Artifacts in window decorations

Window decorations display artifacts in some cases.

For example, when moving a window over other windows, the window decoration of the underlying windows display artifacts.

Another interesting case is when two windows, on partially covering another, have their top decoration aligned. When hovering over the close/min/max buttons of the underlying window, its decoration is redrawn, overwriting the decoration of the window which is on top.

No screenshots for this, unfortunately. The only screenshot tool I have found that can properly handle full-screen compiz shots (shutter), causes a redraw of the screen and eliminates the elusive artifacts.