Re: Calling GUI function from Thread

[Robert Pearce <rob bdt-home demon co uk>]

Hi Taha Ali,

On Sun, 9 Sep 2007 you sent me a message saying :
> Thanks for the reply.

You should reply always to the list, not to me personally. I'm far from 
an expert and even if I was I might miss things. Reply to the list to 
get the benefit of a far wider knowledge base.

> Actually, the API that I am using wants me to
> register a callback function that would report to me the progress of
> the function that I have called in my thread. This callback is not able
> to see the Glib::Dispatcher variable from my application class. 

Is it actually not possible to make it see it? Surely you could use 
libsigc++ to pass a method of your application instance as the 
call-back?

> The
> pseudo code is like this:
>
> class Application
> {
>          ...................
>          -------------------
>             Glib::Dispatcher report_message_signal;
>             static some_callback_func(arg1, arg2, arg3);
>          ...................
>          -------------------
>          ...................
>          -------------------
> }
>
> main()
> {
> ----------
> ----------
> Register_API_Callback_func(some_callback_func, .......);
> ----------
> ---------
> }
>
>
> on_button_clicked()
> {
> Glib::Thread::create(thread_function ......);
> }
>
> thread_function()
> {
> ---------
> ---------
> API_Function(); //Takes around 10 seconds
> ----------
> ----------
>
> }
>
> some_callback_func(Message)
> {
>
> //This function is internally called by the API giving info about the
> progress that API_Function
> //is making and it is from here that I have to set text, in order to
> report guiding messages, in the
> //label. I know that this is not right but what other options do you
> think I have.
>
> }
>
> Thanks and Regards,
> Taha
>
> On 9/8/07, Robert Pearce <rob bdt-home demon co uk> wrote:
>  On Sat, 8 Sep 2007, Taha Ali <tahaarifali gmail com> wrote :
>  >I am facing problem in calling a gui function from a thread.
>
>  Don't do that.
>
>  >I am trying to set_text these messages in a label but after
>  >first normal execution of this thread, the gui hangs on the next
>  call.
>
>  So don't do that.
>
>  >When I dont try to set_text any
>  >thing from this callback function, it works just fine showing me
>  the
>  >display (std::cout) on the screen.
>
>  So don't do that!
>
>  >Need help.
>
>  OK, incase you haven't already guessed, the answer is DON'T call GTK
>  from a thread. It doesn't like it at all.
>
>  The function in your thread should use Glib::Dispatcher (or
>  g_idle_add)
>  to ask the main (gui) thread to set the text.
>  --
>  Rob Pearce                       http://www.bdt-home.demon.co.uk
>
>  The contents of this | Windows NT crashed.
>  message are purely   | I am the Blue Screen of Death.
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>  believe a word.      |
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--
Rob Pearce                       http://www.bdt-home.demon.co.uk

The contents of this | Windows NT crashed.
message are purely   | I am the Blue Screen of Death.
my opinion. Don't    | No one hears your screams.
believe a word.      |