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From: vonhend@ibm.net
Subject: Re: Ada '83 X widget bindings
Date: 1998/04/10
Message-ID: <352e40d5.0@news1.ibm.net>#1/1
X-Deja-AN: 342778578
References: <6gignr$m4g@news.man.fs.lmco.com>
X-Notice: should be forwarded in their entirety to postmaster@ibm.net
X-Trace: 10 Apr 98 15:55:01 GMT, 32.100.169.229
Organization: IBM.NET
Reply-To: vonhend@ibm.net
Newsgroups: comp.lang.ada
Date: 1998-04-10T00:00:00+00:00
List-Id: <comp.lang.ada>


The fact that Ada 83 doesn't support function pointers doesn't mean that you
can't use conventional Xt and Motif bindings.  We use the Verdix-supplied bindings
from the Free Software Foundation (originally developed by DEC) and they work just
fine.  We do have to instantiate an unfortunate number of unchecked conversion 
functions (something I personally don't like, as unchecked conversion defeats
the purpose and value of strong type checking.)

The following code fragment, extracted from a working procedure, demonstrates
one way to create a button and register a callback.  The code which sets the
resources for the button has been omitted.


with Xt;
with Xm_Push_Button;
with Xm_String_Defs;

procedure Create_Some_Dialog is

    function  Create_Playback_Control_Form(Parent : in Xt.Widget) return Xt.Widget;

    ClosePushButton : Xt.Xt_Widget := Xt.Null_Widget;
    PlaybackControlForm : Xt.Xt_Widget := Xt.Null_Widget;
    Args : Xt.Xt_Ancillary_Types.Xt_Arg_List(1..256);

begin


      ClosePushButton := Xm_Push_Button.Xm_Create_Push_Button(Parent => PlaybackControlForm,
                                                              Name => "closePushButton",
                                                              An_Arg_List => args(1..ac-1));
      Xt.Xt_Callbacks.Xt_Add_Callback(Object => ClosePushButton,
                                      Callback_Name => Xm_String_Defs.Xm_N_Activate_Callback, 
                                      Callback => Xt.Xt_Callback_Proc(Close_Dialog_CB'Address),
                                      Client_Data => Xt.Xt_Utilities.To_Xt_Pointer (PlaybackControlForm));
      Xt.Xt_Composite_Management.Xt_Manage_Child(ClosePushButton);

end;

So you really do not need function pointers in Ada.

Mark Von Hendy
Lockheed Martin Technical Operations

In <6gignr$m4g@news.man.fs.lmco.com>, jack.ottofaro@lmco.com (Jack Ottofaro) writes:
>
>We currently have Ada '83 software which uses an X11 bindings package. We'd like
>to enhance our GUI with buttons, menu pulldowns, etc. Any suggestions on a good
>set of X11 widget bindings, for example bindings to Motif, compatable with Ada
>'83. My understanding is that since I'm using Ada '83 I cannot use the Motif
>callbacks since the language does not support function pointers but a package
>that provides routines for drawing widgets would be great.
>
>Thanks in advance,
>Jack Ottofaro