Use of "Function" In Skeleton Program

[Wesley Brown]

Can someone explain the purpose 'Function = 0' in the following code?

'From C:\Program Files\PBDLL60\Samples\Skeleton
    CASE %WM_MENUSELECT
      LoadString hInst, wParam, zText, SIZEOF(zText)
      SendMessage hStatus, %WM_SETTEXT, 0, VARPTR(zText)
      FUNCTION = 0
      EXIT FUNCTION

    CASE %WM_MOUSEMOVE
      zText = "Mouse Position:" + STR$(LOWRD(lParam)) + ","+STR$(HIWRD(lParam))
      SendMessage hStatus, %WM_SETTEXT, 0, VARPTR(zText)
      FUNCTION = 0
      EXIT FUNCTION

'Function' is not declared as a variable and so I'm guessing that it
is something inherent to either Windows, PBDll, or perhaps even both.

Thanks For Your Help

Wesley

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[This message has been edited by Wesley Brown (edited March 19, 2001).]

[Florent Heyworth]

Hi

in PBCC/PBDLL you can return the result from a function using
one the following syntax:

FUNCTION ReturnValue (BYVAL AValue AS LONG) AS LONG

    ReturnValue = AValue

END FUNCTION

Or (I prefer this one since I find it more readable):

FUNCTION ReturnValue (BYVAL AValue AS LONG) AS LONG

    FUNCTION = AValue

END FUNCTION

Cheers

Florent


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[Borje Hagsten]

It is for preventing the DefWindowProc call at the end of the function
to process these particular messages. In Winapi32.hlp, each message is
described with a clause about return value, where it often says,
"If an application processes this message, it should return zero".

However, what MS means by "process this message" isn't always clear.
If you only have code that picks up a value, you don't really process
anything, so in some cases, one actually shall let them pass and let
DefWindowProc send them on to the default window procedure.

One case where this can become obvious is WM_SIZE in MDI applications,
where child windows must let them pass, but Main WinProc must return
zero, to avoid strange multiple system menus for each child, etc.


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[This message has been edited by Borje Hagsten (edited March 19, 2001).]