Refreshing a Custom QwtScaleDraw

Hi, I have reimplemented QwtScaleDraw.

When I start plotting data I would like the current time to be displayed. Not the time when the application started.

I reset my QTime, It does eventually display the right time after the plot starts to auto scale.

Thanks in advance
Brendan

Code:

---

class TimeScaleDraw: public QwtScaleDraw
{
public:
    TimeScaleDraw();
    void start();
    virtual QwtText label(double) const;
 
private:
    QTime m_base_time;
};
 
TimeScaleDraw::TimeScaleDraw()
{
    start();
}
 
QwtText TimeScaleDraw::label(double v) const
{
    QTime upTime = m_base_time.addMSecs((int)v);
 
    return upTime.toString("H:mm:ss.zzz");
}
 
void TimeScaleDraw::start()
{
    m_base_time.start();
//TODO: DO SOMETHING HERE TO REFRESH QwtScaleDraw???
}

---

QwtPlot::replot()

Uwe

I tried calling qwtPlot->replot() after start() was called, this didn't make any difference.

I have also tried passing the QwtPlot pointer to the class and running replot() with that pointer. This didn't make any difference.

When I added QwtPlot::replot() to the class it gave the following error:
"cannot call member function 'virtual void QwtPlot::replot()' without object"
I tried adding friend classes etc.

I don't seem to have the same problem with my custom QwtPlotPicker.

Please excuse my stupidity in advance :)

Code:

---

TimeScaleDraw* scaleDraw = dynamic_cast<TimeScaleDraw*>( plot->axisScaleDraw( ... ) );
scaleDraw->start();
scaleDraw->invalidateCache();
plot->replot();

---

HTH,
Uwe

The scaleDraw->invalidateCache() gives a protected error when compiling.

If I put invalidateCache() inside a new function that changes appearance in TimeScaleDraw class: eg ms, sec, clock etc it changes straight away.

However if invalidateCache() is put in the end of start() time still doesn't update until the plot starts moving etc. I guess this isn't too much of an issue.

I just use the following for time atm:

Code:

---

QwtText TimeScaleDraw::label(double /*v*/) const
{
    return m_base_time.toString("H:mm:ss.zzz");
}

---

The call to invalidateCache() won't cause a replot on its own, it is just a method to ensure that the labels are recalculated the next time there -is- a replot. So after you construct your TimeScaleDraw class, call replot() from where ever you are in the code.

Yeah I was calling replot() last but made no difference.