Refactor SpriteEngine out of StochasticEngine

Also add ParticleGroups which use only StochasticStates
Simplistic change for now, just to focus the API for the
particle system. ParticleGroup elements replace the particleStates
property on the system, and the term "group" is now used more
consistently.

Change-Id: I6456f9c521b8166ccd94ea953275557bcfbf6423
Reviewed-on: http://codereview.qt-project.org/4699
Reviewed-by: Alan Alpert <alan.alpert@nokia.com>

20 files changed, 385 insertions, 124 deletions

diff --git a/src/declarative/particles/particles.pri b/src/declarative/particles/particles.pri
index 527bd9ae61..8676e52172 100644
--- a/src/declarative/particles/particles.pri
+++ b/src/declarative/particles/particles.pri
@@ -29,7 +29,8 @@ HEADERS += \
     $$PWD/qsgtargetaffector_p.h \
     $$PWD/qsgcumulativedirection_p.h \
     $$PWD/qsgv8particledata_p.h \
-    $$PWD/qsgrectangleextruder_p.h
+    $$PWD/qsgrectangleextruder_p.h \
+    $$PWD/qsgparticlegroup_p.h
 
 SOURCES += \
     $$PWD/qsgangledirection.cpp \
@@ -60,7 +61,8 @@ SOURCES += \
     $$PWD/qsgtargetaffector.cpp \
     $$PWD/qsgcumulativedirection.cpp \
     $$PWD/qsgv8particledata.cpp \
-    $$PWD/qsgrectangleextruder.cpp
+    $$PWD/qsgrectangleextruder.cpp \
+    $$PWD/qsgparticlegroup.cpp
 
 RESOURCES += \
     $$PWD/particles.qrc
diff --git a/src/declarative/particles/qsgcustomparticle.cpp b/src/declarative/particles/qsgcustomparticle.cpp
index ab4cfa0a3a..a1d65a5360 100644
--- a/src/declarative/particles/qsgcustomparticle.cpp
+++ b/src/declarative/particles/qsgcustomparticle.cpp
@@ -465,7 +465,7 @@ QSGShaderEffectNode* QSGCustomParticle::buildCustomNodes()
         s.vertexCode = qt_particles_default_vertex_code;
     s.vertexCode = qt_particles_template_vertex_code + s.vertexCode;
     m_material.setProgramSource(s);
-    foreach (const QString &str, m_particles){
+    foreach (const QString &str, m_groups){
         int gIdx = m_system->m_groupIds[str];
         int count = m_system->m_groupData[gIdx]->size();
         //Create Particle Geometry
diff --git a/src/declarative/particles/qsgimageparticle.cpp b/src/declarative/particles/qsgimageparticle.cpp
index 581024d578..b1aef784e8 100644
--- a/src/declarative/particles/qsgimageparticle.cpp
+++ b/src/declarative/particles/qsgimageparticle.cpp
@@ -1021,7 +1021,7 @@ QSGGeometryNode* QSGImageParticle::buildParticleNodes()
         m_material->setFlag(QSGMaterial::Blending);
     }
 
-    foreach (const QString &str, m_particles){
+    foreach (const QString &str, m_groups){
         int gIdx = m_system->m_groupIds[str];
         int count = m_system->m_groupData[gIdx]->size();
         QSGGeometryNode* node = new QSGGeometryNode();
@@ -1151,7 +1151,7 @@ void QSGImageParticle::prepareNextFrame()
         //Advance State
         getState<ImageMaterialData>(m_material)->animcount = m_spriteEngine->spriteCount();
         m_spriteEngine->updateSprites(timeStamp);
-        foreach (const QString &str, m_particles){
+        foreach (const QString &str, m_groups){
             int gIdx = m_system->m_groupIds[str];
             int count = m_system->m_groupData[gIdx]->size();
 
@@ -1199,7 +1199,7 @@ void QSGImageParticle::initialize(int gIdx, int pIdx)
             datum->animT = datum->t;
             datum->animIdx = 0;
             if (m_spriteEngine){
-                m_spriteEngine->startSprite(spriteIdx);
+                m_spriteEngine->start(spriteIdx);
                 datum->frameCount = m_spriteEngine->spriteFrames(spriteIdx);
                 datum->frameDuration = m_spriteEngine->spriteDuration(spriteIdx);
             }else{
diff --git a/src/declarative/particles/qsgimageparticle_p.h b/src/declarative/particles/qsgimageparticle_p.h
index 01eacbad99..1f87b16f63 100644
--- a/src/declarative/particles/qsgimageparticle_p.h
+++ b/src/declarative/particles/qsgimageparticle_p.h
@@ -56,7 +56,7 @@ class ImageMaterialData;
 class QSGGeometryNode;
 
 class QSGSprite;
-class QSGSpriteEngine;
+class QSGStochasticEngine;
 
 struct SimpleVertex {
     float x;
@@ -186,7 +186,7 @@ public:
 
 
     QDeclarativeListProperty<QSGSprite> sprites();
-    QSGSpriteEngine* spriteEngine() {return m_spriteEngine;}
+    QSGStochasticEngine* spriteEngine() {return m_spriteEngine;}
 
     enum EntryEffect {
         None = 0,
diff --git a/src/declarative/particles/qsgitemparticle.cpp b/src/declarative/particles/qsgitemparticle.cpp
index c330880980..2572d67783 100644
--- a/src/declarative/particles/qsgitemparticle.cpp
+++ b/src/declarative/particles/qsgitemparticle.cpp
@@ -226,7 +226,7 @@ void QSGItemParticle::prepareNextFrame()
         return;
 
     //TODO: Size, better fade?
-    foreach (const QString &str, m_particles){
+    foreach (const QString &str, m_groups){
         int gIdx = m_system->m_groupIds[str];
         int count = m_system->m_groupData[gIdx]->size();
 
diff --git a/src/declarative/particles/qsgparticleaffector.cpp b/src/declarative/particles/qsgparticleaffector.cpp
index cff3c29444..7cb4869f3e 100644
--- a/src/declarative/particles/qsgparticleaffector.cpp
+++ b/src/declarative/particles/qsgparticleaffector.cpp
@@ -59,7 +59,7 @@ QT_BEGIN_NAMESPACE
     If the Affector is a direct child of a ParticleSystem, it will automatically be associated with it.
 */
 /*!
-    \qmlproperty list<string> QtQuick.Particles2::Affector::particles
+    \qmlproperty list<string> QtQuick.Particles2::Affector::groups
     Which logical particle groups will be affected.
 
