Particles: code clean-up.

Replace QHash<int, QQuickParticleGroupData*> groupData with a
QVarLengthArray, and make sure that those integers (== indices) are
continuous, re-used, and start at zero. That way a whole bunch of qhash
calls, hash node creatrion/deletion, and other overhead is removed.

Change-Id: Ie74fab8a3e3c7b6efa15b7b9ceff1d1a3e9820e9
Reviewed-by: Lars Knoll <lars.knoll@theqtcompany.com>
Reviewed-by: Robin Burchell <robin.burchell@viroteck.net>

6 files changed, 69 insertions, 36 deletions

diff --git a/src/particles/qquickcustomaffector.cpp b/src/particles/qquickcustomaffector.cpp
index 55310f92d5..6f50c17287 100644
--- a/src/particles/qquickcustomaffector.cpp
+++ b/src/particles/qquickcustomaffector.cpp
@@ -122,11 +122,15 @@ void QQuickCustomAffector::affectSystem(qreal dt)
     updateOffsets();
 
     QList<QQuickParticleData*> toAffect;
-    foreach (QQuickParticleGroupData* gd, m_system->groupData)
-        if (activeGroup(m_system->groupData.key(gd)))
-            foreach (QQuickParticleData* d, gd->data)
-                if (shouldAffect(d))
+    foreach (QQuickParticleGroupData* gd, m_system->groupData) {
+        if (activeGroup(gd->index)) {
+            foreach (QQuickParticleData* d, gd->data) {
+                if (shouldAffect(d)) {
                     toAffect << d;
+                }
+            }
+        }
+    }
 
     if (toAffect.isEmpty())
         return;
diff --git a/src/particles/qquickitemparticle.cpp b/src/particles/qquickitemparticle.cpp
index 86dc04ea5a..4cd8ee9db8 100644
--- a/src/particles/qquickitemparticle.cpp
+++ b/src/particles/qquickitemparticle.cpp
@@ -278,7 +278,7 @@ void QQuickItemParticle::prepareNextFrame()
     //TODO: Size, better fade?
     foreach (const QString &str, m_groups){
         const int gIdx = m_system->groupIds[str];
-        const QVector<QQuickParticleData*> dataVector = m_system->groupData.value(gIdx)->data;
+        const QVector<QQuickParticleData*> dataVector = m_system->groupData[gIdx]->data;
         const int count = dataVector.size();
 
         for (int i=0; i<count; i++){
diff --git a/src/particles/qquickparticleaffector.cpp b/src/particles/qquickparticleaffector.cpp
index 139b0d9bbe..1878908a5d 100644
--- a/src/particles/qquickparticleaffector.cpp
+++ b/src/particles/qquickparticleaffector.cpp
@@ -200,7 +200,7 @@ void QQuickParticleAffector::affectSystem(qreal dt)
     if (m_onceOff)
         dt = 1.0;
     foreach (QQuickParticleGroupData* gd, m_system->groupData) {
-        if (activeGroup(m_system->groupData.key(gd))) {
+        if (activeGroup(gd->index)) {
             foreach (QQuickParticleData* d, gd->data) {
                 if (shouldAffect(d)) {
                     bool affected = false;
diff --git a/src/particles/qquickparticlesystem.cpp b/src/particles/qquickparticlesystem.cpp
index 603515dc66..c0306e9025 100644
--- a/src/particles/qquickparticlesystem.cpp
+++ b/src/particles/qquickparticlesystem.cpp
@@ -330,7 +330,10 @@ void QQuickParticleDataHeap::bubbleDown(int idx)//tends to be called log n times
     }
 }
 
-QQuickParticleGroupData::QQuickParticleGroupData(int id, QQuickParticleSystem* sys):index(id),m_size(0),m_system(sys)
+QQuickParticleGroupData::QQuickParticleGroupData(const QString &name, QQuickParticleSystem* sys)
+    : index(sys->registerParticleGroupData(name, this))
+    , m_size(0)
+    , m_system(sys)
 {
     initList();
 }
@@ -703,6 +706,7 @@ void QQuickParticleData::extendLife(float time)
 QQuickParticleSystem::QQuickParticleSystem(QQuickItem *parent) :
     QQuickItem(parent),
     stateEngine(0),
+    nextFreeGroupId(0),
     m_animation(0),
     m_running(true),
     initialized(0),
@@ -732,11 +736,11 @@ void QQuickParticleSystem::initGroups()
     qDeleteAll(groupData);
     groupData.clear();
     groupIds.clear();
+    nextFreeGroupId = 0;
 
