QCustomPlot Discussion and Comments

I wan't to know is the qcustomplot is painting，so i called paintingActive(); but it's always return false, so i move it in paintEvent, but it's the same。
look the code

void QCustomPlot::paintEvent(QPaintEvent *event)
{
  Q_UNUSED(event)
  QCPPainter painter(this);
  if (painter.isActive())
  {
[i]    qDebug() << this->paintingActive();[/i]
#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
  painter.setRenderHint(QPainter::HighQualityAntialiasing); // to make Antialiasing look good if using the OpenGL graphicssystem
#endif
    if (mBackgroundBrush.style() != Qt::NoBrush)
      painter.fillRect(mViewport, mBackgroundBrush);
    drawBackground(&painter);
    foreach (QSharedPointer<QCPAbstractPaintBuffer> buffer, mPaintBuffers)
      buffer->draw(&painter);
  }
}