JUCE/modules/juce_gui_basics/layout/juce_Grid.cpp

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

   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.

   By using JUCE, you agree to the terms of both the JUCE 7 End-User License
   Agreement and JUCE Privacy Policy.

   End User License Agreement: www.juce.com/juce-7-licence
   Privacy Policy: www.juce.com/juce-privacy-policy

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

   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 Item>
static Array<Item> operator+ (const Array<Item>& a, const Array<Item>& b)
{
    auto copy = a;
    copy.addArray (b);
    return copy;
}

struct Grid::Helpers
{

    struct AllTracksIncludingImplicit
    {
        Array<TrackInfo> items;
        int numImplicitLeading; // The number of implicit items before the explicit items
    };

    struct Tracks
    {
        AllTracksIncludingImplicit columns, rows;
    };

    struct NoRounding
    {
        template <typename T>
        T operator() (T t) const { return t; }
    };

    struct StandardRounding
    {
        template <typename T>
        T operator() (T t) const { return std::round (t); }
    };

    template <typename RoundingFunction>
    struct SizeCalculation
    {
        float getTotalAbsoluteSize (const Array<TrackInfo>& tracks, Px gapSize) noexcept
        {
            float totalCellSize = 0.0f;

            for (const auto& trackInfo : tracks)
                if (! trackInfo.isFractional() || trackInfo.isAuto())
                    totalCellSize += roundingFunction (trackInfo.getSize());

            float totalGap = tracks.size() > 1 ? (float) (tracks.size() - 1) * roundingFunction ((float) gapSize.pixels)
                                               : 0.0f;

            return totalCellSize + totalGap;
        }

        static float getRelativeUnitSize (float size, float totalAbsolute, const Array<TrackInfo>& tracks) noexcept
        {
            const float totalRelative = jlimit (0.0f, size, size - totalAbsolute);
            float factorsSum = 0.0f;

            for (const auto& trackInfo : tracks)
                if (trackInfo.isFractional())
                    factorsSum += trackInfo.getSize();

            jassert (! approximatelyEqual (factorsSum, 0.0f));
            return totalRelative / factorsSum;
        }

        //==============================================================================
        float getTotalAbsoluteHeight (const Array<TrackInfo>& rowTracks, Px rowGapSize)
        {
            return getTotalAbsoluteSize (rowTracks, rowGapSize);
        }

        float getTotalAbsoluteWidth (const Array<TrackInfo>& columnTracks, Px columnGapSize)
        {
            return getTotalAbsoluteSize (columnTracks, columnGapSize);
        }

        float getRelativeWidthUnit (float gridWidth, Px columnGapSize, const Array<TrackInfo>& columnTracks)
        {
            return getRelativeUnitSize (gridWidth, getTotalAbsoluteWidth (columnTracks, columnGapSize), columnTracks);
        }

        float getRelativeHeightUnit (float gridHeight, Px rowGapSize, const Array<TrackInfo>& rowTracks)
        {
            return getRelativeUnitSize (gridHeight, getTotalAbsoluteHeight (rowTracks, rowGapSize), rowTracks);
        }

        //==============================================================================
        static bool hasAnyFractions (const Array<TrackInfo>& tracks)
        {
            return std::any_of (tracks.begin(),
                                tracks.end(),
                                [] (const auto& t) { return t.isFractional(); });
        }

        void computeSizes (float gridWidth, float gridHeight,
                           Px columnGapToUse, Px rowGapToUse,
                           const Tracks& tracks)
        {
            if (hasAnyFractions (tracks.columns.items))
            {
                relativeWidthUnit = getRelativeWidthUnit (gridWidth, columnGapToUse, tracks.columns.items);
                fractionallyDividedWidth = gridWidth - getTotalAbsoluteSize (tracks.columns.items, columnGapToUse);
            }
            else
            {
                remainingWidth = gridWidth - getTotalAbsoluteSize (tracks.columns.items, columnGapToUse);
            }

            if (hasAnyFractions (tracks.rows.items))
            {
                relativeHeightUnit = getRelativeHeightUnit (gridHeight, rowGapToUse, tracks.rows.items);
                fractionallyDividedHeight = gridHeight - getTotalAbsoluteSize (tracks.rows.items, rowGapToUse);
            }
            else
            {
                remainingHeight = gridHeight - getTotalAbsoluteSize (tracks.rows.items, rowGapToUse);
            }

            const auto calculateTrackBounds = [&] (auto& outBounds,
                                                   const auto& trackItems,
                                                   auto relativeUnit,
                                                   auto totalSizeForFractionalItems,
                                                   auto gap)
            {
                const auto lastFractionalIndex = [&]
                {
                    for (int i = trackItems.size() - 1; 0 <= i; --i)
                        if (trackItems[i].isFractional())
                            return i;

                    return -1;
                }();

                float start = 0.0f;
                float carriedError = 0.0f;

                for (int i = 0; i < trackItems.size(); ++i)
                {
                    const auto& currentItem = trackItems[i];

                    const auto currentTrackSize = [&]
                    {
                        if (i == lastFractionalIndex)
                            return totalSizeForFractionalItems;

                        const auto absoluteSize = currentItem.getAbsoluteSize (relativeUnit);

                        if (! currentItem.isFractional())
                            return roundingFunction (absoluteSize);

                        const auto result = roundingFunction (absoluteSize - carriedError);
                        carriedError += result - absoluteSize;
                        return result;
                    }();

                    if (currentItem.isFractional())
                        totalSizeForFractionalItems -= currentTrackSize;

                    const auto end = start + currentTrackSize;
                    outBounds.emplace_back (start, end);
                    start = end + roundingFunction (static_cast<float> (gap.pixels));
                }
            };

            calculateTrackBounds (columnTrackBounds,
                                  tracks.columns.items,
                                  relativeWidthUnit,
                                  fractionallyDividedWidth,
                                  columnGapToUse);

            calculateTrackBounds (rowTrackBounds,
                                  tracks.rows.items,
                                  relativeHeightUnit,
                                  fractionallyDividedHeight,
                                  rowGapToUse);
        }

        float relativeWidthUnit         = 0.0f;
        float relativeHeightUnit        = 0.0f;
        float fractionallyDividedWidth  = 0.0f;
        float fractionallyDividedHeight = 0.0f;
        float remainingWidth            = 0.0f;
        float remainingHeight           = 0.0f;

        std::vector<Range<float>> columnTrackBounds;
        std::vector<Range<float>> rowTrackBounds;
        RoundingFunction roundingFunction;
    };

    //==============================================================================
    struct PlacementHelpers
    {
        enum { invalid = -999999 };
        static constexpr auto emptyAreaCharacter = ".";

        //==============================================================================
        struct LineRange { int start, end; };
        struct LineArea  { LineRange column, row; };
        struct LineInfo  { StringArray lineNames; };

        struct NamedArea
        {
            String name;
            LineArea lines;
        };

        //==============================================================================
        static Array<LineInfo> getArrayOfLinesFromTracks (const Array<TrackInfo>& tracks)
        {
            // fill line info array
            Array<LineInfo> lines;

            for (int i = 1; i <= tracks.size(); ++i)
            {
                const auto& currentTrack = tracks.getReference (i - 1);

                if (i == 1) // start line
                {
                    LineInfo li;
                    li.lineNames.add (currentTrack.getStartLineName());
                    lines.add (li);
                }

                if (i > 1 && i <= tracks.size()) // two lines in between tracks
                {
                    const auto& prevTrack = tracks.getReference (i - 2);

