Qt Cursor Crosshair Lag

Yippiyak

Hello,
I am attempting to implement a crosshair onto a QtChart, that dynamically tracks the cursor's movement. However, I am experiencing a fair amount of lag between my cursor's position, and the painted crosshair lines. My current code is as follows;

void SpectrumCoordinateDisplay::paint(QPainter* painter)
{
    QRectF plotArea = m_chart->plotArea();
    QPointF crossHairPos = m_mousePos;

    if (!m_active || !plotArea.contains(crossHairPos))
    {
        return;
    }

    painter->setBrush(QColor(255, 255, 0, 255));
    painter->setPen(QColor(255, 255, 0, 255));

    const qreal rectSize = 6;

    QPointF left(plotArea.left(), crossHairPos.y());
    QPointF right(plotArea.right(), crossHairPos.y());
    QPointF top(crossHairPos.x(), plotArea.top());
    QPointF bottom(crossHairPos.x(), plotArea.bottom());

    QRectF crosshairRect(crossHairPos.x() - rectSize, crossHairPos.y() - rectSize, rectSize * 2, rectSize * 2);
    QPointF rectLeft(crosshairRect.left(), crossHairPos.y());
    QPointF rectRight(crosshairRect.right(), crossHairPos.y());
    QPointF rectTop(crossHairPos.x(), crosshairRect.top());
    QPointF rectBottom(crossHairPos.x(), crosshairRect.bottom());

    painter->drawLine(left, rectLeft);
    painter->drawLine(right, rectRight);
    painter->drawLine(top, rectTop);
    painter->drawLine(bottom, rectBottom);
    painter->drawLine(crosshairRect.topLeft(), crosshairRect.topRight());
    painter->drawLine(crosshairRect.topLeft(), crosshairRect.bottomLeft());
    painter->drawLine(crosshairRect.bottomRight(), crosshairRect.topRight());
    painter->drawLine(crosshairRect.bottomRight(), crosshairRect.bottomLeft());

    QRectF textRect = crosshairRect;
    textRect.moveTop(textRect.top() - textRect.height());
    textRect.setWidth(plotArea.width());

    textRect = painter->boundingRect(textRect, Qt::TextWordWrap, m_text);
    textRect.moveBottom(crosshairRect.top());
    textRect.moveLeft(crosshairRect.center().x() + 5);

    if (textRect.top() < plotArea.y())
        textRect.moveTop(crosshairRect.bottom());
    if (textRect.right() > plotArea.right())
        textRect.moveRight(crosshairRect.left());

    painter->drawText(textRect, Qt::TextWordWrap, m_text);
}

If anyone has any advice, please let me know.

VRonin

What's the base class of SpectrumCoordinateDisplay?
Did you have a look at the callout example which looks like it does what you are trying to do?

Yippiyak

@VRonin
Qt charts.
The example is not really what I need, as I am basically trying to generate lines that follow the cursor perfectly with no trailing.