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From: hreba <hreba@terra.com.br>
Newsgroups: comp.lang.ada
Subject: Re: Pass a serial port as user data in a GTK callback handler?
Date: Sun, 16 Feb 2014 13:57:42 -0300
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Date: 2014-02-16T13:57:42-03:00
List-Id: <comp.lang.ada>

On 02/16/2014 06:20 AM, Dmitry A. Kazakov wrote:
> On Sat, 15 Feb 2014 21:32:58 -0200, hreba wrote:
>
>> My actual programming exercise has a GTK GUI, and I want a callback
>> handler to communicate through a serial port, so I need to pass the port
>> in my user data, which must be of
>
> Additionally to other responses.
>
> There cannot be any reason to pass a stream object to GTK signal handler.
> It is most certainly wrong to do any I/O from a signal handler, as it would
> block the UI.

So far I am only trying to open/close the port when the window 
opens/closes, or check the availability of /dev/ttyUSB0 upon a button press.

> In some cases the UI may indeed be aware of I/O objects, like a COM port
> configuration dialog or cancel button. In these cases there is a larger
> object that contains the I/O object usually as a private member.

I think this is what I am trying right now.

> Specifically to GTK, you should better use smart pointers rather than raw
> access types when dealing with callbacks and pass them around. The point
> that UI and I/O will run in independent tasks. It is difficult to prevent
> dangling pointers otherwise. [I don't consider global variables, of course]

So I will be back when I have to fight with task programming in Ada, as 
soon as I begin with the real communication part.

I did a fast search without finding a data structure "smart pointer" in 
GObject, GLib or GTK (devhelp), only as part of the C++ language (which 
I don't know). But I am using Ada. Could you give a hint/reference/link 
to that?

-- 
Frank Hrebabetzky		+55 / 48 / 3235 1106
Florianopolis, Brazil