annotate base/LogRange.h @ 1376:d9511f9e04d7 dev/refactor-piper-related

Introduce some POD structs for describing an external server application and the desired libraries to load from it, and disambiguating between empty list request and invalid list request. This allows for overriding PiperVampPluginFactory behaviour for using a PluginScan to populate the list request.

/* -*- c-basic-offset: 4 indent-tabs-mode: nil -*-  vi:set ts=8 sts=4 sw=4: */

/*
    Sonic Visualiser
    An audio file viewer and annotation editor.
    Centre for Digital Music, Queen Mary, University of London.
    This file copyright 2006 Chris Cannam.
    
    This program is free software; you can redistribute it and/or
    modify it under the terms of the GNU General Public License as
    published by the Free Software Foundation; either version 2 of the
    License, or (at your option) any later version.  See the file
    COPYING included with this distribution for more information.
*/

#ifndef _LOG_RANGE_H_
#define _LOG_RANGE_H_

#include <vector>
#include "Debug.h"

class LogRange
{
public:
    /**
     * Map a linear range onto a logarithmic range.  min and max are
     * passed as the extents of the linear range and returned as the
     * extents of the logarithmic range.  thresh is the minimum value
     * for the log range, to be used if the linear range spans zero.
     */
    static void mapRange(double &min, double &max, double thresh = -10);

    /**
     * Map a value onto a logarithmic range.  This just means taking
     * the base-10 log of the absolute value, or using the threshold
     * value if the absolute value is zero.
     */
    static double map(double value, double thresh = -10);

    /**
     * Map a value from the logarithmic range back again.  This just
     * means taking the value'th power of ten.
     */
    static double unmap(double value);

    /**
     * Estimate whether a set of values would be more properly shown
     * using a logarithmic than a linear scale.  This is only ever
     * going to be a rough guess.
     */
    static bool useLogScale(std::vector<double> values);

};

#endif