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Container Widgets
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The TixSelect Widget
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Accessing the Value
Specifying Complex Selection Rules
If you want to have more complex selection rules for the
TixSelect widget, you can use the
-validatecmd
option. This
option works the same as the
-validatecmd
option of the
TixControl widget which we discusses in section
1.2: it specifies a command to be called every
time the user attempts to change the selection inside a TixSelect
widget.
In the example program 1-14, the procedure
TwoMax
will be called every time the user tries to change the
selection of the
.fruits
widget.
TwoMax
limits the
maximum number of fruits that the user to choose to be 2 by always
truncating the value of the TixSelect widget to have no more than
two items. If you run this program, you will find out that you can
never select a third fruit after you have select two fruits.
tixSelect .fruits -label "Fruits: " -radio false -validatecmd TwoMax
.fruits add apple  -text Apple  -width 6
.fruits add orange -text Orange -width 6
.fruits add banana -text Banana -width 6
pack .fruits
proc TwoMax {value} {
if {[llength $value] $>$ 2} {
return [lrange $value 0 1]
} else {
return $value
}
}
(Figure 1-14) Specifying More Complex Selection Rules
http://tix.sourceforge.net
http://tix.sourceforge.net
