Messages from another window in another thread

[nickname_changed]

Howdy,

Just a simple question, is there any way to get messages for a window created in a different thread than my own?

I want to use PeekMessage on Notepad. I tried using FindWindow(NULL, "untitled - Notepad"), which found the window perfectly, but was unable to use GetMessage or PeekMessage(). I think thats because in the MSDN help under GetMessage, it has this:

hWnd

[in] Handle to the window whose messages are to be retrieved. The window must belong to the calling thread. The NULL value has a special meaning[...]

I expect the same is also true for PeekMessage, because I had the same problem there.

Is it possible to check for messages at all from another thread?

[Codeplug]

Read up on the Win32 Hook functions.

gg

[bennyandthejets]

#include <windows.h>
#include <iostream>
#include <string>
#include <conio.h>

const std::string strMod = "easy.dll";

int main()
{
	HWND hWnd = FindWindow(NULL,"Calculator);
	if(hWnd == 0)
	{
		std::cout << "Unable to find Calculator";
		return 0;
	}

	DWORD dwProc;
	
	GetWindowThreadProcessId(hWnd,&dwProc);

	HANDLE hProc = OpenProcess(PROCESS_ALL_ACCESS,FALSE,dwProc);
	if(hProc == 0)
	{
		std::cout << "Unable to open process";
		return 0;
	}

	HMODULE hKern = GetModuleHandle("kernel32.dll");
	if(hKern == 0)
	{
		std::cout << "Unable to get Kernel32 Handle";
		return 0;
	}

	WNDPROC lpfLoadLibraryA = reinterpret_cast<WNDPROC>
		(GetProcAddress(hKern,"LoadLibraryA"));
	if(lpfLoadLibraryA == 0)
	{
		std::cout << "Unable to get LoadLibrary Func";
		return 0;
	}

	LPVOID lpMemAddress = VirtualAllocEx(hProc,0,strMod.length() + 1,
		MEM_COMMIT,PAGE_READWRITE);
	if(lpMemAddress == 0)
	{
		std::cout << "Unable to alloc memory";
		return 0;
	}	
	
	SIZE_T stBytesWritten;
	if(!WriteProcessMemory(hProc,lpMemAddress, (LPVOID) strMod.c_str(),
		strMod.length() + 1,&stBytesWritten))
	{
		std::cout << "Unable to write memory";
		return 0;
	}	 

	DWORD dwThreadID;
	HANDLE hRemThread = CreateRemoteThread(hProc,0,0,
		reinterpret_cast<LPTHREAD_START_ROUTINE>(lpfLoadLibraryA),
		lpMemAddress,0,&dwThreadID);
	if(hRemThread == 0)
	{
		std::cout << "Unable to create thread";
		return 0;
	}

	//This returns once the thread has a signaled state, ie, when it terminates
	//The remote thread, LoadLibraryA, terminates when DLLEntryPoint returns
	std::cout << "Waiting for single object" << std::endl;
	WaitForSingleObject(hRemThread,INFINITE);
	std::cout << "Thread terminated" << std::endl;
	
	getch();
	return 0;
}

#include <windows.h>

BOOL WINAPI DllMain(HANDLE,DWORD,LPVOID);
LRESULT CALLBACK WndProc(HWND,UINT,WPARAM,LPARAM);

char *chHookWindow="Calculator"; //window name of target window
char *chHookClass=NULL; //class name of target window
WNDPROC wpOriginal;
UINT iMsg;

//Any code executed here is in the context of the remotely created thread, which means any windows
//will be destroyed when DllMain returns (because that is when LoadLibraryA terminates)
BOOL WINAPI DllMain(HANDLE hinstDLL,DWORD dwReason,LPVOID lpReserved)
{
	switch (dwReason)
	{
	case DLL_PROCESS_ATTACH: //Dll is attaching to process
		{
			HWND hFind=NULL;
			DWORD dwThisProcessId=GetCurrentProcessId();
			DWORD dwFindWindowProcessId;

			//Loop through every valid window until we get one in the same process
			do
			{
				hFind=FindWindowEx(NULL, hFind, chHookClass, chHookWindow);
				GetWindowThreadProcessId(hFind,&dwFindWindowProcessId);
			} while ( (dwFindWindowProcessId!=dwThisProcessId) && (hFind) );

			//Subclass
			wpOriginal=(WNDPROC)SetWindowLong(hFind, GWL_WNDPROC, (LONG) WndProc);
			
			//Grab us a unique window message, so we can start doing things in the right context
			iMsg=RegisterWindowMessage("HookProjectUniqueInitializationWindowMessage");
			//Run the intialization code
			PostMessage(hFind,iMsg,NULL,NULL);
			break;
		}
	default:
		break;
	}
	return TRUE;
}

//Any code executed here is in the context of the original thread
LRESULT CALLBACK WndProc(HWND hwnd,UINT msg,WPARAM wParam,LPARAM lParam)
{
	if (msg==iMsg)
	{
		//Initialization code
		SetWindowText(hwnd,"Ben's Calculator");
		return 0;
	}

	switch (msg)
	{
	case WM_CREATE:
		break;
	
	case WM_COMMAND:
		break;
			
	default:
		break;
	}
	return CallWindowProc(wpOriginal,hwnd,msg,wParam,lParam);
}

Capeesh?