                    LineInfo li;
                    li.lineNames.add (prevTrack.getEndLineName());
                    li.lineNames.add (currentTrack.getStartLineName());

                    lines.add (li);
                }

                if (i == tracks.size()) // end line
                {
                    LineInfo li;
                    li.lineNames.add (currentTrack.getEndLineName());
                    lines.add (li);
                }
            }

            jassert (lines.size() == tracks.size() + 1);

            return lines;
        }

        //==============================================================================
        static int deduceAbsoluteLineNumberFromLineName (GridItem::Property prop,
                                                         const Array<TrackInfo>& tracks)
        {
            jassert (prop.hasAbsolute());

            const auto lines = getArrayOfLinesFromTracks (tracks);
            int count = 0;

            for (const auto [index, line] : enumerate (lines))
            {
                for (const auto& name : line.lineNames)
                {
                    if (prop.getName() == name)
                    {
                        ++count;
                        break;
                    }
                }

                if (count == prop.getNumber())
                    return (int) index + 1;
            }

            jassertfalse;
            return count;
        }

        static int deduceAbsoluteLineNumber (GridItem::Property prop,
                                             const Array<TrackInfo>& tracks)
        {
            jassert (prop.hasAbsolute());

            if (prop.hasName())
                return deduceAbsoluteLineNumberFromLineName (prop, tracks);

            if (prop.getNumber() > 0)
                return prop.getNumber();

            if (prop.getNumber() < 0)
                return tracks.size() + 2 + prop.getNumber();

            // An integer value of 0 is invalid
            jassertfalse;
            return 1;
        }

        static int deduceAbsoluteLineNumberFromNamedSpan (int startLineNumber,
                                                          GridItem::Property propertyWithSpan,
                                                          const Array<TrackInfo>& tracks)
        {
            jassert (propertyWithSpan.hasSpan());

            const auto lines = getArrayOfLinesFromTracks (tracks);
            int count = 0;

            const auto enumerated = enumerate (lines);

            for (const auto [index, line] : makeRange (enumerated.begin() + startLineNumber, enumerated.end()))
            {
                for (const auto& name : line.lineNames)
                {
                    if (propertyWithSpan.getName() == name)
                    {
                        ++count;
                        break;
                    }
                }

                if (count == propertyWithSpan.getNumber())
                    return (int) index + 1;
            }

            jassertfalse;
            return count;
        }

        static int deduceAbsoluteLineNumberBasedOnSpan (int startLineNumber,
                                                        GridItem::Property propertyWithSpan,
                                                        const Array<TrackInfo>& tracks)
        {
            jassert (propertyWithSpan.hasSpan());

            if (propertyWithSpan.hasName())
                return deduceAbsoluteLineNumberFromNamedSpan (startLineNumber, propertyWithSpan, tracks);

            return startLineNumber + propertyWithSpan.getNumber();
        }

        //==============================================================================
        static LineRange deduceLineRange (GridItem::StartAndEndProperty prop, const Array<TrackInfo>& tracks)
        {
            jassert (! (prop.start.hasAuto() && prop.end.hasAuto()));

            if (prop.start.hasAbsolute() && prop.end.hasAuto())
            {
                prop.end = GridItem::Span (1);
            }
            else if (prop.start.hasAuto() && prop.end.hasAbsolute())
            {
                prop.start = GridItem::Span (1);
            }

            auto s = [&]() -> LineRange
            {
                if (prop.start.hasAbsolute() && prop.end.hasAbsolute())
                {
                    return { deduceAbsoluteLineNumber (prop.start, tracks),
                             deduceAbsoluteLineNumber (prop.end, tracks) };
                }

                if (prop.start.hasAbsolute() && prop.end.hasSpan())
                {
                    const auto start = deduceAbsoluteLineNumber (prop.start, tracks);
                    return { start, deduceAbsoluteLineNumberBasedOnSpan (start, prop.end, tracks) };
                }

                if (prop.start.hasSpan() && prop.end.hasAbsolute())
                {
                    const auto start = deduceAbsoluteLineNumber (prop.end, tracks);
                    return { start, deduceAbsoluteLineNumberBasedOnSpan (start, prop.start, tracks) };
                }

                // Can't have an item with spans on both start and end.
                jassertfalse;
                return {};
            }();

            // swap if start overtakes end
            if (s.start > s.end)
                std::swap (s.start, s.end);
            else if (s.start == s.end)
                s.end = s.start + 1;

            return s;
        }

        static LineArea deduceLineArea (const GridItem& item,
                                        const Grid& grid,
                                        const std::map<String, LineArea>& namedAreas)
        {
            if (item.area.isNotEmpty() && ! grid.templateAreas.isEmpty())
            {
                // Must be a named area!
                jassert (namedAreas.count (item.area) != 0);

                return namedAreas.at (item.area);
            }

            return { deduceLineRange (item.column, grid.templateColumns),
                     deduceLineRange (item.row,    grid.templateRows) };
        }

        //==============================================================================
        static Array<StringArray> parseAreasProperty (const StringArray& areasStrings)
        {
            Array<StringArray> strings;

            for (const auto& areaString : areasStrings)
                strings.add (StringArray::fromTokens (areaString, false));

            if (strings.size() > 0)
            {
                for (auto s : strings)
                {
                    jassert (s.size() == strings[0].size()); // all rows must have the same number of columns
                }
            }

            return strings;
        }

        static NamedArea findArea (Array<StringArray>& stringsArrays)
        {
            NamedArea area;

            for (auto& stringArray : stringsArrays)
            {
                for (auto& string : stringArray)
                {
                    // find anchor
                    if (area.name.isEmpty())
                    {
                        if (string != emptyAreaCharacter)
                        {
                            area.name = string;
                            area.lines.row.start = stringsArrays.indexOf (stringArray) + 1; // non-zero indexed;
                            area.lines.column.start = stringArray.indexOf (string) + 1; // non-zero indexed;

                            area.lines.row.end = stringsArrays.indexOf (stringArray) + 2;
                            area.lines.column.end = stringArray.indexOf (string) + 2;

                            // mark as visited
                            string = emptyAreaCharacter;
                        }
                    }
                    else
                    {
                        if (string == area.name)
                        {
                            area.lines.row.end = stringsArrays.indexOf (stringArray) + 2;
                            area.lines.column.end = stringArray.indexOf (string) + 2;

