Reduce allocations by using reserve()

Change-Id: If34fa53402985f6b3c5e7217bce4a1177af835b6
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>

1 files changed, 4 insertions, 2 deletions

diff --git a/src/widgets/kernel/qwidgetbackingstore.cpp b/src/widgets/kernel/qwidgetbackingstore.cpp
index d9d1c887c1..5e6563b0be 100644
--- a/src/widgets/kernel/qwidgetbackingstore.cpp
+++ b/src/widgets/kernel/qwidgetbackingstore.cpp
@@ -1242,13 +1242,15 @@ void QWidgetBackingStore::doSync()
         // OpenGL content changes. Check if we have such widgets in the special
         // dirty list.
         QVarLengthArray<QWidget *, 16> paintPending;
-        for (int i = 0; i < dirtyRenderToTextureWidgets.count(); ++i) {
+        const int numPaintPending = dirtyRenderToTextureWidgets.count();
+        paintPending.reserve(numPaintPending);
+        for (int i = 0; i < numPaintPending; ++i) {
             QWidget *w = dirtyRenderToTextureWidgets.at(i);
             paintPending << w;
             resetWidget(w);
         }
         dirtyRenderToTextureWidgets.clear();
-        for (int i = 0; i < paintPending.count(); ++i) {
+        for (int i = 0; i < numPaintPending; ++i) {
             QWidget *w = paintPending[i];
             w->d_func()->sendPaintEvent(w->rect());
             if (w != tlw) {