Method checkRange

src/backend/worksheet/plots/cartesian/CartesianPlot.cpp:3667–3693

! * helper function for checkXRange() and checkYRange() */

 * helper function for checkXRange() and checkYRange()
 */
Range<double> CartesianPlotPrivate::checkRange(const Range<double>& range) {
	double start = range.start(), end = range.end();
	const auto scale = range.scale();
	if (scale == RangeT::Scale::Linear || (start > 0 && end > 0)) // nothing to do
		return range;
	if (start >= 0 && end >= 0 && scale == RangeT::Scale::Sqrt) // nothing to do
		return range;
	// TODO: check if start == end?

	double min = 0.01, max = 1.;

	if (scale == RangeT::Scale::Sqrt) {
		if (start < 0)
			start = 0.;
	} else if (start <= 0)
		start = min;
	if (scale == RangeT::Scale::Sqrt) {
		if (end < 0)
			end = max;
	} else if (end <= 0)
		end = max;

	auto newRange = range;
	newRange.setStart(start);
	newRange.setEnd(end);
	return newRange;
}

/*!
 * check for negative values in the range when non-linear scalings are used