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From: Rolf Wester <WESTER@ilt.fhg.de>
Subject: Problems with GLUT on NT and "deeper accessibility"
Date: 1998/10/30
Message-ID: <3639682C.AA824493@ilt.fhg.de>#1/1
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Organization: Fraunhofer Institut Lasertechnik
Mime-Version: 1.0
Reply-To: WESTER@ilt.fhg.de
Newsgroups: comp.lang.ada
Date: 1998-10-30T00:00:00+00:00
List-Id: <comp.lang.ada>

Hi,

I installed GNAT, AdaWin32 and  GLUT according to the instructions on
"Jerry's Ada on Win32 Page". I also downloaded the GLUT sources. When I
try to compile the program ada_sphere_procs.adb (with win32.gl,
win32.glu) I get the following error message:

Compiling...
ada_sphere_procs.adb:41:38: object has deeper accessibility level than
access type
ada_sphere_procs.adb:42:39: object has deeper accessibility level than
access type

The code fragment is:
      procedure init is

       light_diffuse : array(0 .. 3) of aliased GLfloat :=
                    (1.0, 0.0, 0.0, 1.0);
       light_position : array(0 .. 3) of aliased GLfloat :=
                    (1.0, 1.0, 1.0, 0.0);

       begin
       glClearColor(0.1, 0.1, 0.1, 0.0);

       glLightfv(GL_LIGHT0, GL_DIFFUSE, light_diffuse(0)'access); --
line 41
       glLightfv(GL_LIGHT0, GL_POSITION, light_position(0)'access); --
line 42

The function glLightfv is defined in win32-gl.ads as:
       procedure glLightfv(
                light : GLenum;
                pname : GLenum;
                params: ac_GLfloat);

and ac_GLfloat is  defined as:
       type GLfloat is new Win32.FLOAT;
       type ac_GLfloat is access constant GLfloat;

When I change the code to:

     procedure init is

        light_diffuse : array(0 .. 3) of aliased GLfloat :=
               (1.0, 0.0, 0.0, 1.0);
        light_position : array(0 .. 3) of aliased GLfloat :=
               (1.0, 1.0, 1.0, 0.0);
         type my_ac_GLfloat is access constant GLfloat;
         myFA : my_ac_GLfloat;
         FA   : ac_GLfloat;
  begin
        glClearColor(0.1, 0.1, 0.1, 0.0);

         myFA := light_diffuse(0)'access;  --line 43
         FA   := light_diffuse(0)'access;    -- line 44

         glLightfv(GL_LIGHT0, GL_DIFFUSE, light_diffuse(0)'access);
--line 46
         glLightfv(GL_LIGHT0, GL_POSITION, light_position(0)'access); --
line 47

I get the following error messages:

Compiling...
ada_sphere_procs.adb:44:13: object has deeper accessibility level than
access type
ada_sphere_procs.adb:46:38: object has deeper accessibility level than
access type
ada_sphere_procs.adb:47:39: object has deeper accessibility level than
access type

With my own my_ac_GLfloat on line 43 it's O.K. with the win32.gl
ac_GLfloat
used on line 44 it's an error!

I would be very appreciative for any help.

Thanks in anticipation

- Rolf

P.S.: Could anybody explain me the difference between
       type ac_GLfloat is access constant GLfloat;
and
       type ac_GLfloat is access all GLfloat;


----------------------------------------------------------------------------

Rolf Wester
Fraunhofer-Institute for Laser Technology
Aachen
Germany
wester@ilt.fhg.de