[C] How to pass multiple widgets?

ZuLuuuuuu · **Posted:** Mon Dec 08, 2008 8:22 pm

Hello,

Is there an easy way to pass more than 1 widget to a callback function? I guess there is a way to pass a second widget using g_object_set_data but I mean 3, 4, 5 widgets etc...

Edit: I use C language.

tadeboro · **Posted:** Mon Dec 08, 2008 8:53 pm

The data is usually passed as struct pointer. But you may also use array of gpointers.

dreblen · **Posted:** Mon Dec 08, 2008 9:01 pm

Common procedure is to pass a struct containing the variables that the callback needs.
EDIT: Time got away from me and tadeboro posted while I was on the "Post reply" page...

ZuLuuuuuu · **Posted:** Tue Dec 09, 2008 9:58 pm

Thank you very much. Struct is a good idea but you also gave me a clue to use a garray or something similar, which might give me opportunity to create a runtime group of widgets to pass :)

Joel · **Posted:** Tue Dec 09, 2008 10:24 pm

I also use struct, easier..and better idea then global vars.

dov · **Joined:** Fri Dec 19, 2008 8:23 am **Posts:** 4

A cleaner approach than using a struct is to subclass your toplevel and add all other widgets that you may need to access as class members. Though you can do it in plain C, I prefer using gob2 (a c-preprocessor) for this, in which you can simply do the following:

Code:

class My:Applic from Gtk:Window
{
    private GtkWidget *w_menubox = NULL;
    private GtkWidget *w_text_view = NULL;
    private GtkWidget *w_image_dir = NULL;
    private GtkWidget *w_output_dir = NULL;
    :

    public GtkWidget *
    new (int argc, char *argv[])
    {
        MyApplic *self = PA_WIDGET(GET_NEW); 

        selfp->w_menubox = new_...();
        :
        return GTK_WIDGET(self);
    }
}

All you then need to do is to pass the self pointer around as userdata and you can access all your widgets from the whole application.

Another uglier approach is to use the g_object_set_data() to assign the other widgets to the data hash table that is part of all g_objects.

bruce89 · **Posted:** Sat Dec 20, 2008 12:08 am

dov wrote:

A cleaner approach than using a struct is to subclass your toplevel and add all other widgets that you may need to access as class members. Though you can do it in plain C, I prefer using gob2 (a c-preprocessor) for this, in which you can simply do the following:

The GObject Builder (GOB) project is esentially dead now, but Vala isn't:

Code:

using Gtk;

class My.Application : Window
{
   private Widget menubox;
   private Widget text_view;
   private Widget w_image_dir;
   private Widget w_output_dir;

   construct
   {
      menubox = new HBox ();
      [etc.]
   }

   static void main (string[] args)
   {
      Gtk.init (ref args);

      var app = new Application ();
      app.show_all ();

      Gtk.main ();
   }
}

dov · **Joined:** Fri Dec 19, 2008 8:23 am **Posts:** 4

Whether you prefer gob or vala depend on how close you want to be to C. gob has the advantage that you are still using C or C++ for your programming, whereas in Vala you have to create wrappers for all external libraries. After all, Vala is a different language, wheras gob is a preprocessor. So I don't consider gob dead, but your milage may vary.

bruce89 · **Posted:** Sun Dec 21, 2008 11:54 pm

dov wrote:

Whether you prefer gob or vala depend on how close you want to be to C. gob has the advantage that you are still using C or C++ for your programming, whereas in Vala you have to create wrappers for all external libraries. After all, Vala is a different language, wheras gob is a preprocessor. So I don't consider gob dead, but your milage may vary.

That is not the case, valac is a meta-compiler which turns Vala code into C. This is obviously very useful for the reasons you mentioned.

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[C] How to pass multiple widgets?

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