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

[Bob Caryl <bob fis-cal com>]

Oops!  Forgot to "reply all." 

Bob

-------- 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/>/

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