VNC Enables/Causes Windows Apps to Crash

Ron Struempf marvin "at"
Sat, 02 Mar 2002 16:34:44 +0000

Several of my Windows apps, written in CBuilder and Delphi, crash when
WinVNC is running.  I saw the FAQ Q39, but it says "disable any screen
savers" of which I have none.  I've been using Procomm Rapid Remote for a
very long time to access these servers, but switched to WinVNC because Rapid
Remote is the only app I've seen so far that crashes XP.

We are running WinVNC 3.3.3 R9 in App Mode on NT 4.0 Server.

What I've found is:
     - The app crashes in one of several mouse events (such as CM_NCHITTEST)
     - In my debugging, it appears as though the associated WM_NCHITTEST
message never appeared
     - The crash happens when the mouse cursor passes over the statusbar
     - The crash happens whether I am connected via VNC or Rapid Remote, and
probably local as well
     - I believe that the crashes continue to happen even after I close VNC,
but apparently at a much lower

I have also found that if I physically click on each focusable control on
the app, that the crash does not occur again until the app is restarted.

My theory is that WinVNC is absconding with some of the WM_???? messages,
but not suppressing the CM_???? messages they generate.  Thus, when the app
processes the control message (CM_???), it expects initialization to have
been performed when the Windows message (WM_???) was received.  By clicking
on each of the controls, I force it to do that initialization, so the crash
doesn't happen.

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