Multithreading a Windows callback function - c

Question

I have a method to set up a window in Windows, written in C. It uses the standard code which looks like this:
WNCDCLASS w1 = {0};
w1.lpszClassName = TEXT( "the_window" );
w1.lpfnWndProc = methodIWantOnItsOwnThread;
// snip
Now, I have been multithreading with the &ltprocess.h> threads in a method such as:
HANDLE h;
h = (HANDLE) _beginthread(methodIWantOnItsOwnThread, 0, 0);
How can I multithread like this in the windows callback function, such as with w1.lpfnWndProc = methodIWantOnItsOwnThread;?
More code.
HWND SetupWindow(int device)
{
HWND hwnd;
WNDCLASS w1 = {0};
if (device == 1)
{
w1.lpszClassName = TEXT( "window 1" );
w1.lpfnWndProc = methodIWantThreaded;
}
else
{
w1.lpszClassName = TEXT( "window 2" );
w1.lpfnWndProc = otherMethodIWantThreaded;
}
w1.hInstance = 0;
w1.hbrBackground = GetSysColorBrush(COLOR_3DFACE);
w1.hCursor = LoadCursor(0, IDC_ARROW);
RegisterClass(&w1);
hwnd = CreateWindow( w1.lpszClassName, TEXT("The Window"),
WS_OVERLAPPEDWINDOW | WS_VISIBLE, 0, 520, 650, 520, NULL, NULL, 0, NULL);
SetTimer(hwnd, 0,30,NULL);
ShowWindow(hwnd, SW_SHOW);
UpdateWindow(hwnd);
return hwnd;
}

Answer 1

You're going about this backward, and it isn't going to work.
You should be having each window create a thread, not each thread creating a window. Then you simply create multiple instances of the WNDCLASS classname, and each has its own thread that can post and receive messages.
This also gives you a window handle that your main thread's window can use to send and receive messages, allowing you to communicate things to the threads (and vice versa).

Answer 2

Why do you want to do that?
The window proc runs on the thread that created the window handle. Of course, by extension, every thread that creates window handles must have a message loop.