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, 12 insertions, 0 deletions

diff --git a/src/particles/qquickparticleemitter.cpp b/src/particles/qquickparticleemitter.cpp
index 5e5c750e0e..7cce4d481a 100644
--- a/src/particles/qquickparticleemitter.cpp
+++ b/src/particles/qquickparticleemitter.cpp
@@ -237,6 +237,8 @@ QQuickParticleEmitter::QQuickParticleEmitter(QQuickItem *parent) :
   , m_reset_last(true)
   , m_last_timestamp(-1)
   , m_last_emission(0)
+  , m_groupIdNeedRecalculation(false)
+  , m_groupId(QQuickParticleGroupData::DefaultGroupID)
 
 {
     //TODO: Reset velocity/acc back to null vector? Or allow null pointer?
@@ -257,6 +259,16 @@ bool QQuickParticleEmitter::isEmitConnected()
     IS_SIGNAL_CONNECTED(this, QQuickParticleEmitter, emitParticles, (QQmlV4Handle));
 }
 
+void QQuickParticleEmitter::reclaculateGroupId() const
+{
+    if (!m_system) {
+        m_groupId = QQuickParticleGroupData::InvalidID;
+        return;
+    }
+    m_groupId = m_system->groupIds.value(group(), QQuickParticleGroupData::InvalidID);
+    m_groupIdNeedRecalculation = m_groupId == QQuickParticleGroupData::InvalidID;
+}
+
 void QQuickParticleEmitter::componentComplete()
 {
     if (!m_system && qobject_cast<QQuickParticleSystem*>(parentItem()))