-    QQuickParticleGroupData* gd = new QQuickParticleGroupData(0, this);//Default group
-    groupData.insert(0,gd);
-    groupIds.insert(QString(), 0);
-    m_nextGroupId = 1;
+    QQuickParticleGroupData *pd = new QQuickParticleGroupData(QString(), this); // Default group
+    Q_ASSERT(pd->index == 0);
+    Q_UNUSED(pd);
 }
 
 void QQuickParticleSystem::registerParticlePainter(QQuickParticlePainter* p)
@@ -848,6 +852,34 @@ void QQuickParticleSystem::stateRedirect(QQuickParticleGroup* group, QQuickParti
     qWarning() << value << " was placed inside a particle system state but cannot be taken into the particle system. It will be lost.";
 }
 
+
+int QQuickParticleSystem::registerParticleGroupData(const QString &name, QQuickParticleGroupData *pgd)
+{
+    Q_ASSERT(!groupIds.contains(name));
+    int id;
+    if (nextFreeGroupId >= groupData.size()) {
+        groupData.push_back(pgd);
+        nextFreeGroupId = groupData.size();
+        id = nextFreeGroupId - 1;
+    } else {
+        id = nextFreeGroupId;
+        groupData[id] = pgd;
+        searchNextFreeGroupId();
+    }
+    groupIds.insert(name, id);
+    return id;
+}
+
+void QQuickParticleSystem::searchNextFreeGroupId()
+{
+    ++nextFreeGroupId;
+    for (int ei = groupData.size(); nextFreeGroupId != ei; ++nextFreeGroupId) {
+        if (groupData[nextFreeGroupId] == nullptr) {
+            return;
+        }
+    }
+}
+
 void QQuickParticleSystem::componentComplete()
 
 {
@@ -917,11 +949,8 @@ void QQuickParticleSystem::loadPainter(QObject *p)
         groupData[0]->painters << painter;
     } else {
         foreach (const QString &group, painter->groups()) {
-            if (group != QLatin1String("") && !groupIds[group]) {//new group
-                int id = m_nextGroupId++;
-                QQuickParticleGroupData* gd = new QQuickParticleGroupData(id, this);
-                groupIds.insert(group, id);
-                groupData.insert(id, gd);
+            if (!group.isEmpty() && !groupIds.contains(group)) {//new group
+                new QQuickParticleGroupData(group, this);
             }
             particleCount += groupData[groupIds[group]]->size();
             groupData[groupIds[group]]->painters << painter;
@@ -939,9 +968,9 @@ void QQuickParticleSystem::emittersChanged()
 
     QVector<int> previousSizes;
     QVector<int> newSizes;
-    previousSizes.reserve(m_nextGroupId);
-    newSizes.reserve(m_nextGroupId);
-    for (int i=0; i<m_nextGroupId; i++) {
+    previousSizes.reserve(groupData.size());
+    newSizes.reserve(groupData.size());
+    for (int i = 0, ei = groupData.size(); i != ei; ++i) {
         previousSizes << groupData[i]->size();
         newSizes << 0;
     }
@@ -957,10 +986,7 @@ void QQuickParticleSystem::emittersChanged()
 
         if (!e->group().isEmpty() &&
             !groupIds.contains(e->group())) {
-            int id = m_nextGroupId++;
-            QQuickParticleGroupData* gd = new QQuickParticleGroupData(id, this);
-            groupIds.insert(e->group(), id);
-            groupData.insert(id, gd);
+            new QQuickParticleGroupData(e->group(), this);
             previousSizes << 0;
             newSizes << 0;
         }
@@ -970,13 +996,13 @@ void QQuickParticleSystem::emittersChanged()
 
