Curve legend doesn't show a symbol entirely

Hello all,

I faced with a problem that using QwtPlotCurve::LegendShowSymbol doesn't show a symbol (a circle in my case) in a legend entirely:
Attachment 5860

Here is an example code:

Code:

---

class TestPlot: public QwtPlot
{
 
public:
 
    TestPlot(QWidget * parent = NULL);
 
private:
 
    QwtPlotCurve    _curve;
 
};
 
TestPlot::TestPlot(QWidget * parent) : QwtPlot(parent)
{
 
    QwtSymbol *sym = new QwtSymbol(QwtSymbol::Ellipse);
    sym->setSize(5);
    sym->setPen(QColor(Qt::blue));
 
    _curve.setSymbol(sym);
    _curve.setStyle(QwtPlotCurve::NoCurve);
    _curve.setTitle(tr ("Curve"));
    _curve.setLegendAttribute(QwtPlotCurve::LegendShowSymbol);
    _curve.attach(this);
 
    QVector <double> x;
 
    for (unsigned i = 0; i < 10; ++i)
    {
        x.push_back(i);
    }
 
    _curve.setSamples(x, x);
 
    QwtLegend *legend = new QwtLegend(this);
    insertLegend(legend, QwtPlot::BottomLegend);
}

---

If I change a symbol size from 5 to 10 everything looks nice:
Attachment 5861

Does anybody know why this can happen?
Thanks for any help!

I can't confirm this on my box.

What version of Qwt/Qt on which platform do you have. Does it still happen with Qwt from SVN trunk ?

Uwe

Yes, it happens with the last Qwt version from SVN trunk.

I use Qt 4.7.0 and platform is Windows 7 Professional.

I've figured it out!

The problem is in using even/odd QwtSymbol sizes.
E.g. it is better to set an even size using a circle (QwtSymbol::Ellipse), and odd size using QwtSymbol::Star1.

Ah o.k. but then the odd size of the ellipse should be also bad on the plot itself ?

Unfortunately I had to rewrite much of the symbol code for Qwt 6 because of the floating point based render engine ( + symbols can be cached in a pixmap, what is sometimes faster ). So I might have introduced bugs in this version.

Uwe

The ellipse with an odd side looks ok by itself. But if I put a circle with an odd size in a circe with an even size there is a problem that the inner circle looks asymmetrical:

Attachment 5872

Code:

---

QwtSymbol *sym1 = new QwtSymbol(QwtSymbol::Ellipse);
    sym1->setSize(14);
    sym1->setPen(QColor(Qt::blue));
 
    _curve1.setSymbol(sym1);
    _curve1.setStyle(QwtPlotCurve::NoCurve);
    _curve1.attach(this);
 
    QwtSymbol *sym2 = new QwtSymbol(QwtSymbol::Ellipse, Qt::black, QColor(Qt::black), QSize(7, 7));
 
    _curve2.setSymbol(sym2);
    _curve2.setStyle(QwtPlotCurve::NoCurve);
    _curve2.attach(this);
 
    QVector <double> x;
 
    for (unsigned i = 0; i < 10; ++i)
    {
        x.push_back(i);
    }
 
    _curve1.setSamples(x, x);
    _curve2.setSamples(x, x);

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