     If empty, it will affect all particles.
@@ -100,9 +100,9 @@ QT_BEGIN_NAMESPACE
     x,y are the coordinates of the affected particle, relative to the ParticleSystem.
 
 */
-//TODO: Document particle 'type'
+
 /*!
-    \qmlsignal QtQuick.Particles2::Affector::affectParticle(particle, dt)
+    \qmlsignal QtQuick.Particles2::Affector::affectParticle(particle particle, real dt)
 
     This handler is called when particles are selected to be affected.
 
@@ -113,7 +113,7 @@ QT_BEGIN_NAMESPACE
     high-volume particle systems.
 */
 /*!
-    \qmlsignal QtQuick.Particles2::Affector::affected(x, y)
+    \qmlsignal QtQuick.Particles2::Affector::affected(real x, real y)
 
     This handler is called when a particle is selected to be affected. It will
     only be called if signal is set to true.
@@ -142,12 +142,12 @@ void QSGParticleAffector::componentComplete()
 
 bool QSGParticleAffector::activeGroup(int g) {
     if (m_updateIntSet){
-        m_groups.clear();
-        foreach (const QString &p, m_particles)
-            m_groups << m_system->m_groupIds[p];//###Can this occur before group ids are properly assigned?
+        m_groupIds.clear();
+        foreach (const QString &p, m_groups)
+            m_groupIds << m_system->m_groupIds[p];//###Can this occur before group ids are properly assigned?
         m_updateIntSet = false;
     }
-    return m_groups.isEmpty() || m_groups.contains(g);
+    return m_groupIds.isEmpty() || m_groupIds.contains(g);
 }
 
 void QSGParticleAffector::affectSystem(qreal dt)
@@ -195,7 +195,7 @@ bool QSGParticleAffector::affectParticle(QSGParticleData *, qreal )
 void QSGParticleAffector::reset(QSGParticleData* pd)
 {//TODO: This, among other ones, should be restructured so they don't all need to remember to call the superclass
     if (m_onceOff)
-        if (m_groups.isEmpty() || m_groups.contains(pd->group))
+        if (m_groups.isEmpty() || m_groupIds.contains(pd->group))
             m_onceOffed.remove(qMakePair(pd->group, pd->index));
 }
 
diff --git a/src/declarative/particles/qsgparticleaffector_p.h b/src/declarative/particles/qsgparticleaffector_p.h
index 5700969aad..0dadeff6a7 100644
--- a/src/declarative/particles/qsgparticleaffector_p.h
+++ b/src/declarative/particles/qsgparticleaffector_p.h
@@ -56,7 +56,7 @@ class QSGParticleAffector : public QSGItem
 {
     Q_OBJECT
     Q_PROPERTY(QSGParticleSystem* system READ system WRITE setSystem NOTIFY systemChanged)
-    Q_PROPERTY(QStringList particles READ particles WRITE setParticles NOTIFY particlesChanged)
+    Q_PROPERTY(QStringList groups READ groups WRITE setGroups NOTIFY groupsChanged)
     Q_PROPERTY(QStringList whenCollidingWith READ whenCollidingWith WRITE setWhenCollidingWith NOTIFY whenCollidingWithChanged)
     Q_PROPERTY(bool enabled READ enabled WRITE setEnabled NOTIFY enabledChanged)
     Q_PROPERTY(bool once READ onceOff WRITE setOnceOff NOTIFY onceChanged)
@@ -71,9 +71,9 @@ public:
         return m_system;
     }
 
-    QStringList particles() const
+    QStringList groups() const
     {
-        return m_particles;
+        return m_groups;
     }
 
     bool enabled() const
@@ -100,7 +100,7 @@ signals:
 
     void systemChanged(QSGParticleSystem* arg);
 
-    void particlesChanged(QStringList arg);
+    void groupsChanged(QStringList arg);
 
     void enabledChanged(bool arg);
 
@@ -122,12 +122,12 @@ void setSystem(QSGParticleSystem* arg)
     }
 }
 
-void setParticles(QStringList arg)
+void setGroups(QStringList arg)
 {
-    if (m_particles != arg) {
-        m_particles = arg;
+    if (m_groups != arg) {
+        m_groups = arg;
         m_updateIntSet = true;
-        emit particlesChanged(arg);
+        emit groupsChanged(arg);
     }
 }
 
@@ -169,14 +169,14 @@ protected:
     virtual bool affectParticle(QSGParticleData *d, qreal dt);
     bool m_needsReset;//### What is this really saving?
     QSGParticleSystem* m_system;
-    QStringList m_particles;
+    QStringList m_groups;
     bool activeGroup(int g);
     bool m_enabled;
     virtual void componentComplete();
     QPointF m_offset;
     bool isAffectedConnected();
 private:
-    QSet<int> m_groups;
+    QSet<int> m_groupIds;
     QSet<QPair<int, int> > m_onceOffed;
     bool m_updateIntSet;
 
diff --git a/src/declarative/particles/qsgparticleemitter.cpp b/src/declarative/particles/qsgparticleemitter.cpp
index 13ab3e6185..fdba3def41 100644
--- a/src/declarative/particles/qsgparticleemitter.cpp
+++ b/src/declarative/particles/qsgparticleemitter.cpp
@@ -68,9 +68,9 @@ QT_BEGIN_NAMESPACE
     This can be omitted if the Emitter is a direct child of the ParticleSystem
 */
 /*!
-    \qmlproperty string QtQuick.Particles2::Emitter::particle
+    \qmlproperty string QtQuick.Particles2::Emitter::group
 
-    This is the type of logical particle which it will emit.
+    This is the logical particle group which it will emit into.
 
