CTCLTimer

DESCRIPTION

Tcl/Tk provide a mechanism for scheduling functions to be executed after a time delay specified in milliseconds. The CTCLTimer class is an abstract base class that provides an interface into the API for that facility. To use CTCLTimer you must create a class derived from CTCLTimer that overrides and implement the operator() function. Create an object from the resulting function class. Use the object's Set and Clear members to schedule or cancel a scheduled execution. The code fragment example below shows how to do this to create a class that periodically emits the text "Tick" to stderr. Many #include directives are missing for brevity.

// Interface to Ticker normally goes in a header.
class Ticker : public CTCLTimer
{
public:
    Ticker(CTCLInterpreter* pInterp, int seconds);
    virtual ~Ticker();

    virtual void operator()();
};
...
// Implementation of Ticker normally goes in a .cpp

// Constructor of Ticker:

Ticker::Ticker(int seconds) :
    CTCLTimer(pInterp, seconds*1000)
{
    Set();                   // Schedule first one.
}
// Destructor.. chain to base class.
Ticker::~Ticker() {}

// called when timer goes off:
void
Ticker::operator()() {
    cerr << "Tick\n";
    Set();                 // Schedule next one.
}
...


Ticker Tick(pInterp, 1);  // Tick every second.

            

METHODS

CTCLTimer ();
CTCLTimer(CTCLInterpreter* pInterp,
          UInt_t nMsec = 0);
          

Construct timer objects. The first form of the constructor creates a timer object that must be later bound into an interpreter via a call to CTCLInterpreterObject::Bind. The seconf form of the contructor creates a timer object that is already bound to pInterp and has an initial schedule delay of nMsec.

  Tk_TimerToken getToken() const;
  UInt_t getMsec() const;
          

These two members access internal state of the object. getToken returns the Tk_TimerToken associated with the timer object. This is the Tcl/Tk token that identifies the timer request to the interpreter. getMsec retrieves the current value of the delay parameter in milliseconds.

  virtual   void operator() ()   = 0;
        

This function must be overidden and implemented in concrete timer classes. See the example in DESCRIPTION above.

  void Set ()  ;
  void Set(UInt_t nms);
  Bool_t IsSet() const;
        

Set schedules the object for execution. If nms is provided it is saved as the scheduling parameter and determines the delay in milliseconds before operator() is next called. If not provided, the most recently used delay will be used again.

IsSet returns kfTRUE if the timer is currently pending, or kfFALSE if no pending timer request is active.

  void Clear ()  ;
        

If a Timer request is pending, cancels it. If no timer request is pending, this function does nothing, and does not report an error.

SEE ALSO

CTCLInterpreterObject(3)

REFERENCES

Musser, Derge, Saini: STL Tutorial and Reference Guide
Addison-Wesley Professional Computing Series; 2001 ISBN 0-201-37923-6
See section 2.4 for a description and discussion of function objects.