JUCE/modules/juce_audio_plugin_client/detail/juce_WindowsHooks.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.

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

#if JUCE_WINDOWS

namespace juce::detail
{

// This function is in juce_win32_Windowing.cpp
bool offerKeyMessageToJUCEWindow (MSG&);

class WindowsHooks
{
public:
    WindowsHooks() = default;

private:
    static LRESULT CALLBACK mouseWheelHookCallback (int nCode, WPARAM wParam, LPARAM lParam)
    {
        if (nCode >= 0 && wParam == WM_MOUSEWHEEL)
        {
            // using a local copy of this struct to support old mingw libraries
            struct MOUSEHOOKSTRUCTEX_  : public MOUSEHOOKSTRUCT  { DWORD mouseData; };

            auto& hs = *(MOUSEHOOKSTRUCTEX_*) lParam;

            if (auto* comp = Desktop::getInstance().findComponentAt ({ hs.pt.x, hs.pt.y }))
                if (comp->getWindowHandle() != nullptr)
                    return PostMessage ((HWND) comp->getWindowHandle(), WM_MOUSEWHEEL,
                                        hs.mouseData & 0xffff0000, (hs.pt.x & 0xffff) | (hs.pt.y << 16));
        }

        return CallNextHookEx (getSingleton()->mouseWheelHook, nCode, wParam, lParam);
    }

    static LRESULT CALLBACK keyboardHookCallback (int nCode, WPARAM wParam, LPARAM lParam)
    {
        MSG& msg = *(MSG*) lParam;

        if (nCode == HC_ACTION && wParam == PM_REMOVE
             && offerKeyMessageToJUCEWindow (msg))
        {
            zerostruct (msg);
            msg.message = WM_USER;
            return 1;
        }

        return CallNextHookEx (getSingleton()->keyboardHook, nCode, wParam, lParam);
    }

    class Hooks
    {
    public:
        Hooks() = default;

        ~Hooks()
        {
            if (mouseWheelHook != nullptr)
                UnhookWindowsHookEx (mouseWheelHook);

            if (keyboardHook != nullptr)
                UnhookWindowsHookEx (keyboardHook);
        }

        HHOOK mouseWheelHook = SetWindowsHookEx (WH_MOUSE,
                                                 mouseWheelHookCallback,
                                                 (HINSTANCE) juce::Process::getCurrentModuleInstanceHandle(),
                                                 GetCurrentThreadId());
        HHOOK keyboardHook = SetWindowsHookEx (WH_GETMESSAGE,
                                               keyboardHookCallback,
                                               (HINSTANCE) juce::Process::getCurrentModuleInstanceHandle(),
                                               GetCurrentThreadId());
    };

    static std::shared_ptr<const Hooks> getSingleton()
    {
        static std::weak_ptr<const Hooks> weak;

        if (auto locked = weak.lock())
            return locked;

        auto strong = std::make_shared<Hooks>();
        weak = strong;
        return strong;
    }

    std::shared_ptr<const Hooks> hooks = getSingleton();
};

} // namespace juce::detail

#endif