Re: afx_msg (VC++ 6->VS 2005)

From:

"Tom Serface" <tom.nospam@camaswood.com>

Newsgroups:

microsoft.public.vc.mfc

Date:

Tue, 20 Mar 2007 16:28:55 -0700

Message-ID:

<OAWkIe0aHHA.4772@TK2MSFTNGP05.phx.gbl>

For PostMessage() the return (a BOOL) defines whether it could post the
message or not (not a result from the function).

For SendMessage() an LRESULT is just a long pointer so you can return all
sorts of results, but most of the time that I use it I just return 0.

There are some functions that are set up as void (MFC takes care of return
code to OS) and a parameter is passed in for LRESULT that the message
handler can set. I typically just set it to 0, but lots of handlers use
this pointer to get CDC pointers, window handles, etc.

Tom

"Nobody" <Nobody@yahoo.com> wrote in message
news:uIICHgzaHHA.2300@TK2MSFTNGP06.phx.gbl...

I am curious to know why it matters to return a result?

I've never really dealt with having to return an error in a Message.
I just keep forgetting to return a result.

I hark back to an older post where it really didn't matter whether the
poster returned true or false.
I have seen that a lot and wonder it is ever really implemented?

I guess that it is just how it is defined.
WM_COMMAND messages can't have a return type.
ON_MESSAGE has to have a return type.

This, to me is just a message map.
It maps the message to the function.
ON_COMMAND(IDC_MY_BTN, OnBtnMyBtn)
To me, the function is exlusive and not inclusive.
It really shouldn't matter if there is a return type or not.
It probably has something to do with the static_cast and that is just how
it maps to the function.

I can understand why SendMessage() would have a return type, but what
about PostMessage()
How can PostMessage() Fail?

It has been a while since I have had the errors the OP mentioned.
I believe it was when you defined your own messages, so LRESULT would be
true in his case.

I guess there was, or is a need to return a result from SendMessage().
Perhaps that is why MFC didn't define a return type?
They weren't sure if it was important or not?