                            // mark as visited
                            string = emptyAreaCharacter;
                        }
                    }
                }
            }

            return area;
        }

        //==============================================================================
        static std::map<String, LineArea> deduceNamedAreas (const StringArray& areasStrings)
        {
            auto stringsArrays = parseAreasProperty (areasStrings);

            std::map<String, LineArea> areas;

            for (auto area = findArea (stringsArrays); area.name.isNotEmpty(); area = findArea (stringsArrays))
            {
                if (areas.count (area.name) == 0)
                    areas[area.name] = area.lines;
                else
                    // Make sure your template-areas property only has one area with the same name and is well-formed
                    jassertfalse;
            }

            return areas;
        }

        //==============================================================================
        template <typename RoundingFunction>
        static Rectangle<float> getCellBounds (int columnNumber, int rowNumber,
                                               const Tracks& tracks,
                                               const SizeCalculation<RoundingFunction>& calculation)
        {
            const auto correctedColumn = columnNumber - 1 + tracks.columns.numImplicitLeading;
            const auto correctedRow    = rowNumber    - 1 + tracks.rows   .numImplicitLeading;

            jassert (isPositiveAndBelow (correctedColumn, tracks.columns.items.size()));
            jassert (isPositiveAndBelow (correctedRow,    tracks.rows   .items.size()));

            return
            {
                calculation.columnTrackBounds[(size_t) correctedColumn].getStart(),
                calculation.rowTrackBounds[(size_t) correctedRow].getStart(),
                calculation.columnTrackBounds[(size_t) correctedColumn].getEnd() - calculation.columnTrackBounds[(size_t) correctedColumn].getStart(),
                calculation.rowTrackBounds[(size_t) correctedRow].getEnd() - calculation.rowTrackBounds[(size_t) correctedRow].getStart()
            };
        }

        template <typename RoundingFunction>
        static Rectangle<float> alignCell (Rectangle<float> area,
                                           int columnNumber, int rowNumber,
                                           int numberOfColumns, int numberOfRows,
                                           const SizeCalculation<RoundingFunction>& calculation,
                                           AlignContent alignContent,
                                           JustifyContent justifyContent)
        {
            if (alignContent == AlignContent::end)
                area.setY (area.getY() + calculation.remainingHeight);

            if (justifyContent == JustifyContent::end)
                area.setX (area.getX() + calculation.remainingWidth);

            if (alignContent == AlignContent::center)
                area.setY (area.getY() + calculation.remainingHeight / 2);

            if (justifyContent == JustifyContent::center)
                area.setX (area.getX() + calculation.remainingWidth / 2);

            if (alignContent == AlignContent::spaceBetween)
            {
                const auto shift = ((float) (rowNumber - 1) * (calculation.remainingHeight / float (numberOfRows - 1)));
                area.setY (area.getY() + shift);
            }

            if (justifyContent == JustifyContent::spaceBetween)
            {
                const auto shift = ((float) (columnNumber - 1) * (calculation.remainingWidth / float (numberOfColumns - 1)));
                area.setX (area.getX() + shift);
            }

            if (alignContent == AlignContent::spaceEvenly)
            {
                const auto shift = ((float) rowNumber * (calculation.remainingHeight / float (numberOfRows + 1)));
                area.setY (area.getY() + shift);
            }

            if (justifyContent == JustifyContent::spaceEvenly)
            {
                const auto shift = ((float) columnNumber * (calculation.remainingWidth / float (numberOfColumns + 1)));
                area.setX (area.getX() + shift);
            }

            if (alignContent == AlignContent::spaceAround)
            {
                const auto inbetweenShift = calculation.remainingHeight / float (numberOfRows);
                const auto sidesShift = inbetweenShift / 2;
                auto shift = (float) (rowNumber - 1) * inbetweenShift + sidesShift;

                area.setY (area.getY() + shift);
            }

            if (justifyContent == JustifyContent::spaceAround)
            {
                const auto inbetweenShift = calculation.remainingWidth / float (numberOfColumns);
                const auto sidesShift = inbetweenShift / 2;
                auto shift = (float) (columnNumber - 1) * inbetweenShift + sidesShift;

                area.setX (area.getX() + shift);
            }

            return area;
        }

        template <typename RoundingFunction>
        static Rectangle<float> getAreaBounds (PlacementHelpers::LineRange columnRange,
                                               PlacementHelpers::LineRange rowRange,
                                               const Tracks& tracks,
                                               const SizeCalculation<RoundingFunction>& calculation,
                                               AlignContent alignContent,
                                               JustifyContent justifyContent)
        {
            const auto findAlignedCell = [&] (int column, int row)
            {
                const auto cell = getCellBounds (column, row, tracks, calculation);
                return alignCell (cell,
                                  column,
                                  row,
                                  tracks.columns.items.size(),
                                  tracks.rows.items.size(),
                                  calculation,
                                  alignContent,
                                  justifyContent);
            };

            const auto startCell = findAlignedCell (columnRange.start,   rowRange.start);
            const auto endCell   = findAlignedCell (columnRange.end - 1, rowRange.end - 1);

            const auto horizontalRange = startCell.getHorizontalRange().getUnionWith (endCell.getHorizontalRange());
            const auto verticalRange   = startCell.getVerticalRange()  .getUnionWith (endCell.getVerticalRange());
            return { horizontalRange.getStart(),  verticalRange.getStart(),
                     horizontalRange.getLength(), verticalRange.getLength() };
        }
    };

    //==============================================================================
    struct AutoPlacement
    {
        using ItemPlacementArray = Array<std::pair<GridItem*, PlacementHelpers::LineArea>>;

        //==============================================================================
        struct OccupancyPlane
        {
            struct Cell { int column, row; };

            OccupancyPlane (int highestColumnToUse, int highestRowToUse, bool isColumnFirst)
                : highestCrossDimension (isColumnFirst ? highestRowToUse : highestColumnToUse),
                  columnFirst (isColumnFirst)
            {}

            PlacementHelpers::LineArea setCell (Cell cell, int columnSpan, int rowSpan)
            {
                for (int i = 0; i < columnSpan; i++)
                    for (int j = 0; j < rowSpan; j++)
                        setCell (cell.column + i, cell.row + j);

                return { { cell.column, cell.column + columnSpan }, { cell.row, cell.row + rowSpan } };
            }

            PlacementHelpers::LineArea setCell (Cell start, Cell end)
            {
                return setCell (start, std::abs (end.column - start.column),
                                       std::abs (end.row - start.row));
            }

            Cell nextAvailable (Cell referenceCell, int columnSpan, int rowSpan)
            {
                while (isOccupied (referenceCell, columnSpan, rowSpan) || isOutOfBounds (referenceCell, columnSpan, rowSpan))
                    referenceCell = advance (referenceCell);

                return referenceCell;
            }

            Cell nextAvailableOnRow (Cell referenceCell, int columnSpan, int rowSpan, int rowNumber)
            {
                if (columnFirst && (rowNumber + rowSpan) > highestCrossDimension)
                    highestCrossDimension = rowNumber + rowSpan;

                while (isOccupied (referenceCell, columnSpan, rowSpan)
                       || (referenceCell.row != rowNumber))
                    referenceCell = advance (referenceCell);

                return referenceCell;
            }

            Cell nextAvailableOnColumn (Cell referenceCell, int columnSpan, int rowSpan, int columnNumber)
            {
                if (! columnFirst && (columnNumber + columnSpan) > highestCrossDimension)
                    highestCrossDimension = columnNumber + columnSpan;

                while (isOccupied (referenceCell, columnSpan, rowSpan)
                       || (referenceCell.column != columnNumber))
                    referenceCell = advance (referenceCell);

                return referenceCell;
            }

            void updateMaxCrossDimensionFromAutoPlacementItem (int columnSpan, int rowSpan)
            {
                highestCrossDimension = jmax (highestCrossDimension, 1 + getCrossDimension ({ columnSpan, rowSpan }));
            }

        private:
            struct SortableCell
            {
                int column, row;
                bool columnFirst;

                bool operator< (const SortableCell& other) const
                {
                    if (columnFirst)
                    {
                        if (row == other.row)
                            return column < other.column;

