Extract Particles code to an independent library

QtQuick clients that do not use particles features should not have
to load these classes.

Task-number: QTBUG-25178
Change-Id: Ib15f7655dc4d821595e06f9160d2770375279027
Reviewed-by: Glenn Watson <glenn.watson@nokia.com>

1 files changed, 111 insertions, 0 deletions

diff --git a/src/particles/qquickfriction.cpp b/src/particles/qquickfriction.cpp
new file mode 100644
index 0000000000..d37d109f48
--- /dev/null
+++ b/src/particles/qquickfriction.cpp
@@ -0,0 +1,111 @@
+/****************************************************************************
+**
+** Copyright (C) 2012 Nokia Corporation and/or its subsidiary(-ies).
+** Contact: http://www.qt-project.org/
+**
+** This file is part of the QtQuick 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 "qquickfriction_p.h"
+QT_BEGIN_NAMESPACE
+/*!
+    \qmlclass Friction QQuickFrictionAffector
+    \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.
+*/
+/*!
+    \qmlproperty real QtQuick.Particles2::Friction::threshold
+
+    The drag will only be applied to objects with a velocity above the threshold velocity. The
+    drag applied will bring objects down to the threshold velocity, but no further.
+
+    The default threshold is 0
+*/
+static qreal sign(qreal a)
+{
+    return a >= 0 ? 1 : -1;
+}
+
+static const qreal epsilon = 0.00001;
+
+QQuickFrictionAffector::QQuickFrictionAffector(QQuickItem *parent) :
+    QQuickParticleAffector(parent), m_factor(0.0), m_threshold(0.0)
+{
+}
+
+bool QQuickFrictionAffector::affectParticle(QQuickParticleData *d, qreal dt)
+{
+    if (!m_factor)
+        return false;
+    qreal curVX = d->curVX();
+    qreal curVY = d->curVY();
+    if (!curVX && !curVY)
+        return false;
+    qreal newVX = curVX + (curVX * m_factor * -1 * dt);
+    qreal newVY = curVY + (curVY * m_factor * -1 * dt);
+
+    if (!m_threshold) {
+        if (sign(curVX) != sign(newVX))
+            newVX = 0;
+        if (sign(curVY) != sign(newVY))
+            newVY = 0;
+    } else {
+        qreal curMag = sqrt(curVX*curVX + curVY*curVY);
+        if (curMag <= m_threshold + epsilon)
+            return false;
+        qreal newMag = sqrt(newVX*newVX + newVY*newVY);
+        if (newMag <= m_threshold + epsilon || //went past the threshold, stop there instead
+            sign(curVX) != sign(newVX) || //went so far past maybe it came out the other side!
+            sign(curVY) != sign(newVY)) {
+            qreal theta = atan2(curVY, curVX);
+            newVX = m_threshold * cos(theta);
+            newVY = m_threshold * sin(theta);
+        }
+    }
+
+    d->setInstantaneousVX(newVX);
+    d->setInstantaneousVY(newVY);
+    return true;
+}
+QT_END_NAMESPACE