qwt_scale_engine.cpp

/* -*- mode: C++ ; c-file-style: "stroustrup" -*- *****************************
 * Qwt Widget Library
 * Copyright (C) 1997   Josef Wilgen
 * Copyright (C) 2002   Uwe Rathmann
 * 
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the Qwt License, Version 1.0
 *****************************************************************************/

#include "qwt_math.h"
#include "qwt_scale_map.h"
#include "qwt_scale_engine.h"

static const double _eps = 1.0e-6;

int QwtScaleArithmetic::compareEps(double value1, double value2, 
    double intervalSize) 
{
    const double eps = qwtAbs(_eps * intervalSize);

    if ( value2 - value1 > eps )
        return -1;

    if ( value1 - value2 > eps )
        return 1;

    return 0;
}

double QwtScaleArithmetic::ceilEps(double value, 
    double intervalSize) 
{
    const double eps = _eps * intervalSize;

    value = (value - eps) / intervalSize;
    return ceil(value) * intervalSize;
}

double QwtScaleArithmetic::floorEps(double value, double intervalSize) 
{
    const double eps = _eps * intervalSize;

    value = (value + eps) / intervalSize;
    return floor(value) * intervalSize;
}

/*
  \brief Divide an interval into steps

  \f$stepSize = (intervalSize - intervalSize * 10e^{-6}) / numSteps\f$

  \param intervalSize Interval size
  \param numSteps Number of steps
  \return Step size
*/
double QwtScaleArithmetic::divideEps(double intervalSize, double numSteps) 
{
    if ( numSteps == 0.0 || intervalSize == 0.0 )
        return 0.0;

    return (intervalSize - (_eps * intervalSize)) / numSteps;
} 

double QwtScaleArithmetic::ceil125(double x) 
{
    if (x == 0.0) 
        return 0.0;

    const double sign = (x > 0) ? 1.0 : -1.0;
    const double lx = log10(fabs(x));
    const double p10 = floor(lx);
    
    double fr = pow(10.0, lx - p10);
    if (fr <=1.0)
       fr = 1.0; 
    else if (fr <= 2.0)
       fr = 2.0;
    else if (fr <= 5.0) 
       fr = 5.0;
    else
       fr = 10.0;

    return sign * fr * pow(10.0, p10);
}

double QwtScaleArithmetic::floor125(double x) 
{
    if (x == 0.0)
        return 0.0;

    double sign = (x > 0) ? 1.0 : -1.0;
    const double lx = log10(fabs(x));
    const double p10 = floor(lx);

    double fr = pow(10.0, lx - p10);
    if (fr >= 10.0)
       fr = 10.0;
    else if (fr >= 5.0)
       fr = 5.0;
    else if (fr >= 2.0)
       fr = 2.0;
    else
       fr = 1.0;

    return sign * fr * pow(10.0, p10);
}

class QwtScaleEngine::PrivateData
{
public:
    PrivateData():
        attributes(QwtScaleEngine::NoAttribute),
        loMargin(0.0),
        hiMargin(0.0),
        referenceValue(0.0)
    {
    }

    int attributes;       // scale attributes

    double loMargin;      // margins
    double hiMargin;

    double referenceValue; // reference value

};

QwtScaleEngine::QwtScaleEngine()
{
    d_data = new PrivateData;
}


QwtScaleEngine::~QwtScaleEngine ()
{
    delete d_data;
}

double QwtScaleEngine::loMargin() const 
{ 
    return d_data->loMargin; 
}

double QwtScaleEngine::hiMargin() const 
{ 
    return d_data->hiMargin; 
}

void QwtScaleEngine::setMargins(double mlo, double mhi)
{
    d_data->loMargin = qwtMax(mlo,0.0);
    d_data->hiMargin = qwtMax(mhi,0.0);
}

double QwtScaleEngine::divideInterval(
    double intervalSize, int numSteps) const
{
    if ( numSteps <= 0 )
        return 0.0;

    double v = QwtScaleArithmetic::divideEps(intervalSize, numSteps);
    return QwtScaleArithmetic::ceil125(v);
}

bool QwtScaleEngine::contains(
    const QwtDoubleInterval &interval, double value) const
{
    if (!interval.isValid() )
        return false;
    
    if ( QwtScaleArithmetic::compareEps(value, 
        interval.minValue(), interval.width()) < 0 )
    {
        return false;
    }

    if ( QwtScaleArithmetic::compareEps(value, 
        interval.maxValue(), interval.width()) > 0 )
    {
        return false;
    }

    return true;
}

QwtValueList QwtScaleEngine::strip( 
    const QwtValueList& ticks, 
    const QwtDoubleInterval &interval) const
{
    if ( !interval.isValid() || ticks.count() == 0 )
        return QwtValueList();

    if ( contains(interval, ticks.first())
        && contains(interval, ticks.last()) )
    {
        return ticks;
    }

