vc++ replace WndProc form another application window

See more:

C++

Windows

VC9.0

There are some windows where I can't get the text insicde with a WM_GETTEXT, so I tried to replace WndProc with a standard one.

I'm trying to replace the WndProc function from a window that has been created by another application. I'm trying to do it in a thread created by a windows hook to keyboard.

What I've tried without any success (3 different cases):

1. Create a "EDIT" window, get the WndProc and replace the WndProc of the app by the new:
(idea from: http://www.codeguru.com/Cpp/I-N/ieprogram/security/article.php/c4387[^])

String ^ReadWindowText(HWND g_hTarget)
{
	char buff1[MAX_DATASIZE];
	int err;
	
	this->ClearBuffer<char>(buff1, MAX_DATASIZE);
	
	HWND hParent = GetParent(g_hTarget); //g_hTarget is the edit handle we are interested
	HINSTANCE hInstance = (HINSTANCE) GetWindowLongPtr(hParent, GWLP_HINSTANCE); //Handle to the instance of the module to be associated with the window
	
	// Create new Edit window with standard WndProc
	HWND hwndEdit = CreateWindow(_T("EDIT"), NULL, WS_CHILD | WS_VISIBLE | WS_VSCROLL | ES_LEFT | ES_MULTILINE | ES_AUTOVSCROLL, 0, 0, 0, 0, hParent, (HMENU) 111, hInstance, NULL);
	
	if (!hwndEdit) err = GetLastError();
	
	// Get the standard Windows Procedure of Edit class
	LONG_PTR lpNewProc = GetWindowLongPtr(hwndEdit, GWLP_WNDPROC);
	LONG_PTR lastProc = SetWindowLongPtr(g_hTarget, GWLP_WNDPROC, (LONG_PTR)lpNewProc);
	
	if (!lastProc) err = GetLastError();
	//Text reading
	int len = SendMessage(g_hTarget, WM_GETTEXT, MAX_DATASIZE, (LPARAM) buff1);
	len = SendMessage(g_hTarget, WM_GETTEXTLENGTH, 0, 0);
	buff1[len] = 0;
	
	//Reset the original Windows Procedure
	SetWindowLongPtr(g_hTarget, GWLP_WNDPROC, (LONG_PTR)lastProc);
	
	return gcnew String(buff1);
};

2. Same as before, this time create a HWND_MESSAGE window
(idea from: http://msdn.microsoft.com/en-us/library/ms632599%28VS.85%29#message_only[^])

String ^ReadWindowText1(HWND g_hTarget)
{
(...)
	
	// Create Message recieving window
	HWND hwndEdit = CreateWindow(_T("STATIC"), NULL, WS_CHILD | WS_VISIBLE | WS_VSCROLL | ES_LEFT | ES_MULTILINE | ES_AUTOVSCROLL, 0, 0, 0, 0,  HWND_MESSAGE, (HMENU) 111, hInstance, NULL);
	
(...)
};

3. Replace WndProc with my own procedure (in the application that creates the window). I'm not really sure if this could even work, but I wanted to be sure...
(idea from: http://www.gamedev.net/topic/511138-how-to-get-raw-input-data-from-the-win-32-api-thats-not-dependant-on-a-window/[^])

delegate LRESULT StaticWindowProcDelegate( HWND wnd, UINT msg, WPARAM wParam, LPARAM lParam );
delegate LRESULT WindowProcDelegate( HWND wnd, WNDPROC wnd_proc, UINT msg, WPARAM wParam, LPARAM lParam );
WindowProcDelegate^ sWindowStore;
LONG_PTR lastProc;

String ^ReadWindowText2(HWND g_hTarget)
{
(...)
	sWindowStore = gcnew WindowProcDelegate(this, &LectorHD::WindowProc);
	lastProc = GetWindowLongPtr( g_hTarget, GWLP_WNDPROC ); 
	if( !lastProc ) err = GetLastError();
	
	// Override window procedure
	StaticWindowProcDelegate^ swpd = gcnew StaticWindowProcDelegate(this, &LectorHD::StaticWindowProc);
	if(!SetWindowLongPtr( g_hTarget, GWLP_WNDPROC, (LONG_PTR) Marshal::GetFunctionPointerForDelegate(swpd).ToPointer()) ) // This is the override WndProc
		err = GetLastError();
	
(...)
};

LRESULT StaticWindowProc( HWND wnd, UINT msg, WPARAM wParam, LPARAM lParam ) 
{
	return sWindowStore( wnd, (WNDPROC) lastProc, msg, wParam, lParam );
};

LRESULT WindowProc( HWND wnd, WNDPROC wnd_proc, UINT msg, WPARAM wParam, LPARAM lParam ) 
{
	switch( msg ) 
	{
		case WM_GETTEXT:
		default: return CallWindowProc( wnd_proc, wnd, msg, wParam, lParam );
	}
};

Always same problem: lastProc=0 (err=0) with any application (i've tried 3 different programs, one of them is mine so I'm sure I have'nt replaced WndProc).. I can't get the text from the same windows where I could'nt do with WM_GETTEXT.

Maybe (I suspect) it is a problem of what it says in http://msdn.microsoft.com/en-us/library/ms644898%28v=vs.85%29.aspx[^]

"The SetWindowLongPtr function fails if the process that owns the window specified by the hWnd parameter is at a higher process privilege in the UIPI hierarchy than the process the calling thread resides in."

But I'm not sure if it is this, because in the first and second case I create the new window in the HWND that owns g_target (I get hInstance from the parent of g_target, so the processes must be the same for the two windows..) And if it is, I don't know how to assign higher provilege to my process.

Any help is really apreciated!