From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: 
X-Spam-Status: No, score=-1.3 required=5.0 tests=BAYES_00,INVALID_MSGID
	autolearn=no autolearn_force=no version=3.4.4
X-Google-Language: ENGLISH,ASCII-7-bit
X-Google-Thread: 103376,cc260587857d0c81,start
X-Google-Attributes: gid103376,public
From: Frode Tenneb� <frodet@nvg.ntnu.no>
Subject: Thin binding of C++ classes
Date: 2000/07/20
Message-ID: <964084369.995740@tornado.itea.ntnu.no>#1/1
X-Deja-AN: 648552136
Cache-Post-Path: tornado.itea.ntnu.no!frodet@hagbart.nvg.ntnu.no
X-Complaints-To: usenet@itea.ntnu.no
X-Trace: kopp.stud.ntnu.no 964087856 27508 129.241.190.18 (20 Jul 2000
 10:10:56 GMT)
Organization: Norwegian university of science and technology
X-Cache: nntpcache 2.4.0b2 (see http://www.nntpcache.org/)
User-Agent: tin/1.4.3-20000502 ("Marian") (UNIX) (Linux/2.2.12 (i686))
NNTP-Posting-Date: 20 Jul 2000 10:10:56 GMT
Newsgroups: comp.lang.ada
Date: 2000-07-20T10:10:56+00:00
List-Id: <comp.lang.ada>

I'm currently writing a binding to Tenet's MapLink (www.tenet.co.uk). This
is my first atempt on writing a 'serious' binding. I have just stared and
I'm already feeling stomped. :)

This is an example of a simpler class:

class TSLMotifSurface : public TSLDrawingSurface
{
public:
      TSLMotifSurface (Display* display, Window handle, long flags = 0);
      TSLMotifSurface (Display* display, Screen* screen, Colormap
colormap, Pixmap handle, long flags = 0);
      TSLMotifSurface (Display* display, TSLUNIXPrinter* printer);
      virtual ~TSLMotifSurface();
  protected:

  private:
};

I have though of using tagged types for the class representation, however,
I came across ada.finalization which could be benifitial here. But I have
not found any literature on this subject (though, I have just ordered an
update of my library). What is recomended?

My atempt looks like this:

with X_Lib;

package TSL_Drawing_Surface.TSL_Motif_Surface is

   type Object is tagged private;
   type Object_Ptr is access Object'Class;

   function TSL_Motif_Surface (Display : in X_Lib.Display_Pointer;
                             Handle  : in X_Lib.Window_ID;
                             Flags   : in Long_Integer := 1) return
Object_Ptr;

   function TSL_Motif_Surface (Display  : in X_Lib.Display_Pointer;
                             Screen   : in X_Lib.Screen_Pointer;
                             Colormap : in X_Lib.Colormap_ID;
                             Handle   : in X_Lib.Pixmap_ID;
                             Flags    : in Long_Integer := 1) return
Object_Ptr;

--  function Create (Display : in X_Lib.Display_Pointer;
--                 Printer : in TSLUNIXPrinter_Pointer) return Object_Ptr;

private
   pragma Import (C, TSL_Motif_Surface, "TSLMotifSurface");
   type Object is tagged with null record;

end TSL_Drawing_Surface.TSL_Motif_Surface;

However, trying to 

(15)   Ds       : TSL_Drawing_Surface.TSL_Motif_Surface.Object_Ptr;
(23)   Ds := TSL_Drawing_Surface.TSL_Motif_Surface.TSL_Motif_Surface 
         ( Display => Display,
           Handle  => X_Toolkit.XtWindow( toplevel ),
           Flags   => TSL_DOUBLE_BUFFERING);

gives:

example.adb:15:52: "Object_Ptr" not declared in "TSL_Motif_Surface"
example.adb:23:47: "TSL_Motif_Surface" not declared in "TSL_Motif_Surface"
gnatmake: "example.adb" compilation error


What can be wrong?

Then there is the case with the overloaded constructor. Will pragma Import 
handle this accordingly? Should I go for a thicker binding?

Furthermore, the parent class of this one (TSLDrawingSurface) uses friend.
How is that best dealt with?

Regards,
 -Frode