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─────PWB Extensions─────────────────────────────────────────────────────────
 
     Each swiDesc element an extension swiTable array contains a type
     member which determines the kind of values the switch takes and how
     the switch is initialized. The type member must be one of the
     following constants:
 
     SWI_BOOLEAN
          The switch is Boolean. Setting the switch to No in PWB sets
          the variable to FALSE (zero). Setting the switch to Yes sets
          the variable to TRUE (nonzero).
 
          The act member must be a far pointer to a flagType variable.
 
     SWI_NUMERIC
          The switch is numeric. SWI_NUMERIC must be combined with
          either RADIX10 or RADIX16 to specify whether PWB interprets
          switch values as as decimal or hexadecimal.
 
          The act member must be a far pointer to an int variable.
 
     SWI_EXTTEXT
          The switch is a text switch. The act member must be a pointer
          to the function that processes the value of the switch when it
          is initialized or displayed. The prototype for the function
          must be:
 
               char far * pascal EXTERNAL Func( char far *Text,
                                                flagType fQuery );
 
          The fQuery argument specifies the action that the switch
          function is to perform, as follows:
 
          fQuery    Description
 
          FALSE     The switch is being assigned a value. The switch
                    function must set the switch according to the Text
                    argument and return NULL if successful. Otherwise,
                    it must return an error message to display.
 
          TRUE      The value for the switch is being displayed or the
                    switch is being saved in TOOLS.INI. The switch
                    function must return the current value of the
                    switch. The Text argument is normally NULL and
                    should be ignored.
 
     SWI_SPECIAL
     SWI_SPECIAL2
          The switch is a string. These types are obsolete and supported
          for PWB 1.x extensions only. Use SWI_EXTTEXT for new
          extensions.
 
          The act member must be a pointer to the function that will
          process the string. The difference between the two switch
          types is in the prototype of the function.
 
          For SWI_SPECIAL the function prototype must be:
 
               flagType pascal EXTERNAL Func( char far * );
 
          For SWI_SPECIAL2 the function prototype must be:
 
               char far *pascal EXTERNAL Func( char far * );
 
          The text is passed to the function for processing. The
          function may need to check the string for suitability. If the
          string is acceptable, SWI_SPECIAL functions return TRUE.
          SWI_SPECIAL2 functions return NULL. If the string is
          unacceptable, SWI_SPECIAL functions return FALSE. SWI_SPECIAL2
          functions return an error string for PWB to display.
                                    -♦-