    QwtValueList strippedTicks;
    for ( int i = 0; i < (int)ticks.count(); i++ )
    {
        if ( contains(interval, ticks[i]) )
            strippedTicks += ticks[i];
    }
    return strippedTicks;
}

QwtDoubleInterval QwtScaleEngine::buildInterval(double v) const
{
#if 1
    const double delta = (v == 0.0) ? 0.5 : qwtAbs(0.5 * v);
    return QwtDoubleInterval(v - delta, v + delta);
#else
    if ( v == 0.0 )
        return QwtDoubleInterval(-0.5, 0.5);

    return QwtDoubleInterval(0.5 * v, 1.5 * v);
#endif
}

void QwtScaleEngine::setAttribute(Attribute attribute, bool on)
{
    if (on)
       d_data->attributes |= attribute;
    else
       d_data->attributes &= (~attribute);
}

bool QwtScaleEngine::testAttribute(Attribute attribute) const
{
    return bool(d_data->attributes & attribute);
}

void QwtScaleEngine::setAttributes(int attributes)
{
    d_data->attributes = attributes;
}

int QwtScaleEngine::attributes() const
{
    return d_data->attributes;
}

void QwtScaleEngine::setReference(double r)
{
    d_data->referenceValue = r;
}

double QwtScaleEngine::reference() const 
{ 
    return d_data->referenceValue; 
}

QwtScaleTransformation *QwtLinearScaleEngine::transformation() const
{
    return new QwtScaleTransformation(QwtScaleTransformation::Linear);
}

void QwtLinearScaleEngine::autoScale(int maxNumSteps, 
    double &x1, double &x2, double &stepSize) const
{
    QwtDoubleInterval interval(x1, x2);
    interval = interval.normalized();

    interval.setMinValue(interval.minValue() - loMargin());
    interval.setMaxValue(interval.maxValue() + hiMargin());

    if (testAttribute(QwtScaleEngine::Symmetric))
        interval = interval.symmetrize(reference());
 
    if (testAttribute(QwtScaleEngine::IncludeReference))
        interval = interval.extend(reference());

    if (interval.width() == 0.0)
        interval = buildInterval(interval.minValue());

    stepSize = divideInterval(interval.width(), qwtMax(maxNumSteps, 1));

    if ( !testAttribute(QwtScaleEngine::Floating) )
        interval = align(interval, stepSize);

    x1 = interval.minValue();
    x2 = interval.maxValue();

    if (testAttribute(QwtScaleEngine::Inverted))
    {
        qSwap(x1, x2);
        stepSize = -stepSize;
    }
}

QwtScaleDiv QwtLinearScaleEngine::divideScale(double x1, double x2,
    int maxMajSteps, int maxMinSteps, double stepSize) const
{
    QwtDoubleInterval interval = QwtDoubleInterval(x1, x2).normalized();
    if (interval.width() <= 0 )
        return QwtScaleDiv();

    stepSize = qwtAbs(stepSize);
    if ( stepSize == 0.0 )
    {
        if ( maxMajSteps < 1 )
            maxMajSteps = 1;

        stepSize = divideInterval(interval.width(), maxMajSteps);
    }

    QwtScaleDiv scaleDiv;

    if ( stepSize != 0.0 )
    {
        QwtValueList ticks[QwtScaleDiv::NTickTypes];
        buildTicks(interval, stepSize, maxMinSteps, ticks);

        scaleDiv = QwtScaleDiv(interval, ticks);
    }

    if ( x1 > x2 )
        scaleDiv.invert();

    return scaleDiv;
}

void QwtLinearScaleEngine::buildTicks(
    const QwtDoubleInterval& interval, double stepSize, int maxMinSteps,
    QwtValueList ticks[QwtScaleDiv::NTickTypes]) const
{
    const QwtDoubleInterval boundingInterval =
        align(interval, stepSize);
    
    ticks[QwtScaleDiv::MajorTick] = 
        buildMajorTicks(boundingInterval, stepSize);

    if ( maxMinSteps > 0 )
    {
        buildMinorTicks(ticks[QwtScaleDiv::MajorTick], maxMinSteps, stepSize,
            ticks[QwtScaleDiv::MinorTick], ticks[QwtScaleDiv::MediumTick]);
    }
    
    for ( int i = 0; i < QwtScaleDiv::NTickTypes; i++ )
    {
        ticks[i] = strip(ticks[i], interval);

