Function gradient

qcustomplot/qcustomplot.h:5071–5071

  QCPRange dataRange() const { return mDataRange; }
  QCPAxis::ScaleType dataScaleType() const { return mDataScaleType; }
  QCPColorGradient gradient() const { return mGradient; }
  QString label() const;
  int barWidth () const { return mBarWidth; }
  bool rangeDrag() const;