[DUG] Returning a WideString in an Invoke Param

[Rohit Gupta]

Is this code in a DLL ?  If so then you can not transfer ansistrings unless you 
use a sharememory kludge.  

Last time I chose to use shortstrings to get around this.  That worked fine 
except in some instances on some PCs, the exceptions would not work... 
When I thought about it, the exception object itself uses ansistring.  So 
Borlands staement is not true.... if the DLL can possible raise an exception, 
it uses ansistring and you need to use sharemem.

Date sent:	Tue, 18 Jul 2006 11:13:50 +1200
From:	Phil Middlemiss <phil at tumonz.co.nz>
Organization:	MTS Ltd
To:	NZ Borland Developers Group - Delphi List <delphi at ns3.123.co.nz>
Subject:	[DUG] Returning a WideString in an Invoke Param
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Hi all,

I have an automation object with events. One of the events has a couple 
of VAR parameters which I'm not quite sure how to handle. Here is the 
code that is NOT working:

procedure TT3SDKEvents.DoInvoke(Sender : TObject; DispID: Integer; const 
IID: TGUID;
  LocaleID: Integer; Flags: Word; var Params: TDispParams; VarResult, 
ExcepInfo,
  ArgErr: Pointer);
    case DispID of

    ...

    4: { OnIdentify }
      if assigned(FOnIdentify) then
        begin
        //initialise the values
        layermanagerid :=  WideCharToString(Params.rgvarg[1].bStrVal);
        appname := WideCharToString(Params.rgvarg[0].bstrVal);
        if assigned(FOnIdentify) then
          FOnIdentify(layermanagerid, appname);
        Params.rgvarg[1].bstrVal := PWideChar(layermanagerid);
        Params.rgvarg[0].bstrVal := PWideChar(appname);
        end;
    end;
end;

The above code just ends up returning an empty string - I've checked to 
make sure that the call to FOnIdentify is indeed returning values.
So the question is: how should I be returning a widestring in the 
TDispParams?

Cheers,
Phil.
Regards

Rohit

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