How does works QwtScaleDraw::extent()?

[mastupristi]

why if I call extent() from a QwtScaleDraw object the result is less then if I call from QwtScaleWidget::scaleDraw()?
what do I need to setup in QwtScaleDraw object to make extent() return the sam as QwtScaleWidget::scaleDraw().extent()?

her is the code snippet:

// code to test extent() method
 
        QFont f;
 
        QwtScaleDiv *sd = new QwtScaleDiv(-60, 0);
        QList< double > ld;
 
        double q;
        for(q=-60.0; q<=0.0; q+=5.0)
            ld.append(q);
 
        sd->setTicks(QwtScaleDiv::MajorTick, ld);
 
        QwtScaleDraw *sdraw = new QwtScaleDraw;
        sdraw->setScaleDiv(*sd);
        qDebug("extent 1 %f", sdraw->extent(f)); // here is 23.0
 
        QwtScaleWidget *w = new QwtScaleWidget(this);
        w->setScaleDiv(*sd);
 
        qDebug("extent 2 %f", w->scaleDraw()->extent(f)); // here is 31.0

// code to test extent() method

        QFont f;

        QwtScaleDiv *sd = new QwtScaleDiv(-60, 0);
        QList< double > ld;

        double q;
        for(q=-60.0; q<=0.0; q+=5.0)
            ld.append(q);

        sd->setTicks(QwtScaleDiv::MajorTick, ld);

        QwtScaleDraw *sdraw = new QwtScaleDraw;
        sdraw->setScaleDiv(*sd);
        qDebug("extent 1 %f", sdraw->extent(f)); // here is 23.0

        QwtScaleWidget *w = new QwtScaleWidget(this);
        w->setScaleDiv(*sd);

        qDebug("extent 2 %f", w->scaleDraw()->extent(f)); // here is 31.0

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bets regards
max