        // ticks very close to 0.0 are 
        // explicitely set to 0.0

        for ( int j = 0; j < (int)ticks[i].count(); j++ )
        {
            if ( QwtScaleArithmetic::compareEps(ticks[i][j], 0.0, stepSize) == 0 )
                ticks[i][j] = 0.0;
        }
    }
}

QwtValueList QwtLinearScaleEngine::buildMajorTicks(
    const QwtDoubleInterval &interval, double stepSize) const
{
    int numTicks = qRound(interval.width() / stepSize) + 1;
#if 1
    if ( numTicks > 10000 )
        numTicks = 10000;
#endif

    QwtValueList ticks;

    ticks += interval.minValue();
    for (int i = 1; i < numTicks - 1; i++)
        ticks += interval.minValue() + i * stepSize;
    ticks += interval.maxValue();

    return ticks;
}

void QwtLinearScaleEngine::buildMinorTicks(
    const QwtValueList& majorTicks,
    int maxMinSteps, double stepSize,
    QwtValueList &minorTicks, 
    QwtValueList &mediumTicks) const
{   
    double minStep = divideInterval(stepSize, maxMinSteps);
    if (minStep == 0.0)  
        return; 
        
    // # minor steps per interval
    int nMin = qwtAbs(qRound(stepSize / minStep)) - 1;
    
    // Do the minor steps fit into the interval?
    if ( QwtScaleArithmetic::compareEps((nMin +  1) * qwtAbs(minStep), 
        qwtAbs(stepSize), stepSize) > 0)
    {   
        nMin = 1;
        minStep = stepSize * 0.5;
    }

    int medIndex = -1;
    if ( nMin % 2 )
        medIndex = nMin / 2;

    // calculate minor ticks

    for (int i = 0; i < (int)majorTicks.count(); i++)
    {
        double val = majorTicks[i];
        for (int k=0; k< nMin; k++)
        {
            val += minStep;

            double alignedValue = val;
            if (QwtScaleArithmetic::compareEps(val, 0.0, stepSize) == 0) 
                alignedValue = 0.0;

            if ( k == medIndex )
                mediumTicks += alignedValue;
            else
                minorTicks += alignedValue;
        }
    }
}

QwtDoubleInterval QwtLinearScaleEngine::align(
    const QwtDoubleInterval &interval, double stepSize) const
{
    const double x1 = 
        QwtScaleArithmetic::floorEps(interval.minValue(), stepSize);
    const double x2 = 
        QwtScaleArithmetic::ceilEps(interval.maxValue(), stepSize);

    return QwtDoubleInterval(x1, x2);
}

QwtScaleTransformation *QwtLog10ScaleEngine::transformation() const
{
    return new QwtScaleTransformation(QwtScaleTransformation::Log10);
}

void QwtLog10ScaleEngine::autoScale(int maxNumSteps, 
    double &x1, double &x2, double &stepSize) const
{
    if ( x1 > x2 )
        qSwap(x1, x2);

    QwtDoubleInterval interval(x1 / pow(10.0, loMargin()), 
        x2 * pow(10.0, hiMargin()) );

    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;
    }
}

QwtScaleDiv QwtLog10ScaleEngine::divideScale(double x1, double x2,
    int maxMajSteps, int maxMinSteps, double stepSize) const
{
    QwtDoubleInterval interval = QwtDoubleInterval(x1, x2).normalized();
    interval = interval.limited(LOG_MIN, LOG_MAX);

    if (interval.width() <= 0 )
        return QwtScaleDiv();

    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(loMargin(), hiMargin());

        return linearScaler.divideScale(x1, x2, 
            maxMajSteps, maxMinSteps, stepSize);
    }

    stepSize = qwtAbs(stepSize);
    if ( stepSize == 0.0 )
    {
        if ( maxMajSteps < 1 )
            maxMajSteps = 1;

        stepSize = divideInterval(log10(interval).width(), maxMajSteps);
        if ( stepSize < 1.0 )
            stepSize = 1.0; // major step must be >= 1 decade
    }

