QWindowStyle: make sure there is no duplicate in the list of scrollbar.

Otherwise the list grow and waste memory and CPU each time the
stylesheet is changed or the widget is shown

Reviewed-by: Thierry
Task-number: QTBUG-6409

1 files changed, 6 insertions, 4 deletions

diff --git a/src/gui/styles/qwindowsstyle.cpp b/src/gui/styles/qwindowsstyle.cpp
index 30f2f35af6..0a59d6d388 100644
--- a/src/gui/styles/qwindowsstyle.cpp
+++ b/src/gui/styles/qwindowsstyle.cpp
@@ -213,10 +213,12 @@ bool QWindowsStyle::eventFilter(QObject *o, QEvent *e)
     case QEvent::StyleChange:
     case QEvent::Show:
         if (QProgressBar *bar = qobject_cast<QProgressBar *>(o)) {
-            d->bars << bar;
-            if (d->bars.size() == 1) {
-                Q_ASSERT(d->animationFps> 0);
-                d->animateTimer = startTimer(1000 / d->animationFps);
+            if (!d->bars.contains(bar)) {
+                d->bars << bar;
+                if (d->bars.size() == 1) {
+                    Q_ASSERT(d->animationFps> 0);
+                    d->animateTimer = startTimer(1000 / d->animationFps);
+                }
             }
         }
         break;