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++ // Copyright (C) 2016 The Qt Company Ltd.
++ // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
++
++ #include "qquickpointattractor_p.h"
++ #include <cmath>
++ #include <QDebug>
++ QT_BEGIN_NAMESPACE
++ /*!
++ \qmltype Attractor
++ \nativetype QQuickAttractorAffector
++ \inqmlmodule QtQuick.Particles
++ \ingroup qtquick-particles
++ \inherits ParticleAffector
++ \brief Attracts particles towards a specific point.
++
++ Like other affectors, Attractor has the standard properties x, y, width,
++ and height that represent the affected area. The size and position of the
++ Attractor item determine the affected particles.
++
++ The size of the attracting point is always 0x0, and its location is
++ specified by \l pointX and \l pointY properties.
++ */
++
++
++ /*!
++ \qmlproperty real QtQuick.Particles::Attractor::pointX
++
++ The x coordinate of the attracting point, relative
++ to the x coordinate of the Attractor item.
++ */
++ /*!
++ \qmlproperty real QtQuick.Particles::Attractor::pointY
++
++ The y coordinate of the attracting point, relative
++ to the y coordinate of the Attractor item.
++ */
++ /*!
++ \qmlproperty real QtQuick.Particles::Attractor::strength
++
++ The pull, in units per second, to be exerted on an item one pixel away.
++
++ Strength, together with the value of \l proportionalToDistance property,
++ determine the exact amount of pull exerted on particles at a distance.
++ */
++ /*!
++ \qmlproperty enumeration QtQuick.Particles::Attractor::affectedParameter
++
++ The attribute of particles that is directly affected.
++
++ \value Attractor.Position Position
++ \value Attractor.Velocity Velocity
++ \value Attractor.Acceleration Acceleration
++ */
++ /*!
++ \qmlproperty enumeration QtQuick.Particles::Attractor::proportionalToDistance
++
++ The relation between the \l strength of the attraction and the distance from
++ the particle to the attracting point.
++
++ \value Attractor.Constant Constant
++ \value Attractor.Linear Linear
++ \value Attractor.InverseLinear Inverse linear
++ \value Attractor.Quadratic Quadratic
++ \value Attractor.InverseQuadratic Inverse quadratic
++ */
++
++
++ QQuickAttractorAffector::QQuickAttractorAffector(QQuickItem *parent) :
++ QQuickParticleAffector(parent), m_strength(0.0), m_x(0), m_y(0)
++ , m_physics(Velocity), m_proportionalToDistance(Linear)
++ {
++ }
++
++ bool QQuickAttractorAffector::affectParticle(QQuickParticleData *d, qreal dt)
++ {
++ if (m_strength == 0.0)
++ return false;
++ qreal dx = m_x+m_offset.x() - d->curX(m_system);
++ qreal dy = m_y+m_offset.y() - d->curY(m_system);
++ qreal r = std::sqrt((dx*dx) + (dy*dy));
++ qreal theta = std::atan2(dy,dx);
++ qreal ds = 0;
++ switch (m_proportionalToDistance){
++ case InverseQuadratic:
++ ds = (m_strength / qMax<qreal>(1.,r*r));
++ break;
++ case InverseLinear:
++ ds = (m_strength / qMax<qreal>(1.,r));
++ break;
++ case Quadratic:
++ ds = (m_strength * qMax<qreal>(1.,r*r));
++ break;
++ case Linear:
++ ds = (m_strength * qMax<qreal>(1.,r));
++ break;
++ default: //also Constant
++ ds = m_strength;
++ }
++ ds *= dt;
++ dx = ds * std::cos(theta);
++ dy = ds * std::sin(theta);
++ qreal vx,vy;
++ switch (m_physics){
++ case Position:
++ d->x = (d->x + dx);
++ d->y = (d->y + dy);
++ break;
++ case Acceleration:
++ d->setInstantaneousAX(d->ax + dx, m_system);
++ d->setInstantaneousAY(d->ay + dy, m_system);
++ break;
++ case Velocity: //also default
++ default:
++ vx = d->curVX(m_system);
++ vy = d->curVY(m_system);
++ d->setInstantaneousVX(vx + dx, m_system);
++ d->setInstantaneousVY(vy + dy, m_system);
++ }
++
++ return true;
++ }
++ QT_END_NAMESPACE
++
++ #include "moc_qquickpointattractor_p.cpp"