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/****************************************************************************
**
** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies).
** All rights reserved.
** Contact: Nokia Corporation (qt-info@nokia.com)
**
** This file is part of the Declarative module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** GNU Lesser General Public License Usage
** This file may be used under the terms of the GNU Lesser General Public
** License version 2.1 as published by the Free Software Foundation and
** appearing in the file LICENSE.LGPL included in the packaging of this
** file. Please review the following information to ensure the GNU Lesser
** General Public License version 2.1 requirements will be met:
** http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
**
** In addition, as a special exception, Nokia gives you certain additional
** rights. These rights are described in the Nokia Qt LGPL Exception
** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU General
** Public License version 3.0 as published by the Free Software Foundation
** and appearing in the file LICENSE.GPL included in the packaging of this
** file. Please review the following information to ensure the GNU General
** Public License version 3.0 requirements will be met:
** http://www.gnu.org/copyleft/gpl.html.
**
** Other Usage
** Alternatively, this file may be used in accordance with the terms and
** conditions contained in a signed written agreement between you and Nokia.
**
**
**
**
**
** $QT_END_LICENSE$
**
****************************************************************************/
#include "qsgfriction_p.h"
QT_BEGIN_NAMESPACE
/*!
\qmlclass Friction QSGFrictionAffector
\inqmlmodule QtQuick.Particles 2
\inherits Affector
\brief The Friction affector slows down movement proportional to the particle's current speed.
*/
/*!
\qmlproperty real QtQuick.Particles2::Friction::factor
A drag will be applied to moving objects which is this factor of their current velocity.
*/
static qreal sign(qreal a)
{
return a >= 0 ? 1 : -1;
}
QSGFrictionAffector::QSGFrictionAffector(QQuickItem *parent) :
QSGParticleAffector(parent), m_factor(0.0)
{
}
bool QSGFrictionAffector::affectParticle(QSGParticleData *d, qreal dt)
{
if (!m_factor)
return false;
qreal curVX = d->curVX();
qreal curVY = d->curVY();
qreal newVX = curVX + (curVX * m_factor * -1 * dt);
qreal newVY = curVY + (curVY * m_factor * -1 * dt);
//Since we're modelling a continuous function, it will never pass 0.
if (sign(curVX) != sign(newVX))
newVX = 0;
if (sign(curVY) != sign(newVY))
newVY = 0;
d->setInstantaneousVX(newVX);
d->setInstantaneousVY(newVY);
return true;
}
QT_END_NAMESPACE
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