User Defined Messages - Value [modified]

[Cliff Hatch]

The help files recommend that user messages be defined in the range WM_USER to 0x7fff, but opening the Resource Symbols dialog to create a new ID and letting it choose the value seems to work fine. Does anyone know if there is anything wrong with this? Best Regards Cliff Hatch -- modified at 14:42 Wednesday 24th May, 2006

[David Crow]

Cliff Hatch wrote:

The help files recommend that user messages be defined in the range WM_USER to 0x7fff...

It should be WM_APP.

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"The largest fire starts but with the smallest spark." - David Crow

[PJ Arends]

Depends on the usage. If you are defining a message that will only be used within the application, then use WM_APP. If the message is for a control that could be used in other apps the use WM_USER. If it is a message that is used to communicate between different modules then use ::RegisterWindowMessage().

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You may be right I may be crazy -- Billy Joel -- Within you lies the power for good - Use it!

[David Crow]

PJ Arends wrote:

If the message is for a control that could be used in other apps the use WM_USER.

WM_USER should not be used at it can conflict with messages that Microsoft uses. RegisterWindowMessage() is the safest/preferred method in any case.

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"The largest fire starts but with the smallest spark." - David Crow

[Cliff Hatch]

Thanks guys. I can see that there is a problem if messages conflict, but what's puzzling me is why does it matter what the value is so long as it is unique - and if I use the Resource Symbols dialog to create it, doesn't that guarantee uniqueness? Is it a matter of standardisation and ease of maintenance perhaps? Best Regards Cliff

[Michael Dunn]

See Which message numbers belong to whom?[^]

--Mike-- Visual C++ MVP :cool: LINKS~! Ericahist | PimpFish | CP SearchBar v3.0 | C++ Forum FAQ

[Cliff Hatch]

Thanks Michael, that answers my question perfectly. :) Best Regards Cliff