QScrollArea Not Drawing Correctly on Scroll

mainwindow.cpp

#include <QtWidgets>

#include "repeatingwidget.h"
#include "mainwindow.h"

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
{
    QMenu *filemenu = menuBar()->addMenu(tr("File"));
    filemenu->addAction(tr("Quit"), this, &QWidget::close);

    auto *centralWidget = new QWidget;

    scrollArea = new QScrollArea;

    repeatingArea = new RepeatingWidget();
    scrollArea->setWidget(repeatingArea);

    auto *centralLayout = new QVBoxLayout;
    centralLayout->addWidget(scrollArea, 1);

    centralWidget->setLayout(centralLayout);

    setCentralWidget(centralWidget);
    setWindowTitle(tr("Widget Test"));
}

mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include "repeatingwidget.h"

QT_BEGIN_NAMESPACE
class QScrollArea;
QT_END_NAMESPACE

class RepeatingWidget;

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = nullptr);
    ~MainWindow();

private:
    QScrollArea *scrollArea;
    RepeatingWidget *repeatingArea;
};

#endif // MAINWINDOW_H

repeatingwidget.cpp

#include <QtWidgets>

#include "repeatingwidget.h"

RepeatingWidget::RepeatingWidget(QWidget *parent) : QWidget(parent)
{
    itemHeight = 64;
    displayFont = QFont("Luxi Serif", 16.0, 1, false);
    displayItems.append({"first"});
    displayItems.append({"second"});
    displayItems.append({"third"});
    displayItems.append({"fourth"});
    displayItems.append({"fifth"});
    displayItems.append({"sixth"});
}

QSize RepeatingWidget::sizeHint() const {
    return QSize(500, itemHeight * displayItems.size() + 1);
}

void RepeatingWidget::paintEvent(QPaintEvent *event) {
    QPainter painter(this);
    painter.fillRect(event->rect(), QBrush(Qt::white));
    painter.setFont(displayFont);

    QRect itemRect = event->rect();

    int top = itemRect.top();
    
    QFontMetrics fontMetrics(*displayFont);
    for (auto item : displayItems) {
        painter.setPen(QPen(Qt::gray));
        painter.drawRect(itemRect.left(), top, itemRect.right(), itemHeight);
        painter.setPen(QPen(Qt::black));
        painter.drawText(8, 4 + top + fontMetrics.ascent(), item.name);

        top += itemHeight;
    }
}

repeatingwidget.h

#ifndef REPEATINGWIDGET_H
#define REPEATINGWIDGET_H

#include <QWidget>
#include <QFont>

struct RepeatedItem {
    QString name;
};

class RepeatingWidget : public QWidget
{
    Q_OBJECT
public:
    explicit RepeatingWidget(QWidget *parent = nullptr);
    QSize sizeHint() const override;

protected:
    void paintEvent(QPaintEvent *event) override;

private:
    QList<RepeatedItem> displayItems;

    int itemHeight;
    QFont displayFont;
};

#endif // REPEATINGWIDGET_H