#	"... [Y]ou need a binding on the key event for that entry.
#
#	Using the procedures below simply make this call:
#
#		entryLimitWidth .entry 20
#	
#	And it should then do as you wish."

################################################################################
#
# Name:         keyIsDisplayable
#
# Synopsis:     This procedure takes a character value and determines whether
#               or not it is an ASCII displayable character or not.
#
################################################################################

proc keyIsDisplayable { keyChar } {

#
# Empty string is not displayable.
#
        if { $keyChar == "" } {
                return 0
        }
#
# Looks like displayable ASCII.
#
        if { $keyChar >= " " && $keyChar <= "~" } {
                return 1
        }
#
# Don't know what it is.
#
        return 0
}

################################################################################
#
# Name:         entryLimitWidth
#
# Synopsis:     This procedure is used to limit the number of characters
#               allowed in an entry widget. This is done by creating a binding
#               for the entry widget on the <Key> event so that each time the
#               user types a key in the entry widget, the binding is executed
#               to check the current size of the input string. The entry wigdet
#               and its maximum size will be passed as parameters, so to use
#               them in the bind command a string representing that bind command
#               must be built and then evaluated using "eval".
#
################################################################################

proc entryLimitWidth { entryWidget maxWidth } {

#
# Do not allow more than maxWidth characters in the entry field. A "bind
# command" string is built so that the passed variables may be used in the
# binding. If the length of the entry string exceeds the desinated maximum
# width, else sound the bell and do not allow the user to enter any more
# characters.
#
        set bindCommand [ format "bind %s <Key> { \n \
                if { \[ keyIsDisplayable %%A \] } { \n
                   if { \[ string length \[ %%W get \] \] >= %d } { \n \
                        bell \n \
                        break
                   }
                } }" $entryWidget $maxWidth ]
#
# Use "eval" to execute the "bind command" string.
#
        eval $bindCommand
}