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  Sx_DefTrigger():

  Syntax:   Sx_DefTrigger( <nEvent>, <nArea>, <nFieldPos>, <xTrigVal> )

        nEvent = A numeric value indicating the type of event that is
                 activating the trigger.  These values are defined as
                 manifest constants in the SIXCDX.CH file, and are as
                 follows:

                 EVENT_PREUSE       = A DBF file is about to be opened
               * EVENT_POSTUSE      = A DBF file has just been opened
               * EVENT_UPDATE       = An index is being updated
                 EVENT_APPEND       = A new record is being appended
                 EVENT_DELETE       = A record is being deleted
                 EVENT_RECALL       = A deleted record is being recalled
                 EVENT_PACK         = The DBF file is being packed
                 EVENT_ZAP          = The DBF file is being zapped
                 EVENT_PUT          = A value is being stored in the DBF
                 EVENT_GET          = A value is being retrieved from the DBF
                 EVENT_PRECLOSE     = The DBF file is about to be closed
               * EVENT_POSTCLOSE    = The DBF file has just been closed
                 EVENT_PREMEMOPACK  = A MEMOPACK is just about to occur
                 EVENT_POSTMEMOPACK = A MEMOPACK has just been completed

                 NOTE:  Although these constants preprocess into numeric
                        values, you should not use the numeric values in
                        your source code.  Instead, you should use the
                        constants, as defined above.  This will insure
                        compatibility with all future releases of the
                        SIx Driver.

               (*) - The events marked with an asterisk (*) will continue
                     even if the return value for that event is set to false
                     (.F.).  This is to insure data integrity.

         nArea = The currently active workarea number.

     nFieldPos = The field position for the PUT or GET, if applicable.

      xTrigVal = This parameter contains the value, if any, associated with
                 the event being processed.  If no value of significance is
                 associated with the event, a zero (0) is passed down.

  Returns:   Logical.  TRUE (.T.) if the current event should be allowed to
             successfully complete, FALSE (.F.) if not.

  Description:  By default, this function is automatically called whenever
                any of the events listed above occurs.  It contains the
                default triggers (none) to be attached to each event.

                The parameters are passed to it automatically by the SIx
                Driver.  This is similar to the way parameters are
                automatically passed to a UDF used in Clipper's MemoEdit()
                or AChoice() functions.

                To cause the SIx Driver to use a different set of triggers,
                you would USE the file with the TRIGGER keyword, specifying
                the name of the desired trigger function in quotes.  For
                example, to use a modified Sx_DefTrigger() function called
                DemoTrigger(), you would do this:

                    USE test VIA "SIXCDX" TRIGGER "DemoTrigger"

                This would cause all triggerable events for this workarea to
                be handled through DemoTrigger(), rather than the SIx
                Driver's default Sx_DefTrigger() function.

                The Clipper source code for Sx_DefTrigger() is contained in
                SIXTRIG.PRG, and can be modified as desired.  Just insure
                that the new SIXTRIG.OBJ module is linked into your
                application ahead of the SIXCDX.LIB file.  The complete
                source for Sx_DefTrigger() is also listed below in the
                Example section.

                In its present condition, Sx_DefTrigger() maintains the
                exact same behavior as in previous SIx Driver releases.
                The call to Sx_SetTrigger( TRIGGER_REMOVE ) under the
                EVENT_PREUSE case effectively removes the trigger controls
                just prior to a database being opened.  To allow support
                for event trigger handling, just comment out this call to
                Sx_SetTrigger().

                Also, if you want the SIx Driver to automatically look for
                an associated .INI file when a .DBF is USEd, you need to
                uncomment the _sx_INIinit( nArea ) call.  See the section
                on ".INI Files" for more details on these.  The _sx_INIinit()
                function can ONLY be used in this manner.  If it is called
                anywhere else in your application, unpredictable results can
                occur.


    NOTE:  See the TRIGDEMO.PRG file for an example of using event triggers.


  Example:

    #include "SIXCDX.CH"

    FUNC Sx_DefTrigger( nEvent, nArea, nFieldPos, xTrigVal )

      DO CASE

        CASE nEvent == EVENT_PREUSE
    //    _sx_INIinit( nArea )
          Sx_SetTrigger( TRIGGER_REMOVE )

        CASE nEvent == EVENT_POSTUSE

        CASE nEvent == EVENT_UPDATE

        CASE nEvent == EVENT_APPEND

        CASE nEvent == EVENT_DELETE

        CASE nEvent == EVENT_RECALL

        CASE nEvent == EVENT_PACK

        CASE nEvent == EVENT_ZAP

        CASE nEvent == EVENT_PUT

        CASE nEvent == EVENT_GET

        CASE nEvent == EVENT_PRECLOSE

        CASE nEvent == EVENT_POSTCLOSE

        CASE nEvent == EVENT_PREMEMOPACK

        CASE nEvent == EVENT_POSTMEMOPACK

      ENDCASE

    Return( .T. )