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# Variable.tcl --

#

#       Routines in this file are used to set up and operate variables

#       for classes that support the -variable option

#

# Copyright (c) 1996, Expert Interface Technologies

#

# See the file "license.terms" for information on usage and redistribution

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

#

# tixVariable:ConfigVariable --

#

#       Set up the -variable option for the object $w

#

# Side effects:

#

#       data(-variable) is changed to the name of the global variable

#       if the global variable exists, data(-value) takes the value of this

#       variable.

#       if the global variable does not exist, it is created with the

#       current data(-value)

#

# Return value:

#

#       true is data(-value) is changed, indicating that data(-command)

#       should be invoked.

#

proc tixVariable:ConfigVariable {w arg} {

    upvar #0 $w data

    set changed 0

    if {$data(-variable) != ""} {

        uplevel #0 \

            [list trace vdelete $data(-variable) w "tixVariable:TraceProc $w"]

    }

    if {$arg != ""} {

        if [uplevel #0 info exists [list $arg]] {

            # This global variable exists, we use its value

            #

            set data(-value) [uplevel #0 set [list $arg]]

            set changed 1

        } else {

            # This global variable does not exist; let's set it 

            #

            uplevel #0 [list set $arg $data(-value)]

        }

        uplevel #0 \

            [list trace variable $arg w "tixVariable:TraceProc $w"]

    }

    return $changed

}

proc tixVariable:UpdateVariable {w} {

    upvar #0 $w data

    if {$data(-variable) != ""} {

        uplevel #0 \

            [list trace vdelete  $data(-variable) w "tixVariable:TraceProc $w"]

        uplevel #0 \

            [list set $data(-variable) $data(-value)]

        uplevel #0 \

            [list trace variable $data(-variable) w "tixVariable:TraceProc $w"]

        # just in case someone has another trace and restricted my change

        #

        set data(-value) [uplevel #0 set [list $data(-variable)]]

    }

}

proc tixVariable:TraceProc {w name1 name2 op} {

    upvar #0 $w data

    set varname $data(-variable)

    if [catch {$w config -value [uplevel #0 [list set $varname]]} err] {

        uplevel #0 [list set $varname [list [$w cget -value]]]

        error $err

    }

    return

}

proc tixVariable:DeleteVariable {w} {

    upvar #0 $w data

    # Must delete the trace command of the -variable

    #

    if {$data(-variable) != ""} {

        uplevel #0 \

            [list trace vdelete $data(-variable) w "tixVariable:TraceProc $w"]

    }

}