                        return row < other.row;
                    }

                    if (row == other.row)
                        return column < other.column;

                    return row < other.row;
                }
            };

            void setCell (int column, int row)
            {
                occupiedCells.insert ({ column, row, columnFirst });
            }

            bool isOccupied (Cell cell) const
            {
                return occupiedCells.count ({ cell.column, cell.row, columnFirst }) > 0;
            }

            bool isOccupied (Cell cell, int columnSpan, int rowSpan) const
            {
                for (int i = 0; i < columnSpan; i++)
                    for (int j = 0; j < rowSpan; j++)
                        if (isOccupied ({ cell.column + i, cell.row + j }))
                            return true;

                return false;
            }

            bool isOutOfBounds (Cell cell, int columnSpan, int rowSpan) const
            {
                const auto highestIndexOfCell = getCrossDimension (cell) + getCrossDimension ({ columnSpan, rowSpan });
                const auto highestIndexOfGrid = getHighestCrossDimension();

                return highestIndexOfGrid < highestIndexOfCell;
            }

            int getHighestCrossDimension() const
            {
                Cell cell { 1, 1 };

                if (occupiedCells.size() > 0)
                    cell = { occupiedCells.crbegin()->column, occupiedCells.crbegin()->row };

                return std::max (getCrossDimension (cell), highestCrossDimension);
            }

            Cell advance (Cell cell) const
            {
                if ((getCrossDimension (cell) + 1) >= getHighestCrossDimension())
                    return fromDimensions (getMainDimension (cell) + 1, 1);

                return fromDimensions (getMainDimension (cell), getCrossDimension (cell) + 1);
            }

            int getMainDimension (Cell cell) const   { return columnFirst ? cell.column : cell.row; }
            int getCrossDimension (Cell cell) const  { return columnFirst ? cell.row : cell.column; }

            Cell fromDimensions (int mainDimension, int crossDimension) const
            {
                if (columnFirst)
                    return { mainDimension, crossDimension };

                return { crossDimension, mainDimension };
            }

            int highestCrossDimension;
            bool columnFirst;
            std::set<SortableCell> occupiedCells;
        };

        //==============================================================================
        static bool isFixed (GridItem::StartAndEndProperty prop)
        {
            return prop.start.hasName() || prop.start.hasAbsolute() || prop.end.hasName() || prop.end.hasAbsolute();
        }

        static bool hasFullyFixedPlacement (const GridItem& item)
        {
            if (item.area.isNotEmpty())
                return true;

            if (isFixed (item.column) && isFixed (item.row))
                return true;

            return false;
        }

        static bool hasPartialFixedPlacement (const GridItem& item)
        {
            if (item.area.isNotEmpty())
                return false;

            if (isFixed (item.column) ^ isFixed (item.row))
                return true;

            return false;
        }

        static bool hasAutoPlacement (const GridItem& item)
        {
            return ! hasFullyFixedPlacement (item) && ! hasPartialFixedPlacement (item);
        }

        //==============================================================================
        static bool hasDenseAutoFlow (AutoFlow autoFlow)
        {
            return autoFlow == AutoFlow::columnDense
                || autoFlow == AutoFlow::rowDense;
        }

        static bool isColumnAutoFlow (AutoFlow autoFlow)
        {
            return autoFlow == AutoFlow::column
                || autoFlow == AutoFlow::columnDense;
        }

        //==============================================================================
        static int getSpanFromAuto (GridItem::StartAndEndProperty prop)
        {
            if (prop.end.hasSpan())
                return prop.end.getNumber();

            if (prop.start.hasSpan())
                return prop.start.getNumber();

            return 1;
        }

        //==============================================================================
        ItemPlacementArray deduceAllItems (Grid& grid) const
        {
            const auto namedAreas = PlacementHelpers::deduceNamedAreas (grid.templateAreas);

            OccupancyPlane plane (jmax (grid.templateColumns.size() + 1, 2),
                                  jmax (grid.templateRows.size() + 1, 2),
                                  isColumnAutoFlow (grid.autoFlow));

            ItemPlacementArray itemPlacementArray;
            Array<GridItem*> sortedItems;

            for (auto& item : grid.items)
                sortedItems.add (&item);

            std::stable_sort (sortedItems.begin(), sortedItems.end(),
                              [] (const GridItem* i1, const GridItem* i2)  { return i1->order < i2->order; });

            // place fixed items first
            for (auto* item : sortedItems)
            {
                if (hasFullyFixedPlacement (*item))
                {
                    const auto a = PlacementHelpers::deduceLineArea (*item, grid, namedAreas);
                    plane.setCell ({ a.column.start, a.row.start }, { a.column.end, a.row.end });
                    itemPlacementArray.add ({ item, a });
                }
            }

            OccupancyPlane::Cell lastInsertionCell = { 1, 1 };

            for (auto* item : sortedItems)
            {
                if (hasPartialFixedPlacement (*item))
                {
                    if (isFixed (item->column))
                    {
                        const auto p = PlacementHelpers::deduceLineRange (item->column, grid.templateColumns);
                        const auto columnSpan = std::abs (p.start - p.end);
                        const auto rowSpan = getSpanFromAuto (item->row);

                        const auto insertionCell = hasDenseAutoFlow (grid.autoFlow) ? OccupancyPlane::Cell { p.start, 1 }
                                                                                    : lastInsertionCell;
                        const auto nextAvailableCell = plane.nextAvailableOnColumn (insertionCell, columnSpan, rowSpan, p.start);
                        const auto lineArea = plane.setCell (nextAvailableCell, columnSpan, rowSpan);
                        lastInsertionCell = nextAvailableCell;

                        itemPlacementArray.add ({ item, lineArea });
                    }
                    else if (isFixed (item->row))
                    {
                        const auto p = PlacementHelpers::deduceLineRange (item->row, grid.templateRows);
                        const auto columnSpan = getSpanFromAuto (item->column);
                        const auto rowSpan = std::abs (p.start - p.end);

                        const auto insertionCell = hasDenseAutoFlow (grid.autoFlow) ? OccupancyPlane::Cell { 1, p.start }
                                                                                    : lastInsertionCell;

                        const auto nextAvailableCell = plane.nextAvailableOnRow (insertionCell, columnSpan, rowSpan, p.start);
                        const auto lineArea = plane.setCell (nextAvailableCell, columnSpan, rowSpan);

                        lastInsertionCell = nextAvailableCell;

                        itemPlacementArray.add ({ item, lineArea });
                    }
                }
            }

