transparent window in windows 7 classic theme

[yupengfei]

Hi,
I create a transparent qml window and everything works well until I change my windows 7 theme to classic, the area I want it to be transparent is black.

import QtQuick 2.6
import QtQuick.Window 2.2
import QtGraphicalEffects 1.0

Window {
 id: window
 visible: true
 width: 640
 height: 480
 color: "#00000000"
 flags: Qt.Window | Qt.FramelessWindowHint//去掉标题栏

 RectangularGlow {
   anchors.fill: background
   glowRadius: 10
   spread: 0
   cornerRadius: 10
   color: "#99999999"
}

 Rectangle{
     id: background
     anchors.topMargin: 50
     anchors.centerIn: parent
     radius: 15
     width: parent.width *2/3
     height: parent.height - 10
     color: "#ffdbeef5"
 }

}

and the cpp

#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include <QtQuick>

int main(int argc, char *argv[])
{
    QGuiApplication app(argc, argv);
//    QQuickWindow::setDefaultAlphaBuffer(true);
    QQmlApplicationEngine engine;
    engine.load(QUrl(QStringLiteral("qrc:/main.qml")));
    if (engine.rootObjects().isEmpty())
        return -1;

    return app.exec();
}

Here is a screenshot, anyone has some idea?

[small_bird]

@yupengfei Have you solved this problem?