Constant Grid

[myzinsky]

I Set the stepsize to 10...

But, whe I zoom everything changed again

[Uwe]

But, whe I zoom everything changed again

Setting a fixed step size doesn't make too much sense when zooming ( consider a step size of 10 for a range of 5-6 ).

But as I wrote before - simply decouple the grid from the ticks of the scales by overloading QwtPlotGrid::updateScaleDiv().

class YourGrid: public QwtPlotGrid
{
public:
    ...
   virtual void updateScaleDiv( const QwtScaleDiv& xScaleDiv, const QwtScaleDiv& yScaleDiv )
   {
        QwtScaleDiv scaleDiv;
        scaleDiv.setInterval( xScaleDiv.interval() );
 
        double min = xScaleDiv.interval().lowerBound();
        double max = xScaleDiv.interval.upperBound();
        if ( min > max )
            qSwap( min, max );
 
        const int stepSize = 10.0;
 
        min = static_cast<int>( min / stepSize ) * stepSize;
 
        QList<double > ticks;
        for ( double tick = min; tick <= max; tick += stepSize )
            ticks += tick;
 
       scaleDiv.setTicks( QwtScaleDiv::MajorTick, ticks );
 
       QwtPlotGrid::updateScaleDiv( scaleDiv, yScaleDiv );
}

class YourGrid: public QwtPlotGrid
{
public:
    ...
   virtual void updateScaleDiv( const QwtScaleDiv& xScaleDiv, const QwtScaleDiv& yScaleDiv )
   {
        QwtScaleDiv scaleDiv;
        scaleDiv.setInterval( xScaleDiv.interval() );

        double min = xScaleDiv.interval().lowerBound();
        double max = xScaleDiv.interval.upperBound();
        if ( min > max )
            qSwap( min, max );

        const int stepSize = 10.0;

        min = static_cast<int>( min / stepSize ) * stepSize;

        QList<double > ticks;
        for ( double tick = min; tick <= max; tick += stepSize )
            ticks += tick;

       scaleDiv.setTicks( QwtScaleDiv::MajorTick, ticks );

       QwtPlotGrid::updateScaleDiv( scaleDiv, yScaleDiv );
}

To copy to clipboard, switch view to plain text mode 

Uwe

[myzinsky]

It works fine!

But I had to change this:

double min = xScaleDiv.interval().minValue();
double max = xScaleDiv.interval().maxValue();

double min = xScaleDiv.interval().minValue();
double max = xScaleDiv.interval().maxValue();

To copy to clipboard, switch view to plain text mode 

Tank You Uwe!
Regards