Windows sends a WM_NCPAINT message to the window whenever the non-client area of the window, such as the title bar, menu bar, and window frame, needs painting. Processing this message is not recommended since a window that does so must be able to paint all the required parts of the nonclient area for the window. In other words, a window should pass this message on to the DefWindowProc function for default processing unless the Windows application is creating a custom nonclient area for a child window.