How to setup QToolBar's background image?

Question

//MainWindow.cpp
MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent)
{
    //...

    QToolBar * toolbar = new QToolBar(this);

    this->addToolBar(Qt::BottomToolBarArea, toolbar);
    toolbar->setMovable(false);

    QToolButton * button = new QToolButton(this);
    toolbar->addWidget(button);

    //way 1: It display a picture
    toolbar->setStyleSheet("background-image: url(:/images/toolbarBg)");

    //way 2: It doesn't display picture
    //qApp->setStyleSheet("QToolBar {background-image: url(:/images/toolbarBg)}");
}

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way (1) can display toolbarBg2x picture, but way (2) display nothing. why?

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My expected result is to apply the picture as background of the toolbar.
However the toolbar's size actually is in 100x30 via method 1.
Additional information : background picture's resolution is 800x60, MainWindow size is 800x600.

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Qt5.1 clang 64 bit, MacOSX10.8

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Answer 1

Working Sample:

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , m_toolbar( new QToolBar )
{
    this->addToolBar(Qt::BottomToolBarArea, m_toolbar);
    //m_toolbar->setStyleSheet("background-image: url(:/image/toolbar.png);");   
    m_toolbar->setStyleSheet("background-image: url(:/images/toolbar.png); border: 0px")
}

The following line doesn't work,

m_toolbar->setStyleSheet("background-image: url(:/image/toolbar.png);"); 

Add border : 0px to enforce drawing, and then it shows picture.

m_toolbar->setStyleSheet("background-image: url(:/images/toolbar.png); border: 0px")

to apply style,

m_toolbar->setStyleSheet("background-image: url(:/images/toolbar.png); border: 0px")

or

this->setStyleSheet("QToolBar{background-image: url(:/images/toolbar.png); border: 0px;}");

Both of them work well.

Tested under MacOS 10.9, Qt5.1.1