qcpaxisrect边长

Question

axisRect->width(),axisRect->height()的值是0
想要将一条轴偏移至QCPAxisRect中间,setoffset的偏移量应该怎样计算

        QCPAxisRect* volumeAxisRect = new QCPAxisRect(mPlot);
        mPlot->plotLayout()->addElement(i, 0, volumeAxisRect);
        volumeAxisRect->setMinimumSize(mPlot->axisRect()->layout()->minimumSize());
        volumeAxisRect->setAutoMargins(QCP::msRight | QCP::msBottom);
        volumeAxisRect->setMinimumMargins(QMargins(0, 0, 0, 0));

volumeAxisRect->width()是0

Answer 1

double offset = axisRect->width() / 2.0 - axis->range().center() / axis->range().size() * axisRect->width();
axis->setOffset(offset);