transparent QScrollArea and blurry scrolling

Hi All,

I have the following code to create a QScrollArea that is transparent with it's content also being transparent. So I want the northPanel's parent to show through.

Code:

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QWidget* northPanel = new QWidget(this);    
northPanel->setAttribute(Qt::WA_NoBackground);    
// add some content to northPanel
QScrollArea* scroller = new QScrollArea(this);    
scroller->setAttribute(Qt::WA_NoBackground);
scroller->setWidget(northPanel);

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This works fine. However, when I scroll, the northPanel becomes blurred. I'm pretty sure it's because NoBackground attribute causes those widgets to not paint the background. What am I missing here? How do I make a transparent QScrollArea? Do I need to force a repaint or something?

many thanks,

B

Hi Guys,

I still have not figured out how to handle this. Here is a code sample. A VS project is also attached. If you make the window small and scroll the scroller horizontally and vertically, you will see the QLabel text blurring. ( I'm not sure blur is the correct word to use. )
In this example, the scroller is not really transparent ( not sure why ), but anyway that's not the point. It shows the effect I am trying to show. ( actually not show. :)

many thanks,

B

Code:

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#include "testwindow.h"
 
#include <QLabel>
#include <QScrollArea>
#include <QVBoxLayout>
 
TestWindow::TestWindow(QWidget *parent, Qt::WFlags flags)
	: QDialog(parent, flags)
{
	ui.setupUi(this);
	init();	
}
 
TestWindow::~TestWindow()
{
 
}
 
void TestWindow::init()
{	
	this->setStyleSheet("QDialog { background-color: blue; }");
 
	QVBoxLayout* layout = new QVBoxLayout(this);	
	QScrollArea* scroller = new QScrollArea(this);
    scroller->setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOn);
	scroller->setAttribute(Qt::WA_NoBackground);	
 
	QWidget* panel = new QWidget(this);
	panel->setAttribute(Qt::WA_NoBackground);	
	scroller->setWidget(panel);
 
	QHBoxLayout* panelLayout = new QHBoxLayout(this);
	panelLayout->setSizeConstraint(QLayout::SetMinAndMaxSize);
	panel->setLayout(panelLayout);
 
	QLabel* label = new QLabel(this);	
	label->setStyleSheet("QLabel { color: red; }");
	label->setText("Qt rocks!");
	label->setMinimumSize(600, 600);	
	QFont font("Courier", 24);
	label->setFont(font);
	panelLayout->addWidget(label);
 
	layout->addWidget(scroller);
	setLayout(layout);
}

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In case anyone is interested. Use this instead of the attribute.

Code:

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northPanel->setStyleSheet("background: transparent");
scroller->setStyleSheet("background: transparent");

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