Changed the BackToFront sorting of QQuickItem3Dv5.0.0-beta1

I changed the sort algorithm to qSort, because the implemented bubble sort seems not to be the best choice especially when dealing with a huge amount of children.

Change-Id: Ib28dae6e1718bb8c9801277a65194fc10098a1e8
Reviewed-by: Julian de Bhal <julian.debhal@nokia.com>

1 files changed, 10 insertions, 13 deletions

diff --git a/src/quick3d/qquickitem3d.cpp b/src/quick3d/qquickitem3d.cpp
index 5e4792648..e8ff72afd 100644
--- a/src/quick3d/qquickitem3d.cpp
+++ b/src/quick3d/qquickitem3d.cpp
@@ -1236,25 +1236,22 @@ void QQuickItem3D::drawChildren(QGLPainter *painter)
 
     if (d->sortChildren == QQuickItem3D::BackToFront) {
         // Collect up the transformed z positions of all children.
-        QList<qreal> zlist;
+        QList<QPair<qreal, QQuickItem3D*> > zlist;
         QMatrix4x4 mv = painter->modelViewMatrix();
         for (int index = 0; index < list.size(); ++index) {
             QVector3D position = list.at(index)->position();
-            zlist.append(mv.map(position).z());
+            zlist.append(QPair<qreal, QQuickItem3D*> (mv.map(position).z(), list.at(index)));
         }
 
-        // Sort the item list (Caution: really dumb sort algorithm).
-        for (int i = 0; i < list.size() - 1; ++i) {
-            for (int j = i + 1; j < list.size(); ++j) {
-                if (zlist.at(i) > zlist.at(j)) {
-                    qSwap(list[i], list[j]);
-                    qSwap(zlist[i], zlist[j]);
-                }
-            }
-        }
+        qSort(zlist);
+        for (int index = 0; index < zlist.size(); ++index)
+            zlist.at(index).second->draw(painter);
+
+    }
+    else {
+        for (int index = 0; index < list.size(); ++index)
+            list.at(index)->draw(painter);
     }
-    for (int index = 0; index < list.size(); ++index)
-        list.at(index)->draw(painter);
 }
 
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