How to display a widget on top of other widgets in the same window

[Cucumber]

Hi there,
I have widget containing a layout. Sometimes I need to display another widget.
And I would like to do it on top of that layout. As well I would like to have a semi-transparent background of top widget.
To make things more clear I give you a photoshopped example:

How can I do it with Qt?
Thanks in advance.

[tbscope]

Don't set a parent.

[Cucumber]

I've managed to solve that problem:

MainWidget::MainWidget(QObject* parent)
{
	mainLayout = new QVBoxLayout;
	mainLayout->addWidget(widget1);
	mainLayout->addWidget(widget2);
	mainLayout->addWidget(widget3);
	setLayout(mainLayout);
}
 
 
void MainWidget::addInFront()
{
	if (mainLayout)
		delete mainLayout;
	newWidget = new NewWidget(this);
	mainLayout = new QVBoxLayout;
	mainLayout->addWidget(newWidget);
	setLayout(mainLayout);
}

MainWidget::MainWidget(QObject* parent)
{
	mainLayout = new QVBoxLayout;
	mainLayout->addWidget(widget1);
	mainLayout->addWidget(widget2);
	mainLayout->addWidget(widget3);
	setLayout(mainLayout);
}


void MainWidget::addInFront()
{
	if (mainLayout)
		delete mainLayout;
	newWidget = new NewWidget(this);
	mainLayout = new QVBoxLayout;
	mainLayout->addWidget(newWidget);
	setLayout(mainLayout);
}

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NewWidget::NewWidget(QObject* parent)
{
	setAutoFillBackground(true);
	//setAttribute(Qt::WA_OpaquePaintEvent);
	QPalette palette = this->palette();
	palette.setColor(QPalette::Window, QColor(255,255,255,192));
	this->setPalette(palette);
 
	newLayout = new QVBoxLayout;
	newLayout->addWidget(widget0);
	setLayout(newLayout);
}

NewWidget::NewWidget(QObject* parent)
{
	setAutoFillBackground(true);
	//setAttribute(Qt::WA_OpaquePaintEvent);
	QPalette palette = this->palette();
	palette.setColor(QPalette::Window, QColor(255,255,255,192));
	this->setPalette(palette);
	
	newLayout = new QVBoxLayout;
	newLayout->addWidget(widget0);
	setLayout(newLayout);
}

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That code does everything what I want.
As for placing widgets in front of parent's I've found two useful links:

• http://www.qtcentre.org/wiki/index.p...Widget_Overlay
• http://www.wiki.crossplatform.ru/ind...ts_with_Qt_4.1

But now I have to new questions:

• As for Qt::WA_OpaquePaintEvent, am I right that I need that attribute only when re-implement paintEvent and want to draw background by myself?
• And the big one for me. When I follow the described tactic it works only when the margin is -20, otherwise there is some space not covered with the background of NewWidget.
  
  The widget and it's background are pink. How can I resize it to fill the whole window?