How do you center QGraphicsTextItem in its parent?

[A Former User]

Right now it centers horizontally:

with these in PieView:

PieView::PieView(QWidget *parent) : QGraphicsView(parent){
    auto scene = new QGraphicsScene(this);
    setScene(scene);
    setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
    setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
    ellipse = new QGraphicsEllipseItem();
    ellipse->setBrush(Qt::white);
    ellipse->setPen(Qt::NoPen);
    ellipse->setAcceptHoverEvents(false);
    text = new QGraphicsTextItem(ellipse);
    text->setAcceptHoverEvents(false);
    connect(this, &PieView::mouseOver, this, &PieView::onMouseOver);
    connect(this, &PieView::mouseLeave, this, &PieView::onMouseLeave);
}
void PieView::resizeEvent(QResizeEvent*){
    fitInView(scene()->itemsBoundingRect(), Qt::KeepAspectRatio);
    centerOn(0, 0);
}
void PieView::onMouseOver(PieSeries &s){
    text->document()->clear();
    auto cursor = QTextCursor(text->document());
    QTextBlockFormat blockFormat;
    QTextCharFormat charFormat;

    blockFormat.setAlignment(Qt::AlignCenter | Qt::AlignVCenter);
    charFormat.setForeground(Qt::darkGreen);
    charFormat.setFontPointSize(16);
    cursor.setBlockFormat(blockFormat);
    cursor.setBlockCharFormat(charFormat);
    cursor.insertText(s.name);

    charFormat.setForeground(Qt::red);
    charFormat.setFontPointSize(14);
    cursor.insertBlock(blockFormat, charFormat);
    cursor.insertText(QString::number(s.value));

    charFormat.setForeground(Qt::black);
    charFormat.setFontPointSize(12);
    cursor.insertBlock(blockFormat, charFormat);
    cursor.insertText(QString::number(s.value / m_total * 100) + "%");
    scene()->addItem(ellipse);
}
void PieView::onMouseLeave(){ scene()->removeItem(ellipse); }
void PieView::makePie(QVector<PieSeries>& series){
    scene()->clear();
    m_total = 0;
    float startAngle = 0, spanAngle;
    for (int i = 0; i < series.size(); i++) m_total += series[i].value;
    QRandomGenerator rand;
    auto rect = QRectF(0,0, 200,200);
    for (int i = 0; i < series.size(); i++){
        spanAngle = series[i].value / m_total * 360;
        auto color = QColor::fromRgb(rand.global()->bounded(0,255), rand.global()->bounded(0,255), rand.global()->bounded(0,255));
        auto slice = new Slice(startAngle, spanAngle, color, rect, series[i]);
        scene()->addItem(slice);
        startAngle += spanAngle;
    }
    auto eRect = QRectF(QPoint(sceneRect().center().x() - 75, sceneRect().center().y() - 75), QSize(150,150));
    ellipse->setRect(eRect);
    text->setTextWidth(rect.width());
}

it also moves the whole scene first time. When I first hover over the first slice, those two other slices moved. Here's what is in Slice, QGraphicsItem, right now:

#define whats16 16
Slice::Slice(float start, float sweep, QColor color, QRectF rect, PieSeries& series)
    : m_start(start), m_sweep(sweep), m_color(color), m_series(series){
    m_realColor = color;
    m_rect = rect;
    m_path = QPainterPath(QPointF(m_rect.width() / 2, m_rect.height() / 2));
    m_path.arcTo(m_rect, -m_start, -m_sweep);
    m_path.closeSubpath();
    dx = 10 * cos((m_start + m_sweep / 2) * M_PI / 180);
    dy = 10 * sin((m_start + m_sweep / 2) * M_PI / 180);
    float dimension = m_rect.width() + 2 * 20;
    m_boundingRect = QRectF(-20, -20, dimension, dimension);
    setAcceptHoverEvents(true);
}
QRectF Slice::boundingRect() const { return m_boundingRect; }
QPainterPath Slice::shape() const { return m_path;}
void Slice::hoverEnterEvent(QGraphicsSceneHoverEvent*){
    m_color = Qt::gray;
    moveBy(dx, dy);
    auto view = static_cast<PieView*>(scene()->parent());
    emit view->mouseOver(m_series);
}
void Slice::hoverLeaveEvent(QGraphicsSceneHoverEvent*){
    m_color = m_realColor;
    moveBy(-dx, -dy);
    auto view = static_cast<PieView*>(scene()->parent());
    emit view->mouseLeave();
}
void Slice::paint(QPainter *painter, const QStyleOptionGraphicsItem*, QWidget*){
    painter->setRenderHint(QPainter::Antialiasing);
    painter->setPen(Qt::NoPen);
    painter->setBrush(m_color);
    painter->drawPie(m_rect, whats16 * -m_start, whats16 * -m_sweep);
}

in main window, I've a QComboBox and PieView in a QVboxLayout:

Window::Window(QWidget *parent) : QWidget(parent){
    auto combo = new QComboBox(this);
    combo->addItems(QStringList() << "6" << "3");
    pie = new PieView(this);
    pie->setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
    auto lay = new QVBoxLayout(this);
    lay->setContentsMargins(0,0,0,0);
    lay->addWidget(combo);
    lay->addWidget(pie);
    setLayout(lay);
    connect(combo, &QComboBox::currentIndexChanged, this, &Window::oSelectionChanged);
    combo->setCurrentIndex(1);
}
void Window::oSelectionChanged(int index){
    QVector<PieSeries> series;
    if(index == 0){
        series.append(PieSeries("Series 1", 100));
        series.append(PieSeries("Series 2", 200));
        series.append(PieSeries("Series 3", 300));
        series.append(PieSeries("Series 4", 150));
        series.append(PieSeries("Series 5", 225));
        series.append(PieSeries("Series 6", 275));
    }
    else if(index == 1){
        series.append(PieSeries("Series 2", 200));
        series.append(PieSeries("Series 3", 300));
        series.append(PieSeries("Series 4", 150));
    }
    pie->makePie(series);
}

PieSeries is a struct with these:

struct PieSeries{
    QString name;
    float value;
    PieSeries(QString name, float value){
        this->name = name;
        this->value = value;
    }
};

[A Former User]

For the text alignment, this setY

...
text->setY(ellipse->boundingRect().center().y() - text->boundingRect().height()/2);
scene()->addItem(ellipse);

in void PieView::onMouseOver(PieSeries &s) works:

Still couldn't figure out why the remaining slices moves once or more when I first start hovering over slices