focus.tcl –

This file defines several procedures for managing the input

focus.

RCS: @(#) $Id: focus.tcl,v 1.9.4.1 2006/01/25 18:21:41 dgp Exp $

Copyright (c) 1994-1995 Sun Microsystems, Inc.

See the file “license.terms” for information on usage and redistribution

of this file, and for a DISCLAIMER OF ALL WARRANTIES.

::tk_focusNext –

This procedure returns the name of the next window after “w” in

“focus order” (the window that should receive the focus next if

Tab is typed in w). “Next” is defined by a pre-order search

of a top-level and its non-top-level descendants, with the stacking

order determining the order of siblings. The “-takefocus” options

on windows determine whether or not they should be skipped.

Arguments:

w - Name of a window.

proc ::tk_focusNext w {
set cur $w
while {1} {

# Descend to just before the first child of the current widget.

set parent $cur
set children [winfo children $cur]
set i -1

# Look for the next sibling that isn't a top-level.

while {1} {
    incr i
    if {$i < [llength $children]} {
	set cur [lindex $children $i]
          if {[winfo toplevel $cur] eq $cur} {
	    continue
	} else {
	    break
	}
    }

    # No more siblings, so go to the current widget's parent.
    # If it's a top-level, break out of the loop, otherwise
    # look for its next sibling.

    set cur $parent
    if {[winfo toplevel $cur] eq $cur} {
	break
    }
    set parent [winfo parent $parent]
    set children [winfo children $parent]
    set i [lsearch -exact $children $cur]
}
if {$w eq $cur || [tk::FocusOK $cur]} {
    return $cur
}
}

}

::tk_focusPrev –

This procedure returns the name of the previous window before “w” in

“focus order” (the window that should receive the focus next if

Shift-Tab is typed in w). “Next” is defined by a pre-order search

of a top-level and its non-top-level descendants, with the stacking

order determining the order of siblings. The “-takefocus” options

on windows determine whether or not they should be skipped.

Arguments:

w - Name of a window.

proc ::tk_focusPrev w {
set cur $w
while {1} {

# Collect information about the current window's position
# among its siblings.  Also, if the window is a top-level,
# then reposition to just after the last child of the window.

if {[winfo toplevel $cur] eq $cur}  {
    set parent $cur
    set children [winfo children $cur]
    set i [llength $children]
} else {
    set parent [winfo parent $cur]
    set children [winfo children $parent]
    set i [lsearch -exact $children $cur]
}

# Go to the previous sibling, then descend to its last descendant
# (highest in stacking order.  While doing this, ignore top-levels
# and their descendants.  When we run out of descendants, go up
# one level to the parent.

while {$i > 0} {
    incr i -1
    set cur [lindex $children $i]
    if {[winfo toplevel $cur] eq $cur} {
	continue
    }
    set parent $cur
    set children [winfo children $parent]
    set i [llength $children]
}
set cur $parent
if {$w eq $cur || [tk::FocusOK $cur]} {
    return $cur
}
}

}

::tk::FocusOK –

This procedure is invoked to decide whether or not to focus on

a given window. It returns 1 if it’s OK to focus on the window,

0 if it’s not OK. The code first checks whether the window is

viewable. If not, then it never focuses on the window. Then it

checks the -takefocus option for the window and uses it if it’s

set. If there’s no -takefocus option, the procedure checks to

see if (a) the widget isn’t disabled, and (b) it has some key

bindings. If all of these are true, then 1 is returned.

Arguments:

w - Name of a window.

proc ::tk::FocusOK w {
set code [catch {w cget -takefocus} value] if {(code == 0) && (value ne "")} { if {value == 0} {
return 0
} elseif {$value == 1} {
return [winfo viewable $w]
} else {
set value [uplevel #0 $value [list w]] if {value ne “”} {
return $value
}
}
}
if {![winfo viewable w]} { return 0 } set code [catch {w cget -state} value]
if {($code == 0) && $value eq “disabled”} {
return 0
}
regexp Key|Focus “[bind $w] [bind [winfo class $w]]”
}

::tk_focusFollowsMouse –

If this procedure is invoked, Tk will enter “focus-follows-mouse”

mode, where the focus is always on whatever window contains the

mouse. If this procedure isn’t invoked, then the user typically

has to click on a window to give it the focus.

Arguments:

None.

proc ::tk_focusFollowsMouse {} {
set old [bind all ]
set script {
if {”%d” eq “NotifyAncestor”
|| “%d” eq “NotifyNonlinear”
|| “%d” eq “NotifyInferior”} {
if {[tk::FocusOK %W]} {
focus %W
}
}
}
if {old ne ""} { bind all <Enter> "old; $script”
} else {
bind all $script
}
}