focus(3Tk)							    focus(3Tk)

NAME    [Toc]    [Back]

     focus - Manage the	input focus

SYNOPSIS    [Toc]    [Back]

     focus
     focus window
     focus option ?arg arg ...?

DESCRIPTION    [Toc]    [Back]

     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 |
     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      |
	  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 |



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focus(3Tk)							    focus(3Tk)



	  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 currently	have the input focus for the display. |
	  This command should be used sparingly, 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 |
	  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.

KEYWORDS    [Toc]    [Back]

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


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