callback function

[Emil_halim]

Hi all

can any one show me a working example of callback function system in oxygen.

and how can i declare import function that accept a function pointer (the callback).

[JRS]

Do you want to see that in single or multi-threaded?

Sorry Charles, I couldn't resist. 

[Emil_halim]

Oh , it seems i am willing  leave this forum.

BTW this is the first forum seeing it's members are so funny and not serious.

[JRS]

That was a big Thank You to Charles for his multi-threading and shared callback work with DLLC and not a response to your question. Sorry Emil.

[Emil_halim]

no problem John,

but it hurts my alot.

[Aurel]

Emil ..do you mean callback like this:

Code: [Select]

'gui-skeleton app
Include "awinh.inc"
#lookahead
INT win,win2
INT x,y,w,h,x2,y2,w2,h2
x=0:y=10:w=400:h=400
x2=410:y2=10:w2=400:h2=300
INT winstyle,wstyle2
winstyle = WS_MINMAXSIZE or WS_CLIPCHILDREN
wstyle2 = WS_MINMAXSIZE or WS_CLIPCHILDREN
INT b0ID = 100
'############################################
print "WIN:" +str(win)
'############################################
'create window **************************************************
win = SetWindow("Skeleton App",x,y,w,h,0,winstyle)
print "WIN:" +str(win)
'create button on win
button0 = SetButton(win,80,4,80,26,"Close Win2",0x50000000,0x200,b0ID)
'create second window
win2 = SetWindow("New Window",x2,y2,w2,h2,0,winstyle)
print "WIN2:" +str(win2)
'****************************************************************

'/////////
Wait()
'\\\\\\\\\

Function WndProc (sys hwnd,wmsg,wparam,lparam) as sys callback

SELECT hwnd
'----------------------------------------
CASE win
'----------------------------------------
Select wmsg
CASE WM_CLOSE
DestroyWindow win
MsgBox "Quit...","End program!"
PostQuitMessage 0

    CASE WM_COMMAND
controlID = LoWord(wParam) 'get control ID
notifyCode = HiWord(wParam) 'get notification message

Select controlID
   CASE b0ID
If notifycode=0 
MsgBox "Close New Window!","To Win2"
         CloseWindow(win2)
End If
    End Select
End select
'----------------------------------------
CASE win2
'-----------------------------------------
Select wmsg
CASE WM_CLOSE
DestroyWindow win2
MsgBox "Win2 Closed!","WIN2"
End select

END SELECT

RETURN Default

END FUNCTION
or something else ?

[Charles Pegge]

Yes, wndproc is one example of a callback.

A more generalised form might look like this:


function cbk(sys v) as sys , callback
...
return -1
end function

the address of the callback function is then @cbk

SetCallBackFunction("type spec",@cbk)


Callbacks are automatically extern, but if they are expected to be cdecl then that must be made explicit.

[Emil_halim]

thanks you Aurel & Charles,


actually the callback function will be in the exe file , then i have to pass it's address to an import function
in dll , so how to declare the import function.

[Charles Pegge]

On the other (usually the DLL) side:

extern

! SendCallBackA(sys v)
! SendCallBackB(sys v)
...others

extern export

function SetCallBackFunction(char*spec,sys f)
...
@sendcallbackA=f
...
end function

end extern

if @SendCallBackA then SendCallBackA 42


Charles