C / C++ / MFC

4-Apr-02 9:13

Hi
is it possible to create a window from a DLL?
The window shall display some debug output in this window, but I can't get it to work.
This is what I have so far, but it doesn't work Frown | :(

long WINAPI WindowProc(HWND hWnd, UINT wMessage, WPARAM wParam, LPARAM lParam)
{
    return DefWindowProc(hWnd, wMessage, wParam, lParam);
}

void CreateLogWindow()
{
	static char szAppName[] = "LogWindow" ;
	
	HWND		hWnd;
	WNDCLASS	WndClass;

	WndClass.style = CS_HREDRAW | CS_VREDRAW;
	WndClass.lpfnWndProc = WindowProc;
	WndClass.cbClsExtra = 0;
	WndClass.cbWndExtra = 0;
	WndClass.hbrBackground = (HBRUSH) GetStockObject(LTGRAY_BRUSH);
	WndClass.hCursor = LoadCursor(NULL, IDC_ARROW);
	WndClass.hIcon = 0;
	WndClass.hInstance = hInstance;
	WndClass.lpszClassName = "Testprogramm";
	WndClass.lpszMenuName = NULL;

	RegisterClass(&WndClass);

	hWnd = CreateWindow(
		"LogWindow",
		"LogWindow",
		WS_CAPTION | WS_THICKFRAME | WS_VISIBLE,
		0,
		0,
		250,//GetSystemMetrics(SM_CXSCREEN),
		250,//GetSystemMetrics(SM_CYSCREEN),
		NULL,
		NULL,
		hInstance,
		NULL
	);

	ShowWindow(hWnd, SW_SHOW);
	UpdateWindow(hWnd);
	SetFocus(hWnd);
}

Any help is greatly appreciated

regards

modified 12-Sep-18 21:01pm.

Tomasz Sowinski4-Apr-02 9:16

Tomasz Sowinski

4-Apr-02 9:16

If you move this code to .exe, does it work OK?

Tomasz Sowinski -- http://www.shooltz.com

- It's for protection
- Protection from what? Zee Germans?

User 66584-Apr-02 9:27

4-Apr-02 9:27

Inside an .exe it works fine!

regards

modified 12-Sep-18 21:01pm.

Joaquín M López Muñoz4-Apr-02 9:37

4-Apr-02 9:37

Try setting the hInstance parameter of the WNDCLASS structure to ~~NULL~~ GetModuleHandle(NULL).

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo

User 66584-Apr-02 9:55

4-Apr-02 9:55

Thanks, but it doesn't work Frown | :(

modified 12-Sep-18 21:01pm.

Joaquín M López Muñoz4-Apr-02 9:58

4-Apr-02 9:58

And if you replace also the hInstance occurrence in CreateWindow?

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo

User 66584-Apr-02 10:02

4-Apr-02 10:02

Same result, no window is created

modified 12-Sep-18 21:01pm.

Joaquín M López Muñoz4-Apr-02 10:07

4-Apr-02 10:07

Ummm this is getting weird. In which context is CreateLogWindow being called? Does a message pump exist in the calling EXE? Please note that whether CreateLogWindow is inside a DLL or the EXE itself is immaterial from the system point of view (if you used GetModuleHandle(NULL) throughout), so the behavior observed is really odd.

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo

User 66584-Apr-02 10:12

4-Apr-02 10:12

CreateWindow is called from the DllMain function:

BOOL APIENTRY DllMain( HINSTANCE hModule, DWORD dwReason, LPVOID lpReserved )
{
     hInstance = hModule;
    
     if (dwReason == DLL_PROCESS_ATTACH) 
     {
        CreateLogWindow(hInstance);		
     }
     else if (dwReason == DLL_PROCESS_DETACH) 
     {
     }

     return TRUE;
}

And I think the EXE has a message pump since it has a main window.

Probably there is to mention that my Dll is one using the Microsoft Detours libary. Perhaps you know about it. My Dll attaches itself to an exe and thus can interupt Api calls from the main app and modify them.

This way I want to intercept the send() and sendto() functions in order to watch what the apps are sending. The window I want to create shall display the buffer of send() and sendto()

regards

modified 12-Sep-18 21:01pm.

