Dear Qt experts,

I am having a problem in setting the background color of a QTabWidget to transparent.
What I would like to achieve is to have an image in the mainWindow background that shows through all the small windows on top of it.
I managed to do that with QTableView and QStackedWidget by setting the styelSheet.
For the QTabWidget instead there seems to be some additional default background which is set to white and that I cannot manage to make transparent.
Here are the settings I have tried in the styleSheet:

QString style("");
style += (QString::fromUtf8("QTableView, "));
style += QString::fromUtf8("QTabBar::tab, ");
style += QString::fromUtf8("QTabWidget, ");
style += QString::fromUtf8("QTextEdit, ");
style += QString::fromUtf8("QListView, ");
style += QString::fromUtf8("QWidget, ");
style += QString::fromUtf8("QStackedWidget, ");
style += QString::fromUtf8("QStackedLayout, ");
style += QString::fromUtf8("QRect, ");
style += QString::fromUtf8("QTableCornerButton, ");
style += QString::fromUtf8("QAbstractButton, ");
style += QString::fromUtf8("QTabWidget:ane, ");
style += QString::fromUtf8("QTabWidget::left-corner, ");
style += QString::fromUtf8("QTabWidget::right-corner, ");
style += QString::fromUtf8("QAbstractScrollArea, ");
style += QString::fromUtf8("QCheckBox, ");
style += QString::fromUtf8("QComboBox, ");
style += QString::fromUtf8("QSpinBox, ");
style += QString::fromUtf8("QFrame, ");
style += QString::fromUtf8("QGroupBox, ");
style += QString::fromUtf8("QHeaderView, ");
style += QString::fromUtf8("QLineEdit, ");
style += QString::fromUtf8("QMenu, ");
style += QString::fromUtf8("QMenuBar, ");
style += QString::fromUtf8("QProgressBar, ");
style += QString::fromUtf8("QPushButton, ");
style += QString::fromUtf8("QRadioButton, ");
style += QString::fromUtf8("QScrollBar, ");
style += QString::fromUtf8("QSizeGrip, ");
style += QString::fromUtf8("QSlider, ");
style += QString::fromUtf8("QSplitter, ");
style += QString::fromUtf8("QStatusBar, ");
style += QString::fromUtf8("QTabWidget, ");
style += QString::fromUtf8("QTabBar, ");
style += QString::fromUtf8("QTableWidget, ");
style += QString::fromUtf8("QToolBar, ");
style += QString::fromUtf8("QToolBox, ");
style += QString::fromUtf8("QToolButton, ");
style += QString::fromUtf8("QToolTip, ");
style += QString::fromUtf8("QTreeView ");
style += QString::fromUtf8("{");
style += QString::fromUtf8("background-color: rgba(255, 255, 55, 55);");
style += QString::fromUtf8("alternate-background-color: rgba(255, 255, 55, 55);");
style += QString::fromUtf8("selection-color: rgba(255, 255, 55, 55);");
style += QString::fromUtf8("selection-background-color: rgba(255, 255, 55, 55);");
style += QString::fromUtf8("background-origin: content;");
style += QString::fromUtf8("background-clip: margin;");
style += QString::fromUtf8("}");

ui->tabWidget->setStyleSheet(style);

With these settings (that are overly exagerated) I get the transparent background for the tab bar and I also get a yellow (255, 255, 55) color over a white background on the main QTabWidget area.
The very same settings work on a QTableView or QStakcedWidget.

I also tried to use:
QPalette p = ui->tabWidget->palette();
p.setBrush( QPalette::Base, QBrush( QColor::fromRgbF(255, 255, 55, 55) ) );
ui->tabWidget->setPalette(p);
which I found on another thread of this forum, but it does not change anything.

I should add that I am testing this on windows xp using Qt 4.5 in QtCreator 1.0.

Any help would be greatly appreciated!