Member Avatar for sickle

Hi,

This concerns Microsoft Windows. I want to know when a window from other processes is made visible. Also, I want the handle of the window. I've tried to catch the message WM_SHOWWINDOW with SetWindowsHookEx(WH_GETMESSAGE, &MessageProc, g_hInstance, 0) but I receive no events ! The only events I receive is when I do a call to MessageBox after the call to SetWindowsHookEx. But the events only come from user32.dll. I call MessageBox to tell me that the call to SetWindowsHookEx is successful. Please, I need your help. Thank you.

// HideMeHook.cpp : Defines the entry point for the DLL application.
//

#include "stdafx.h"
#include "HideMeHook.h"

HINSTANCE g_hInstance = NULL;
HWND g_hHideMeWnd = NULL;
DWORD g_dwAppProcessId = 0;
UINT g_uiHideMeHookMsg = 0;
HHOOK g_hMessageHook = NULL;


BOOL APIENTRY DllMain( HANDLE hModule, 
                       DWORD  ul_reason_for_call, 
                       LPVOID lpReserved
					 )
{
	switch (ul_reason_for_call)
	{
	case DLL_PROCESS_ATTACH:
	//case DLL_THREAD_ATTACH:
		g_hInstance = (HINSTANCE)hModule;
		break;
	//case DLL_THREAD_DETACH:
	case DLL_PROCESS_DETACH:
		UnsetHook();
		break;
	}
    return TRUE;
}

HIDEMEHOOK_API void SetHook(HWND hHideMeWnd, DWORD dwAppProcessId)
{
	g_hHideMeWnd = hHideMeWnd;
	g_dwAppProcessId = dwAppProcessId;
	g_uiHideMeHookMsg = RegisterWindowMessage("HideMeHook");
	if (g_hHideMeWnd && g_dwAppProcessId && g_uiHideMeHookMsg)
	{
		g_hMessageHook = SetWindowsHookEx(WH_GETMESSAGE, &MessageProc, g_hInstance, 0);
		//g_hMessageHook = SetWindowsHookEx(WH_CALLWNDPROCRET, &CallWndProc, g_hInstance, 0);
		//if (g_hMessageHook)
		//{
		//	MessageBox(NULL, "Hook installed", "Hook", MB_OK);
		//}
	}
}

HIDEMEHOOK_API void UnsetHook()
{
	g_hHideMeWnd = NULL;
	g_dwAppProcessId = 0;
	g_uiHideMeHookMsg = 0;
	if (g_hMessageHook)
	{
		UnhookWindowsHookEx(g_hMessageHook);
		g_hMessageHook = NULL;
	}
}

LRESULT CALLBACK MessageProc(int code, WPARAM wParam, LPARAM lParam)
{
	if (code == HC_ACTION)
	{
		DWORD dwWndProcessId = 0;
		GetWindowThreadProcessId(((MSG *)lParam)->hwnd, &dwWndProcessId);
		//HMODULE hModule = (HMODULE)GetWindowLong(((MSG *)lParam)->hwnd, GWL_HINSTANCE);
		//TCHAR tmp[300];
		//HANDLE hProcess = OpenProcess(PROCESS_ALL_ACCESS, FALSE, dwWndProcessId);
		//GetModuleFileNameEx(hProcess, hModule, tmp, 299);
		//CloseHandle(hProcess);
		if (dwWndProcessId == g_dwAppProcessId)
		{
			if ((LOWORD(((MSG *)lParam)->message) == WM_SHOWWINDOW))
			{
				PostMessage(g_hHideMeWnd, g_uiHideMeHookMsg, wParam, lParam);
			}
		}
	}
	return CallNextHookEx(g_hMessageHook, code, wParam, lParam);
}

//LRESULT CALLBACK CallWndProc(int code, WPARAM wParam, LPARAM lParam)
//{
//	if (code == HC_ACTION)
//	{
//		DWORD dwWndProcessId = 0;
//		GetWindowThreadProcessId(((CWPSTRUCT *)lParam)->hwnd, &dwWndProcessId);
//		if (dwWndProcessId == g_dwAppProcessId)
//		{
//			if ((((CWPSTRUCT *)lParam)->message == WM_SHOWWINDOW))
//			{
////				MessageBox(NULL, "Post Message", "Hook", MB_OK);
//				PostMessage(g_hHideMeWnd, g_uiHideMeHookMsg, wParam, lParam);
//			}
//		}
//	}
//	return CallNextHookEx(g_hMessageHook, code, wParam, lParam);
//}

//// This is the constructor of a class that has been exported.
//// see HideMeHook.h for the class definition
//CHideMeHook::CHideMeHook()
//{ 
//	return; 
//}
  • 3 Contributors
  • 8 Replies
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  • 2 Days Discussion Span
  • Latest Post Latest Post by sickle

Recommended Answers

All 8 Replies

Member Avatar for Duoas

You have to hook external objects using global hooks (those residing in a DLL). Process hooks can only be used with your own application's processes.

Member Avatar for sickle

You have to hook external objects using global hooks (those residing in a DLL). Process hooks can only be used with your own application's processes.

Sorry, but I don't understand. My hook is already in a DLL, or do you mean that exists other hook functions that are more global to the system ? What I don't understand, is this is supposed to work according to Microsoft documentation :

SetWindowsHookEx
...
These events are associated either with a specific thread or with all threads in the same desktop as the calling thread.

Member Avatar for Duoas

I'm sorry, I mixed-up that last two arguments to SetWindowsHookEx() and thought you were installing a process hook.

The WM_SHOWWINDOW message is not a queued message --it is sent directly to the target window procedure. Hence, the WH_GETMESSAGE hook will never see it. You'll need to install a WH_CALLWNDPROC hook to catch it.

Annoying, isn't it?

(Sorry it took me this long to pay enough attention to answer your question...)

Member Avatar for sickle

Thanks for your answer. Yes, I already tried WH_CALLWNDPROC with no luck. Please, see the file attachment to my first message.

Member Avatar for sickle

see news://194.177.96.26/comp.os.ms-windows.programmer.win32
where it has been explained hundreds of times...

If you know how, it will be great that you explain it here. Newsgroups have no archives as I know. If I ask it here, it's because I found nothing. This will take you 5 minutes or less.

Member Avatar for Duoas

Newsgroups are archived. For ever and ever. (But they are annoying to search.)

Yes, I already tried WH_CALLWNDPROC with no luck. Please, see the file attachment to my first message.

No, you tried WH_CALLWNDPROCRET, which is entirely different.

If you are still having problems I'll see if I can't compile your code myself and figure out what's wrong.

Member Avatar for sickle

I also tried with WH_CALLWNDPROC and it doesn't work. Ok, I have no choice to send you the complete code, make what you want with it ;) It was supposed to be a simple program to practice and learn C/C++. It's developped under Visual Studio .NET 2002. I'll do cleanup when the hook will work.

HideMe.zip (76.27 KB)
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