Version 4 of Entering Unicode characters in a widget

MJ - The following script adds the <Control-u> binding to text or entry widgets which allows entry of Unicode characters directly.

 text .t
 entry .e
 pack .t
 pack .e

 # enable functionality by adding the UnicodeEntry tag to the bindtags
 bindtags .t [list .t UnicodeEntry Text . all]
 bindtags .e [list .e UnicodeEntry Entry . all]

namespace eval unicode_entry {

 variable uc_keys

 proc enable_unicode_entry {widget} {
      variable uc_keys
      set uc_keys($widget) {}
 }

 proc disable_unicode_entry {widget} {
      variable uc_keys
      unset -nocomplain uc_keys($widget)
 }

 proc handle_uc_key {widget key} {
      variable uc_keys
      if {![info exists uc_keys($widget)]} {
         return
      }

      upvar 0 uc_keys($widget) keys
      switch -glob -- [string toupper $key] {
        {[0-9A-F]} {
                       append keys $key
                       if {[string length $keys] >= 4} {
                           $widget insert insert [subst \\u$keys]
                           disable_unicode_entry $widget
                       }
                       return -code break
                   }
        default    {
                       $widget insert insert $keys
                       disable_unicode_entry $widget
                   }      
        }                
 }

 bind UnicodeEntry <Control-Key-u> [namespace code [list enable_unicode_entry %W]]
 bind UnicodeEntry <Key> [namespace code [list handle_uc_key %W %A]]

}