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QwtSystemClock Class Reference

QwtSystemClock provides high resolution clock time functions. More...

#include <qwt_system_clock.h>

Public Member Functions

 QwtSystemClock ()
 Constructs a null clock object.
 
virtual ~QwtSystemClock ()
 Destructor.
 
bool isNull () const
 
void start ()
 
double restart ()
 
double elapsed () const
 

Detailed Description

QwtSystemClock provides high resolution clock time functions.

Sometimes the resolution offered by QTime ( millisecond ) is not accurate enough for implementing time measurements ( f.e. sampling ). QwtSystemClock offers a subset of the QTime functionality using higher resolution timers ( if possible ).

Precision and time intervals are multiples of milliseconds (ms).

Note
The implementation uses high-resolution performance counter on Windows, mach_absolute_time() on the Mac or POSIX timers on other systems. If none is available it falls back on QTimer.

Member Function Documentation

double QwtSystemClock::elapsed ( ) const
Returns
Number of milliseconds that have elapsed since the last time start() or restart() was called or 0.0 for null clocks.
bool QwtSystemClock::isNull ( ) const
Returns
true if the clock has never been started.
double QwtSystemClock::restart ( )

Set the start time to the current time

Returns
Time, that is elapsed since the previous start time.
void QwtSystemClock::start ( )

Sets the start time to the current time.