            // https://www.w3.org/TR/css-grid-1/#auto-placement-algo step 3.3
            for (auto* item : sortedItems)
                if (hasAutoPlacement (*item))
                    plane.updateMaxCrossDimensionFromAutoPlacementItem (getSpanFromAuto (item->column), getSpanFromAuto (item->row));

            lastInsertionCell = { 1, 1 };

            for (auto* item : sortedItems)
            {
                if (hasAutoPlacement (*item))
                {
                    const auto columnSpan = getSpanFromAuto (item->column);
                    const auto rowSpan = getSpanFromAuto (item->row);

                    const auto nextAvailableCell = plane.nextAvailable (lastInsertionCell, columnSpan, rowSpan);
                    const auto lineArea = plane.setCell (nextAvailableCell, columnSpan, rowSpan);

                    if (! hasDenseAutoFlow (grid.autoFlow))
                        lastInsertionCell = nextAvailableCell;

                    itemPlacementArray.add ({ item,  lineArea });
                }
            }

            return itemPlacementArray;
        }

        //==============================================================================
        template <typename Accessor>
        static PlacementHelpers::LineRange findFullLineRange (const ItemPlacementArray& items, Accessor&& accessor)
        {
            if (items.isEmpty())
                return { 1, 1 };

            const auto combine = [&accessor] (const auto& acc, const auto& item)
            {
                const auto newRange = accessor (item);
                return PlacementHelpers::LineRange { std::min (acc.start, newRange.start),
                                                     std::max (acc.end,   newRange.end) };
            };

            return std::accumulate (std::next (items.begin()), items.end(), accessor (*items.begin()), combine);
        }

        static PlacementHelpers::LineArea findFullLineArea (const ItemPlacementArray& items)
        {
            return { findFullLineRange (items, [] (const auto& item) { return item.second.column; }),
                     findFullLineRange (items, [] (const auto& item) { return item.second.row; }) };
        }

        template <typename Item>
        static Array<Item> repeated (int repeats, const Item& item)
        {
            Array<Item> result;
            result.insertMultiple (-1, item, repeats);
            return result;
        }

        static Tracks createImplicitTracks (const Grid& grid, const ItemPlacementArray& items)
        {
            const auto fullArea = findFullLineArea (items);

            const auto leadingColumns = std::max (0, 1 - fullArea.column.start);
            const auto leadingRows    = std::max (0, 1 - fullArea.row.start);

            const auto trailingColumns = std::max (0, fullArea.column.end - grid.templateColumns.size() - 1);
            const auto trailingRows    = std::max (0, fullArea.row   .end - grid.templateRows   .size() - 1);

            return  { { repeated (leadingColumns, grid.autoColumns) + grid.templateColumns + repeated (trailingColumns, grid.autoColumns),
                        leadingColumns },
                      { repeated (leadingRows,    grid.autoRows)    + grid.templateRows    + repeated (trailingRows,    grid.autoRows),
                        leadingRows } };
        }

        //==============================================================================
        static void applySizeForAutoTracks (Tracks& tracks, const ItemPlacementArray& placements)
        {
            const auto setSizes = [&placements] (auto& tracksInDirection, const auto& getItem, const auto& getItemSize)
            {
                auto& array = tracksInDirection.items;

                for (int index = 0; index < array.size(); ++index)
                {
                    if (array.getReference (index).isAuto())
                    {
                        const auto combiner = [&] (const auto acc, const auto& element)
                        {
                            const auto item = getItem (element.second);
                            const auto isNotSpan = std::abs (item.end - item.start) <= 1;
                            return isNotSpan && item.start == index + 1 - tracksInDirection.numImplicitLeading
                                   ? std::max (acc, getItemSize (*element.first))
                                   : acc;
                        };

                        array.getReference (index).size = std::accumulate (placements.begin(), placements.end(), 0.0f, combiner);
                    }
                }
            };

            setSizes (tracks.rows,
                      [] (const auto& i) { return i.row; },
                      [] (const auto& i) { return i.height + i.margin.top + i.margin.bottom; });

            setSizes (tracks.columns,
                      [] (const auto& i) { return i.column; },
                      [] (const auto& i) { return i.width + i.margin.left + i.margin.right; });
        }
    };

    //==============================================================================
    struct BoxAlignment
    {
        static Rectangle<float> alignItem (const GridItem& item, const Grid& grid, Rectangle<float> area)
        {
            // if item align is auto, inherit value from grid
            const auto alignType = item.alignSelf == GridItem::AlignSelf::autoValue
                                 ? grid.alignItems
                                 : static_cast<AlignItems> (item.alignSelf);

            const auto justifyType = item.justifySelf == GridItem::JustifySelf::autoValue
                                   ? grid.justifyItems
                                   : static_cast<JustifyItems> (item.justifySelf);

            // subtract margin from area
            area = BorderSize<float> (item.margin.top, item.margin.left, item.margin.bottom, item.margin.right)
                      .subtractedFrom (area);

            // align and justify
            auto r = area;

            if (! approximatelyEqual (item.width,     (float) GridItem::notAssigned))  r.setWidth  (item.width);
            if (! approximatelyEqual (item.height,    (float) GridItem::notAssigned))  r.setHeight (item.height);
            if (! approximatelyEqual (item.maxWidth,  (float) GridItem::notAssigned))  r.setWidth  (jmin (item.maxWidth,  r.getWidth()));
            if (item.minWidth  > 0.0f)                            r.setWidth  (jmax (item.minWidth,  r.getWidth()));
            if (! approximatelyEqual (item.maxHeight, (float) GridItem::notAssigned))  r.setHeight (jmin (item.maxHeight, r.getHeight()));
            if (item.minHeight > 0.0f)                            r.setHeight (jmax (item.minHeight, r.getHeight()));

            if (alignType == AlignItems::start && justifyType == JustifyItems::start)
                return r;

            if (alignType   == AlignItems::end)       r.setY (r.getY() + (area.getHeight() - r.getHeight()));
            if (justifyType == JustifyItems::end)     r.setX (r.getX() + (area.getWidth()  - r.getWidth()));
            if (alignType   == AlignItems::center)    r.setCentre (r.getCentreX(),    area.getCentreY());
            if (justifyType == JustifyItems::center)  r.setCentre (area.getCentreX(), r.getCentreY());

            return r;
        }
    };

};

//==============================================================================
Grid::TrackInfo::TrackInfo() noexcept : hasKeyword (true) {}

Grid::TrackInfo::TrackInfo (Px sizeInPixels) noexcept
    : size (static_cast<float> (sizeInPixels.pixels)), isFraction (false) {}

Grid::TrackInfo::TrackInfo (Fr fractionOfFreeSpace) noexcept
    : size ((float)fractionOfFreeSpace.fraction), isFraction (true) {}

Grid::TrackInfo::TrackInfo (Px sizeInPixels, const String& endLineNameToUse) noexcept
    : TrackInfo (sizeInPixels)
{
    endLineName = endLineNameToUse;
}

Grid::TrackInfo::TrackInfo (Fr fractionOfFreeSpace, const String& endLineNameToUse) noexcept
    : TrackInfo (fractionOfFreeSpace)
{
    endLineName = endLineNameToUse;
}

Grid::TrackInfo::TrackInfo (const String& startLineNameToUse, Px sizeInPixels) noexcept
    : TrackInfo (sizeInPixels)
{
    startLineName = startLineNameToUse;
}

Grid::TrackInfo::TrackInfo (const String& startLineNameToUse, Fr fractionOfFreeSpace) noexcept
    : TrackInfo (fractionOfFreeSpace)
{
    startLineName = startLineNameToUse;
}

Grid::TrackInfo::TrackInfo (const String& startLineNameToUse, Px sizeInPixels, const String& endLineNameToUse) noexcept
    : TrackInfo (startLineNameToUse, sizeInPixels)
{
    endLineName = endLineNameToUse;
}

