Re: Setting Up Callback

Phil Grace wrote:
> Hi,
> 
> I'm trying to set up a callback from a function in a .dll and can't
> seem to land on the right syntax....
> 
> The function itself is defined like this :
> 
> { typedefs with special meaning }
> aDHandle = integer;	{ database file handle }
> aLong = Longint;	{ 32-bit signed integer }
> aResult = integer;	{ returned result code }
> 
> function  PclReindex (fdh:aDHandle; kmask:aLong;
> callback:integer):aResult; stdcall;
> 
> ... and then I need to define a function like this :
> 
>    aReindexCallback = function (funcno:anInt; par1:aLong;
> par2:aLong):aResult;
> 
> ... what I have ben playing around with is the following, the compiler
> complains with "Not enough actual parameters".
> 
> function ReindexCallback (funcno:anInt; par1:aLong;
> par2:aLong):aResult; 
> begin
>   result := 0;
> end;
> 
> procedure TMainForm.Reindex (sPath, sFile : string ); var
>   sFilename : string;
>   fh : integer;
>   cb : aReindexCallback;
> begin
>   sFilename := (sPath + '\' + sFile);
>   fh := OpenAFile ( sFilename );
>   Progress ( format('Reindexing %s ...',[sFilename]) );
> 
>   cb := ReindexCallback;
>   PclReindex( fh, 0, cb);
>   PclClose(fh);
> end;
> 
> 
> 
> any help would be much appreciated.
> 
> Regards,
> Phil.
> 
  not sure what your trying here but is an an example
of an API in the system that is a call back..

  --- in your app code ----

  Function EnumWIndowsProc(handle:Thandle, UserData:Dword):Booland;
stdcall
   Begin
     if // what ever Result := true else
    result := false;
   End;

--- some where in your initiation of this. ---
   EnumWindows(@[EMAIL PROTECTED]
);

--------------
   the EnumWindows is a function in one of the
systems DLL's that sets up a vector address to
your EnumWindowsProc..
   by using the "@[EMAIL PROTECTED]
" you can pass the address of
this function ot the procedure call in the DLL.
  you have to create a function/procedure in the
DLL to accept the address and set up the vector
ect....

  - for example in the DLL ----
Var
  DLLEnumWindowsProcVector:function(Handle:Thandle, 
UserData)Boolean;Stdcall;

---- now the call your app would make to the DLL ----
  procedure SetUpMyCallBackVector(P:Pointer);
   Begin
     DLLEnumWIndowsProcVector := P;
   End;

---- now some where in your DLL code  ----
   DLLEnumWindowsProcVector(SomeHandle, SomeUserData);

   this will actually call the function in your APP..
  all you need to do is ex****t the SetUpMyCallBackVector procedure
so that you can link it in the main APP>.
for example..

  procedure SetCallBack(P:Pointer) external 'DLLNAME.DLL' name 
'SetUpMyCallBackVector';

  and to use it in the app
  SetCallBack(@[EMAIL PROTECTED]
);
ect...
  etc ... and the list goes on...


-- 
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5