IRIX Base Documentation 2001 May/SGI IRIX Base Documentation 2001 May.iso/usr/share/catman/p_man/cat3/Vk/VkPeriodic.z/VkPeriodic

Text File | 1998-10-20 | 6.5 KB | 199 lines

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     VkPeriodic - Support for performing actions at regular periodic intervals

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     VkCallbackObject

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     #include <Vk/VkPeriodic.h>

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           VkPeriodic(int interval);
           virtual void ~VkPeriodic(void);


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           void start(void);
           void stop(void);


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           virtual void tick(void);


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          VkPeriodic provides a simple, convenient interface to the Xt timeout
          mechanism. For many applications, it is sufficient to call
          _X_t_A_p_p_A_d_d_T_i_m_e_O_u_t() directly. However, VkPeriodic provides the ability
          to encapsulate a common use of _X_t_A_p_p_A_d_d_T_i_m_e_O_u_t(), 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 _t_i_c_k() virtual
          member function. The _t_i_c_k() 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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           virtual void tick(void);


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

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           VkPeriodic(int interval);


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

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           virtual void ~VkPeriodic(void);


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

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           void start(void);


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

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           void stop(void);


          Stop the timer.

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           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.

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          callCallbacks(), addCallback(), removeCallback(),
          removeAllCallbacks()

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