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#include "qsgtargetaffector_p.h"
#include <QDebug>

QSGTargetAffector::QSGTargetAffector(QSGItem *parent) :
    QSGParticleAffector(parent), m_targetX(0), m_targetY(0),
    m_targetWidth(0), m_targetHeight(0), m_defaultShape(new QSGParticleExtruder(this)),
    m_targetShape(m_defaultShape), m_targetTime(-1)
{
    m_needsReset = true;
}

void QSGTargetAffector::reset(QSGParticleData* d)
{
    QSGParticleAffector::reset(d);
    m_targets[qMakePair<int,int>(d->group, d->index)] = m_targetShape->extrude(QRectF(m_targetX, m_targetY, m_targetWidth, m_targetHeight));
}

bool QSGTargetAffector::affectParticle(QSGParticleData *d, qreal dt)
{
    Q_UNUSED(dt);
    QPointF target = m_targets[qMakePair<int,int>(d->group, d->index)];
    if (target.isNull())
        return false;
    qreal tt = m_targetTime==-1?d->lifeSpan:(m_targetTime / 1000.0);
    qreal t = tt - (d->lifeSpan - d->lifeLeft());
    if (t <= 0)
        return false;
    qreal tx = d->x + d->vx * tt + 0.5 * d->ax * tt * tt;
    qreal ty = d->y + d->vy * tt + 0.5 * d->ay * tt * tt;

    if (QPointF(tx,ty) == target)
        return false;

    qreal vX = (target.x() - d->x) / tt;
    qreal vY = (target.y() - d->y) / tt;

    qreal w = 1 - (t / tt) + 0.05;
    w = qMin<qreal>(w, 1.0);
    qreal wvX = vX * w + d->vx * (1 - w);
    qreal wvY = vY * w + d->vy * (1 - w);
    //Screws with the acceleration so that the given start pos with the chosen weighted velocity will still end at the target coordinates
    qreal ax = (2*(target.x() - d->x - wvX*tt)) / (tt*tt);
    qreal ay = (2*(target.y() - d->y - wvY*tt)) / (tt*tt);

    d->vx = wvX;
    d->vy = wvY;
    d->ax = ax;
    d->ay = ay;

    return true;
}