 
 subsubsection3_3_2_4.html  subsection3_3_2.html  subsubsection3_3_2_2.html  tableofcontents3_1.html   Next: subsubsection3_3_2_4.html Validating User Inputs Up: subsection3_3_2.html Getting Started: the  Previous: subsubsection3_3_2_2.html Accessing The Value     Disabling Callbacks Temporarily  
Now, if you want to change a value from within the program, you have to
  disable the callback. The reason is that the callback runs whenever you
  (as well as the user) makes a change. In particular, if you make a change
  within the callback procedure and forget to disable the callback, it will
  recursively call itself and enter an infinite loop. To avoid this
  problem, you should use the 
-disablecallback option. Here is an
  example:
     tixControl .c -command addOne    proc addOne {value} {
        .c config -disablecallback true
        .c config -value [incr value]
        .c config -disablecallback false
    }
The procedure 
addOne adjusts the value of .c by one whenever
  the user enters a new value into 
.c. Notice that it is necessary to
  set 
-disablecallback here or otherwise addOne will be
  infinitely recursed! That is because 
addOne is called every
  time
 the value changes, either by the user or by the program.
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