Re: GTK Widget assertion problem

[Michael T. <myso77 seznam cz>]

Hi,
> Hello, this all looks like utter voodoo.  

Yes it does. I tried 10 other ways and they didn't work. This one works perfectly (so far).
> You have probably a trivial
> bug somewhere (elsewhere) in your code, maybe some
> extern/static/initialization confusion? 

All initialization was shown in the previous examples. All my initializations are taken directly from the 
GTK+ documentation and I never had one problem. More people have been developing this very same application 
and there was no problem until I needed to work with the progress bar widget.
There is no static identifier used because it is not needed. The extern identifier is used only, when the 
widget is accessed from other files which is precisely what this identifier was designed for.

>  Or you overwrite the stack and
> calling progressBarHack() causes a change of the layout so that you
> overwrite a less sensitive place now?  

progressBarHack() does nothing with the layout. All it does is a proper initialization of the global variable 
which should work without the hack, but doesn't. 

> Anyway, it is recommended fix to
> avoid global variables, they are evil, and externs are double-evil. 

Why? I've personally read the first book on C called The C programming language from 1978 written by the 
inventor of the language and using global variables is explained there as a proper way to implement things. I 
wonder what is the source of the 'evil global variables' legend, but if I'm wrong, please correct me. The 
extern identifier is just a way to access the global variable from a different file. I don't see why it 
should be a double-evil.

> But
> perhaps if you show a minimal *complete* example that exhibits the error
> some will be able to help you.  Or, likely, you will find the root cause
> while trying to extract the bad behaviour into a simple example...

I tried to do so in my first email (not the one you responded to). I also mentioned that I use several 
widgets as global variables because I need to access them from multiple functions. Hence, callbacks are not 
sufficient, in my opinion.
There was never one problem with using widgets as global variables and the application uses a lot of them. 
That's why I think there's a problem particularly with the Progress bar widget. 
My hack just initializes the global variable properly, all it does is re-initializing the global variable 
outside the current function stack.

Anywayz, a another simple example:

// global variables
GtkWidget *combobox;
GtkWidget *textField; 
GtkWidget *progBar;

GtkWidget* create_main_window (void)
{
    .... //necessary window initializations, vertical boxes, tables etc.

   combobox = gtk_combo_box_new_text();
   
      gtk_combo_box_append_text(GTK_COMBO_BOX (combobox), (const char*) "U/t");
      gtk_combo_box_append_text(GTK_COMBO_BOX (combobox), (const char*) "Q/t");
      gtk_combo_box_set_active(GTK_COMBO_BOX (combobox), 0);

      gtk_widget_show(combobox);
      gtk_box_pack_start (GTK_BOX (vbox3), combobox, FALSE, FALSE, 0);

   textField = gtk_text_view_new ();
      gtk_widget_show (textField);      
      gtk_table_attach_defaults(table, textField, 3, 5, 0, 1);

   progBar = gtk_progress_bar_new();  
     gtk_box_pack_start (GTK_BOX (vboxGr), GTK_PROGRESS_BAR(progBar), FALSE, FALSE, 0);
     gtk_widget_show (progBar);
  
   // progressBarHack(progBar);

   ...
}

All the widgets are used as global variables due to reasons I have explained. All of them work perfectly and 
can be accessed from various functions except the progress bar widget. With the hack, progress bar works 
perfectly, too. There are about twenty or more widgets in the application that are used the same way - as 
global variables, there's never been one single problem.

Please correct me, if I'm wrong anywhere.

Thanks,

Michael