1.3.3.3 Drawing Operations Management
After a logical surface and its associated redirection surface are created, the redirection surface is targeted by primary, secondary, and alternate secondary drawing orders, as specified in section 1.3.1.2 of [MS-RDPEGDI]. The SWITCH_SURFOBJ message is sent when a drawing order targets a different redirection surface than the previous one.
The following illustration shows the overall sequence of drawing operations on a redirection surface.

Figure 4: Sequence of drawing operations on a redirection surface
Drawing to a redirection surface can happen only after a redirection surface is created and is attached to a logical surface.
The FLUSH_COMPOSEONCE command causes an explicit flush for the compose-once sprite. See Drawing Operations Management in section 3.2.5.3 for more detail.