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GNU/Linux Desktop Survival Guide
by Graham Williams
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Finding Your Widget


If you use Glade to generate source code for your interface (rather than using ) you should make use of the lookup_widget() function that Glade defines for you (in support.c) to access your widgets. You pass this function a pointer to any widget in a window and the name of the widget that you want to get (where the name is a string and is the same as the Name in the Properties dialog for the widget). The function will return a pointer to the widget whose name matches the string you supply.

The lookup_widget() function relies on you giving a pointer to any other widget in the same tree (perhaps a pointer to the root of the widget hierarchy for that particular application window or dialog). Usually in a signal handler (the callbacks that you write in callbacks.c) you can use the first argument to the signal handler as the first parameter to lookup_widget(). For example you may have a button in you window called button1 and when it is clicked you may want to access some text entry field that has the name ``entry1.'' In callbacks.c you may have a callback:



void
on_button1_clicked                     (GtkButton       *button,
                                        gpointer         user_data)
{
  GtkWidget *entry1;

  entry1 = lookup_widget (GTK_WIDGET (button), "entry1");

  ... 
}

Internally Glade uses gtk_object_set_data() for storing pointers to all the widgets in a window using the names set in the property editor as the key. Then, inside lookup_widget(), gtk_object_get_data() is used to retrieve the pointer indexed by this key. These two functions are also available to the developer for their own purposes.


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