Re: wh_callwndProc hook problem

"xiaosi" <>
Tue, 8 Sep 2009 13:13:27 +0800
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The hookdll.cpp is a sample I wrote to log WM_MENUSELECT:
1) This sample log WM_MENUSELECT, no matter whether the menuitem is clicked (WM_COMMAND) or not.
2) This sample can only log MIIM_STRING (not MF_OWNERDRAW) type menu.
3) This sample can not log Internet Explorer-style menu bar.
4) This sample is designed to log only one process, if you want to log multi-processes in one log file, you need to share and
synchronize logging.

"Sridhar" <> wrote:

Thank you for your valuable suggestions xiaosi ,

i modified the code..according to your suggestions..
by using spy++(visual studio6.0) i monitor the messages and i came to know
that when i click on the "File" menu of the notepad it generating WM_CREATE
message and if i move cursor to File->New then it generating WM_MENUSELECT
and when i click the new menuitem it generating WH_COMMAND.
i changed my code to monitor WM_MENUSELECT. but now what problem i am
getting is when i open the notepad it is not giving error..if i click on the
menu..notepad is asking to close. if i see in the text file it showing the
following output(this is happening only after closing of notepad).




really i am not understanding what is going on...if the message is not
WM_MENUSELELCT it should not do any thing right..but why notepad encountering
the problem(i tried with mspaint also..same problem).
i am posting the modified code of my filter funtion here.


char window_class_name[250]={0};
CWPSTRUCT *msg_str = NULL;

return CallNextHookEx(ghKeyHook,nCode,wParam,lParam);

msg_str = (CWPSTRUCT *) lParam;

HWND hWndMenu= msg_str->hwnd;
HMENU hMenuHandle=GetMenu(hWndMenu);

if (msg_str->message == WM_MENUSELECT)
GetClassName(msg_str->hwnd, window_class_name, sizeof(window_class_name) -

FILE *fp;

if (strcmp(window_class_name, "Notepad") == 0)
  fprintf(fp,"\nSTART RECORDING....\n ");
  fprintf(fp,"\nClassName==%s\n ",window_class_name);
  fprintf(fp,"\nMenuHandle==%s\n ",hMenuHandle);

return CallNextHookEx(ghKeyHook,nCode,wParam,lParam);


My motive is to know which menu item is "File" is
selected.."New" is that.

Please help me on this...

At last i learned something for today...:)

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#include <stdio.h>
#include <conio.h>
#pragma warning(disable:4996) //_cgets

__declspec(dllimport) bool __stdcall InstallMsgHookProc();

int __cdecl main() {
    if (!InstallMsgHookProc()) {
        printf("InstallMsgHookProc fail\n");
        return 1;
    printf("InstallMsgHookProc ok, press enter to unhook\n");
    char buffer[16] = {10};
    _cgets(buffer); //keep main running, if main exit, the hook installed =
by main (call InstallMsgHookProc) will be removed immediately by system.
    return 0;

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#include <windows.h>
#include <stdio.h> //fprintf, _snprintf
#pragma warning(disable:4996) //fopen

HINSTANCE ghInstance;
HHOOK ghKeyHook;
FILE *gfp;

int __stdcall PrintErr(char *sz, UINT sizeofsz) {
    DWORD er = GetLastError(); char bue[128]; *bue = 0;
    if (er && !FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM|FORMAT_MESSAGE_IGNORE_INSERTS, 0, er, 0, bue, sizeof(bue), 0))
        *(DWORD*) bue = '*!*';
    return _snprintf(sz, sizeofsz, "ErrorCode %#x(%d) %s", er, er, bue);

void __cdecl WriteLog(const char *format, ...) {
    SystemTimeToTzSpecificLocalTime(0, &t, &t);
    char sztime[64];
    _snprintf(sztime, sizeof(sztime), "%04u-%02u-%02u %02u:%02u:%02u.%03u",
        t.wYear, t.wMonth, t.wDay, t.wHour, t.wMinute, t.wSecond, t.wMilliseconds);
    char buf[1024];
    _vsnprintf(buf, sizeof(buf), format, (char*)&format + sizeof(format));
    fprintf(gfp, "%s %s\r\n", sztime, buf);

void __stdcall LogMemuSelect(CWPSTRUCT *cwp) {
    HMENU hmenu = (HMENU) cwp->lParam;
    WORD flag = HIWORD(cwp->wParam);
    if (hmenu && (MF_HILITE & flag) && !(MF_OWNERDRAW & flag)) {
        //when click menubar and no menuitem selected, hmenu is null
        //SEPARATOR menuitem is not MF_HILITE
        //MF_OWNERDRAW menuitem string can not directly get string with GetMenuItemInfo or GetMenuString.
        MENUITEMINFO info = {sizeof(MENUITEMINFO)};
        char szmenu[250]; szmenu[0] = 0;
        info.fMask = MIIM_STRING;
        info.dwTypeData = szmenu;
        info.cch = sizeof(szmenu)/sizeof(*szmenu);
        UINT item = LOWORD(cwp->wParam);
        BOOL byPosition = FALSE;
        if (MF_POPUP & flag)
            byPosition = TRUE;
        int result = GetMenuItemInfo(hmenu, item, byPosition, &info);
        if (!result)
            PrintErr(szmenu, sizeof(szmenu));
        char buf[1024];
        _snprintf(buf, sizeof(buf), "hmenu\t%x\nitem\t%x\nflag\t%x\nresult\t%x\nszmenu\t%s\n",
            hmenu, item, flag, result, szmenu);
        if (*szmenu) //not log null string

LRESULT CALLBACK MsgHookProc(int nCode, WPARAM wParam, LPARAM lParam) {
    CWPSTRUCT *cwp = (CWPSTRUCT*) lParam;
    if (HC_ACTION == nCode && WM_MENUSELECT == cwp->message) {
    return CallNextHookEx(ghKeyHook, nCode, wParam, lParam);

__declspec(dllexport) bool __stdcall InstallMsgHookProc() {
    if (ghKeyHook)
        return false;
    HWND hWnd = FindWindow("NotePad" , NULL);
    //HWND hWnd = FindWindow("OpusApp" , NULL); //Miceosoft Word
    //HWND hWnd = FindWindow("AdobeAcrobat" , NULL);
    if (!hWnd)
        return false;
    DWORD processId;
    DWORD threadId = GetWindowThreadProcessId(hWnd, &processId);
    ghKeyHook = SetWindowsHookEx(WH_CALLWNDPROC, MsgHookProc, ghInstance, threadId);
    if (!ghKeyHook)
        return false;
    return true;

void __stdcall LogProcess(DWORD reason) {
    char szapp[MAX_PATH*2];
    GetModuleFileName(0, szapp, sizeof(szapp));
    if (DLL_PROCESS_ATTACH == reason) {
        WriteLog("PROCESS_ATTACH %s", szapp);
        WriteLog("fopen gfp %x", gfp);
    } else if (DLL_PROCESS_DETACH == reason) {
        WriteLog("PROCESS_DETACH %s", szapp);
        WriteLog("fclose gfp %x", gfp);

BOOL APIENTRY DllMain(HMODULE hModule, DWORD reason, LPVOID lpReserved) {
    if (DLL_PROCESS_ATTACH == reason) {
        ghInstance = hModule;
        gfp = fopen("J:\\Logdll.txt","ab");
        if (!gfp) {
            OutputDebugStringA("fopen fail");
            return FALSE;
    } else if (DLL_PROCESS_DETACH == reason) {
        if (gfp) {
    return TRUE;


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