VkBackground(3x)					      VkBackground(3x)

NAME    [Toc]    [Back]

     VkBackground - Support for	simple work procedure-based background tasks

INHERITS FROM    [Toc]    [Back]

     VkCallbackObject

HEADER FILE    [Toc]    [Back]

     #include <Vk/VkBackground.h>

PUBLIC PROTOCOL	SUMMARY
   Constructor/Destructor
	   VkBackground(void);
	   void	~VkBackground(void);


   Starting and	Stopping
	   void	start(void);
	   void	stop(void);

PROTECTED PROTOCOL SUMMARY    [Toc]    [Back]

	   virtual Boolean timeSlice(void);

CLASS DESCRIPTION    [Toc]    [Back]

	  VkBackground is an abstract class that provides a simple C++
	  interface to handling	background tasks based on Xt work procedures
	  (functions that are called whenever there are	no events pending in
	  the application's event queue).  VkBackground	handles	the details of
	  registering a	work procedure and provides a convenient way to
	  maintain state between calls to the work procedure.

DERIVING SUBCLASSES    [Toc]    [Back]

	  The VkBackground class is intended to	be subclassed. Derived classes
	  must override	the timeSlice()	member function	which behaves just
	  like an Xt work procedure. This member function is called whenever
	  no events are	pending	in the application's event queue. It is
	  expected to perform a	small amount of	work and return	quickly. The
	  function must	return TRUE if the class has completed its task	is
	  done,	or FALSE if the	member function	should be called again.

	  The primary for using	this class instead of using a work procedure
	  directly is the ability to store state in class data members between
	  calls	to the timeSlice() function.









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VkBackground(3x)					      VkBackground(3x)



FUNCTION DESCRIPTIONS
   timeSlice()
	   virtual Boolean timeSlice(void);


	  Called whenever no events are	pending	in the application's event
	  queue.  This function	must return quickly and	return a value of TRUE
	  if the class has completed its task and the member function should
	  not be called	again, or FALSE	if it should be	called again at	the
	  next possible	time.

   VkBackground()    [Toc]    [Back]
	   VkBackground(void);


	  Initialize a VkBackground object. The	constructor does not start the
	  work procedure.

   ~VkBackground()
	   void	~VkBackground(void);


	  Free all storage associated with a VkBackground object. If this
	  object's work	procedure is currently active, the destructor removes
	  it.

   start()
	   void	start(void);


	  Start	the background task by installing a work procedure.

   stop()
	   void	stop(void);


	  Stop the background task by removing any currently installed work
	  procedure.

INHERITED MEMBER FUNCTIONS    [Toc]    [Back]

SEE ALSO
     ViewKit Programmer's Guide
     The X Window System, DEC Press, Bob Sheifler and Jim Gettys
     The X Window System Toolkit, DEC Press, Paul Asente and Ralph Swick
     The OSF/Motif Programmers Reference, Prentice Hall, OSF


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