     Default value is "" (empty string).
 */
@@ -396,7 +396,7 @@ void QSGParticleEmitter::emitWindow(int timeStamp)
         pt = time;
     while ((pt < time && m_emitCap) || !m_burstQueue.isEmpty()) {
         //int pos = m_last_particle % m_particle_count;
-        QSGParticleData* datum = m_system->newDatum(m_system->m_groupIds[m_particle], !m_overwrite);
+        QSGParticleData* datum = m_system->newDatum(m_system->m_groupIds[m_group], !m_overwrite);
         if (datum){//actually emit(otherwise we've been asked to skip this one)
             datum->e = this;//###useful?
             qreal t = 1 - (pt - opt) / dt;
diff --git a/src/declarative/particles/qsgparticleemitter_p.h b/src/declarative/particles/qsgparticleemitter_p.h
index 8ed7ee7053..8bd205b207 100644
--- a/src/declarative/particles/qsgparticleemitter_p.h
+++ b/src/declarative/particles/qsgparticleemitter_p.h
@@ -61,7 +61,7 @@ class QSGParticleEmitter : public QSGItem
 {
     Q_OBJECT
     Q_PROPERTY(QSGParticleSystem* system READ system WRITE setSystem NOTIFY systemChanged)
-    Q_PROPERTY(QString particle READ particle WRITE setParticle NOTIFY particleChanged)
+    Q_PROPERTY(QString group READ group WRITE setGroup NOTIFY groupChanged)
     Q_PROPERTY(QSGParticleExtruder* shape READ extruder WRITE setExtruder NOTIFY extruderChanged)
     Q_PROPERTY(bool enabled READ enabled WRITE setEnabled NOTIFY enabledChanged)
     Q_PROPERTY(int startTime READ startTime WRITE setStartTime NOTIFY startTimeChanged)
@@ -109,9 +109,9 @@ public:
         return m_system;
     }
 
-    QString particle() const
+    QString group() const
     {
-        return m_particle;
+        return m_group;
     }
 
     int particleDurationVariation() const
@@ -130,7 +130,7 @@ signals:
 
     void systemChanged(QSGParticleSystem* arg);
 
-    void particleChanged(QString arg);
+    void groupChanged(QString arg);
 
     void particleDurationVariationChanged(int arg);
 
@@ -185,11 +185,11 @@ public slots:
         }
     }
 
-    void setParticle(QString arg)
+    void setGroup(QString arg)
     {
-        if (m_particle != arg) {
-            m_particle = arg;
-            emit particleChanged(arg);
+        if (m_group != arg) {
+            m_group = arg;
+            emit groupChanged(arg);
         }
     }
 