    QwtScaleDiv scaleDiv;
    if ( stepSize != 0.0 )
    {
        QwtValueList ticks[QwtScaleDiv::NTickTypes];
        buildTicks(interval, stepSize, maxMinSteps, ticks);

        scaleDiv = QwtScaleDiv(interval, ticks);
    }

    if ( x1 > x2 )
        scaleDiv.invert();

    return scaleDiv;
}

void QwtLog10ScaleEngine::buildTicks(
    const QwtDoubleInterval& interval, double stepSize, int maxMinSteps,
    QwtValueList ticks[QwtScaleDiv::NTickTypes]) const
{
    const QwtDoubleInterval boundingInterval =
        align(interval, stepSize);
    
    ticks[QwtScaleDiv::MajorTick] = 
        buildMajorTicks(boundingInterval, stepSize);

    if ( maxMinSteps > 0 )
    {
        ticks[QwtScaleDiv::MinorTick] = buildMinorTicks(
            ticks[QwtScaleDiv::MajorTick], maxMinSteps, stepSize);
    }
    
    for ( int i = 0; i < QwtScaleDiv::NTickTypes; i++ )
        ticks[i] = strip(ticks[i], interval);
}

QwtValueList QwtLog10ScaleEngine::buildMajorTicks(
    const QwtDoubleInterval &interval, double stepSize) const
{
    double width = log10(interval).width();

    int numTicks = qRound(width / stepSize) + 1;
    if ( numTicks > 10000 )
        numTicks = 10000;

    const double lxmin = log(interval.minValue());
    const double lxmax = log(interval.maxValue());
    const double lstep = (lxmax - lxmin) / double(numTicks - 1);

    QwtValueList ticks;

    ticks += interval.minValue();

    for (int i = 1; i < numTicks; i++)
       ticks += exp(lxmin + double(i) * lstep);

    ticks += interval.maxValue();

    return ticks;
}

QwtValueList QwtLog10ScaleEngine::buildMinorTicks(
    const QwtValueList &majorTicks, 
    int maxMinSteps, double stepSize) const
{   
    if (stepSize < 1.1)            // major step width is one decade
    {
        if ( maxMinSteps < 1 )
            return QwtValueList();
            
        int k0, kstep, kmax;
        
        if (maxMinSteps >= 8)
        {
            k0 = 2;
            kmax = 9;
            kstep = 1;
        }   
        else if (maxMinSteps >= 4)
        {
            k0 = 2;
            kmax = 8;
            kstep = 2;
        }   
        else if (maxMinSteps >= 2)
        {
            k0 = 2;
            kmax = 5;
            kstep = 3;
        }
        else
        {
            k0 = 5;
            kmax = 5;
            kstep = 1;
        }

        QwtValueList minorTicks;

        for (int i = 0; i < (int)majorTicks.count(); i++)
        {
            const double v = majorTicks[i];
            for (int k = k0; k<= kmax; k+=kstep)
                minorTicks += v * double(k);
        }

        return minorTicks;
    }
    else  // major step > one decade
    {
        double minStep = divideInterval(stepSize, maxMinSteps);
        if ( minStep == 0.0 )
            return QwtValueList();

        if ( minStep < 1.0 )
            minStep = 1.0;

        // # subticks per interval
        int nMin = qRound(stepSize / minStep) - 1;

        // Do the minor steps fit into the interval?

        if ( QwtScaleArithmetic::compareEps((nMin +  1) * minStep, 
            qwtAbs(stepSize), stepSize) > 0)
        {
            nMin = 0;
        }

        if (nMin < 1)
            return QwtValueList();      // no subticks

        // substep factor = 10^substeps
        const double minFactor = qwtMax(pow(10.0, minStep), 10.0);

        QwtValueList minorTicks;
        for (int i = 0; i < (int)majorTicks.count(); i++)
        {
            double val = majorTicks[i];
            for (int k=0; k< nMin; k++)
            {
                val *= minFactor;
                minorTicks += val;
            }
        }
        return minorTicks;
    }
}

QwtDoubleInterval QwtLog10ScaleEngine::align(
    const QwtDoubleInterval &interval, double stepSize) const
{
    const QwtDoubleInterval intv = log10(interval);

    const double x1 = QwtScaleArithmetic::floorEps(intv.minValue(), stepSize);
    const double x2 = QwtScaleArithmetic::ceilEps(intv.maxValue(), stepSize);

    return pow10(QwtDoubleInterval(x1, x2));
}

QwtDoubleInterval QwtLog10ScaleEngine::log10(
    const QwtDoubleInterval &interval) const
{
    return QwtDoubleInterval(::log10(interval.minValue()),
            ::log10(interval.maxValue()));
}

QwtDoubleInterval QwtLog10ScaleEngine::pow10(
    const QwtDoubleInterval &interval) const
{
    return QwtDoubleInterval(pow(10.0, interval.minValue()),
            pow(10.0, interval.maxValue()));
}

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