JUCE/modules/juce_gui_basics/layout/juce_StretchableObjectResizer.cpp

/*
  ==============================================================================

   This file is part of the JUCE 6 technical preview.
   Copyright (c) 2020 - Raw Material Software Limited

   You may use this code under the terms of the GPL v3
   (see www.gnu.org/licenses).

   For this technical preview, this file is not subject to commercial licensing.

   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
{

StretchableObjectResizer::StretchableObjectResizer() {}
StretchableObjectResizer::~StretchableObjectResizer() {}

void StretchableObjectResizer::addItem (const double size,
                                        const double minSize, const double maxSize,
                                        const int order)
{
    // the order must be >= 0 but less than the maximum integer value.
    jassert (order >= 0 && order < std::numeric_limits<int>::max());
    jassert (maxSize >= minSize);

    Item item;
    item.size = size;
    item.minSize = minSize;
    item.maxSize = maxSize;
    item.order = order;
    items.add (item);
}

double StretchableObjectResizer::getItemSize (const int index) const noexcept
{
    return isPositiveAndBelow (index, items.size()) ? items.getReference (index).size
                                                    : 0.0;
}

void StretchableObjectResizer::resizeToFit (const double targetSize)
{
    int order = 0;

    for (;;)
    {
        double currentSize = 0;
        double minSize = 0;
        double maxSize = 0;

        int nextHighestOrder = std::numeric_limits<int>::max();

        for (int i = 0; i < items.size(); ++i)
        {
            const Item& it = items.getReference(i);
            currentSize += it.size;

            if (it.order <= order)
            {
                minSize += it.minSize;
                maxSize += it.maxSize;
            }
            else
            {
                minSize += it.size;
                maxSize += it.size;
                nextHighestOrder = jmin (nextHighestOrder, it.order);
            }
        }

        const double thisIterationTarget = jlimit (minSize, maxSize, targetSize);

        if (thisIterationTarget >= currentSize)
        {
            const double availableExtraSpace = maxSize - currentSize;
            const double targetAmountOfExtraSpace = thisIterationTarget - currentSize;
            const double scale = availableExtraSpace > 0 ? targetAmountOfExtraSpace / availableExtraSpace : 1.0;

            for (int i = 0; i < items.size(); ++i)
            {
                Item& it = items.getReference(i);

                if (it.order <= order)
                    it.size = jlimit (it.minSize, it.maxSize, it.size + (it.maxSize - it.size) * scale);
            }
        }
        else
        {
            const double amountOfSlack = currentSize - minSize;
            const double targetAmountOfSlack = thisIterationTarget - minSize;
            const double scale = targetAmountOfSlack / amountOfSlack;

            for (int i = 0; i < items.size(); ++i)
            {
                Item& it = items.getReference(i);

                if (it.order <= order)
                    it.size = jmax (it.minSize, it.minSize + (it.size - it.minSize) * scale);
            }
        }

        if (nextHighestOrder < std::numeric_limits<int>::max())
            order = nextHighestOrder;
        else
            break;
    }
}

} // namespace juce