@@ -308,7 +308,7 @@ protected:
        int m_particleDurationVariation;
        bool m_enabled;
        QSGParticleSystem* m_system;
-       QString m_particle;
+       QString m_group;
        QSGParticleExtruder* m_extruder;
        QSGParticleExtruder* m_defaultExtruder;
        QSGParticleExtruder* effectiveExtruder();
diff --git a/src/declarative/particles/qsgparticlegroup.cpp b/src/declarative/particles/qsgparticlegroup.cpp
new file mode 100644
index 0000000000..28eb4d2c85
--- /dev/null
+++ b/src/declarative/particles/qsgparticlegroup.cpp
@@ -0,0 +1,142 @@
+/****************************************************************************
+**
+** 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 "qsgparticlegroup_p.h"
+
+/*!
+    \qmlclass ParticleGroup QSGParticleGroup
+    \inqmlmodule QtQuick.Particles 2
+    \brief ParticleGroup elements allow you to set attributes on a logical particle group.
+
+    This element allows you to set timed transitions on particle groups.
+
+    You can also use this element to group particle system elements related to the logical
+    particle group. Emitters, Affectors and Painters set as direct children of a ParticleGroup
+    will automatically apply to that logical particle group. TrailEmitters will automatically follow
+    the group.
+
+    If a ParticleGroup element is not defined for a group, the group will function normally as if
+    none of the transition properties were set.
+*/
+/*!
+    \qmlproperty ParticleSystem QtQuick.Particles2::ParticleGroup::system
+    This is the system which will contain the group.
+
+    If the ParticleGroup is a direct child of a ParticleSystem, it will automatically be associated with it.
+*/
+/*!
+    \qmlproperty string QtQuick.Particles2::ParticleGroup::name
+    This is the name of the particle group, and how it is generally referred to by other elements.
+
+    If elements refer to a name which does not have an explicit ParticleGroup created, it will
+    work normally (with no transitions specified for the group). If you do not need to assign
+    duration based transitions to a group, you do not need to create a ParticleGroup with that name (although you may).
+*/
+/*!
+    \qmlproperty int QtQuick.Particles2::ParticleGroup::duration
+    The time in milliseconds before the group will attempt to transition.
+
+*/
+/*!
+    \qmlproperty ParticleSystem QtQuick.Particles2::ParticleGroup::durationVariation
+    The maximum number of milliseconds that the duration of the transition cycle varies per particle in the group.
+
+    Default value is zero.
+*/
+/*!
+    \qmlproperty ParticleSystem QtQuick.Particles2::ParticleGroup::to
+    The weighted list of transitions valid for this group.
+
+    If the chosen transition stays in this group, another duration (+/- up to durationVariation)
+    milliseconds will occur before another transition is attempted.
+*/
+
+QSGParticleGroup::QSGParticleGroup(QObject* parent)
+    : QSGStochasticState(parent)
+{
+
+}
+
+void delayedRedirect(QDeclarativeListProperty<QObject> *prop, QObject *value)
+{
+    QSGParticleGroup* pg = qobject_cast<QSGParticleGroup*>(prop->object);
+    if (pg)
+        pg->delayRedirect(value);
+}
+
+QDeclarativeListProperty<QObject> QSGParticleGroup::particleChildren()
+{
+    QSGParticleSystem* system = qobject_cast<QSGParticleSystem*>(parent());
+    if (system)
+        return QDeclarativeListProperty<QObject>(this, 0, &QSGParticleSystem::statePropertyRedirect);
+    else
+        return QDeclarativeListProperty<QObject>(this, 0, &delayedRedirect);
+}
+
+void QSGParticleGroup::setSystem(QSGParticleSystem* arg)
+{
+    if (m_system != arg) {
+        m_system = arg;
+        m_system->registerParticleGroup(this);
+        performDelayedRedirects();
+        emit systemChanged(arg);
+    }
+}
+
+void QSGParticleGroup::delayRedirect(QObject *obj)
+{
+    m_delayedRedirects << obj;
+}
+
+void QSGParticleGroup::performDelayedRedirects()
+{
+    if (!m_system)
+        return;
+    foreach (QObject* obj, m_delayedRedirects)
+        m_system->stateRedirect(this, m_system, obj);
+
+    m_delayedRedirects.clear();
+}
+
+void QSGParticleGroup::componentComplete(){
+    if (!m_system && qobject_cast<QSGParticleSystem*>(parent()))
+        setSystem(qobject_cast<QSGParticleSystem*>(parent()));
+}
diff --git a/src/declarative/particles/qsgparticlegroup_p.h b/src/declarative/particles/qsgparticlegroup_p.h
new file mode 100644
index 0000000000..346b4ab77e
--- /dev/null
+++ b/src/declarative/particles/qsgparticlegroup_p.h
@@ -0,0 +1,107 @@
+/****************************************************************************
+**
+** 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.
+**
+**
+**
+**
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+#ifndef QSGPARTICLEGROUP
+#define QSGPARTICLEGROUP
+#include "qsgspriteengine_p.h"
+#include "qsgparticlesystem_p.h"
+#include "qdeclarativeparserstatus.h"
+
+class QSGParticleGroup : public QSGStochasticState, public QDeclarativeParserStatus
+{
+    Q_OBJECT
+    //### Would setting limits per group be useful? Or clutter the API?
+    //Q_PROPERTY(int maximumAlive READ maximumAlive WRITE setMaximumAlive NOTIFY maximumAliveChanged)
+
+    Q_PROPERTY(QSGParticleSystem* system READ system WRITE setSystem NOTIFY systemChanged)
+
+    //Intercept children requests and assign to the group & system
+    Q_PROPERTY(QDeclarativeListProperty<QObject> particleChildren READ particleChildren DESIGNABLE false)//### Hidden property for in-state system definitions - ought not to be used in actual "Sprite" states
+    Q_CLASSINFO("DefaultProperty", "particleChildren")
+
+public:
+    explicit QSGParticleGroup(QObject* parent = 0);
+
+    QDeclarativeListProperty<QObject> particleChildren();
+
+    int maximumAlive() const
+    {
+        return m_maximumAlive;
+    }
+
+    QSGParticleSystem* system() const
+    {
+        return m_system;
+    }
+
+public slots:
+
+    void setMaximumAlive(int arg)
+    {
+        if (m_maximumAlive != arg) {
+            m_maximumAlive = arg;
+            emit maximumAliveChanged(arg);
+        }
+    }
+
+    void setSystem(QSGParticleSystem* arg);
+
+    void delayRedirect(QObject* obj);
+
+signals:
+
+    void maximumAliveChanged(int arg);
+
+    void systemChanged(QSGParticleSystem* arg);
+
+protected:
+    virtual void componentComplete();
+    virtual void classBegin(){;}
+
+private:
+
+    void performDelayedRedirects();
+
+    int m_maximumAlive;
+    QSGParticleSystem* m_system;
+    QList<QObject*> m_delayedRedirects;
+};
+
+#endif
diff --git a/src/declarative/particles/qsgparticlepainter.cpp b/src/declarative/particles/qsgparticlepainter.cpp
index f4639c20a2..670c1f2118 100644
--- a/src/declarative/particles/qsgparticlepainter.cpp
+++ b/src/declarative/particles/qsgparticlepainter.cpp
@@ -58,10 +58,10 @@ QT_BEGIN_NAMESPACE
     If the ParticlePainter is a direct child of a ParticleSystem, it will automatically be associated with it.
 */
 /*!
-    \qmlproperty list<string> QtQuick.Particles2::ParticlePainter::particles
+    \qmlproperty list<string> QtQuick.Particles2::ParticlePainter::groups
     Which logical particle groups will be painted.
 
-    If empty, it will paint the default particle ("").
+    If empty, it will paint the default particle group ("").
 */
 QSGParticlePainter::QSGParticlePainter(QSGItem *parent) :
     QSGItem(parent),
@@ -144,7 +144,7 @@ void QSGParticlePainter::calcSystemOffset(bool resetPending)
     m_systemOffset = -1 * this->mapFromItem(m_system, QPointF(0.0, 0.0));
     if (lastOffset != m_systemOffset && !resetPending){
         //Reload all particles//TODO: Necessary?
-        foreach (const QString &g, m_particles){
+        foreach (const QString &g, m_groups){
             int gId = m_system->m_groupIds[g];
             foreach (QSGParticleData* d, m_system->m_groupData[gId]->data)
                 reload(d);
diff --git a/src/declarative/particles/qsgparticlepainter_p.h b/src/declarative/particles/qsgparticlepainter_p.h
index 08ae3aede8..d469947453 100644
--- a/src/declarative/particles/qsgparticlepainter_p.h
+++ b/src/declarative/particles/qsgparticlepainter_p.h
@@ -58,7 +58,7 @@ class QSGParticlePainter : public QSGItem
 {
     Q_OBJECT
     Q_PROPERTY(QSGParticleSystem* system READ system WRITE setSystem NOTIFY systemChanged)
-    Q_PROPERTY(QStringList particles READ particles WRITE setParticles NOTIFY particlesChanged)
+    Q_PROPERTY(QStringList groups READ groups WRITE setGroups NOTIFY groupsChanged)
 
 public:
     explicit QSGParticlePainter(QSGItem *parent = 0);
@@ -74,25 +74,25 @@ public:
     }
 
 
-    QStringList particles() const
+    QStringList groups() const
     {
-        return m_particles;
+        return m_groups;
     }
 
 signals:
     void countChanged();
     void systemChanged(QSGParticleSystem* arg);
 