     //TODO: Garbage collection?
     particleCount = 0;
-    for (int i=0; i<m_nextGroupId; i++) {
+    for (int i = 0, ei = groupData.size(); i != ei; ++i) {
         groupData[i]->setSize(qMax(newSizes[i], previousSizes[i]));
         particleCount += groupData[i]->size();
     }
 
     if (m_debugMode)
-        qDebug() << "Particle system emitters changed. New particle count: " << particleCount;
+        qDebug() << "Particle system emitters changed. New particle count: " << particleCount << "in" << groupData.size() << "groups.";
 
     if (particleCount > bySysIdx.size())//New datum requests haven't updated it
         bySysIdx.resize(particleCount);
@@ -1008,17 +1034,15 @@ void QQuickParticleSystem::createEngine()
             }
         }
         if (!exists) {
-            int id = m_nextGroupId++;
-            QQuickParticleGroupData* gd = new QQuickParticleGroupData(id, this);
-            groupIds.insert(group->name(), id);
-            groupData.insert(id, gd);
+            new QQuickParticleGroupData(group->name(), this);
         }
     }
 
     if (m_groups.count()) {
         //Reorder groups List so as to have the same order as groupData
+        // TODO: can't we just merge the two lists?
         QList<QQuickParticleGroup*> newList;
-        for (int i=0; i<m_nextGroupId; i++) {
+        for (int i = 0, ei = groupData.size(); i != ei; ++i) {
             bool exists = false;
             QString name = groupData[i]->name();
             foreach (QQuickParticleGroup* existing, m_groups) {
diff --git a/src/particles/qquickparticlesystem_p.h b/src/particles/qquickparticlesystem_p.h
index 5a1ab5022d..7805f87094 100644
--- a/src/particles/qquickparticlesystem_p.h
+++ b/src/particles/qquickparticlesystem_p.h
@@ -111,7 +111,7 @@ private:
 
 class Q_QUICKPARTICLES_PRIVATE_EXPORT QQuickParticleGroupData {
 public:
-    QQuickParticleGroupData(int id, QQuickParticleSystem* sys);
+    QQuickParticleGroupData(const QString &name, QQuickParticleSystem* sys);
     ~QQuickParticleGroupData();
 
     int size();
@@ -119,7 +119,7 @@ public:
 
     void setSize(int newSize);
 
-    int index;
+    const int index;
     QSet<QQuickParticlePainter*> painters;//TODO: What if they are dynamically removed?
 
     //TODO: Refactor particle data list out into a separate class
@@ -317,10 +317,13 @@ public:
     //Data members here for ease of related class and auto-test usage. Not "public" API. TODO: d_ptrize
     QSet<QQuickParticleData*> needsReset;
     QVector<QQuickParticleData*> bySysIdx; //Another reference to the data (data owned by group), but by sysIdx
-    QHash<QString, int> groupIds;
-    QHash<int, QQuickParticleGroupData*> groupData;
     QQuickStochasticEngine* stateEngine;
 
+    QHash<QString, int> groupIds;
+    QVarLengthArray<QQuickParticleGroupData*, 32> groupData;
+    int nextFreeGroupId;
+    int registerParticleGroupData(const QString &name, QQuickParticleGroupData *pgd);
+
     //Also only here for auto-test usage
     void updateCurrentTime( int currentTime );
     QQuickParticleSystemAnimation* m_animation;
@@ -349,6 +352,9 @@ public:
     }
 
 private:
+    void searchNextFreeGroupId();
+
+private:
     void initializeSystem();
     void initGroups();
     QList<QPointer<QQuickParticleEmitter> > m_emitters;
@@ -356,7 +362,6 @@ private:
     QList<QPointer<QQuickParticlePainter> > m_painters;
     QList<QPointer<QQuickParticlePainter> > m_syncList;
     QList<QQuickParticleGroup*> m_groups;
-    int m_nextGroupId;
     int m_nextIndex;
     QSet<int> m_reusableIndexes;
     bool m_componentComplete;
diff --git a/src/particles/qquickturbulence.cpp b/src/particles/qquickturbulence.cpp
index 154235441b..eed8604438 100644
--- a/src/particles/qquickturbulence.cpp
+++ b/src/particles/qquickturbulence.cpp
@@ -181,7 +181,7 @@ void QQuickTurbulenceAffector::affectSystem(qreal dt)
 
     QRect boundsRect(0,0,m_gridSize,m_gridSize);
     foreach (QQuickParticleGroupData *gd, m_system->groupData){
-        if (!activeGroup(m_system->groupData.key(gd)))
+        if (!activeGroup(gd->index))
             continue;
         foreach (QQuickParticleData *d, gd->data){
             if (!shouldAffect(d))