What are the differences between RedrawWindow and UpdateWindow in Win32?

Question

What are the differences between RedrawWindow and UpdateWindow in Win32?

Since they seem to have the same purpose to refresh a window, what are the differences?

Answer 1

RedrawWindow is typically used to force a redraw of the entire window (or some specified region within) right now.

UpdateWindow will force a redraw of only the update region of the window, i.e. that part of the window that has been invalidated (e.g. by calling InvalidateRect) since the last paint cycle.