setScaleDraw(QwtScaleDraw * scaleDraw) function in QwtPlotScaleItem class

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Hi, everyone.
I am using qwt-6.1.0 library. I want to draw scales inside the plot canvas. I have read the example which is given in QwtPlotScaleItem class reference and created a subclass of QwtPlot where in constructor I wrote this:

QwtPlotScaleItem *scaleItemY =
        new QwtPlotScaleItem(QwtScaleDraw::RightScale);
    scaleItemY->setBorderDistance(0);
    scaleItemY->attach(this);
    this->enableAxis(QwtPlot::yLeft, false);
 
    QwtPlotScaleItem *scaleItemX =
        new QwtPlotScaleItem(QwtScaleDraw::TopScale);
    scaleItemX->setBorderDistance(0);
    scaleItemX->attach(this);
    this->enableAxis(QwtPlot::xBottom, false);

QwtPlotScaleItem *scaleItemY =
        new QwtPlotScaleItem(QwtScaleDraw::RightScale);
    scaleItemY->setBorderDistance(0);
    scaleItemY->attach(this);
    this->enableAxis(QwtPlot::yLeft, false);

    QwtPlotScaleItem *scaleItemX =
        new QwtPlotScaleItem(QwtScaleDraw::TopScale);
    scaleItemX->setBorderDistance(0);
    scaleItemX->attach(this);
    this->enableAxis(QwtPlot::xBottom, false);

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Here everythig is ok. When I attach grid it cross labels, and now I want to shift labels, so that there would be no intersections of grids and labels. For that I have created a subclasses (XScaleDraw and YScaleDraw) of QwtScaleDraw class where i override virtual void drawLabel (QPainter* painter, double value) const function: instead of

lbl.draw ( painter, QRect( QPoint( 0, 0 ), labelSize.toSize() ) );

lbl.draw ( painter, QRect( QPoint( 0, 0 ), labelSize.toSize() ) );

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I wrote (for X shift) :

lbl.draw ( painter, QRect( QPoint( 0+(int)(labelSize.width()/2), 0 ), labelSize.toSize() ) );

lbl.draw ( painter, QRect( QPoint( 0+(int)(labelSize.width()/2), 0 ), labelSize.toSize() ) );

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and for Y shift:

lbl.draw ( painter, QRect( QPoint(0, 0+(int)(labelSize.height()/2) ), labelSize.toSize() ) );

lbl.draw ( painter, QRect( QPoint(0, 0+(int)(labelSize.height()/2) ), labelSize.toSize() ) );

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Now I set scale draw and after that problems arise:

QwtPlotScaleItem *scaleItemY =
        new QwtPlotScaleItem(QwtScaleDraw::RightScale);
    scaleItemY->setScaleDraw(new YScaleDraw);
    scaleItemY->setBorderDistance(0);
    scaleItemY->attach(this);
    this->enableAxis(QwtPlot::yLeft, false);
 
    QwtPlotScaleItem *scaleItemX =
        new QwtPlotScaleItem(QwtScaleDraw::TopScale);
    scaleItemX->setScaleDraw(new XScaleDraw);
    scaleItemX->setBorderDistance(0);
    scaleItemX->attach(this);
    this->enableAxis(QwtPlot::xBottom, false);

QwtPlotScaleItem *scaleItemY =
        new QwtPlotScaleItem(QwtScaleDraw::RightScale);
    scaleItemY->setScaleDraw(new YScaleDraw);
    scaleItemY->setBorderDistance(0);
    scaleItemY->attach(this);
    this->enableAxis(QwtPlot::yLeft, false);

    QwtPlotScaleItem *scaleItemX =
        new QwtPlotScaleItem(QwtScaleDraw::TopScale);
    scaleItemX->setScaleDraw(new XScaleDraw);
    scaleItemX->setBorderDistance(0);
    scaleItemX->attach(this);
    this->enableAxis(QwtPlot::xBottom, false);

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XScale is drawn at the top (instead of bottom) and YScale is disappeared. Actually it happens even if I don't override virtual void drawLabel (QPainter* painter, double value) const function and create empty subclass of QwtScaleDraw. Any idea what is going on here?