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Using RegisterWindowMessage Defined Variable within Switch Statement

Posted on 2004-08-30
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Last Modified: 2013-12-03
I have been trying to use a RegisterWindowMessage defined variable within a switch statement expression, but my compiler keeps producing an error (i.e., case expression not  constant).  Can anyone tell me what I am doing wrong?  Here are my declarations for everything:

const UINT WM_WGMSG = RegisterWindowMessage (TEXT ("WG_Message"));

Within WndProc procedure:

switch (message) {
                        
  case WM_WGMSG:
  return 1;

}

Finally, I am programming in C under Microsoft Visual Studio .net 2003.  
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Question by:jtrades
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3 Comments
 
LVL 22

Assisted Solution

by:cookre
cookre earned 50 total points
ID: 11938438
Switch requires a compile time constants for its cases.  The value of your WM_WGMSG is not known until runtime.

Do you really need a system wide unique message code?

If it's just for use within your progrm(s), make up your own message code - some value above WM_USER (0x0400), say WM_USER+123.

If you must have system wide uniqueness, just add an explicit check for your message in the switch's 'default'.
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LVL 48

Accepted Solution

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AlexFM earned 200 total points
ID: 11938866
Agree with coorke about constant unknown at compile time.
However, RegisterWindowMessage is much better than constant messages. Just replace swithch with if - else if - ... else. If you want to use constant messages, use WM_APP and not WM_USER to prevent conflicts (Microsoft is already using some messages with values WM_USER + n).
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LVL 22

Expert Comment

by:cookre
ID: 11938893
The nerve of them!  I've always taken that as sacrosanct.

Guess that's what I get for being lazxy.
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