KWin's shadows and frameless window

[EuroElessar]

setMask() is very low quality. If used "compiz" (KWin effects off), FramelessWindow shadow no draw.
If used FramelessWindow with KWin (without setMask()) and send "qdbus org.kde.kwin /KWin reconfigure", shadow disappears, but not immediately.
May be a bug in KWin?

Would it save shadows under other windows? I don't think so..