c++ WTL/ATL How to find a window handle from the current process?

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I have a library function (that does not know anything about the application its linked to) that sometimes opens a window.

If the application's main window is closed while the library window is open, the process gets into a weird state that wont exit, even after the library function widow is closed.

If the library function is "owned" by the main window, everything closed fine. However, in general the library function has no idea what windows are open.

The standard windows functions appear to either search all windows for all processes, or they require a window handle to find another window handle.

How do I find ANY top level window of the process my function is running in?
=======================================================================
Solution, clunky but tested, works.

static BOOL CALLBACK MyEnumThreadWndProc( HWND hwnd, LPARAM param ){
HWND *oW = reinterpret_cast<hwnd*> (param);
(*oW) = hwnd;
return false;
}

...
HWND oWind=0;
EnumThreadWindows(GetCurrentThreadId(), &MyEnumThreadWndProc, reinterpret_cast<lparam>(&oWind) );

Posted 18-Apr-12 10:48am

mrbll

Updated 19-Apr-12 12:47pm

v2

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2 solutions

Solution 2

You should be able to call AfxGetMainWnd() from the exported function and get the top-level window from the thread calling the exported function (may return NULL if there's no window associated with the thread).

See documentation:
http://msdn.microsoft.com/en-US/library/waas15s1%28v=vs.80%29.aspx[^]

Or... you can use AfxGetApp(), then call CWinThread::GetMainWnd() (rememeber CWinApp is derived from CWinThread).
Reference:
http://msdn.microsoft.com/en-US/library/5k9f064x%28v=vs.80%29.aspx[^]
http://msdn.microsoft.com/en-US/library/sazyysab%28v=VS.80%29.aspx[^]

Posted 18-Apr-12 11:53am

Albert Holguin

Comments

mrbll 19-Apr-12 13:26pm

Sounded perfect, but when I included afxwin.h, its unhappy.
1>c:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\atlmfc\include\afxv_w32.h(16) : fatal error C1189: #error : WINDOWS.H already included. MFC apps must not #include <windows.h>

Apparently the atl library and mfc don't play together? I thought they could coexist.

Albert Holguin 19-Apr-12 15:11pm

They should be able to coexist fine, compilation order may cause issues though. Does your project already use MFC? ...control which libraries you're using through the project settings so that the compilation order will be correct, don't #include the files.

mrbll 19-Apr-12 15:49pm

Thanks. I tried altering the project to add "use mfc "(making my windows with WTL.) It did not make the afx call visible. Tried putting afxwin.h in stdafx.h at the place the comment says visual studio will add it, but it got the same compile error. Whats the trick to make visual studio do the right includes for afxwin.h?

mrbll 19-Apr-12 15:48pm

Thanks. I tried altering the project to add "use mfc "(making my windows with WTL.) It did not make the afx call visible. Tried putting afxwin.h in stdafx.h at the place the comment says visual studio will add it, but it got the same compile error. Whats the trick to make visual studio do the right includes for afxwin.h?

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nv3 · Accepted Answer · 2012-04-18T11:52:00

You can use the system call EnumWindows to find all of your top-level windows. After your application has closed all its own windows, no other window should remain. If EnumWindows detects anything, then it's probably the additional window that your function has created.

If you know the window class or window name of that window, you could do a further verification that you have found the right window.

If you have a multi-threaded application with multiple UI threads you can use EnumThreadWindows to enumerate all top-level windows belonging to a particular thread.