qt-everywhere-src-5.15.1/qtquickcontrols2/src/quicktemplates2/qquickvelocitycalculator.cpp

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** This file is part of the Qt Quick Templates 2 module of the Qt Toolkit.
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#include "qquickvelocitycalculator_p_p.h"

#include <QtCore/qdebug.h>

QT_BEGIN_NAMESPACE

/*
    Usage:

    QQuickVelocityCalculator velocityCalculator;

    // ...

    velocityCalcular.startMeasuring(event->pos(), event->timestamp());
    velocityCalcular.stopMeasuring(event->pos(), event->timestamp());

    // ...

    if (velocityCalculator.velocity().x() > someAmount)
        doSomething();
    else if (velocityCalculator.velocity().x() < -someAmount)
        doSomethingElse();
*/

void QQuickVelocityCalculator::startMeasuring(const QPointF &point1, qint64 timestamp)
{
    m_point1 = point1;

    if (timestamp != 0)
        m_point1Timestamp = timestamp;
    else
        m_timer.start();
}

void QQuickVelocityCalculator::stopMeasuring(const QPointF &point2, qint64 timestamp)
{
    if (timestamp == 0 && !m_timer.isValid()) {
        qWarning() << "QQuickVelocityCalculator: a call to stopMeasuring() must be preceded by a call to startMeasuring()";
        return;
    }

    m_point2 = point2;
    m_point2Timestamp = timestamp != 0 ? timestamp : m_timer.elapsed();
    m_timer.invalidate();
}

void QQuickVelocityCalculator::reset()
{
    m_point1 = QPointF();
    m_point2 = QPointF();
    m_point1Timestamp = 0;
    m_point2Timestamp = 0;
    m_timer.invalidate();
}

QPointF QQuickVelocityCalculator::velocity() const
{
    if ((m_point2Timestamp == 0 || m_point1Timestamp == m_point2Timestamp) && !m_timer.isValid())
        return QPointF();

    const qreal secondsElapsed = (m_point2Timestamp != 0 ? m_point2Timestamp - m_point1Timestamp : m_timer.elapsed()) / 1000.0;
    const QPointF distance = m_point2 - m_point1;
    return distance / secondsElapsed;
}

QT_END_NAMESPACE