QQuickSpriteEngine: Optimistic speedup for updateSprites

Switch from QList to QVector, and avoid using pop_front -- remove all in one
operation instead.

The idea here was to provide some gain to sprite-sequence in qmlbench, but any
possible gain is pretty miniscule due to the lack of batching that example
suffers. Still, we end up with less CPU time taken, which is a win of sorts.

Change-Id: Ib7c101afa71ee617c3c4506b14701d6a4143ed3a
Reviewed-by: Gunnar Sletta <gunnar@sletta.org>

2 files changed, 7 insertions, 6 deletions

diff --git a/src/quick/items/qquickspriteengine.cpp b/src/quick/items/qquickspriteengine.cpp
index 10e0d51709..b1905f2cc5 100644
--- a/src/quick/items/qquickspriteengine.cpp
+++ b/src/quick/items/qquickspriteengine.cpp
@@ -664,13 +664,14 @@ uint QQuickStochasticEngine::updateSprites(uint time)//### would returning a lis
     //Sprite State Update;
     m_timeOffset = time;
     m_addAdvance = false;
-    while (!m_stateUpdates.isEmpty() && time >= m_stateUpdates.constFirst().first){
-        const auto copy = m_stateUpdates.constFirst().second;
+    int i = 0;
+    for (; i < m_stateUpdates.count() && time >= m_stateUpdates.at(i).first; ++i) {
+        const auto copy = m_stateUpdates.at(i).second;
         for (int idx : copy)
             advance(idx);
-        m_stateUpdates.pop_front();
     }
 
+    m_stateUpdates.remove(0, i);
     m_advanceTime.start();
     m_addAdvance = true;
     if (m_stateUpdates.isEmpty())
@@ -760,13 +761,13 @@ void QQuickStochasticEngine::addToUpdateList(uint t, int idx)
             m_stateUpdates[i].second << idx;
             return;
         } else if (m_stateUpdates.at(i).first > t) {
-            QList<int> tmpList;
+            QVector<int> tmpList;
             tmpList << idx;
             m_stateUpdates.insert(i, qMakePair(t, tmpList));
             return;
         }
     }
-    QList<int> tmpList;
+    QVector<int> tmpList;
     tmpList << idx;
     m_stateUpdates << qMakePair(t, tmpList);
 }
diff --git a/src/quick/items/qquickspriteengine_p.h b/src/quick/items/qquickspriteengine_p.h
index cf50cd2d84..3b7fcfb1f1 100644
--- a/src/quick/items/qquickspriteengine_p.h
+++ b/src/quick/items/qquickspriteengine_p.h
@@ -254,7 +254,7 @@ protected:
     QVector<int> m_goals;
     QVector<int> m_duration;
     QVector<int> m_startTimes;
-    QList<QPair<uint, QList<int> > > m_stateUpdates;//### This could be done faster - priority queue?
+    QVector<QPair<uint, QVector<int> > > m_stateUpdates;//### This could be done faster - priority queue?
 
     QTime m_advanceTime;
     uint m_timeOffset;