QwtSystemClock man page

QwtSystemClock —

QwtSystemClock provides high resolution clock time functions.


#include <qwt_system_clock.h>

Public Member Functions

QwtSystemClock ()
Constructs a null clock object.
virtual ~QwtSystemClock ()
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).


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


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


true if the clock has never been started.

double QwtSystemClock::restart ()

Set the start time to the current time


Time, that is elapsed since the previous start time.

void QwtSystemClock::start ()

Sets the start time to the current time.


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Qwt User's Guide Version 6.1.2 Thu Dec 11 2014