-    void particlesChanged(QStringList arg);
+    void groupsChanged(QStringList arg);
 
 public slots:
 void setSystem(QSGParticleSystem* arg);
 
-void setParticles(QStringList arg)
+void setGroups(QStringList arg)
 {
-    if (m_particles != arg) {
-        m_particles = arg;
-        emit particlesChanged(arg);
+    if (m_groups != arg) {
+        m_groups = arg;
+        emit groupsChanged(arg);
     }
 }
 
@@ -121,7 +121,7 @@ protected:
     friend class QSGParticleSystem;
     int m_count;
     bool m_pleaseReset;
-    QStringList m_particles;
+    QStringList m_groups;
     QPointF m_systemOffset;
 
 private:
diff --git a/src/declarative/particles/qsgparticlesmodule.cpp b/src/declarative/particles/qsgparticlesmodule.cpp
index 9fa0ebad97..f880842acb 100644
--- a/src/declarative/particles/qsgparticlesmodule.cpp
+++ b/src/declarative/particles/qsgparticlesmodule.cpp
@@ -67,6 +67,7 @@
 #include "qsgcumulativedirection_p.h"
 #include "qsgcustomaffector_p.h"
 #include "qsgrectangleextruder_p.h"
+#include "qsgparticlegroup_p.h"
 
 QT_BEGIN_NAMESPACE
 
@@ -75,6 +76,7 @@ void QSGParticlesModule::defineModule()
     const char* uri = "QtQuick.Particles";
 
     qmlRegisterType<QSGParticleSystem>(uri, 2, 0, "ParticleSystem");
+    qmlRegisterType<QSGParticleGroup>(uri, 2, 0, "ParticleGroup");
 
     qmlRegisterType<QSGImageParticle>(uri, 2, 0, "ImageParticle");
     qmlRegisterType<QSGCustomParticle>(uri, 2, 0, "CustomParticle");
diff --git a/src/declarative/particles/qsgparticlesystem.cpp b/src/declarative/particles/qsgparticlesystem.cpp
index 085e6afe64..bc27073142 100644
--- a/src/declarative/particles/qsgparticlesystem.cpp
+++ b/src/declarative/particles/qsgparticlesystem.cpp
@@ -47,6 +47,7 @@
 #include "qsgspriteengine_p.h"
 #include "qsgsprite_p.h"
 #include "qsgv8particledata_p.h"
+#include "qsgparticlegroup_p.h"
 
 #include "qsgtrailemitter_p.h"//###For auto-follow on states, perhaps should be in emitter?
 #include <private/qdeclarativeengine_p.h>
@@ -549,8 +550,8 @@ void QSGParticleData::debugDump()
 {
     qDebug() << "Particle" << systemIndex << group << "/" << index << stillAlive()
              << "Pos: " << x << "," << y
-             //<< "Vel: " << vx << "," << sy
-             //<< "Acc: " << ax << "," << ay
+             << "Vel: " << vx << "," << vy
+             << "Acc: " << ax << "," << ay
              << "Size: " << size << "," << endSize
              << "Time: " << t << "," <<lifeSpan << ";" << (system->m_timeInt / 1000.0) ;
 }
@@ -559,7 +560,6 @@ bool QSGParticleData::stillAlive()
 {
     if (!system)
         return false;
-    //fprintf(stderr, "%.9lf %.9lf\n",((qreal)system->m_timeInt/1000.0), (t+lifeSpan));
     return (t + lifeSpan - EPSILON) > ((qreal)system->m_timeInt/1000.0);
 }
 
@@ -601,7 +601,7 @@ void QSGParticleData::extendLife(float time)
 
 QSGParticleSystem::QSGParticleSystem(QSGItem *parent) :
     QSGItem(parent), m_particle_count(0), m_running(true), m_paused(false)
-  , m_nextIndex(0), m_componentComplete(false), m_spriteEngine(0)
+  , m_nextIndex(0), m_componentComplete(false), m_stateEngine(0)
 {
     connect(&m_painterMapper, SIGNAL(mapped(QObject*)),
             this, SLOT(loadPainter(QObject*)));
@@ -630,16 +630,11 @@ void QSGParticleSystem::initGroups()
     m_nextGroupId = 1;
 }
 
-    QDeclarativeListProperty<QSGSprite> QSGParticleSystem::particleStates()
-{
-    return QDeclarativeListProperty<QSGSprite>(this, &m_states, spriteAppend, spriteCount, spriteAt, spriteClear);
-}
-
 void QSGParticleSystem::registerParticlePainter(QSGParticlePainter* p)
 {
     //TODO: a way to Unregister emitters, painters and affectors
     m_painters << QPointer<QSGParticlePainter>(p);//###Set or uniqueness checking?
-    connect(p, SIGNAL(particlesChanged(QStringList)),
+    connect(p, SIGNAL(groupsChanged(QStringList)),
             &m_painterMapper, SLOT(map()));
     loadPainter(p);
 }
@@ -649,7 +644,7 @@ void QSGParticleSystem::registerParticleEmitter(QSGParticleEmitter* e)
     m_emitters << QPointer<QSGParticleEmitter>(e);//###How to get them out?
     connect(e, SIGNAL(particleCountChanged()),
             this, SLOT(emittersChanged()));
-    connect(e, SIGNAL(particleChanged(QString)),
+    connect(e, SIGNAL(groupChanged(QString)),
             this, SLOT(emittersChanged()));
     emittersChanged();
     e->reset();//Start, so that starttime factors appropriately
@@ -660,6 +655,12 @@ void QSGParticleSystem::registerParticleAffector(QSGParticleAffector* a)
     m_affectors << QPointer<QSGParticleAffector>(a);
 }
 
+void QSGParticleSystem::registerParticleGroup(QSGParticleGroup* g)
+{
+    m_groups << QPointer<QSGParticleGroup>(g);
+    createEngine();
+}
+
 void QSGParticleSystem::setRunning(bool arg)
 {
     if (m_running != arg) {
@@ -685,40 +686,45 @@ void QSGParticleSystem::setPaused(bool arg){
     }
 }
 
