qt-everywhere-src-5.14.1/qtdeclarative/src/particles/qquickwander.cpp

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#include "qquickwander_p.h"
#include "qquickparticlesystem_p.h"//for ParticlesVertices
#include <QRandomGenerator>
QT_BEGIN_NAMESPACE
/*!
    \qmltype Wander
    \instantiates QQuickWanderAffector
    \inqmlmodule QtQuick.Particles
    \ingroup qtquick-particles
    \inherits Affector
    \brief For applying random particle trajectory.

*/
/*!
    \qmlproperty real QtQuick.Particles::Wander::pace

    Maximum attribute change per second.
*/
/*!
    \qmlproperty real QtQuick.Particles::Wander::xVariance

    Maximum attribute x value (as a result of Wander).

    If unset, Wander will not affect x values.
*/
/*!
    \qmlproperty real QtQuick.Particles::Wander::yVariance

    Maximum attribute y value (as a result of Wander).

    If unset, Wander will not affect y values.
*/
/*!
    \qmlproperty AffectableParameter QtQuick.Particles::Wander::affectedParameter

    What attribute of particles is directly affected.
    \list
    \li PointAttractor.Position
    \li PointAttractor.Velocity
    \li PointAttractor.Acceleration
    \endlist
*/

QQuickWanderAffector::QQuickWanderAffector(QQuickItem *parent) :
    QQuickParticleAffector(parent), m_xVariance(0), m_yVariance(0), m_pace(0)
    , m_affectedParameter(Velocity)
{
    m_needsReset = true;
}

QQuickWanderAffector::~QQuickWanderAffector()
{
    for (QHash<int, WanderData*>::const_iterator iter=m_wanderData.constBegin();
        iter != m_wanderData.constEnd(); ++iter)
        delete (*iter);
}

WanderData* QQuickWanderAffector::getData(int idx)
{
    if (m_wanderData.contains(idx))
        return m_wanderData[idx];
    WanderData* d = new WanderData;
    d->x_vel = 0;
    d->y_vel = 0;
    d->x_peak = m_xVariance;
    d->y_peak = m_yVariance;
    d->x_var = m_pace * QRandomGenerator::global()->generateDouble();
    d->y_var = m_pace * QRandomGenerator::global()->generateDouble();

    m_wanderData.insert(idx, d);
    return d;
}

// TODO: see below
//void QQuickWanderAffector::reset(int systemIdx)
//{
//    if (m_wanderData.contains(systemIdx))
//        delete m_wanderData[systemIdx];
//    m_wanderData.remove(systemIdx);
//}

bool QQuickWanderAffector::affectParticle(QQuickParticleData* data, qreal dt)
{
    /*TODO: Add a mode which does basically this - picking a direction, going in it (random velocity) and then going back
    WanderData* d = getData(data->systemIndex);
    if (m_xVariance != 0.) {
        if ((d->x_vel > d->x_peak && d->x_var > 0.0) || (d->x_vel < -d->x_peak && d->x_var < 0.0)) {
            d->x_var = -d->x_var;
            d->x_peak = m_xVariance + m_xVariance * QRandomGenerator::global()->generateDouble();
        }
        d->x_vel += d->x_var * dt;
    }
    qreal dx = dt * d->x_vel;

    if (m_yVariance != 0.) {
        if ((d->y_vel > d->y_peak && d->y_var > 0.0) || (d->y_vel < -d->y_peak && d->y_var < 0.0)) {
            d->y_var = -d->y_var;
            d->y_peak = m_yVariance + m_yVariance * QRandomGenerator::global()->generateDouble();
        }
        d->y_vel += d->y_var * dt;
    }
    qreal dy = dt * d->x_vel;

    //### Should we be amending vel instead?
    ParticleVertex* p = &(data->pv);
    p->x += dx;

    p->y += dy;
    return true;
    */
    qreal dx = dt * m_pace * (2 * QRandomGenerator::global()->generateDouble() - 1);
    qreal dy = dt * m_pace * (2 * QRandomGenerator::global()->generateDouble() - 1);
    qreal newX, newY;
    switch (m_affectedParameter){
    case Position:
        newX = data->curX(m_system) + dx;
        if (m_xVariance > qAbs(newX) )
            data->x += dx;
        newY = data->curY(m_system) + dy;
        if (m_yVariance > qAbs(newY) )
            data->y += dy;
        break;
    default:
    case Velocity:
        newX = data->curVX(m_system) + dx;
        if (m_xVariance > qAbs(newX))
            data->setInstantaneousVX(newX, m_system);
        newY = data->curVY(m_system) + dy;
        if (m_yVariance > qAbs(newY))
            data->setInstantaneousVY(newY, m_system);
        break;
    case Acceleration:
        newX = data->ax + dx;
        if (m_xVariance > qAbs(newX))
            data->setInstantaneousAX(newX, m_system);
        newY = data->ay + dy;
        if (m_yVariance > qAbs(newY))
            data->setInstantaneousAY(newY, m_system);
        break;
    }
    return true;
}
QT_END_NAMESPACE

#include "moc_qquickwander_p.cpp"