Question

I use an extended QGroupBox as the widget for QDockWidget in my QMainWindow.
Here is the code snippet:

RzPlaneViewerControlPanelWidget::RzPlaneViewerControlPanelWidget(QWidget *parent) : QGroupBox(parent) {
        // TODO Auto-generated constructor stub
        init();

    }

void RzPlaneViewerControlPanelWidget::init()
    {

            QHBoxLayout *hbox=new QHBoxLayout;
            hbox->setSizeConstraint(hbox->SetMinimumSize);
            hbox->setSpacing(0);
            hbox->setStretch(1,0);

            setMaximumHeight(50);

            QScrollBar *scrollbar=new QScrollBar;
            scrollbar->setOrientation(Qt::Horizontal);
            scrollbar->setMouseTracking(true);
            scrollbar->setFocusPolicy(Qt::StrongFocus);
            scrollbar->setMinimum(0);
            scrollbar->setSingleStep(1);



            QLineEdit *qlineedit = new QLineEdit;
            qlineedit->setMaximumWidth(60);
            qlineedit->setReadOnly(true);

            hbox->addWidget(scrollbar);
            hbox->addWidget(qlineedit);

            //hbox->addWidget(new )
            setLayout(hbox);

}

Here is how I add this widget to QDockWidget :

RzPlaneViewerControlPanelWidget *controlPanel=new RzPlaneViewerControlPanelWidget ;
controlPanel->init();

QDockWidget controlPanelDockWidet=new QDockWidget;
controlPanelDockWidet->setAllowedAreas(Qt::BottomDockWidgetArea);
controlPanelDockWidet->setFeatures(QDockWidget::DockWidgetVerticalTitleBar);
controlPanelDockWidet->setWidget(controlPanel);

But the ScrollBar is not stretched as I expected –
Here’s how it looks like –

This is what I want –

Answer 1

From a quick read, I’d try doing:

hbox->addWidget(scrollbar, 1);

The second (optional) argument to addWidget is the stretch factor. From the Qt docs:

If the stretch factor is 0 and nothing else in the QBoxLayout has a stretch factor greater than zero, the space is distributed according to the QWidget:sizePolicy() of each widget that’s involved.

Also, note that your:

hbox->setStretch(1,0);

call does not have any effect, as it is setting the qlineedit‘s stretch factor to 0, but that’s already the default.