JUCE/modules/juce_gui_basics/detail/juce_TopLevelWindowManager.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
{

/** Keeps track of the active top level window. */
class TopLevelWindowManager  : private Timer,
                               private DeletedAtShutdown
{
public:
    TopLevelWindowManager() = default;

    ~TopLevelWindowManager() override
    {
        clearSingletonInstance();
    }

    JUCE_DECLARE_SINGLETON_SINGLETHREADED_MINIMAL (TopLevelWindowManager)

    static void checkCurrentlyFocusedTopLevelWindow()
    {
        if (auto* wm = TopLevelWindowManager::getInstanceWithoutCreating())
            wm->checkFocusAsync();
    }

    void checkFocusAsync()
    {
        startTimer (10);
    }

    void checkFocus()
    {
        startTimer (jmin (1731, getTimerInterval() * 2));

        auto* newActive = findCurrentlyActiveWindow();

        if (newActive != currentActive)
        {
            currentActive = newActive;

            for (int i = windows.size(); --i >= 0;)
                if (auto* tlw = windows[i])
                    tlw->setWindowActive (isWindowActive (tlw));

            Desktop::getInstance().triggerFocusCallback();
        }
    }

    bool addWindow (TopLevelWindow* const w)
    {
        windows.add (w);
        checkFocusAsync();

        return isWindowActive (w);
    }

    void removeWindow (TopLevelWindow* const w)
    {
        checkFocusAsync();

        if (currentActive == w)
            currentActive = nullptr;

        windows.removeFirstMatchingValue (w);

        if (windows.isEmpty())
            deleteInstance();
    }

    Array<TopLevelWindow*> windows;

private:
    TopLevelWindow* currentActive = nullptr;

    void timerCallback() override
    {
        checkFocus();
    }

    bool isWindowActive (TopLevelWindow* const tlw) const
    {
        return (tlw == currentActive
                || tlw->isParentOf (currentActive)
                || tlw->hasKeyboardFocus (true))
               && tlw->isShowing();
    }

    TopLevelWindow* findCurrentlyActiveWindow() const
    {
        if (Process::isForegroundProcess())
        {
            auto* focusedComp = Component::getCurrentlyFocusedComponent();
            auto* w = dynamic_cast<TopLevelWindow*> (focusedComp);

            if (w == nullptr && focusedComp != nullptr)
                w = focusedComp->findParentComponentOfClass<TopLevelWindow>();

            if (w == nullptr)
                w = currentActive;

            if (w != nullptr && w->isShowing())
                return w;
        }

        return nullptr;
    }

    JUCE_DECLARE_NON_COPYABLE (TopLevelWindowManager)
};

JUCE_IMPLEMENT_SINGLETON (TopLevelWindowManager)

} // namespace juce::detail