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From: risto@tuura.UUCP (Risto Lankinen)
Newsgroups: comp.windows.ms
Subject: Re: MessageBox problem
Message-ID: <767@tuura.UUCP>
Date: 21 Sep 90 12:09:06 GMT
References: <1990Sep9.224303.10981@bdmrrr.bdm.com> <1990Sep11.074217.18928@ciba-geigy.ch> <1990Sep12.043315.10404@Neon.Stanford.EDU> <1990S
Organization: Nokia Data Systems Oy
Lines: 34

poffen@sj.ate.slb.com (Russell Poffenberger) writes:

>I have found that MessageBox doesn't work properly in all cases. In attempting
>to write a dll (Screen Peace saver extension), I called MessageBox to try and
>debug a problem, this failed and caused the system to hang. Running CVW spit
>out a continuous ream of messages indicating that there were no more Device
>Contexts available. It seemed to get stuck forever in a loop at that point.

Hi!

I have run into similar problem with DLL's.  I would have liked to show a
messagebox if the LibMain failed to initialize the DLL for some reason.
Since the actual application is unaware of LibMain being called, there's
no window handle to associate the MessageBox with.  So, I used the handle
returned from GetDesktopWindow(), but it wouldn't work (even though it does
when an *application* wants to display a MessageBox without having created
a window handle).  On the other hand, if the LibMain() returned false to
indicate the failure, there's no chance to tell the user what went wrong,
because the DLL-related application will not start in case LibMain fails.

What I've made myself a habit to do is always return TRUE from LibMain(),
but set a flag, which would be returned by the first call made to the DLL
by the application itself.  The application would call, say, InitDLL(),
which 'pseudo-initializes' the DLL and actually returns the possible error
condition flagged by LibMain().  There's an added convenience that the WEP
also knows which initializations were succesfully done in order to free
just those resources that were grabbed.

Terveisin: Risto Lankinen
-- 
Risto Lankinen / product specialist ***************************************
Nokia Data Systems, Technology Dept *  2                              2   *
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