VkPeriodic(3x)							VkPeriodic(3x)

NAME    [Toc]    [Back]

     VkPeriodic	- Support for performing actions at regular periodic intervals

INHERITS FROM    [Toc]    [Back]

     VkCallbackObject

HEADER FILE    [Toc]    [Back]

     #include <Vk/VkPeriodic.h>

PUBLIC PROTOCOL	SUMMARY
   Constructor/Destructor
	   VkPeriodic(int interval);
	   virtual void	~VkPeriodic(void);


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

PROTECTED PROTOCOL SUMMARY    [Toc]    [Back]

   Updates
	   virtual void	tick(void);


   Protected Data Members    [Toc]    [Back]

CLASS DESCRIPTION    [Toc]    [Back]

	  VkPeriodic provides a	simple,	convenient interface to	the Xt timeout
	  mechanism. For many applications, it is sufficient to	call
	  XtAppAddTimeOut() directly. However, VkPeriodic provides the ability
	  to encapsulate a common use of XtAppAddTimeOut(), as a cyclic	timer,
	  in a C++ class.

	  The VkPeriodic class can be used in one of two way. The first	is to
	  derive a new class from VkPeriodic that overrides the	tick() virtual
	  member function. The tick() member function is called	for each cycle
	  of the periodic timeout. This	approach has the advantage that	any
	  data being used in connection	with the timeout can be	declared and
	  maintained as	data member(s) of the derived class.

	  The VkPeriodic class also supports a ViewKit callback	that allows
	  other	C++ classes to register	member functions to be called with
	  each periodic	timeout. This approach is more convenient when a
	  simple timer is needed to drive some other class.

	  These	two methods are	not mutually-exclusive,	and both approaches
	  may be used together at once.








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VkPeriodic(3x)							VkPeriodic(3x)

FUNCTION DESCRIPTIONS    [Toc]    [Back]

   tick()
	   virtual void	tick(void);


	  This function	can be overridden by derived classes to	allow them to
	  be notified when each	timeout	occurs.

   VkPeriodic()    [Toc]    [Back]
	   VkPeriodic(int interval);


	  The constructor initializes a	VkPeriodic object, creating a timer to
	  be called every interval milliseconds. The interval is approximate
	  because it relies on the underlying Xt mechanism, which is based on
	  select(). If an application does not return to the Xt	event loop
	  regularly, the timeout will not occur.

   ~VkPeriodic()
	   virtual void	~VkPeriodic(void);


	  Clean	up all memory allocated	by a VkPeriodic	object.	Any pending
	  timer	is removed.

   start()
	   void	start(void);


	  Start	the timer. This	function must be called	to start the periodic
	  timeouts.

   stop()
	   void	stop(void);


	  Stop the timer.

   static const	char *const timerCallback;
	   static const	char *const timerCallback;


	  This callback	list allows other C++ classes derived from
	  VkCallbackObject to register member functions	to be called at
	  periodic intervals.

INHERITED MEMBER FUNCTIONS    [Toc]    [Back]

   Inherited from VkCallbackObject
	  callCallbacks(), addCallback(), removeCallback(),
	  removeAllCallbacks()

     ViewKit Programmer's Guide



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VkPeriodic(3x)							VkPeriodic(3x)



     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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