Qt 5, QML 2.0 and transparent borderless window incompatibility - c++

Question

Tasks:
Rounded-corners window
Custom borders
QML in QWidget
Because there is no way to change border style in parent widget, I made two of them. First parent widget is transparent, it's set in QSS. Second one is the one with rounded-corners, also set in QSS. p.s. I guess it isn't smartest idea. Not even close.
To make it work, I've set up Qt::WA_TranslucentBackground attribute.
Set up Qt::FramelessWindowHint window flag.
QML 2.0 style.[in code below]
So problem is:
When WA_TranslucentBackground and FramelessWindowHint is on - NO QML
When FramelessWindowHint is on - Only QML view
When WA_TranslucentBackground or both are off - still system BORDERS
Also I've tried to set mask on MainWindow
QPixmap pixmap = QWidget::grab(this->rect());
this->setMask(pixmap.createMaskFromColor(Qt::transparent, Qt::MaskInColor));
Works well, no system borders, custom one is rounded and QML works, but whole other area became white, don't know how to fix.
MainWindow:
QFile styleFile("style.qss");
styleFile.open(QFile::ReadOnly), qApp->setStyleSheet(QLatin1String(styleFile.readAll()));
QWidget *container = QWidget::createWindowContainer(new QQuickView(QUrl("main.qml")), this);
ui->verticalLayout->addWidget(container);
//this->setAttribute(Qt::WA_TranslucentBackground, true);
//this->setWindowFlags(Qt::FramelessWindowHint | Qt::Window);
QPixmap pixmap = QWidget::grab(this->rect());
this->setMask(pixmap.createMaskFromColor(Qt::transparent, Qt::MaskInColor));
Styles:
QWidget#MainWindow{
background:transparent;
}
QWidget#MainWindowRounded{
background-color: grey;
border: 1px solid black;
border-radius: 5px;
}
Is this possible to resolve?
HERE SOURCE CODE