-void QSGParticleSystem::stateRedirect(QDeclarativeListProperty<QObject> *prop, QObject *value)
+void QSGParticleSystem::statePropertyRedirect(QDeclarativeListProperty<QObject> *prop, QObject *value)
 {
     //Hooks up automatic state-associated stuff
     QSGParticleSystem* sys = qobject_cast<QSGParticleSystem*>(prop->object->parent());
-    QSGSprite* sprite = qobject_cast<QSGSprite*>(prop->object);
-    if (!sprite || !sys)
+    QSGParticleGroup* group = qobject_cast<QSGParticleGroup*>(prop->object);
+    if (!group || !sys || !value)
         return;
+    stateRedirect(group, sys, value);
+}
+
+void QSGParticleSystem::stateRedirect(QSGParticleGroup* group, QSGParticleSystem* sys, QObject *value)
+{
     QStringList list;
-    list << sprite->name();
+    list << group->name();
     QSGParticleAffector* a = qobject_cast<QSGParticleAffector*>(value);
     if (a){
         a->setParentItem(sys);
-        a->setParticles(list);
+        a->setGroups(list);
         a->setSystem(sys);
         return;
     }
     QSGTrailEmitter* fe = qobject_cast<QSGTrailEmitter*>(value);
     if (fe){
         fe->setParentItem(sys);
-        fe->setFollow(sprite->name());
+        fe->setFollow(group->name());
         fe->setSystem(sys);
         return;
     }
     QSGParticleEmitter* e = qobject_cast<QSGParticleEmitter*>(value);
     if (e){
         e->setParentItem(sys);
-        e->setParticle(sprite->name());
+        e->setGroup(group->name());
         e->setSystem(sys);
         return;
     }
     QSGParticlePainter* p = qobject_cast<QSGParticlePainter*>(value);
     if (p){
         p->setParentItem(sys);
-        p->setParticles(list);
+        p->setGroups(list);
         p->setSystem(sys);
         return;
     }
@@ -785,14 +791,14 @@ void QSGParticleSystem::loadPainter(QObject *p)
     foreach (QSGParticleGroupData* sg, m_groupData)
         sg->painters.remove(painter);
     int particleCount = 0;
-    if (painter->particles().isEmpty()){//Uses default particle
+    if (painter->groups().isEmpty()){//Uses default particle
         QStringList def;
         def << "";
-        painter->setParticles(def);
+        painter->setGroups(def);
         particleCount += m_groupData[0]->size();
         m_groupData[0]->painters << painter;
     }else{
-        foreach (const QString &group, painter->particles()){
+        foreach (const QString &group, painter->groups()){
             if (group != QLatin1String("") && !m_groupIds[group]){//new group
                 int id = m_nextGroupId++;
                 QSGParticleGroupData* gd = new QSGParticleGroupData(id, this);
@@ -824,16 +830,16 @@ void QSGParticleSystem::emittersChanged()
     }
 
     foreach (QSGParticleEmitter* e, m_emitters){//Populate groups and set sizes.
-        if (!m_groupIds.contains(e->particle())
-                || (!e->particle().isEmpty() && !m_groupIds[e->particle()])){//or it was accidentally inserted by a failed lookup earlier
+        if (!m_groupIds.contains(e->group())
+                || (!e->group().isEmpty() && !m_groupIds[e->group()])){//or it was accidentally inserted by a failed lookup earlier
             int id = m_nextGroupId++;
             QSGParticleGroupData* gd = new QSGParticleGroupData(id, this);
-            m_groupIds.insert(e->particle(), id);
+            m_groupIds.insert(e->group(), id);
             m_groupData.insert(id, gd);
             previousSizes << 0;
             newSizes << 0;
         }
-        newSizes[m_groupIds[e->particle()]] += e->particleCount();
+        newSizes[m_groupIds[e->group()]] += e->particleCount();
         //###: Cull emptied groups?
     }
 
@@ -850,7 +856,7 @@ void QSGParticleSystem::emittersChanged()
     foreach (QSGParticlePainter *p, m_painters)
         loadPainter(p);
 
-    if (!m_states.isEmpty())
+    if (!m_groups.isEmpty())
         createEngine();
 
     if (m_debugMode)
@@ -861,58 +867,63 @@ void QSGParticleSystem::createEngine()
 {
     if (!m_componentComplete)
         return;
+    if (m_stateEngine && m_debugMode)
+        qDebug() << "Resetting Existing Sprite Engine...";
     //### Solve the losses if size/states go down
-    foreach (QSGSprite* sprite, m_states){
+    foreach (QSGParticleGroup* group, m_groups){
         bool exists = false;
         foreach (const QString &name, m_groupIds.keys())
-            if (sprite->name() == name)
+            if (group->name() == name)
                 exists = true;
         if (!exists){
             int id = m_nextGroupId++;
             QSGParticleGroupData* gd = new QSGParticleGroupData(id, this);
-            m_groupIds.insert(sprite->name(), id);
+            m_groupIds.insert(group->name(), id);
             m_groupData.insert(id, gd);
         }
     }
 
-    if (m_states.count()){
-        //Reorder Sprite List so as to have the same order as groups
-        QList<QSGSprite*> newList;
+    if (m_groups.count()){
+        //Reorder groups List so as to have the same order as groupData
+        QList<QSGParticleGroup*> newList;
         for (int i=0; i<m_nextGroupId; i++){
             bool exists = false;
             QString name = m_groupData[i]->name();
-            foreach (QSGSprite* existing, m_states){
+            foreach (QSGParticleGroup* existing, m_groups){
                 if (existing->name() == name){
                     newList << existing;
                     exists = true;
                 }
             }
             if (!exists){
-                newList << new QSGSprite(this);
+                newList << new QSGParticleGroup(this);
                 newList.back()->setName(name);
             }
         }
-        m_states = newList;
+        m_groups = newList;
+        QList<QSGStochasticState*> states;
+        foreach (QSGParticleGroup* g, m_groups)
+            states << (QSGStochasticState*)g;
 
