QwtKnob, how to obtain de startAngle and the spanAngle

[Hogwarts]

how can I, given 2 values within the range defined for the widget knob, get the arc joining these 2 points?...I mean the starting angle and the spanAngle. I need it to use the fallowing function void QPainter::drawArc ( const QRect & rectangle, int startAngle, int spanAngle ).
Thanks in advanced.

[Uwe]

Good question, but looking into the code I can see: knob->scaleDraw()->scaleMap() returns the map, that is used to translate between angles and scale values. p1()/p2() are the min/max angles in degrees/16.

Uwe

[Hogwarts]

What means the fallowing code lines:

const int tval = map().transform(value);

( ... )

const double arc = double(tval) / 16.0 * M_PI / 180.0;

these lines are in the function void QwtRoundScaleDraw::drawTick(QPainter *painter, double value, int len) const

perhaps arc is the angle corresponding to value parameter??