[fpc-pascal] support for using an activex

Roberto Padovani padovani.r at gmail.com
Wed May 25 22:52:11 CEST 2011

Always thanks!

Given your evident experience on this matter, I kindly ask your advice
on what is best to do.

opt 1) create a fpc class with some pascal style methods, which in
their implementation use variants and call the IDevice class with
late-binding ..... meaning that there is no compiler check and if my
collegue changes the dll, then I have to change these implementations

opt 2) in a reference of those you sent me, there is some example code
from which I take the lines below. In the tlb conversion unit, the
interface and dispinterface of the class are some replicated. Then
also the eventinterface is defined.
The main interface class is defined without and with dispids. With the
dispids, only the properties are defined and not the methods.

  IFileZapper = interface(IDispatch)
    function Get_Directory: WideString; safecall;
    procedure Set_Directory(const Value: WideString); safecall;
    function Get_FileMask: WideString; safecall;
    procedure Set_FileMask(const Value: WideString); safecall;
    procedure BringToFront; safecall;
    property Directory: WideString read Get_Directory write Set_Directory;
    property FileMask: WideString read Get_FileMask write Set_FileMask;

  IFileZapperDisp = dispinterface
    property Directory: WideString dispid 1;
    property FileMask: WideString dispid 3;
    procedure BringToFront; dispid 10;

  IFileZapperEvents = dispinterface
    procedure OnSelectionChanged; dispid 1;
    procedure OnDirectoryChanged(const DirName: WideString); dispid 2;

Is this somewhat the same thing as the wrapper of option 1? If I write
all of this conversion (and, by the way, how to convert C++ data types
to pascal?? widestring ?), then how can I use it?

In the end, maybe the wiki page about COM interfaces should be update
to something more than 'Word.Application.NewFile'.
I can't share the activex I have, otherwise it would be a good example
to see something useful to start with.


2011/5/25 Ludo Brands <ludo.brands at free.fr>:
> Using variants you can transparently "walk" along the exposed objects. The
> variant contains the Idispatch of the object and gets the exposed methods at
> runtime. Properties are implemented as get and put methods or just get
> methods for read only properties.
> If you have something like
> Itransducers = interface
>  ..
>  property transducer[Index:integer]:Itransducer;
> end;
> Then you would do
> transducer := transducers.transducer[index];
> transducer := transducers[index];  works only if transducer is the default
> property for Itransducers. I'm not sure if fpc supports this.
> Ludo
> -----Message d'origine-----
> De : fpc-pascal-bounces at lists.freepascal.org
> [mailto:fpc-pascal-bounces at lists.freepascal.org] De la part de Roberto
> Padovani
> Envoyé : mercredi 25 mai 2011 19:34
> À : FPC-Pascal users discussions
> Objet : Re: RE : RE : RE : RE : RE : [fpc-pascal] support for using an
> activex
> 2011/5/25 Ludo Brands <ludo.brands at free.fr>:
>> The code in article
>> http://www.informit.com/articles/article.aspx?p=130494&seqNum=5 goes a
>> long way in doing what you want to do. Unit Eventsink does pretty much
>> of the legwork. You should remove the procedure register since that is
>> the Delphi way to get a component on the toolbar. Remove also the
>> {$IFDEF VER100} and {$ENDIF}. The unit actually includes the code for
>> InterfaceConnect!!
> found that! great!
>> As for the tlb conversion, in your case
>> IEventIntfEvents = dispinterface
>>  ['{168F5642-5751-49F5-9AA4-B8A7A5F6A5B8}']
>>  end;
>> should do (that is for the events part). AFAIK the procedure and
>> dispid definitions are only needed for the server. You are only
>> concerned with dispid's. No need to create prototypes for
>> OnCommChanged() etc. EventSink1Invoke would be a simple case DispID of
>>  1: // do CommChanged
>>  2: // do StatesChanged
>> ...
>> end;
> Now I am "wasting" time making the tlb pascal definitions.
> For the event part I'm fine with the dispid's
> Until now I was calling the activex method with variants, in and out, but
> now I discovered that this IDevice class has a property like: property
> Sensors: ISensors;
> which inside is a list of items like   Sensor: ISensor.
> Can I read the sensores with a variant? Then, to see the fields inside each
> sensor, I think a I need a class to do that... The activex has all of these
> classes with the suitable dispinterfaces and uuids and so on. But if I
> define
>     var device, transducers, transducer : variant;
> and create
>     device := CreateOleObject('Device');
> then, can i simply write the following ?
>     transducers := device.Transducers;
>     transducer := transducers[index];
> It's a long path until I get this stuff working...
> R#
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