juce_NormalisableRange.h

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 /*
  ==============================================================================
 
   This file is part of the JUCE library.
   Copyright (c) 2022 - Raw Material Software Limited
 
   JUCE is an open source library subject to commercial or open-source
   licensing.
 
   The code included in this file is provided under the terms of the ISC license
   http://www.isc.org/downloads/software-support-policy/isc-license. Permission
   To use, copy, modify, and/or distribute this software for any purpose with or
   without fee is hereby granted provided that the above copyright notice and
   this permission notice appear in all copies.
 
   JUCE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL WARRANTIES, WHETHER
   EXPRESSED OR IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR PURPOSE, ARE
   DISCLAIMED.
 
  ==============================================================================
*/
 
namespace juce
{
 
//==============================================================================
template <typename ValueType>
class NormalisableRange
{
public:
    NormalisableRange() = default;
 
    NormalisableRange (const NormalisableRange&) = default;
    NormalisableRange& operator= (const NormalisableRange&) = default;
    NormalisableRange (NormalisableRange&&) = default;
    NormalisableRange& operator= (NormalisableRange&&) = default;
 
    NormalisableRange (ValueType rangeStart,
                       ValueType rangeEnd,
                       ValueType intervalValue,
                       ValueType skewFactor,
                       bool useSymmetricSkew = false) noexcept
        : start (rangeStart), end (rangeEnd), interval (intervalValue),
          skew (skewFactor), symmetricSkew (useSymmetricSkew)
    {
        checkInvariants();
    }
 
    NormalisableRange (ValueType rangeStart,
                       ValueType rangeEnd) noexcept
        : start (rangeStart), end (rangeEnd)
    {
        checkInvariants();
    }
 
    NormalisableRange (ValueType rangeStart,
                       ValueType rangeEnd,
                       ValueType intervalValue) noexcept
        : start (rangeStart), end (rangeEnd), interval (intervalValue)
    {
        checkInvariants();
    }
 
    NormalisableRange (Range<ValueType> range) noexcept
        : NormalisableRange (range.getStart(), range.getEnd())
    {
    }
 
    NormalisableRange (Range<ValueType> range, ValueType intervalValue) noexcept
        : NormalisableRange (range.getStart(), range.getEnd(), intervalValue)
    {
    }
 
    using ValueRemapFunction = std::function<ValueType(ValueType rangeStart,
                                                       ValueType rangeEnd,
                                                       ValueType valueToRemap)>;
 
    NormalisableRange (ValueType rangeStart,
                       ValueType rangeEnd,
                       ValueRemapFunction convertFrom0To1Func,
                       ValueRemapFunction convertTo0To1Func,
                       ValueRemapFunction snapToLegalValueFunc = {}) noexcept
        : start (rangeStart),
          end   (rangeEnd),
          convertFrom0To1Function  (std::move (convertFrom0To1Func)),
          convertTo0To1Function    (std::move (convertTo0To1Func)),
          snapToLegalValueFunction (std::move (snapToLegalValueFunc))
    {
        checkInvariants();
    }
 
    ValueType convertTo0to1 (ValueType v) const noexcept
    {
        if (convertTo0To1Function != nullptr)
            return clampTo0To1 (convertTo0To1Function (start, end, v));
 
        auto proportion = clampTo0To1 ((v - start) / (end - start));
 
        if (exactlyEqual (skew, static_cast<ValueType> (1)))
            return proportion;
 
        if (! symmetricSkew)
            return std::pow (proportion, skew);
 
        auto distanceFromMiddle = static_cast<ValueType> (2) * proportion - static_cast<ValueType> (1);
 
        return (static_cast<ValueType> (1) + std::pow (std::abs (distanceFromMiddle), skew)
                                           * (distanceFromMiddle < ValueType() ? static_cast<ValueType> (-1)
                                                                               : static_cast<ValueType> (1)))
               / static_cast<ValueType> (2);
    }
 
    ValueType convertFrom0to1 (ValueType proportion) const noexcept
    {
        proportion = clampTo0To1 (proportion);
 
        if (convertFrom0To1Function != nullptr)
            return convertFrom0To1Function (start, end, proportion);
 
        if (! symmetricSkew)
        {
            if (! exactlyEqual (skew, static_cast<ValueType> (1)) && proportion > ValueType())
                proportion = std::exp (std::log (proportion) / skew);
 
            return start + (end - start) * proportion;
        }
 
        auto distanceFromMiddle = static_cast<ValueType> (2) * proportion - static_cast<ValueType> (1);
 
        if (! exactlyEqual (skew, static_cast<ValueType> (1)) && ! exactlyEqual (distanceFromMiddle, static_cast<ValueType> (0)))
            distanceFromMiddle = std::exp (std::log (std::abs (distanceFromMiddle)) / skew)
                                 * (distanceFromMiddle < ValueType() ? static_cast<ValueType> (-1)
                                                                     : static_cast<ValueType> (1));
 
        return start + (end - start) / static_cast<ValueType> (2) * (static_cast<ValueType> (1) + distanceFromMiddle);
    }
 
    ValueType snapToLegalValue (ValueType v) const noexcept
    {
        if (snapToLegalValueFunction != nullptr)
            return snapToLegalValueFunction (start, end, v);
 
        if (interval > ValueType())
            v = start + interval * std::floor ((v - start) / interval + static_cast<ValueType> (0.5));
 
        return (v <= start || end <= start) ? start : (v >= end ? end : v);
    }
 
    Range<ValueType> getRange() const noexcept          { return { start, end }; }
 
    void setSkewForCentre (ValueType centrePointValue) noexcept
    {
        jassert (centrePointValue > start);
        jassert (centrePointValue < end);
 
        symmetricSkew = false;
        skew = std::log (static_cast<ValueType> (0.5)) / std::log ((centrePointValue - start) / (end - start));
        checkInvariants();
    }
 
    ValueType start = 0;
 
    ValueType end = 1;
 
    ValueType interval = 0;
 
    ValueType skew = 1;
 
    bool symmetricSkew = false;
 
private:
    void checkInvariants() const
    {
        jassert (end > start);
        jassert (interval >= ValueType());
        jassert (skew > ValueType());
    }
 
    static ValueType clampTo0To1 (ValueType value)
    {
        auto clampedValue = jlimit (static_cast<ValueType> (0), static_cast<ValueType> (1), value);
 
        // If you hit this assertion then either your normalisation function is not working
        // correctly or your input is out of the expected bounds.
        jassert (exactlyEqual (clampedValue, value));
 
        return clampedValue;
    }
 
    ValueRemapFunction convertFrom0To1Function, convertTo0To1Function, snapToLegalValueFunction;
};
 
} // namespace juce