JUCE/modules/juce_gui_basics/detail/juce_FocusHelpers.h

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

   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::detail
{

struct FocusHelpers
{
    FocusHelpers() = delete;

    static int getOrder (const Component* c)
    {
        auto order = c->getExplicitFocusOrder();
        return order > 0 ? order : std::numeric_limits<int>::max();
    }

    template <typename FocusContainerFn>
    static void findAllComponents (Component* parent,
                                   std::vector<Component*>& components,
                                   FocusContainerFn isFocusContainer)
    {
        if (parent == nullptr || parent->getNumChildComponents() == 0)
            return;

        std::vector<Component*> localComponents;

        for (auto* c : parent->getChildren())
            if (c->isVisible() && c->isEnabled())
                localComponents.push_back (c);

        const auto compareComponents = [&] (const Component* a, const Component* b)
        {
            const auto getComponentOrderAttributes = [] (const Component* c)
            {
                return std::make_tuple (getOrder (c),
                                        c->isAlwaysOnTop() ? 0 : 1,
                                        c->getY(),
                                        c->getX());
            };

            return getComponentOrderAttributes (a) < getComponentOrderAttributes (b);
        };

        // This will sort so that they are ordered in terms of explicit focus,
        // always on top, left-to-right, and then top-to-bottom.
        std::stable_sort (localComponents.begin(), localComponents.end(), compareComponents);

        for (auto* c : localComponents)
        {
            components.push_back (c);

            if (! (c->*isFocusContainer)())
                findAllComponents (c, components, isFocusContainer);
        }
    }

    enum class NavigationDirection { forwards, backwards };

    template <typename FocusContainerFn>
    static Component* navigateFocus (Component* current,
                                     Component* focusContainer,
                                     NavigationDirection direction,
                                     FocusContainerFn isFocusContainer)
    {
        if (focusContainer != nullptr)
        {
            std::vector<Component*> components;
            findAllComponents (focusContainer, components, isFocusContainer);

            const auto iter = std::find (components.cbegin(), components.cend(), current);

            if (iter == components.cend())
                return nullptr;

            switch (direction)
            {
                case NavigationDirection::forwards:
                    if (iter != std::prev (components.cend()))
                        return *std::next (iter);

                    break;

                case NavigationDirection::backwards:
                    if (iter != components.cbegin())
                        return *std::prev (iter);

                    break;
            }
        }

        return nullptr;
    }
};

} // namespace juce::detail