10. App Windows UI object Windows object App code Windows object

14. Desktop STA thread Dispatch call 1 Outgoing call Processing input and calls Dispatch call 2 Processing input and calls

15. ASTA thread Dispatch call 1 Outgoing call completes Call 1 completes Processing input and all calls Processing input and related calls

16. ASTA thread Dispatch call 1 Outgoing call Outgoing call completes Call 1 completes Dispatch call 2 Outgoing call Outgoing call completes Call 2 completes Processing input and related calls Processing input and all calls Processing input and related calls Processing input and all calls Related callback Call 2 waiting

17. ASTA thread X X

30. Thread pool thread Async op start Real work Async complete delivery Projection returns to ASTA thread

31. Thread Pool threadThread pool thread Async op start Real work Async complete delivery Completion delivered where work was done

44. ASTA thread Dispatch call 1 Outgoing call Outgoing call completes Call 1 completes Dispatch call 2 Outgoing call Outgoing call completes Call 2 completes Processing input and related calls Processing input and all calls Processing input and related calls Processing input and all calls Related callback Call 2 waiting