not same between Qt 4.5.3 and Qt 4.6.0 on framebuffer

It's not same between Qt 4.5.3 and Qt 4.6.0 when QWidget displayed on framebuffer by setWindowOpacity().

• source : main.cpp
  #include <QWSServer>
  #include <QApplication>
  #include <QDialog>

int main(int argc, char *argv[])

{ QApplication a(argc, argv); QWSServer::setBackground(QBrush(QColor(0, 0, 0, 0))); QDialog dlg1, dlg2; dlg1.setWindowOpacity(0.5); dlg1.show(); dlg2.setWindowOpacity(0.5); dlg2.show(); return a.exec(); }

• Qt 4.5.3 : qte_4.5.3.png
  $ export QTDIR=/usr/local/qte_4.5.3
  $ export LD_LIBRARY_PATH=$QTDIR/lib:
  $ export PATH=$QTDIR/bin:$PATH
  $ qmake -project -o test.pro
  $ qmake
  $ make
  $ ./test -qws -display qvfb:0 &

• Qt 4.6.0 : qte_4.6.0.png
  $ export QTDIR=/usr/local/qte_4.6.0
  $ export LD_LIBRARY_PATH=$QTDIR/lib:
  $ export PATH=$QTDIR/bin:$PATH
  $ qmake
  $ make
  $ ./test -qws -display qvfb:0 &

It's normal situation in Qt 4.5.3 but can check noise when move the widget in Qt 4.6.0

And, please let me know which version of ARGB4444 format support.