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


       focus - Manage the input focus


       focus window

       focus option ?arg arg ...?

       The  focus command is used to manage the Tk input focus.  At any given time, one window on
       each display is designated 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 application 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_focusPrev 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

       The focus command can take any of the following forms:

       focus  Returns the path name of the focus window on the display	containing  the  applica-
	      tion's  main  window,   or an empty string if no window in this application has the
	      focus on that display.   Note:  it is better  to	specify  the  display  explicitly
	      using  -displayof (see below) so that the code will work in applications using mul-
	      tiple 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 window'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 cur-
	      rently have the input focus for the display.  This command  should  be  used  spar-
	      ingly,  if  at all.  In normal usage, an application 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

       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 con-
       taining 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.

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

Tk					       4.0					 focus(n)
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