Grid::TrackInfo::TrackInfo (const String& startLineNameToUse, Fr fractionOfFreeSpace, const String& endLineNameToUse) noexcept
    : TrackInfo (startLineNameToUse, fractionOfFreeSpace)
{
    endLineName = endLineNameToUse;
}

float Grid::TrackInfo::getAbsoluteSize (float relativeFractionalUnit) const
{
    return isFractional() ? size * relativeFractionalUnit : size;
}

//==============================================================================
void Grid::performLayout (Rectangle<int> targetArea)
{
    const auto itemsAndAreas = Helpers::AutoPlacement().deduceAllItems (*this);

    auto implicitTracks = Helpers::AutoPlacement::createImplicitTracks (*this, itemsAndAreas);

    Helpers::AutoPlacement::applySizeForAutoTracks (implicitTracks, itemsAndAreas);

    Helpers::SizeCalculation<Helpers::NoRounding> calculation;
    Helpers::SizeCalculation<Helpers::StandardRounding> roundedCalculation;

    const auto doComputeSizes = [&] (auto& sizeCalculation)
    {
        sizeCalculation.computeSizes (targetArea.toFloat().getWidth(),
                                      targetArea.toFloat().getHeight(),
                                      columnGap,
                                      rowGap,
                                      implicitTracks);
    };

    doComputeSizes (calculation);
    doComputeSizes (roundedCalculation);

    for (auto& itemAndArea : itemsAndAreas)
    {
        auto* item = itemAndArea.first;

        const auto getBounds = [&] (const auto& sizeCalculation)
        {
            const auto a = itemAndArea.second;

            const auto areaBounds = Helpers::PlacementHelpers::getAreaBounds (a.column,
                                                                              a.row,
                                                                              implicitTracks,
                                                                              sizeCalculation,
                                                                              alignContent,
                                                                              justifyContent);

            const auto rounded = [&] (auto rect) -> decltype (rect)
            {
                return { sizeCalculation.roundingFunction (rect.getX()),
                         sizeCalculation.roundingFunction (rect.getY()),
                         sizeCalculation.roundingFunction (rect.getWidth()),
                         sizeCalculation.roundingFunction (rect.getHeight()) };
            };

            return rounded (Helpers::BoxAlignment::alignItem (*item, *this, areaBounds));
        };

        item->currentBounds = getBounds (calculation) + targetArea.toFloat().getPosition();

        if (auto* c = item->associatedComponent)
            c->setBounds (getBounds (roundedCalculation).toNearestIntEdges() + targetArea.getPosition());
    }
}

//==============================================================================
#if JUCE_UNIT_TESTS

struct GridTests final : public UnitTest
{
    GridTests()
        : UnitTest ("Grid", UnitTestCategories::gui)
    {}

    void runTest() override
    {
        using Fr = Grid::Fr;
        using Tr = Grid::TrackInfo;
        using Rect = Rectangle<float>;

        beginTest ("Layout calculation of an empty grid is a no-op");
        {
            const Rectangle<int> bounds { 100, 200 };
            Grid grid;
            grid.performLayout (bounds);
        }

        {
            Grid grid;

            grid.templateColumns.add (Tr (1_fr));
            grid.templateRows.addArray ({ Tr (20_px), Tr (1_fr) });

            grid.items.addArray ({ GridItem().withArea (1, 1),
                                   GridItem().withArea (2, 1) });

            grid.performLayout (Rectangle<int> (200, 400));

            beginTest ("Layout calculation test: 1 column x 2 rows: no gap");
            expect (grid.items[0].currentBounds == Rect (0.0f, 0.0f,  200.f, 20.0f));
            expect (grid.items[1].currentBounds == Rect (0.0f, 20.0f, 200.f, 380.0f));

            grid.templateColumns.add (Tr (50_px));
            grid.templateRows.add (Tr (2_fr));

            grid.items.addArray ( { GridItem().withArea (1, 2),
                                    GridItem().withArea (2, 2),
                                    GridItem().withArea (3, 1),
                                    GridItem().withArea (3, 2) });

            grid.performLayout (Rectangle<int> (150, 170));

            beginTest ("Layout calculation test: 2 columns x 3 rows: no gap");
            expect (grid.items[0].currentBounds == Rect (0.0f,   0.0f,  100.0f, 20.0f));
            expect (grid.items[1].currentBounds == Rect (0.0f,   20.0f, 100.0f, 50.0f));
            expect (grid.items[2].currentBounds == Rect (100.0f, 0.0f,  50.0f,  20.0f));
            expect (grid.items[3].currentBounds == Rect (100.0f, 20.0f, 50.0f,  50.0f));
            expect (grid.items[4].currentBounds == Rect (0.0f,   70.0f, 100.0f, 100.0f));
            expect (grid.items[5].currentBounds == Rect (100.0f, 70.0f, 50.0f,  100.0f));

            grid.columnGap = 20_px;
            grid.rowGap    = 10_px;

            grid.performLayout (Rectangle<int> (200, 310));

            beginTest ("Layout calculation test: 2 columns x 3 rows: rowGap of 10 and columnGap of 20");
            expect (grid.items[0].currentBounds == Rect (0.0f, 0.0f, 130.0f, 20.0f));
            expect (grid.items[1].currentBounds == Rect (0.0f, 30.0f, 130.0f, 90.0f));
            expect (grid.items[2].currentBounds == Rect (150.0f, 0.0f, 50.0f, 20.0f));
            expect (grid.items[3].currentBounds == Rect (150.0f, 30.0f, 50.0f, 90.0f));
            expect (grid.items[4].currentBounds == Rect (0.0f, 130.0f, 130.0f, 180.0f));
            expect (grid.items[5].currentBounds == Rect (150.0f, 130.0f, 50.0f,  180.0f));
        }

        {
            Grid grid;

            grid.templateColumns.addArray ({ Tr ("first", 20_px, "in"), Tr ("in", 1_fr, "in"), Tr (20_px, "last") });
            grid.templateRows.addArray ({ Tr (1_fr),
                                          Tr (20_px)});

            {
                beginTest ("Grid items placement tests: integer and custom ident, counting forward");

                GridItem i1, i2, i3, i4, i5;
                i1.column = { 1, 4 };
                i1.row    = { 1, 2 };

                i2.column = { 1, 3 };
                i2.row    = { 1, 3 };

                i3.column = { "first", "in" };
                i3.row    = { 2, 3 };

                i4.column = { "first", { 2, "in" } };
                i4.row    = { 1, 2 };

                i5.column = { "first", "last" };
                i5.row    = { 1, 2 };

                grid.items.addArray ({ i1, i2, i3, i4, i5 });

                grid.performLayout ({ 140, 100 });

                expect (grid.items[0].currentBounds == Rect (0.0f, 0.0f,  140.0f, 80.0f));
                expect (grid.items[1].currentBounds == Rect (0.0f, 0.0f,  120.0f, 100.0f));
                expect (grid.items[2].currentBounds == Rect (0.0f, 80.0f, 20.0f,  20.0f));
                expect (grid.items[3].currentBounds == Rect (0.0f, 0.0f,  120.0f, 80.0f));
                expect (grid.items[4].currentBounds == Rect (0.0f, 0.0f,  140.0f, 80.0f));
            }
        }

