Can't get layout to work - QScrollArea with form layout in tab

[xtal256]

I am trying to use a QScrollArea as a tab page, but for some reason I cannot get the child widgets to layout correctly using a QFormLayout.
I am not using Qt Designer in this case as i am dynamically adding rows to the form layout.

Here is the code. AbstractPropertyPage is the class that is added to the tab widget. For the purpose of this post, i have omitted all but the relevant code, but i have other subclasses of AbstractPropertyPage which add specific properties to the page.

class AbstractPropertyPage : public QScrollArea{
    Q_OBJECT
protected:
    QScrollArea* scrollArea;
    QWidget* scrollAreaContents;
    QFormLayout* formLayout;
 
public:
    AbstractPropertyPage(QWidget* parent = 0);
 
    void addRow(String labelText, QWidget* widget) {
        formLayout->addRow(labelText, widget);
    }
    //...
};
 
AbstractPropertyPage::AbstractPropertyPage(QWidget* parent) :
    QWidget(parent) {
    scrollAreaContents = new QWidget(this);
    formLayout = new QFormLayout(scrollAreaContents);
    formLayout->setFieldGrowthPolicy(QFormLayout::AllNonFixedFieldsGrow);
    this->setWidget(scrollAreaContents);
}
 
//...

class AbstractPropertyPage : public QScrollArea{
    Q_OBJECT
protected:
    QScrollArea* scrollArea;
    QWidget* scrollAreaContents;
    QFormLayout* formLayout;

public:
    AbstractPropertyPage(QWidget* parent = 0);

    void addRow(String labelText, QWidget* widget) {
        formLayout->addRow(labelText, widget);
    }
    //...
};

AbstractPropertyPage::AbstractPropertyPage(QWidget* parent) :
    QWidget(parent) {
    scrollAreaContents = new QWidget(this);
    formLayout = new QFormLayout(scrollAreaContents);
    formLayout->setFieldGrowthPolicy(QFormLayout::AllNonFixedFieldsGrow);
    this->setWidget(scrollAreaContents);
}

//...

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The subclasses then add rows:

somePropertyWidget = makeLineEdit();
addRow(tr("Some Property"), somePropertyWidget);

somePropertyWidget = makeLineEdit();
addRow(tr("Some Property"), somePropertyWidget);

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These widgets are then added to the tab widget:

void PropertiesWindow::createPages() {
    //...
    tabWidget->addTab(new SomePropertyPage());
    //...
}

void PropertiesWindow::createPages() {
    //...
    tabWidget->addTab(new SomePropertyPage());
    //...
}

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I have also tried different approaches, such as subclassing QWidget instead of QScrollArea and add a QScrollArea to the widget. The widget would have a layout (e.g. vertical layout) such that the scroll area would fill the entire widget.

I tried it in Designer, laying it out how it should look. As i could not set a QScrollArea as the tab widget (it automatically put a QWidget in), i did the second approach. But the generated code looked identical to mine.

I don't know what i am doing wrong.