Execution timeliness (immediate versus delayed operation) in Windowing API
Each Windowing API function can be categorized based on whether it executes immediately or whether it is delayed. Additionally, the Windowing API members that execute immediately can either flush any delayed commands or not. Finally, the functions that flush any accumulated commands may or may not cause the contents on the display to change.
It's important to understand this distinction between each function type, and to understand how and when these function calls will execute in the scope of your Windowing API application. In the included API reference, each function is marked with a given type. Each type is described in greater detail in this chapter.