        {
            Grid grid;

            grid.templateColumns.addArray ({ Tr ("first", 20_px, "in"), Tr ("in", 1_fr, "in"), Tr (20_px, "last") });
            grid.templateRows.addArray ({ Tr (1_fr),
                                          Tr (20_px)});

            beginTest ("Grid items placement tests: integer and custom ident, counting forward, reversed end and start");

            GridItem i1, i2, i3, i4, i5;
            i1.column = { 4, 1 };
            i1.row    = { 2, 1 };

            i2.column = { 3, 1 };
            i2.row    = { 3, 1 };

            i3.column = { "in", "first" };
            i3.row    = { 3, 2 };

            i4.column = { "first", { 2, "in" } };
            i4.row    = { 1, 2 };

            i5.column = { "last", "first" };
            i5.row    = { 1, 2 };

            grid.items.addArray ({ i1, i2, i3, i4, i5 });

            grid.performLayout ({ 140, 100 });

            expect (grid.items[0].currentBounds == Rect (0.0f, 0.0f,  140.0f, 80.0f));
            expect (grid.items[1].currentBounds == Rect (0.0f, 0.0f,  120.0f, 100.0f));
            expect (grid.items[2].currentBounds == Rect (0.0f, 80.0f, 20.0f,  20.0f));
            expect (grid.items[3].currentBounds == Rect (0.0f, 0.0f,  120.0f, 80.0f));
            expect (grid.items[4].currentBounds == Rect (0.0f, 0.0f,  140.0f, 80.0f));
        }

        {
            Grid grid;

            grid.templateColumns = { Tr ("first", 20_px, "in"), Tr ("in", 1_fr, "in"), Tr (20_px, "last") };
            grid.templateRows = { Tr (1_fr), Tr (20_px) };

            beginTest ("Grid items placement tests: integer, counting backward");

            grid.items = { GridItem{}.withColumn ({  -2, -1 }).withRow ({ 1,  3 }),
                           GridItem{}.withColumn ({ -10, -1 }).withRow ({ 1, -1 }) };

            grid.performLayout ({ 140, 100 });

            expect (grid.items[0].currentBounds == Rect (120.0f, 0.0f, 20.0f, 100.0f));
            expect (grid.items[1].currentBounds == Rect (0.0f, 0.0f,  140.0f, 100.0f));
        }

        {
            beginTest ("Grid items placement tests: areas");

            Grid grid;

            grid.templateColumns =       { Tr (50_px), Tr (100_px), Tr (Fr (1_fr)), Tr (50_px) };
            grid.templateRows = { Tr (50_px),
                                  Tr (1_fr),
                                  Tr (50_px) };

            grid.templateAreas = { "header header header header",
                                   "main main . sidebar",
                                   "footer footer footer footer" };

            grid.items.addArray ({ GridItem().withArea ("header"),
                                   GridItem().withArea ("main"),
                                   GridItem().withArea ("sidebar"),
                                   GridItem().withArea ("footer"),
                                });

            grid.performLayout ({ 300, 150 });

            expect (grid.items[0].currentBounds == Rect (0.f,   0.f,   300.f, 50.f));
            expect (grid.items[1].currentBounds == Rect (0.f,   50.f,  150.f, 50.f));
            expect (grid.items[2].currentBounds == Rect (250.f, 50.f,  50.f,  50.f));
            expect (grid.items[3].currentBounds == Rect (0.f,   100.f, 300.f, 50.f));
        }

        {
            beginTest ("Grid implicit rows and columns: triggered by areas");

            Grid grid;

            grid.templateColumns =       { Tr (50_px), Tr (100_px), Tr (1_fr), Tr (50_px) };
            grid.templateRows = { Tr (50_px),
                                  Tr (1_fr),
                                  Tr (50_px) };

            grid.autoRows = Tr (30_px);
            grid.autoColumns = Tr (30_px);

            grid.templateAreas = { "header header header header header",
                                   "main main . sidebar sidebar",
                                   "footer footer footer footer footer",
                                   "sub sub sub sub sub"};

            grid.items.addArray ({ GridItem().withArea ("header"),
                                   GridItem().withArea ("main"),
                                   GridItem().withArea ("sidebar"),
                                   GridItem().withArea ("footer"),
                                   GridItem().withArea ("sub"),
                                });

            grid.performLayout ({ 330, 180 });

            expect (grid.items[0].currentBounds == Rect (0.f,   0.f,   330.f, 50.f));
            expect (grid.items[1].currentBounds == Rect (0.f,   50.f,  150.f, 50.f));
            expect (grid.items[2].currentBounds == Rect (250.f, 50.f,  80.f,  50.f));
            expect (grid.items[3].currentBounds == Rect (0.f,   100.f, 330.f, 50.f));
            expect (grid.items[4].currentBounds == Rect (0.f,   150.f, 330.f, 30.f));
        }

        {
            beginTest ("Grid implicit rows and columns: triggered by areas");

            Grid grid;

            grid.templateColumns =       { Tr (50_px), Tr (100_px), Tr (1_fr), Tr (50_px) };
            grid.templateRows = { Tr (50_px),
                                  Tr (1_fr),
                                  Tr (50_px) };

            grid.autoRows = Tr (1_fr);
            grid.autoColumns = Tr (1_fr);

            grid.templateAreas = { "header header header header",
                                   "main main . sidebar",
                                   "footer footer footer footer" };

            grid.items.addArray ({ GridItem().withArea ("header"),
                                   GridItem().withArea ("main"),
                                   GridItem().withArea ("sidebar"),
                                   GridItem().withArea ("footer"),
                                   GridItem().withArea (4, 5, 6, 7)
                                });

            grid.performLayout ({ 350, 250 });

            expect (grid.items[0].currentBounds == Rect (0.f,   0.f,   250.f, 50.f));
            expect (grid.items[1].currentBounds == Rect (0.f,   50.f,  150.f, 50.f));
            expect (grid.items[2].currentBounds == Rect (200.f, 50.f,  50.f,  50.f));
            expect (grid.items[3].currentBounds == Rect (0.f,   100.f, 250.f, 50.f));
            expect (grid.items[4].currentBounds == Rect (250.f, 150.f, 100.f, 100.f));
        }

        {
            beginTest ("Grid implicit rows and columns: triggered by out-of-bounds indices");

            Grid grid;

            grid.templateColumns = { Tr (1_fr),  Tr (1_fr) };
            grid.templateRows    = { Tr (60_px), Tr (60_px) };

            grid.autoColumns = Tr (20_px);
            grid.autoRows    = Tr (1_fr);

            grid.items = { GridItem{}.withColumn ({  5,  8 }).withRow ({ -5, -4 }),
                           GridItem{}.withColumn ({  4,  7 }).withRow ({ -4, -3 }),
                           GridItem{}.withColumn ({ -2, -1 }).withRow ({  4,  5 }) };

            grid.performLayout ({ 500, 400 });