Joaquín M López Muñoz4-Apr-02 10:18

4-Apr-02 10:18

Could you trace where the error is hapenning? RegisterClass, CreateWindow, everything silently working but no window appears?

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo

User 66584-Apr-02 10:22

4-Apr-02 10:22

I just mixed up two different names for the class in the WNDCLASS style and CreateWindow.
Tim Smith found the error here: http://www.codeproject.com/script/comments/forums.asp?forumid=1647&select=147264#xx147264xx

Thanks anyway Smile | :)

modified 12-Sep-18 21:01pm.

Joaquín M López Muñoz4-Apr-02 10:25

4-Apr-02 10:25

I'm glad the mistery solved Smile | :)

This bears a moral (IMHO): when you said the same code worked inside an EXE, you obviously used some other code that you deemed equivalent (otherwise the same problem persists). Many debugging efforts are lost due to this kind of assumptions.

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo

Jeremy Falcon4-Apr-02 9:39

Jeremy Falcon

4-Apr-02 9:39

You need a DLLMain (entry point) function for the DLL. Here's an example pulled from MSDN...

BOOL WINAPI DllMain(
    HINSTANCE hinstDLL,  // handle to DLL module
    DWORD fdwReason,     // reason for calling function
    LPVOID lpReserved )  // reserved
{
    // Perform actions based on the reason for calling.
    switch( fdwReason ) 
    { 
        case DLL_PROCESS_ATTACH:
         // Initialize once for each new process.
         // Return FALSE to fail DLL load.
            break;

        case DLL_THREAD_ATTACH:
         // Do thread-specific initialization.
            break;

        case DLL_THREAD_DETACH:
         // Do thread-specific cleanup.
            break;

        case DLL_PROCESS_DETACH:
         // Perform any necessary cleanup.
            break;
    }
    return TRUE;  // Successful DLL_PROCESS_ATTACH.
}

Take the instance param from that function and pass it to your CreateLogWindow() function. Use that instanace in the window's class. This is the done the same way you would use WinMain in an executable.

Also, don't forget to specify the entry point to the linker when compiling the DLL -- this has to be done.

Jeremy L. Falcon
"The One Who Said, 'The One Who Said...'"
<nobr>
Homepage : Feature Article : Sonork = 100.16311

User 66584-Apr-02 9:46

4-Apr-02 9:46

Well, hInstance HAS the value of hinstDLL.
But what do you mean by
Jeremy Falcon wrote:
don't forget to specify the entry point to the linker when compiling the DLL
?

modified 12-Sep-18 21:01pm.

Jeremy Falcon4-Apr-02 10:12

Jeremy Falcon

4-Apr-02 10:12

The entry point is the starting address of the DLL -- the first of your code that's called. You need to let the linker know about it.

You need a user-defined entry point for the DLL. I believe it defaults to DLLMain, but if your DLL doesn't use that naming you must specify it somehow. I chose using the linker and specify it anyway regardless. I'm crazy like that. Smile | :)

I'm assuming you're using VC6...

Goto project settings.
Link Tab
Category: Output

You'll see an edit box for the Entry-point symbol. Put the name of your entry function in there.

Jeremy L. Falcon
"The One Who Said, 'The One Who Said...'"
<nobr>
Homepage : Feature Article : Sonork = 100.16311

Tim Smith4-Apr-02 10:19

Tim Smith

4-Apr-02 10:19

Ummm...

The class name in WndClass is "Testprogramm" and in CreateWindow it is "LogWindow".

Hopefully that is it.

Tim Smith

I know what you're thinking punk, you're thinking did he spell check this document? Well, to tell you the truth I kinda forgot myself in all this excitement. But being this here's CodeProject, the most powerful forums in the world and would blow your head clean off, you've got to ask yourself one question, Do I feel lucky? Well do ya punk?

User 66584-Apr-02 10:16

4-Apr-02 10:16

Ummm how stupid Big Grin | :-D

I just corrected it and suddenly it works

Thanks a lot! Smile | :)

modified 12-Sep-18 21:01pm.