QT chart PlotArea

[IknowQT]

In the qt chart, the value of m_pChartViewer->chart()->plotArea(); rect is 0,0,0,0. Why is that? I can't get a chart size.

[eyllanesc]

@IknowQT Try changing UpdateChart(); to QTimer::singleShot(0, this, &ExChart::UpdateChart);

[eyllanesc]

@IknowQT Could you provide a minimal and verifiable example, maybe some configuration has been done incorrectly, or maybe it is the expected output.

[IknowQT]

void ExChart::InitializeChart()
{
	m_pChartViewer = new QChartView(createLineChart());

    m_pChartViewer->setRenderHint(QPainter::Antialiasing);
    m_pChartViewer->chart()->legend()->hide();

    this->ui.verticalLayout->addWidget(m_pChartViewer);

    UpdateChart();  
}

QChart* ExChart::createLineChart()
{
	m_pChart = new QChart();
	m_pChart->setTitle("Line chart");

	QPen pen(QColor(47, 245, 76));
	pen.setWidth(3);

    QString name("Series ");
    int nameIndex = 0;

    m_pLineSeries = new QLineSeries(m_pChart);
    m_pLineSeries->setPen(pen);
   
    m_pScatSeries = new QScatterSeries(m_pChart);

    m_pChart->addSeries(m_pLineSeries);
    m_pChart->addSeries(m_pScatSeries);
    m_pChart->createDefaultAxes();

    m_pChart->axes(Qt::Horizontal).first()->setRange(0, 100);
    m_pChart->axes(Qt::Vertical).first()->setRange(0, 100);

    return m_pChart;
}

void ExChart::UpdateChart()
{
    QRectF	rect = m_pChartViewer->chart()->plotArea();		// only 차트 사이즈 (마진 제외)

    for (int i = 0; i < 100; i++)
    {
        qreal	spacing = (((rect.right() - rect.left()) / ((qreal)100 - (qreal)0)) * i) + rect.right();

        int y = QRandomGenerator::global()->bounded(0, 101);
        m_pLineSeries->append(i, y);
        m_pScatSeries->append(i, y);

        m_vPoint.push_back(QPointF(i, y));

        QString str = QString("X: %1\nY: %2").arg(i).arg(y);
        m_pTextItem = new QGraphicsTextItem(m_pChart);
        m_pTextItem->setFont(QFont("Bahnschrift Condensed"));
        m_pTextItem->setZValue(12);
        m_pTextItem->setDefaultTextColor(Qt::white);
        m_pTextItem->setHtml(QString("<div style='background-color: rgba(255,0,0,150);'>") + str + "</div>");

        qreal PosX = m_pChart->mapToPosition(QPointF(i, y), m_pLineSeries).x();
        qreal PosY = m_pChart->mapToPosition(QPointF(i, y), m_pLineSeries).y();

        m_pChart->mapToScene(PosX, PosY);
        m_pTextItem->setPos(PosX, PosY);
    }
}

What I want to do is to mark the x,y values for each position of the scatter.

I don't think it's working. It's always zero.
qreal PosX = m_pChart->mapToPosition(QPointF(i, y), m_pLineSeries).x();
qreal PosY = m_pChart->mapToPosition(QPointF(i, y), m_pLineSeries).y();

[eyllanesc]

@IknowQT Try changing UpdateChart(); to QTimer::singleShot(0, this, &ExChart::UpdateChart);

[IknowQT]

@eyllanesc

Wow, thank you so much.
I didn't know it was this simple.
But why do you need to update me with a timer?

[eyllanesc]

@IknowQT Sometimes it happens that for efficiency reasons Qt does not update some properties and it does so when the widgets are just displayed. And it seems that this is the case.