Function dropdownIndexFromPoint

src/OpenLoco/src/Ui/Dropdown.cpp:1095–1154

    }

    std::optional<int> dropdownIndexFromPoint(Ui::Window* window, int x, int y)
    {
        // Check whether x and y are over a list item
        int left = x - window->x;
        if (left < 0)
        {
            return std::nullopt;
        }
        if (left >= window->width)
        {
            return std::nullopt;
        }

        // 2px of padding on the top of the list?
        int top = y - window->y - 2;
        if (top < 0)
        {
            return std::nullopt;
        }

        unsigned int itemY = top / _dropdownItemHeight;
        if (itemY >= _dropdownItemCount)
        {
            return std::nullopt;
        }

        left -= 2;
        if (left < 0)
        {
            return std::nullopt;
        }

        unsigned int itemX = left / _dropdownItemWidth;
        if (itemX >= _dropdownColumnCount)
        {
            return std::nullopt;
        }
        if (itemY >= _dropdownRowCount)
        {
            return std::nullopt;
        }

        int item = itemY * _dropdownColumnCount + itemX;
        if (item >= _dropdownItemCount)
        {
            return std::nullopt;
        }

        if (item < 32 && (_dropdownDisabledItems & (1ULL << item)) != 0)
        {
            return std::nullopt;
        }

        if (_dropdownItemFormats[item] == 0)
        {
            return std::nullopt;
        }