            //       -3  -2  -1
            //        1   2   3   4   5   6   7   8
            //  -5    +---+---+---+---+---+---+---+   0
            //        |   |   |   |   | 0 | 0 | 0 |
            //  -4    +---+---+---+---+---+---+---+  70
            //        |   |   |   | 1 | 1 | 1 |   |
            //  -3  1 +---+---+---+---+---+---+---+ 140
            //        | x | x |   |   |   |   |   |
            //  -2  2 +---+---+---+---+---+---+---+ 200  y positions
            //        | x | x |   |   |   |   |   |
            //  -1  3 +---+---+---+---+---+---+---+ 260
            //        |   |   |   |   |   |   |   |
            //      4 +---+---+---+---+---+---+---+ 330
            //        |   | 2 |   |   |   |   |   |
            //      5 +---+---+---+---+---+---+---+ 400
            //
            //        0  200 400 420 440 460 480 500
            //                 x positions
            //
            // The cells marked "x" are the explicit cells specified by the template rows
            // and columns.
            //
            // The cells marked 0/1/2 correspond to the GridItems at those indices in the
            // items array.
            //
            // Note that negative indices count back from the last explicit line
            // number in that direction, so "2" and "-2" both correspond to the same line.

            expect (grid.items[0].currentBounds == Rect (440.0f,   0.0f,  60.0f, 70.0f));
            expect (grid.items[1].currentBounds == Rect (420.0f,  70.0f,  60.0f, 70.0f));
            expect (grid.items[2].currentBounds == Rect (200.0f, 330.0f, 200.0f, 70.0f));
        }

        {
            beginTest ("Items with specified sizes should translate to correctly rounded Component dimensions");

            static constexpr int targetSize = 100;

            juce::Component component;
            juce::GridItem item { component };
            item.alignSelf   = juce::GridItem::AlignSelf::center;
            item.justifySelf = juce::GridItem::JustifySelf::center;
            item.width       = (float) targetSize;
            item.height      = (float) targetSize;

            juce::Grid grid;
            grid.templateColumns = { juce::Grid::Fr { 1 } };
            grid.templateRows    = { juce::Grid::Fr { 1 } };
            grid.items           = { item };

            for (int totalSize = 100 - 20; totalSize < 100 + 20; ++totalSize)
            {
                Rectangle<int> bounds { 0, 0, totalSize, totalSize };
                grid.performLayout (bounds);

                expectEquals (component.getWidth(), targetSize);
                expectEquals (component.getHeight(), targetSize);
            }
        }

        {
            beginTest ("Track sizes specified in Px should translate to correctly rounded Component dimensions");

            static constexpr int targetSize = 100;

            juce::Component component;
            juce::GridItem item { component };
            item.alignSelf   = juce::GridItem::AlignSelf::center;
            item.justifySelf = juce::GridItem::JustifySelf::center;
            item.setArea (1, 3);

            juce::Grid grid;
            grid.templateColumns = { juce::Grid::Fr { 1 },
                                     juce::Grid::Fr { 1 },
                                     juce::Grid::Px { targetSize },
                                     juce::Grid::Fr { 1 } };
            grid.templateRows    = { juce::Grid::Fr { 1 } };
            grid.items           = { item };

            for (int totalSize = 100 - 20; totalSize < 100 + 20; ++totalSize)
            {
                Rectangle<int> bounds { 0, 0, totalSize, totalSize };
                grid.performLayout (bounds);

                expectEquals (component.getWidth(), targetSize);
            }
        }

        {
            beginTest ("Evaluate invariants on randomised Grid layouts");

            struct Solution
            {
                Grid grid;
                std::deque<Component> components;
                int absoluteWidth;
                Rectangle<int> bounds;
            };

            auto createSolution = [this] (int numColumns,
                                          float probabilityOfFractionalColumn,
                                          Rectangle<int> bounds) -> Solution
            {
                auto random = getRandom();

                Grid grid;
                grid.templateRows = { Grid::Fr { 1 } };

                // Ensuring that the sum of absolute item widths never exceed total width
                const auto widthOfAbsolute = (int) ((float) bounds.getWidth() / (float) (numColumns + 1));

                for (int i = 0; i < numColumns; ++i)
                {
                    if (random.nextFloat() < probabilityOfFractionalColumn)
                        grid.templateColumns.add (Grid::Fr { 1 });
                    else
                        grid.templateColumns.add (Grid::Px { widthOfAbsolute });
                }

                std::deque<Component> itemComponents (static_cast<size_t> (grid.templateColumns.size()));

                for (auto& c : itemComponents)
                    grid.items.add (GridItem { c });

                grid.performLayout (bounds);

                return { std::move (grid), std::move (itemComponents), widthOfAbsolute, bounds };
            };

            const auto getFractionalComponentWidths = [] (const Solution& solution)
            {
                std::vector<int> result;

                for (int i = 0; i < solution.grid.templateColumns.size(); ++i)
                    if (solution.grid.templateColumns[i].isFractional())
                        result.push_back (solution.components[(size_t) i].getWidth());

                return result;
            };

            const auto getAbsoluteComponentWidths = [] (const Solution& solution)
            {
                std::vector<int> result;

                for (int i = 0; i < solution.grid.templateColumns.size(); ++i)
                    if (! solution.grid.templateColumns[i].isFractional())
                        result.push_back (solution.components[(size_t) i].getWidth());

                return result;
            };

            const auto evaluateInvariants = [&] (const Solution& solution)
            {
                const auto fractionalWidths = getFractionalComponentWidths (solution);

                if (! fractionalWidths.empty())
                {
                    const auto [min, max] = std::minmax_element (fractionalWidths.begin(),
                                                                 fractionalWidths.end());
                    expectLessOrEqual (*max - *min, 1, "Fr { 1 } items are expected to share the "
                                                       "rounding errors equally and hence couldn't "
                                                       "deviate in size by more than 1 px");
                }

                const auto absoluteWidths = getAbsoluteComponentWidths (solution);

                for (const auto& w : absoluteWidths)
                    expectEquals (w, solution.absoluteWidth, "Sizes specified in absolute dimensions should "
                                                             "be preserved");

                Rectangle<int> unionOfComponentBounds;

                for (const auto& c : solution.components)
                    unionOfComponentBounds = unionOfComponentBounds.getUnion (c.getBoundsInParent());

                if ((size_t) solution.grid.templateColumns.size() == absoluteWidths.size())
                    expect (solution.bounds.contains (unionOfComponentBounds), "Non-oversized absolute Components "
                                                                               "should never be placed outside the "
                                                                               "provided bounds.");
                else
                    expect (unionOfComponentBounds == solution.bounds, "With fractional items, positioned items "
                                                                       "should cover the provided bounds exactly");
            };

            const auto knownPreviousBad = createSolution (5, 1.0f, Rectangle<int> { 0, 0, 600, 200 }.reduced (16));
            evaluateInvariants (knownPreviousBad);

            auto random = getRandom();

            for (int i = 0; i < 1000; ++i)
            {
                const auto numColumns = random.nextInt (Range<int> { 1, 26 });
                const auto probabilityOfFractionalColumn = random.nextFloat();
                const auto bounds = Rectangle<int> { random.nextInt (Range<int> { 0, 3 }),
                                                     random.nextInt (Range<int> { 0, 3 }),
                                                     random.nextInt (Range<int> { 300, 1200 }),
                                                     random.nextInt (Range<int> { 100, 500 }) }
                                        .reduced (random.nextInt (Range<int> { 0, 16 }));

                const auto randomSolution = createSolution (numColumns, probabilityOfFractionalColumn, bounds);
                evaluateInvariants (randomSolution);
            }
        }
    }
};

static GridTests gridUnitTests;

#endif

} // namespace juce