Issue with QwtPlot::setAxisScaleDiv();

[Uwe]

Will overloading QwtPlot::setAxisScaleEngine() allow me to reflect irregularity from prepared QwtScaleDiv ?

class YourScaleEngine: public QwtLinearScaleEngine
{
public:
   virtual QwtScaleDiv divideScale( double x1, double x2, int , int , double  ) const
   {
        const QwtInterval interval = QwtInterval( x1, x2 ).normalized();
        QList<double> ticks[QwtScaleDiv::NTickTypes];
 
        // fill the ticks somehow according to interval
        // here you can set whatever ticks you want as long as
        // they are inside the interval x1/x2
 
        ticks[QwtScaleDiv::MajorTick] += ...;
        ....
 
        QwtScaleDiv scaleDiv( interval, ticks );
        if ( x1 > x2 )
            scaleDiv.invert();
 
        return scaleDiv;       
   }
};

class YourScaleEngine: public QwtLinearScaleEngine
{
public:
   virtual QwtScaleDiv divideScale( double x1, double x2, int , int , double  ) const
   {
        const QwtInterval interval = QwtInterval( x1, x2 ).normalized();
        QList<double> ticks[QwtScaleDiv::NTickTypes];

        // fill the ticks somehow according to interval
        // here you can set whatever ticks you want as long as
        // they are inside the interval x1/x2

        ticks[QwtScaleDiv::MajorTick] += ...;
        ....

        QwtScaleDiv scaleDiv( interval, ticks );
        if ( x1 > x2 )
            scaleDiv.invert();

        return scaleDiv;       
   }
};

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and

plot->setAxisScaleEngine( axis, new YourScaleEngine() );

plot->setAxisScaleEngine( axis, new YourScaleEngine() );

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Also it completely puzzles me why setAxisScaleDiv() works only once at plot creation time ?

Because all what modifies a scale ( f.e panning, zooming ) has to do it in the end with setAxisScaleDiv() and your initial assignment gets overwritten.

Uwe