Re: WIA

["Frank J. Lhota" <NOSPAM.lhota@adarose.com>]

david wrote:
> Hello,
> 
> I'm trying to use wia in an ADA software.
> 
> I have found little code samples to write com objects and this seems to
> work well.
> 
> My problem is to use  (Wia_Property_Storage_Interface.Lpvtbl.)
> Writemultiple : i'm not sure about interfacing the two types propspec
> and propvariant and the writemultiple call.
> In C, writemultiple is :
> 
> HRESULT WriteMultiple(
>   ULONG cpspec,
>   const PROPSPEC rgpspec[],
>   const PROPVARIANT rgpropvar[],
>   PROPID propidNameFirst
> );

Well, not quite. WriteMultiple is really a method for objects of type 
IPropertyStorage. If you're working in C++, then this is implemented as 
a C++ method. If you're working in C, then the first parameter is a 
pointer to the object, e.g.

  HRESULT __stdcall WriteMultiple(
    IPropertyStorage* This,
    ULONG cpspec,
    const PROPSPEC rgpspec[],
    const PROPVARIANT rgpropvar[],
    PROPID propidNameFirst
  );

Every call to IPropertyStorage::WriteMultiple needs to include the a 
pointer / reference to the object.


> I'm not sure about the ada corresponding specifications for the "const
> type var[]".
> I wrote :
> 
>    type Propspec (Kind : Win32.Ulong) is
>       record
>          case Kind is
>             when Prspec_Propid =>
>                Propid : Win32.Oleauto.Propid;
>             when Prspec_Lpwstr =>
>                Lpwstr : Win32.Objbase.Lpolestr;
>             when others =>
>                null;
>          end case;
>       end record;
>    pragma Convention (C, Propspec);
>    type Ppropspec is access all Propspec;
>    function To_Ppropspec is new Ada.Unchecked_Conversion
> (System.Address, Ppropspec);
> 
>    type Tab_Propspec_Propid is array (Positive range <>) of Propspec
> (Prspec_Propid);
> 
>       type Propvariant (Vt : Win32.Oleauto.Varenum) is
>       record
>          Wreserved1 : Win32.Word;
>          Wreserved2 : Win32.Word;
>          Wreserved3 : Win32.Word;
>          case Vt is
>             when Win32.Oleauto.Vt_I4 =>
>                Ival : Win32.Long;
>             when Win32.Oleauto.Vt_Bstr =>
>                Bstrval : Win32.Oleauto.Bstr;
>             when others =>
>                null;
>          end case;
>       end record;
>    pragma Convention (C, Propvariant);
>    type Ppropvariant is access all Propvariant;
>    function To_Ppropvar is new Ada.Unchecked_Conversion
> (System.Address, Ppropvariant);
> 
>    type Tab_Propvariant_Vt_I4 is array (Positive range <>) of
> Propvariant (Win32.Oleauto.Vt_I4);
> 
>    type Af_I_Wia_Property_Storage_Writemultiple is access
>      function (This      : access I_Wia_Property_Storage;
>                Cpspec    : Win32.Ulong; -- in
>                Rgpspec   : Ppropspec;-- in const propspec []
>                Rgpropvar : Ppropvariant;-- in const propvariant []
>                Propidnamefirst : Win32.Oleauto.Propid) -- in essayer
> avec 2
>        return Win32.Objbase.HRESULT;
>    pragma Convention (Stdcall,
> Af_I_Wia_Property_Storage_Writemultiple);
> 
> When calling this method, I write :
> 
> Propspec_Flash_Mode   : Tab_Propspec_Propid (1 .. 1) := (1 => (Kind =>
> Prspec_Propid,
> 
> Propid => Win32.Oleauto.Propid (Wia_Dpc_Flash_Mode)));
> Propvar_Flash_Fill   : Tab_Propvariant_Vt_I4 (1 .. 1) := (1 =>
> (Win32.Oleauto.Vt_I4,
> 
> Win32.Word (0),
> 
> Win32.Word (0),
> 
> Win32.Word (0),
> 
> Win32.Long (Wia_Flash_Mode_Fill)));
> 
> 
> My_Hresult := Wia_Property_Storage_Interface.Lpvtbl.Writemultiple
> (Wia_Property_Storage_Interface,
> 
>     1,
> 
>     To_Ppropspec (Propspec_Flash_Mode (1)'Address),
> 
>     To_Ppropvar (Propvar_Flash_Fill (1)'Address),
> 
>     2);
> 
> I tried to work without tab_prospec_propid and tab_propvariant_vt_i4
> but this doesn't work.
> When executing, my_hresult is s_false.
> 
> I tried to use gnatcom to verify my interfacing but createcom seems to
> not work on wiaservc.dll (whereas it works on wiaaut.dll for example.
> 
> So, I have 2 questions :
> 
> Is someone see a mistake on my interface code ?
> Does someone know why gnatcom doesn't work on wiaservc.dll ?
> 
> thank you very much and.....
> 
> best wishes for 2006
> 
> David
> 


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