-        if (!m_spriteEngine)
-            m_spriteEngine = new QSGSpriteEngine(this);
-        m_spriteEngine->setCount(m_particle_count);
-        m_spriteEngine->m_states = m_states;
+        if (!m_stateEngine)
+            m_stateEngine = new QSGStochasticEngine(this);
+        m_stateEngine->setCount(m_particle_count);
+        m_stateEngine->m_states = states;
 
-        connect(m_spriteEngine, SIGNAL(stateChanged(int)),
+        connect(m_stateEngine, SIGNAL(stateChanged(int)),
                 this, SLOT(particleStateChange(int)));
 
     }else{
-        if (m_spriteEngine)
-            delete m_spriteEngine;
-        m_spriteEngine = 0;
+        if (m_stateEngine)
+            delete m_stateEngine;
+        m_stateEngine = 0;
     }
 
 }
 
 void QSGParticleSystem::particleStateChange(int idx)
 {
-    moveGroups(m_bySysIdx[idx], m_spriteEngine->spriteState(idx));
+    moveGroups(m_bySysIdx[idx], m_stateEngine->curState(idx));
 }
 
 void QSGParticleSystem::moveGroups(QSGParticleData *d, int newGIdx)
@@ -934,8 +945,8 @@ int QSGParticleSystem::nextSystemIndex()
     }
     if (m_nextIndex >= m_bySysIdx.size()){
         m_bySysIdx.resize(m_bySysIdx.size() < 10 ? 10 : m_bySysIdx.size()*1.1);//###+1,10%,+10? Choose something non-arbitrarily
-        if (m_spriteEngine)
-            m_spriteEngine->setCount(m_bySysIdx.size());
+        if (m_stateEngine)
+            m_stateEngine->setCount(m_bySysIdx.size());
 
     }
     return m_nextIndex++;
@@ -954,8 +965,8 @@ QSGParticleData* QSGParticleSystem::newDatum(int groupId, bool respectLimits, in
             ret->systemIndex = nextSystemIndex();
     }else{
         if (ret->systemIndex != -1){
-            if (m_spriteEngine)
-                m_spriteEngine->stopSprite(ret->systemIndex);
+            if (m_stateEngine)
+                m_stateEngine->stop(ret->systemIndex);
             m_reusableIndexes << ret->systemIndex;
             m_bySysIdx[ret->systemIndex] = 0;
         }
@@ -963,8 +974,8 @@ QSGParticleData* QSGParticleSystem::newDatum(int groupId, bool respectLimits, in
     }
     m_bySysIdx[ret->systemIndex] = ret;
 
-    if (m_spriteEngine)
-        m_spriteEngine->startSprite(ret->systemIndex, ret->group);
+    if (m_stateEngine)
+        m_stateEngine->start(ret->systemIndex, ret->group);
 
     m_empty = false;
     return ret;
@@ -1011,8 +1022,8 @@ void QSGParticleSystem::updateCurrentTime( int currentTime )
     foreach (QSGParticleGroupData* gd, m_groupData)//Recycle all groups and see if they're out of live particles
         m_empty = gd->recycle() && m_empty;
 
-    if (m_spriteEngine)
-        m_spriteEngine->updateSprites(m_timeInt);
+    if (m_stateEngine)
+        m_stateEngine->updateSprites(m_timeInt);
 
     foreach (QSGParticleEmitter* emitter, m_emitters)
         if (emitter)
diff --git a/src/declarative/particles/qsgparticlesystem_p.h b/src/declarative/particles/qsgparticlesystem_p.h
index 25a0c87f53..f531e7fcf9 100644
--- a/src/declarative/particles/qsgparticlesystem_p.h
+++ b/src/declarative/particles/qsgparticlesystem_p.h
@@ -65,9 +65,10 @@ class QSGParticleEmitter;
 class QSGParticlePainter;
 class QSGParticleData;
 class QSGParticleSystemAnimation;
-class QSGSpriteEngine;
+class QSGStochasticEngine;
 class QSGSprite;
 class QSGV8ParticleData;
+class QSGParticleGroup;
 
 struct QSGParticleDataHeapNode{
     int time;//in ms
@@ -223,12 +224,10 @@ class QSGParticleSystem : public QSGItem
     Q_PROPERTY(bool running READ isRunning WRITE setRunning NOTIFY runningChanged)
     Q_PROPERTY(bool paused READ isPaused WRITE setPaused NOTIFY pausedChanged)
     Q_PROPERTY(bool empty READ isEmpty NOTIFY emptyChanged)
-    Q_PROPERTY(QDeclarativeListProperty<QSGSprite> particleStates READ particleStates)
 
 public:
     explicit QSGParticleSystem(QSGItem *parent = 0);
     ~QSGParticleSystem();
-    QDeclarativeListProperty<QSGSprite> particleStates();
 
     //TODO: Hook up running and temporal manipulators to the animation
     bool isRunning() const
@@ -286,7 +285,7 @@ public://###but only really for related class usage. Perhaps we should all be fr
     QVector<QSGParticleData*> m_bySysIdx; //Another reference to the data (data owned by group), but by sysIdx
     QHash<QString, int> m_groupIds;
     QHash<int, QSGParticleGroupData*> m_groupData;
-    QSGSpriteEngine* m_spriteEngine;
+    QSGStochasticEngine* m_stateEngine;
 
     int m_timeInt;
     bool m_initialized;
@@ -294,9 +293,11 @@ public://###but only really for related class usage. Perhaps we should all be fr
     void registerParticlePainter(QSGParticlePainter* p);
     void registerParticleEmitter(QSGParticleEmitter* e);
     void registerParticleAffector(QSGParticleAffector* a);
+    void registerParticleGroup(QSGParticleGroup* g);
 
     int m_particle_count;
-    static void stateRedirect(QDeclarativeListProperty<QObject> *prop, QObject *value);//From QSGSprite
+    static void statePropertyRedirect(QDeclarativeListProperty<QObject> *prop, QObject *value);
+    static void stateRedirect(QSGParticleGroup* group, QSGParticleSystem* sys, QObject *value);
     bool isPaused() const
     {
         return m_paused;
@@ -315,11 +316,11 @@ private:
     QList<QPointer<QSGParticleAffector> > m_affectors;
     QList<QPointer<QSGParticlePainter> > m_painters;
     QList<QPointer<QSGParticlePainter> > m_syncList;
+    QList<QSGParticleGroup*> m_groups;
     int m_nextGroupId;
     int m_nextIndex;
     QSet<int> m_reusableIndexes;
     bool m_componentComplete;
-    QList<QSGSprite*> m_states;
 
