/*!
Align and divide an interval
\param maxNumSteps Max. number of steps
\param x1 First limit of the interval (In/Out)
\param x2 Second limit of the interval (In/Out)
\param stepSize Step size (Out)
\sa QwtScaleEngine::setAttribute()
*/
void QwtLog10ScaleEngine::autoScale(int maxNumSteps,
double &x1, double &x2, double &stepSize) const
{
if ( x1 > x2 )
qSwap(x1, x2);
QwtDoubleInterval interval(x1 / pow(10.0, lowerMargin()),
x2 * pow(10.0, upperMargin()) );
if (interval.maxValue() / interval.minValue() < 10.0)
{
// scale width is less than one decade -> build linear scale
QwtLinearScaleEngine linearScaler;
linearScaler.setAttributes(attributes());
linearScaler.setReference(reference());
linearScaler.setMargins(lowerMargin(), upperMargin());
linearScaler.autoScale(maxNumSteps, x1, x2, stepSize);
stepSize = ::log10(stepSize);
return;
}
double logRef = 1.0;
if (reference() > LOG_MIN / 2)
logRef = qwtMin(reference(), LOG_MAX / 2);
if (testAttribute(QwtScaleEngine::Symmetric))
{
const double delta = qwtMax(interval.maxValue() / logRef,
logRef / interval.minValue());
interval.setInterval(logRef / delta, logRef * delta);
}
if (testAttribute(QwtScaleEngine::IncludeReference))
interval = interval.extend(logRef);
interval = interval.limited(LOG_MIN, LOG_MAX);
if (interval.width() == 0.0)
interval = buildInterval(interval.minValue());
stepSize = divideInterval(log10(interval).width(), qwtMax(maxNumSteps, 1));
if ( stepSize < 1.0 )
stepSize = 1.0;
if (!testAttribute(QwtScaleEngine::Floating))
interval = align(interval, stepSize);
x1 = interval.minValue();
x2 = interval.maxValue();
if (testAttribute(QwtScaleEngine::Inverted))
{
qSwap(x1, x2);
stepSize = -stepSize;
}
}
/*!
Align and divide an interval
\param maxNumSteps Max. number of steps
\param x1 First limit of the interval (In/Out)
\param x2 Second limit of the interval (In/Out)
\param stepSize Step size (Out)
\sa QwtScaleEngine::setAttribute()
*/
void QwtLogScaleEngine::autoScale( int maxNumSteps,
double &x1, double &x2, double &stepSize ) const
{
if ( x1 > x2 )
qSwap( x1, x2 );
const double logBase = base();
QwtInterval interval( x1 / qPow( logBase, lowerMargin() ),
x2 * qPow( logBase, upperMargin() ) );
if ( interval.maxValue() / interval.minValue() < logBase )
{
// scale width is less than one step -> try to build a linear scale
QwtLinearScaleEngine linearScaler;
linearScaler.setAttributes( attributes() );
linearScaler.setReference( reference() );
linearScaler.setMargins( lowerMargin(), upperMargin() );
linearScaler.autoScale( maxNumSteps, x1, x2, stepSize );
QwtInterval linearInterval = QwtInterval( x1, x2 ).normalized();
linearInterval = linearInterval.limited( LOG_MIN, LOG_MAX );
if ( linearInterval.maxValue() / linearInterval.minValue() < logBase )
{
// the aligned scale is still less than one step
if ( stepSize < 0.0 )
stepSize = -qwtLog( logBase, qAbs( stepSize ) );
else
stepSize = qwtLog( logBase, stepSize );
return;
}
}
double logRef = 1.0;
if ( reference() > LOG_MIN / 2 )
logRef = qMin( reference(), LOG_MAX / 2 );
if ( testAttribute( QwtScaleEngine::Symmetric ) )
{
const double delta = qMax( interval.maxValue() / logRef,
logRef / interval.minValue() );
interval.setInterval( logRef / delta, logRef * delta );
}
if ( testAttribute( QwtScaleEngine::IncludeReference ) )
interval = interval.extend( logRef );
interval = interval.limited( LOG_MIN, LOG_MAX );
if ( interval.width() == 0.0 )
interval = buildInterval( interval.minValue() );
stepSize = divideInterval( qwtLogInterval( logBase, interval ).width(),
qMax( maxNumSteps, 1 ) );
if ( stepSize < 1.0 )
stepSize = 1.0;
if ( !testAttribute( QwtScaleEngine::Floating ) )
interval = align( interval, stepSize );
x1 = interval.minValue();
x2 = interval.maxValue();
if ( testAttribute( QwtScaleEngine::Inverted ) )
{
qSwap( x1, x2 );
stepSize = -stepSize;
}
}
