Subclassing?

I am looking for information on subclasing a window in an application not written by me. I can get the HWND of the window, but any attempts to manipulate the window in any way fail. I can SetWindowText and send messages such as WM_CLOSE easily, they work fine. But when I try to use SetWindowLong with GWL_WNDPROC to replace the window proc with my own, it fails.

I have tried creating a CWnd and calling SubclassWindow, it returns true, and yet no calls are made top PreTranslateMessage or DefWindowProc. Any help? Thanks.

JL

If SetWindowLong() fails, you can call GetLastError() to get the error. If
something else is failing, it could be a number of things. Subclassing should
*always* works, unless you did something wrong. How about posting the part of
the code that fails.

Personally, I've always subclassed a window using good old Windows API and have
never used CWnd::SubclassWindow(). I wanted to know exactly where my old
handler was and knew when/where to call it, and when to restore the old
handler. The CWnd::SubclassWindow() was too convoluted (my opinion).

Regards,

Paul

I prefer to use the Win32 route rather than the MFC route also. At first I tried using SetWindowLong with the HWND of the window and passed my WNDPROC. Only it returns a NULL HWND as the previous one, and GetLastError() just returns 0 (no error), when I pass an HWND returned by GetSafeHwnd(), for my app. It works fine.

Thanks,
JL