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The focus command is used to manage the Tk input focus. At any given time, one window in an application is designated as the focus window for that application; any key press or key release events directed to any window in the application will be redirected instead to the focus window. If there is no focus window for an application then keyboard events are discarded. Typically, windows that are prepared to deal with the focus (e.g. entries and other widgets that display editable text) will claim the focus when mouse button 1 is pressed in them. When an application is created its main window is initially given the focus.

The focus command can take any of the following forms:

If invoked with no arguments, focus returns the path name of the current focus window, or none if there is no focus window.
focus window
If invoked with a single argument consisting of a window's path name, focus sets the input focus to that window. The return value is an empty string.
focus :default ?window?
If window is specified, it becomes the default focus window (the window that receives the focus whenever the focus window is deleted) and the command returns an empty string. If window isn't specified, the command returns the path name of the current default focus window, or none if there is no default. Window may be specified as none to clear its existing value. The default window is initially none.
focus :none
Clears the focus window, so that keyboard input to this application will be discarded.

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  Copyright 2003   by The Free Software Foundation     Updated Jun 2003