JUCE/modules/juce_audio_plugin_client/utility/juce_WindowsHooks.h

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

   This file is part of the JUCE 7 technical preview.
   Copyright (c) 2022 - Raw Material Software Limited

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

   For the technical preview this file cannot be licensed commercially.

   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
{

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

static HHOOK mouseWheelHook = nullptr, keyboardHook = nullptr;
static int numHookUsers = 0;

struct WindowsHooks
{
    WindowsHooks()
    {
        if (numHookUsers++ == 0)
        {
            mouseWheelHook = SetWindowsHookEx (WH_MOUSE, mouseWheelHookCallback,
                                               (HINSTANCE) juce::Process::getCurrentModuleInstanceHandle(),
                                               GetCurrentThreadId());

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

    ~WindowsHooks()
    {
        if (--numHookUsers == 0)
        {
            if (mouseWheelHook != nullptr)
            {
                UnhookWindowsHookEx (mouseWheelHook);
                mouseWheelHook = nullptr;
            }

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

    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 (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 (keyboardHook, nCode, wParam, lParam);
    }
};

} // namespace juce

#endif