Particles: reduce excessive hash accesses to a more passable level.

By caching the group id in the particle emitter, and groups in the
painter.

Test case: samegame, 1 player, click 1 set of 3 stones, quit.
QQuickParticleSystem::emittersChanged(), before patch:
 - 64M instr. inclusive
 - 145,880 calls to findNode (29M instr.)
after:
 - 21M instr. inclusive
 - 0 calls to findNode
 - 25 calls to QQuickParticlePainter::recalculateGroupIds (9800 instr.
   inclusive).

Change-Id: I4aba9d50100513c6b7cdd230e30b3aecaf84485a
Reviewed-by: Lars Knoll <lars.knoll@theqtcompany.com>

1 files changed, 17 insertions, 2 deletions

diff --git a/src/particles/qquickparticleemitter_p.h b/src/particles/qquickparticleemitter_p.h
index bb77d132cc..9b114ad46b 100644
--- a/src/particles/qquickparticleemitter_p.h
+++ b/src/particles/qquickparticleemitter_p.h
@@ -119,6 +119,13 @@ public:
         return m_group;
     }
 
+    QQuickParticleGroupData::ID groupId() const
+    {
+        if (m_groupIdNeedRecalculation)
+            reclaculateGroupId();
+        return m_groupId;
+    }
+
     int particleDurationVariation() const
     {
         return m_particleDurationVariation;
@@ -185,6 +192,7 @@ public Q_SLOTS:
     {
         if (m_system != arg) {
             m_system = arg;
+            m_groupIdNeedRecalculation = true;
             if (m_system)
                 m_system->registerParticleEmitter(this);
             Q_EMIT systemChanged(arg);
@@ -195,6 +203,7 @@ public Q_SLOTS:
     {
         if (m_group != arg) {
             m_group = arg;
+            m_groupIdNeedRecalculation = true;
             Q_EMIT groupChanged(arg);
         }
     }
@@ -319,7 +328,6 @@ protected:
        int m_particleDurationVariation;
        bool m_enabled;
        QQuickParticleSystem* m_system;
-       QString m_group;
        QQuickParticleExtruder* m_extruder;
        QQuickParticleExtruder* m_defaultExtruder;
        QQuickParticleExtruder* effectiveExtruder();
@@ -350,7 +358,14 @@ protected:
        QPointF m_last_last_last_emitter;
 
        bool isEmitConnected();
-private:
+
+private: // methods
+       void reclaculateGroupId() const;
+
+private: // data
+       QString m_group;
+       mutable bool m_groupIdNeedRecalculation;
+       mutable QQuickParticleGroupData::ID m_groupId;
        QQuickDirection m_nullVector;
 
 };