How to remove extra space around QGraphicsItem and round top corners of Rectangle?

[deleted385]

Here's what I've in the Bar, QGraphicsItem:

Bar::Bar(QRectF rect, BarSeries& s, float max, QGraphicsItem *parent)
    : QGraphicsItem(parent), m_rect(rect), m_series(s), m_max(max){ }
QRectF Bar::boundingRect() const { return m_rect; }
void Bar::paint(QPainter *painter, const QStyleOptionGraphicsItem *, QWidget *){
    painter->setRenderHints(QPainter::Antialiasing);
    painter->setBrush(Qt::black);
    painter->setPen(Qt::white);
    painter->translate(0, m_rect.height());
    painter->scale(1.0, -1.0);
    float h1 = m_series.value1 / m_max * m_rect.height();
    float h2 = m_series.value2 / m_max * m_rect.height();
    auto rect = QRectF(m_rect.left(), 0, m_rect.width(), h1);
    painter->drawRect(rect);
    painter->setBrush(Qt::gray);
    rect = QRectF(m_rect.left(), h1, m_rect.width(), h2);
    //painter->drawRoundedRect(rect, 0, 5); // tried this to round only top corners
    painter->drawRect(rect);
}

and here's how it looks:

it adds some extra spaces around those rectangles. How to remove those extra spaces and round only top corners of these rectangles? In the BarView, QGraphicsView, I add Bar in the scene with these:

BarView::BarView(QWidget *parent) : QGraphicsView(parent), m_spacing(5){
    setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
    setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
    auto scene = new QGraphicsScene(this);
    scene->setSceneRect(0,0,200,200);
    setScene(scene);
}
void BarView::fit(){
    fitInView(scene()->itemsBoundingRect());
    centerOn(0,0);
}
void BarView::resizeEvent(QResizeEvent*){ fit(); }
void BarView::addBars(QVector<BarSeries>& series){
    scene()->clear();
    float max = 0, start = 0, total;
    for (int i = 0; i < series.size(); i++) {
        total = series[i].value1 + series[i].value2;
        if(max < total) max = total;
    }
    auto rect = sceneRect();
    auto barWidth = rect.width() / series.size() - series.size() * m_spacing - m_spacing;
    for (int i = 0; i < series.size(); i++) {
        //auto proportion = (series[i].value1 + series[i].value2) / max * rect.height();
        auto barRect = QRectF(start, rect.top(), barWidth, rect.height());
        auto bar = new Bar(barRect, series[i], max);
        scene()->addItem(bar);
        start += m_spacing + barWidth;
    }
    fit();
}

and in the Window I've these:

Window::Window(QWidget *parent) : QWidget(parent){
    auto lay = new QVBoxLayout(this);
    setLayout(lay);
    auto combo = new QComboBox(this);
    combo->addItems(QStringList() << "4" << "5");
    barChart = new BarView(this);
    barChart->setFrameShape(QFrame::Box);
    lay->addWidget(combo);
    lay->addWidget(barChart);
    connect(combo, &QComboBox::currentIndexChanged, this, &Window::onSelectionChanged);
    combo->setCurrentIndex(1);
}
Window::~Window(){}
void Window::onSelectionChanged(int index){
    QVector<BarSeries> series;
    series.append(BarSeries("S1", 100, 100));
    series.append(BarSeries("S2", 200, 100));
    series.append(BarSeries("S3", 300, 100));
    series.append(BarSeries("S4", 200, 0));
    if(index == 1) series.append(BarSeries("S5", 100, 50));
    barChart->addBars(series);
}

and BarSeries is a struct:

struct BarSeries{
    QString name;
    float value1;
    float value2;
    BarSeries(const QString& name, float value1, float value2){
        this->name = name;
        this->value1 = value1;
        this->value2 = value2;
    }
};

EDIT
with painter->setPen(Qt::NoPen); in Bar the white space between stacked rectangles is removed BUT feels like it still adds some extra space around the whole GraphicsItem. In WPF I used SnapsToDevicePixel, is there anything like that?

[mchinand]

I think you could have also fixed the extra space issue by accounting for the pen width when computing the boundingRect of your Bar QGraphicsItem class; see the note here.

[deleted385]

@mchinand, for the pie, I used that technique to put some extra margin around the pie. In this case I, probably, would have to use the boundingRect instead of m_rect, in paint, to get the desired output.