don’t like that bug. It worked on Beryl and earlier Compiz Fusion.
Notification daemon had shadows like the normal tooltips.
we have a similar problem in metacity because of the way we generate the shadows. We pregenerate a rectangular gaussian shadow map and then scale it to the size needed. This works fine for normal windows, and for nearly rectangular shaped windows (such as metacity’s rounded corners). But for obscurely shaped windows, it fails miserably because the shadow shape doesn’t follow the window shape.
I don’t know how compiz does it but it may be a similar reason, and so they’ve disabled shadows for those windows.
Or maybe it’s because some software (ie Firefox) use windows for menus ? I guess we don’t want drop shadow for all popup menus that can appear in Firefox.
I would agree its to discourage the use of shaped windows. I dont think you’ll find a way round it.
Sadly, that makes the feature we’re about to release a lot less awesome.