Disabled Windows

A window can be disabled. A disabled window receives no keyboard or mouse input from the user, but it can receive messages from other windows, from other applications, and from Windows. An application typically disables a window to prevent the user from using the window. For example, an application may disable a push button in a dialog box to prevent the user from choosing it. An application can enable a disabled window at any time; enabling a window restores normal input.

By default, a window is enabled when created. An application can specify the WS_DISABLED style, however, to disable a new window. An application enables or disables an existing window by using the EnableWindow function. Windows sends a WM_ENABLE message to a window when its enabled state is about to change. An application can determine whether a window is enabled by using the IsWindowEnabled function.

When a child window is disabled, Windows passes the child's mouse input messages to the parent window. The parent uses the messages to determine whether to enable the child window. For more information about mouse input, see Mouse Input.

Only one window at a time can receive keyboard input; that window is said to have the keyboard focus. If an application uses the EnableWindow function to disable a keyboard-focus window, the window loses the keyboard focus in addition to being disabled. EnableWindow then sets the keyboard focus to NULL, meaning no window has the focus. If a child window, or other descendant window, has the keyboard focus, the descendant window loses the focus when the parent window is disabled. For more information about the keyboard focus, see Keyboard Input.

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