C# グローバルフックでメッセージを編集して送り返す。

#include "stdafx.h"
#include <windows.h>
#include "SystemHookCore.h"

HookProc userHookProc;
HHOOK hook = NULL;
static LRESULT CALLBACK InternalHookCallback(int code, WPARAM wparam, LPARAM lparam);

//
// Store the application instance of this module to pass to
// hook initialization. This is set in DLLMain().
//
HINSTANCE g_appInstance = NULL;

HHOOK SetWindowsHookExWrapper(int idHook,
    HookProc lpfn,
    /*HINSTANCE hMod,*/
    DWORD dwThreadId
)
{
	userHookProc = lpfn;
	hook = SetWindowsHookEx(idHook,(HOOKPROC)InternalHookCallback,::GetModuleHandle("SystemHookCore.dll"),dwThreadId);
	return hook;
}

BOOL UnhookWindowsHookExWrapper(          HHOOK hhk
)
{
	return UnhookWindowsHookEx(hook /*hhk*/);
}

LRESULT CallNextHookExWrapper(      

    HHOOK hhk,
    int nCode,
    WPARAM wParam,
    LPARAM lParam
)
{
	return CallNextHookEx(hook /*hhk*/,nCode,wParam,lParam);
}

static LRESULT CALLBACK InternalHookCallback(int code, WPARAM wparam, LPARAM lparam)
{
	if (code < 0)
	{
		return CallNextHookEx(hook, code, wparam, lparam);
	}

	userHookProc(code, wparam, lparam);

	return CallNextHookEx(hook, code, wparam, lparam);
}

const string DLL_FILENAME = "SystemHookCore.dll";
[DllImport(DLL_FILENAME, CharSet = CharSet.Auto,
   CallingConvention = CallingConvention.StdCall, SetLastError = true)]
private static extern int SetWindowsHookEx(
    int idHook,
    HookProc lpfn,
    /*IntPtr hMod,*/
    int dwThreadId);


[DllImport(DLL_FILENAME, CharSet = CharSet.Auto,
    CallingConvention = CallingConvention.StdCall, SetLastError = true)]
private static extern int UnhookWindowsHookEx(int idHook);


[DllImport(DLL_FILENAME, CharSet = CharSet.Auto,
     CallingConvention = CallingConvention.StdCall)]
private static extern int CallNextHookEx(
    int idHook,
    int nCode,
    int wParam,
    IntPtr lParam);

private delegate int HookProc(int nCode, int wParam, IntPtr lParam);