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focus(n)	       Tk Built-In Commands		 focus(n)

_________________________________________________________________

NAME
       focus - Manage the input focus

SYNOPSIS
       focus

       focus window

       focus option ?arg arg ...?
_________________________________________________________________

DESCRIPTION
       The  focus  command  is used to manage the Tk input focus.
       At any given time, one window on each  display  is  desig-
       nated  as  the focus window;  any key press or key release
       events for the display are sent to  that	 window.   It  is
       normally	 up  to	 the window manager to redirect the focus
       among the top-level windows of a	 display.   For	 example,
       some  window managers automatically set the input focus to
       a top-level window whenever the mouse enters  it;   others
       redirect	 the  input  focus only when the user clicks on a
       window.	Usually the window manager  will  set  the  focus
       only  to	 top-level windows, leaving it up to the applica-
       tion to redirect the focus among the children of the  top-
       level.

       Tk remembers one focus window for each top-level (the most
       recent descendant of that top-level to receive the focus);
       when the window manager gives the focus to a top-level, Tk
       automatically  redirects	 it  to	 the  remembered  window.
       Within  a  top-level  Tk	 uses  an explicit focus model by
       default.	 Moving the mouse within  a  top-level	does  not
       normally	 change the focus;  the focus changes only when a
       widget  decides	explicitly  to	claim  the  focus  (e.g.,
       because	of  a button click), or when the user types a key
       such as Tab that moves the focus.

       The Tcl procedure tk_focusFollowsMouse may be  invoked  to
       create  an  implicit  focus  model:  it reconfigures Tk so
       that the focus is set  to  a  window  whenever  the  mouse
       enters  it.  The Tcl procedures tk_focusNext and tk_focus-
       Prev implement a focus order among the windows of  a  top-
       level;	they are used in the default bindings for Tab and
       Shift-Tab, among other things.

       The focus command can take any of the following forms:

       focus  Returns the path name of the focus  window  on  the
	      display  containing  the application's main window,
	      or an empty string if no window in this application
	      has  the	focus  on  that	 display.    Note:  it is

Tk			       4.0				1

focus(n)	       Tk Built-In Commands		 focus(n)

	      better to	 specify  the  display	explicitly  using
	      -displayof  (see	below) so that the code will work
	      in applications using multiple displays.

       focus window
	      If the application currently has the input focus on
	      window's	display,  this	command	 resets the input
	      focus for window's display to window and returns an
	      empty string.  If the application doesn't currently
	      have the	input focus on window's	 display,  window
	      will  be remembered as the focus for its top-level;
	      the next time the focus arrives at  the  top-level,
	      Tk  will	redirect  it  to window.  If window is an
	      empty string then the command does nothing.

       focus -displayof window
	      Returns the name of the focus window on the display
	      containing  window.   If	the focus window for win-
	      dow's display isn't in this application, the return
	      value is an empty string.

       focus -force window
	      Sets  the focus of window's display to window, even
	      if the application doesn't currently have the input
	      focus for the display.  This command should be used
	      sparingly, if at all.  In normal usage, an applica-
	      tion   should  not  claim	 the  focus  for  itself;
	      instead, it should wait for the window  manager  to
	      give  it	the  focus.  If window is an empty string
	      then the command does nothing.

       focus -lastfor window
	      Returns the name of the most recent window to  have
	      the  input  focus among all the windows in the same
	      top-level as window.  If no  window  in  that  top-
	      level  has ever had the input focus, or if the most
	      recent focus window has been deleted, then the name
	      of  the top-level is returned.  The return value is
	      the window that will receive the	input  focus  the
	      next time the window manager gives the focus to the
	      top-level.

QUIRKS
       When an internal	 window	 receives  the	input  focus,  Tk
       doesn't	actually  set the X focus to that window;  as far
       as X is concerned, the focus will stay  on  the	top-level
       window  containing the window with the focus.  However, Tk
       generates FocusIn and FocusOut events just  as  if  the	X
       focus  were  on	the internal window.   This approach gets
       around a number of problems that	 would	occur  if  the	X
       focus were actually moved; the fact that the X focus is on
       the top-level is invisible unless you use C code to  query
       the X server directly.

Tk			       4.0				2

focus(n)	       Tk Built-In Commands		 focus(n)

KEYWORDS
       events, focus, keyboard, top-level, window manager

Tk			       4.0				3

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