qwt_scale_map.h

/* -*- 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
 *****************************************************************************/

#ifndef QWT_SCALE_MAP_H
#define QWT_SCALE_MAP_H

#include "qwt_global.h"
#include "qwt_math.h"

/*!
   \brief Operations for linear or logarithmic (base 10) transformations
*/
class QWT_EXPORT QwtScaleTransformation
{
public:
    enum Type
    {
        Linear,
        Log10,

        Other
    };

    QwtScaleTransformation(Type type);
    virtual ~QwtScaleTransformation();

    virtual double xForm(double x, double s1, double s2,
        double p1, double p2) const;
    virtual double invXForm(double x, double s1, double s2,
        double p1, double p2) const;

    inline Type type() const { return d_type; }
    
    virtual QwtScaleTransformation *copy() const;

private:
    QwtScaleTransformation();
    QwtScaleTransformation &operator=( const QwtScaleTransformation);

    const Type d_type;
};

/*!
   \brief A scale map

   QwtScaleMap offers transformations from a scale 
   into a paint interval and vice versa.
*/
class QWT_EXPORT QwtScaleMap
{
public:
    QwtScaleMap();
    QwtScaleMap(const QwtScaleMap&);

    ~QwtScaleMap();

    QwtScaleMap &operator=(const QwtScaleMap &);

    void setTransformation(QwtScaleTransformation * );
    const QwtScaleTransformation *transformation() const;

    void setPaintInterval(int p1, int p2);
    void setPaintXInterval(double p1, double p2);
    void setScaleInterval(double s1, double s2);

    int transform(double x) const;
    double invTransform(double i) const;

    double xTransform(double x) const;

    inline double p1() const;
    inline double p2() const;

    inline double s1() const;
    inline double s2() const;

    inline double pDist() const;
    inline double sDist() const;

    QT_STATIC_CONST double LogMin;
    QT_STATIC_CONST double LogMax;

private:
    void newFactor();   

    double d_s1, d_s2;     // scale interval boundaries
    double d_p1, d_p2;     // paint device interval boundaries

    double d_cnv;       // conversion factor

    QwtScaleTransformation *d_transformation;
};

/*!
    \return First border of the scale interval
*/
inline double QwtScaleMap::s1() const 
{
    return d_s1;
}

/*!
    \return Second border of the scale interval
*/
inline double QwtScaleMap::s2() const 
{
    return d_s2;
}

/*!
    \return First border of the paint interval
*/
inline double QwtScaleMap::p1() const 
{
    return d_p1;
}

/*!
    \return Second border of the paint interval
*/
inline double QwtScaleMap::p2() const 
{
    return d_p2;
}

inline double QwtScaleMap::pDist() const
{
    return qwtAbs(d_p2 - d_p1);
}

inline double QwtScaleMap::sDist() const
{
    return qwtAbs(d_s2 - d_s1);
}

/*!
  Transform a point related to the scale interval into an point 
  related to the interval of the paint device
*/
inline double QwtScaleMap::xTransform(double s) const
{
    // try to inline code from QwtScaleTransformation

    if ( d_transformation->type() == QwtScaleTransformation::Linear )
        return d_p1 + (s - d_s1) * d_cnv;

    if ( d_transformation->type() == QwtScaleTransformation::Log10 )
        return d_p1 + log(s / d_s1) * d_cnv;

    return d_transformation->xForm(s, d_s1, d_s2, d_p1, d_p2 );
}

/*!
  \brief Transform an paint device value into a value in the
         interval of the scale.
*/
inline double QwtScaleMap::invTransform(double p) const
{
    return d_transformation->invXForm(p, d_p1, d_p2, d_s1, d_s2 );
}

/*!
  Transform a point related to the scale interval into an point 
  related to the interval of the paint device and round it to
  an integer. (In Qt <= 3.x paint devices are integer based. )

  \sa QwtScaleMap::xTransform
*/
inline int QwtScaleMap::transform(double s) const
{
    return qRound(xTransform(s));
}

#endif