Qwt : align center the date/time label text on an bottom axis

[vcloarec]

With Qwt, I want that the time and the date are both center under the stick under a bottom axis, but the time is still on the left side like in this picture :

Capture.jpg

I have tried to use

QwtDateScaleDraw::setLabelAlignment(Qt::AlignHCenter|Qt::AlignBottom);

QwtDateScaleDraw::setLabelAlignment(Qt::AlignHCenter|Qt::AlignBottom);

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But the time is still on the left.

I have tried to subclass the QwtScaleDraw like this:

class MyDateScaleDraw:public QwtDateScaleDraw
{
public:
    QwtText label(double value) const override
    {
        QwtText txt=QwtDateScaleDraw::label(value);
        txt.setRenderFlags(Qt::AlignHCenter);
        return txt;
    }
};

class MyDateScaleDraw:public QwtDateScaleDraw
{
public:
    QwtText label(double value) const override
    {
        QwtText txt=QwtDateScaleDraw::label(value);
        txt.setRenderFlags(Qt::AlignHCenter);
        return txt;
    }
};

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But the time is still on the left side.

Somebody know how to center the time ?