Comment 4 for bug 1398849

Also, I think we should not be supporting or encouraging client-drawn shadows. They do create the edge placement extents problem mentioned in the description, but also result in an inconsistent look to the overall desktop. I think even if a client provides its own "decoration", that should not include shadows. The shell should be in charge of shadows so that they all appear consistent and seamless (if present at all).

As for what to do about odd-shaped surfaces with an alpha channel, I know generating a shadow for those is not efficient and needs to not be recalculated on every frame. I suggest that following the surface's input region shape is best there, or to add a client function to notify the server of shape changes (roll it in with resizing?).