How to draw plot with gap

[BulSV]

Hi everyone!
How to draw plot with gap like tg(x), 1/(1-x) or parametric plots, for example:

x > 0, f(x) = 1;
x < -3, f(x) = sin(x);
x = [-3, 0], f(x) = -10;

x > 0, f(x) = 1;
x < -3, f(x) = sin(x);
x = [-3, 0], f(x) = -10;

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?
Need to draw one curve for one function.

[Sintegrial]

You should draw every range of the data with separate curve.

[BulSV]

I need to monitor functions by signal void QwtPolarPlot::itemAttached (QwtPolarItem *plotItem, bool on), to know, which functions are added.
The approach with using separate curves for one function is not suitable for me.

[Uwe]

Then overload QwtPolarCurve::drawLines() and split it into 2 QPainter:drawPolyline calls.

Uwe

[BulSV]

Thanks, but QwtPolarCurve::drawLines() not virtual.
I did something like this:

class A : public QwtPolarCurve
{
private:
    QwtPolarCurve *m_firstCurve;
    QwtPolarCurve *m_secondCurve;
};

class A : public QwtPolarCurve
{
private:
    QwtPolarCurve *m_firstCurve;
    QwtPolarCurve *m_secondCurve;
};

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