^^&&^^

Edit File: check.tcl

# check.tcl --
#
# This demonstration script creates a toplevel window containing
# several checkbuttons.

if {![info exists widgetDemo]} {
    error "This script should be run from the \"widget\" demo."
}

package require Tk

set w .check
catch {destroy $w}
toplevel $w
wm title $w "Checkbutton Demonstration"
wm iconname $w "check"
positionWindow $w

label $w.msg -font $font -wraplength 4i -justify left -text "Four checkbuttons are displayed below.  If you click on a button, it will toggle the button's selection state and set a Tcl variable to a value indicating the state of the checkbutton.  The first button also follows the state of the other three.  If only some of the three are checked, the first button will display the tri-state mode. Click the \"See Variables\" button to see the current values of the variables."
pack $w.msg -side top

## See Code / Dismiss buttons
set btns [addSeeDismiss $w.buttons $w [list safety wipers brakes sober]]
pack $btns -side bottom -fill x

checkbutton $w.b0 -text "Safety Check" -variable safety -relief flat \
    -onvalue "all" \
    -offvalue "none" \
    -tristatevalue "partial"
checkbutton $w.b1 -text "Wipers OK" -variable wipers -relief flat
checkbutton $w.b2 -text "Brakes OK" -variable brakes -relief flat
checkbutton $w.b3 -text "Driver Sober" -variable sober -relief flat
pack $w.b0 -side top -pady 2 -anchor w
pack $w.b1 $w.b2 $w.b3 -side top -pady 2 -anchor w -padx 15

## This code makes $w.b0 function as a tri-state button; it's not
## needed at all for just straight yes/no buttons.

set in_check 0
proc tristate_check {n1 n2 op} {
    global safety wipers brakes sober in_check
    if {$in_check} {
	return
    }
    set in_check 1
    if {$n1 eq "safety"} {
	if {$safety eq "none"} {
	    set wipers 0
	    set brakes 0
	    set sober 0
	} elseif {$safety eq "all"} {
	    set wipers 1
	    set brakes 1
	    set sober 1
	}
    } else {
	if {$wipers == 1 && $brakes == 1 && $sober == 1} {
	    set safety all
	} elseif {$wipers == 1 || $brakes == 1 || $sober == 1} {
	    set safety partial
	} else {
	    set safety none
	}
    }
    set in_check 0
}

trace variable wipers w tristate_check
trace variable brakes w tristate_check
trace variable sober  w tristate_check
trace variable safety w tristate_check