Segfault when calling setAxisScaleEngine more than 2 times

[jord]

I presume QwtPlot takes ownership of the scale engine after the call to setAxisScaleEngine. This sort of thing is standard behaviour with Qt, so I would say it is logical in this context.

Having said that, the Qt documentation is very explicit about when ownership of an object is and is not transferred. The Qwt documentation should be updated to be very explicit about when this does and does not occur.

[windsword]

Jord,
So what should one do to address or circumvent the behaviour? In my case, the call works only in Mac OS and not in Linux, the second call to either change the scale between Linear and Log, or change the Min and Max values is called as show here:

calibPlot->setAxisScale(QwtPlot::xBottom, xMinVal.toInt(&ok,10),axisXEnd->text().toInt(&ok,10) );

calibPlot->setAxisScale(QwtPlot::xBottom, xMinVal.toInt(&ok,10),axisXEnd->text().toInt(&ok,10) );

To copy to clipboard, switch view to plain text mode 

When called to change the Scale:

void CentralPage::xAxisScaleChange( const QString &xAxisScaleType)
{
	if (xAxisScaleType == "[X]Linear") { 
		calibPlot->setAxisScaleEngine(QwtPlot::xBottom, new QwtLinearScaleEngine ());
		calibPlot->replot();
	} else {
		calibPlot->setAxisScaleEngine(QwtPlot::xBottom, new QwtLog10ScaleEngine());
		calibPlot->replot();
	}
}

void CentralPage::xAxisScaleChange( const QString &xAxisScaleType)
{
	if (xAxisScaleType == "[X]Linear") { 
		calibPlot->setAxisScaleEngine(QwtPlot::xBottom, new QwtLinearScaleEngine ());
		calibPlot->replot();
	} else {
		calibPlot->setAxisScaleEngine(QwtPlot::xBottom, new QwtLog10ScaleEngine());
		calibPlot->replot();
	}
}

To copy to clipboard, switch view to plain text mode