Expected type-specifier before 'QwtLog10ScaleEngine'?

问题

Version: qwt 6.0.1 I've tried to develop logarithmic scaling for Spectrum. I've used simple line to enable scaling plotspectrum->setAxisScaleEngine(QwtPlot::yLeft, new QwtLog10ScaleEngine);

Problems: the data are not drawn, so the plot is empty and the compiler returns following error:"expected type-specifier before 'QwtLog10ScaleEngine'" Any help woulb be appreciated Here is my code:

class SpectrumPlot : public QWidget
{
Q_OBJECT
public:
PlotSpektrum();
private:
QHBoxLayout*    m_SpectrumLayout;
QwtPlot*        m_SpectrumPlot;
QwtPlotCurve*   m_SpectrumCurve;
QwtPlotMarker*  m_Marker;

};

SpectrumPlot::SpectrumPlot()
{
m_SpectrumLayout = new QHBoxLayout();
m_SpectrumPlot = new QwtPlot();
m_SpectrumCurve = new QwtPlotCurve();
QwPlotGrid* pGrid = new QwtPlotGrid();
QPen GridPen;
GridPen.setColor(Qt::green);
GridPen.setWidthF(0.7);
GridPen.setStyle(Qt::DashLine);
QPen SpectrumPen;
SpectrumPen.setColor(Qt::white);

pGrid->setRenderHint(QwtPlotItem::RenderAntialiased);
pGrid->setPen(GridPen);
pGrid->enableXMin(true);
pGrid->attach(m_SpectrumPlot);
m_SpectrumPlot->setTitle("Spectrum");
m_SpectrumPlot->setCanvasBackground(QBrush(Qt::black));
m_SpectrumPlot->setAutoDelete(true);
m_SpectrumPlot->setAxisTitle(QwtPlot::xBottom, "Frequency Hz");
m_SpectrumPlot->setAxisScale(QwtPlot::xBottom, 100, nNyquistFrequency);
m_SpectrumPlot->setAxisScale(QwtPlot::yLeft, 0, 150);
m_SpectrumPlot->setAxisScaleEngine(QwtPlot::xBottom, new QwtLog10ScaleEngine());
m_SpectrumLayout->addWidget(m_SpectrumPlot);

this->setLayout(m_SpectrumLayout);
}

回答1:

I think you should be using:

new QwtLogScaleEngine(10)

The manual for QwtScaleEngine doesn't show any classes called QwtLog10ScaleEngine.

来源：https://stackoverflow.com/questions/24567737/expected-type-specifier-before-qwtlog10scaleengine

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