3.3.5.4.9 MILCMD_WINDOWNODE_SETCOMPOSEONCE

The fComposeOnce message field specifies whether the targeted window node MUST be marked as a composed-once visual. A visual marked for composed-once accumulates rendering instructions like a normal visual, but the instructions are executed only once at the next available composition pass, and then they are discarded. This construct is useful for emulating direct writes to the screen in a composed desktop environment.