     QSignalMapper m_painterMapper;
     QSignalMapper m_emitterMapper;
diff --git a/src/declarative/particles/qsgspritegoal.cpp b/src/declarative/particles/qsgspritegoal.cpp
index 1837167813..ec2be02326 100644
--- a/src/declarative/particles/qsgspritegoal.cpp
+++ b/src/declarative/particles/qsgspritegoal.cpp
@@ -64,16 +64,12 @@ QT_BEGIN_NAMESPACE
     \qmlproperty bool QtQuick.Particles2::SpriteGoal::systemStates
 */
 
-    Q_PROPERTY(QString goalState READ goalState WRITE setGoalState NOTIFY goalStateChanged)
-    Q_PROPERTY(bool jump READ jump WRITE setJump NOTIFY jumpChanged)
-    Q_PROPERTY(bool systemStates READ systemStates WRITE setSystemStates NOTIFY systemStatesChanged)
-
 QSGSpriteGoalAffector::QSGSpriteGoalAffector(QSGItem *parent) :
     QSGParticleAffector(parent), m_goalIdx(-1), m_jump(false), m_systemStates(false), m_lastEngine(0), m_notUsingEngine(false)
 {
 }
 
-void QSGSpriteGoalAffector::updateStateIndex(QSGSpriteEngine* e)
+void QSGSpriteGoalAffector::updateStateIndex(QSGStochasticEngine* e)
 {
     if (m_systemStates){
         m_goalIdx = m_system->m_groupIds[m_goalState];
@@ -104,14 +100,14 @@ void QSGSpriteGoalAffector::setGoalState(QString arg)
 bool QSGSpriteGoalAffector::affectParticle(QSGParticleData *d, qreal dt)
 {
     Q_UNUSED(dt);
-    QSGSpriteEngine *engine = 0;
+    QSGStochasticEngine *engine = 0;
     if (!m_systemStates){
         //TODO: Affect all engines
         foreach (QSGParticlePainter *p, m_system->m_groupData[d->group]->painters)
             if (qobject_cast<QSGImageParticle*>(p))
                 engine = qobject_cast<QSGImageParticle*>(p)->spriteEngine();
     }else{
-        engine = m_system->m_spriteEngine;
+        engine = m_system->m_stateEngine;
         if (!engine)
             m_notUsingEngine = true;
     }
@@ -126,7 +122,7 @@ bool QSGSpriteGoalAffector::affectParticle(QSGParticleData *d, qreal dt)
     if (m_notUsingEngine){//systemStates && no stochastic states defined. So cut out the engine
         //TODO: It's possible to move to a group that is intermediate and not used by painters or emitters - but right now that will redirect to the default group
         m_system->moveGroups(d, m_goalIdx);
-    }else if (engine->spriteState(index) != m_goalIdx){
+    }else if (engine->curState(index) != m_goalIdx){
         engine->setGoal(m_goalIdx, index, m_jump);
         emit affected(QPointF(d->curX(), d->curY()));//###Expensive if unconnected? Move to Affector?
         return true; //Doesn't affect particle data, but necessary for onceOff
diff --git a/src/declarative/particles/qsgspritegoal_p.h b/src/declarative/particles/qsgspritegoal_p.h
index 7c799b13b1..043970b90b 100644
--- a/src/declarative/particles/qsgspritegoal_p.h
+++ b/src/declarative/particles/qsgspritegoal_p.h
@@ -49,7 +49,7 @@ QT_BEGIN_NAMESPACE
 
 QT_MODULE(Declarative)
 
-class QSGSpriteEngine;
+class QSGStochasticEngine;
 
 class QSGSpriteGoalAffector : public QSGParticleAffector
 {
@@ -106,10 +106,10 @@ void setSystemStates(bool arg)
 }
 
 private:
-    void updateStateIndex(QSGSpriteEngine* e);
+    void updateStateIndex(QSGStochasticEngine* e);
     QString m_goalState;
     int m_goalIdx;
-    QSGSpriteEngine* m_lastEngine;
+    QSGStochasticEngine* m_lastEngine;
     bool m_jump;
     bool m_systemStates;
 
diff --git a/src/declarative/particles/qsgtrailemitter.cpp b/src/declarative/particles/qsgtrailemitter.cpp
index 427b587caf..5a19ac508b 100644
--- a/src/declarative/particles/qsgtrailemitter.cpp
+++ b/src/declarative/particles/qsgtrailemitter.cpp
@@ -166,7 +166,7 @@ void QSGTrailEmitter::emitWindow(int timeStamp)
     qreal sizeAtEnd = m_particleEndSize >= 0 ? m_particleEndSize : m_particleSize;
 
     int gId = m_system->m_groupIds[m_follow];
-    int gId2 = m_system->m_groupIds[m_particle];
+    int gId2 = m_system->m_groupIds[m_group];
     foreach (QSGParticleData *d, m_system->m_groupData[gId]->data){
         if (!d || !d->stillAlive()){
             m_lastEmission[d->index] = time; //Should only start emitting when it returns to life
diff --git a/src/declarative/particles/qsgtrailemitter_p.h b/src/declarative/particles/qsgtrailemitter_p.h
index 5ab6f24270..009ccd508c 100644
--- a/src/declarative/particles/qsgtrailemitter_p.h
+++ b/src/declarative/particles/qsgtrailemitter_p.h
@@ -94,7 +94,7 @@ public:
     }
 
 signals:
-    void emitFollowParticle(QDeclarativeV8Handle particle, QDeclarativeV8Handle followed);
+    void emitFollowParticle(QDeclarativeV8Handle group, QDeclarativeV8Handle followed);
 
     void particlesPerParticlePerSecondChanged(int arg);