3.3.5.3.2 Constructing a Closing Drawing Order
When an application performs a drawing operation on the compose-once sprite, the graphics engine notifies the compose desktop mediator which redirection surface the drawing operation is targeting. The compose desktop mediator looks up the redirection surface (previously attached to the compose-once sprite) and extracts the cacheId and hLSurface field values.
The compose desktop mediator constructs a TS_COMPDESK_FLUSH_COMPOSEONCE message by using the cacheId and hLSurface values.
The compose desktop mediator sends the TS_COMPDESK_FLUSH_COMPOSEONCE message subsequent to any drawing order associated with the drawing operation that has been placed in the transmission buffer.