An application uses the WinEnableWindow function to enable or disable window input. By default, a window is enabled when it is created. However, an application can disable a newly created window.
An application usually disables a window to prevent the user from using the window. For example, an application might disable a push button in a dialog window. Enabling a window restores normal input; an application can enable a disabled window at any time.
When an application uses the WinEnableWindow function to disable an existing window, that window also loses keyboard focus. WinEnableWindow sets the keyboard focus to NULL, which means that no window has the focus. If a child window or other descendant window has the keyboard focus, it loses the focus when the parent window is disabled.
An application can determine whether a window is enabled by calling WinIsWindowEnabled.