Function

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  MGH_IS_CALLBACK

Purpose

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  This function determines whether a variable represents a widget
  callback, in the sense used elsewhere in my widget code. The
  function has been created and given its name to allow clearer
  event-handling code.

Calling Sequence

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  Result = mgh_is_callback(value)

Positional Parameters

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  var (input)
    The variable to be examined.

Return Value

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  This function returns 1 if the variable is a single-element
  MGH_WIDGET_CALLBACK structure, otherwise 0.
###########################################################################
  Copyright (c) 2001 NIWA:
  http://www.niwa.co.nz/
  Licensed under the MIT open source license:
  http://www.opensource.org/licenses/mit-license.php
###########################################################################

Modification History

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  Mark Hadfield, 2001=06:
    Written.
  Mark Hadfield, 2013-11:
    Code updated.