[Fwd: Re: signal_timeout vs loops (changing label text continuously)]

[Bob Caryl <bob fis-cal com>]

This is my morning for multiple goofs:  I mistakenly identified the 
dispatcher class as Gtk::Dispatcher....   I should have said 
Glib::Dispatcher.  Sorry folks. 

Bob Caryl

-------- Original Message --------
Subject: 	Re: signal_timeout vs loops (changing label text continuously)
Date: 	Tue, 27 Jun 2006 08:41:31 -0500
From: 	Bob Caryl <bob fis-cal com>
Reply-To: 	bob fis-cal com
Organization: 	Fiscal Systems, Inc.
To: 	Gezim Hoxha <gezimetc shaw ca>
References: 	<1151388900 7752 7 camel localhost localdomain>



Anytime you create a "loop" in the GUI thread, all GUI operations 
(including your call to Gtk::Label::set_text()) are suspended until your 
loop finishes and the function in which it runs returns.  You must allow 
Gtk::Main to do its job at some point during your loop iteration by 
inserting the following statements:

while(Gtk::Main::events_pending())
   Gtk::Main::iteration();

After your call to Gtk::Label::set_text().  This will allow the GUI to 
update.  However, you should always avoid doing this sort of processing 
in the GUI thread.  A well written application will do such processing 
in a separate thread and use a Gtk::Dispatcher to update the GUI if 
needed.  See  Gtk::Dispatcher 
<http://www.gtkmm.org/docs/glibmm-2.4/docs/reference/html/classGlib_1_1Dispatcher.html>  
for more information on how to do this.
<http://www.gtkmm.org/docs/glibmm-2.4/docs/reference/html/classGlib_1_1Dispatcher.html> 


Bob Caryl


Gezim Hoxha wrote:
> Hi all.
>
> Luis Federico in the "displaying text" thread asks how can he print some
> text to the screen on each loop iteration.
>
> I though I should try to help him but I found myself in trouble. I
> thought that having a Label and just changing it's text with the
> set_text() method would do the job. However this doesn't really work,
> and I was wondering if someone could help me understand why the label
> changes only after the last loop iteration completes. It seems that when
> the loop is executing the window doesn't redraw itself at all. What
> gives?
>
> Thanks,
> -Gezim
>   
> ------------------------------------------------------------------------
>
> #include <gtkmm.h>
> #include <sstream>
> #include <iostream>
> #include <unistd.h>
>
> class MyWindow: public Gtk::Window
> {
>     public:
>     MyWindow ();
>     virtual ~MyWindow ();
>
>     void on_button1_clicked ();
>     void loop ();
>
>     Gtk::Label showIterLabel;
>     Gtk::Button button1;
>     Gtk::HBox boxy;
>     int i;
> };
>
> int main (int argc, char * argv[])
> {
>     Gtk::Main kit (argc, argv);
>
>     MyWindow window;
>
>     kit.run (window);
>
>     return 0;
> }
>
> MyWindow::MyWindow ()
>     : button1("Start"),
>     i(0)
> {
>     set_default_size (400, 400);
>     add (boxy);
>     showIterLabel.set_text("stopped");
>
>     boxy.pack_start (showIterLabel);
>     boxy.pack_start (button1);
>
>     button1.signal_clicked ().connect (sigc::mem_fun (*this, &MyWindow::loop) );
>     show_all_children();
> }
>
> MyWindow::~MyWindow ()
> {}
>
> void MyWindow::loop ()
> {
>     std::ostringstream stream1;
>
>     while (i < 5)
>     {
>         stream1.str("");
>         stream1 << i;
>         std::cout << i << std::endl;
>         showIterLabel.set_text (stream1.str());
>         i++;
>         sleep (1);
>     }
> }
>   
> ------------------------------------------------------------------------
>
> _______________________________________________
> gtkmm-list mailing list
> gtkmm-list gnome org
> http://mail.gnome.org/mailman/listinfo/gtkmm-list
>   



--

/*Bob Caryl*
Fiscal Systems,Inc.
256.772.8920 Ext. 108
http://www.fis-cal.com <http://www.fis-cal.com/>/

/This email message may contain privileged or confidential information. 
If you are not the intended recipient, you may not disclose, use, 
disseminate, distribute, copy or rely on this message or attachment in 
any way. If you received this email message in error, please return by 
forwarding the message and its attachment to the sender and then delete 
the message and its attachment from your computer.

Neither Fiscal Systems, Inc., nor its affiliates, accept any liability 
for any errors, omissions, corruption or virus in the contents of this 
message or any attachments that arise as a result of e-mail transmission./

begin:vcard
fn:Robert Caryl
n:Caryl;Robert
org:Fiscal Systems, Inc.
adr:;;102 Commerce Circle;Madison;AL;35758;USA
email;internet:bob fis-cal com
title:Senior Software Design Engineer
tel;work:356-772-8920 X108
x-mozilla-html:TRUE
url:http://www.fis-cal.com
version:2.1
end:vcard