title: Get the selected text from GTK3 ComboBox in C
body: <p>I'm only starting to learn GTK3, but I'm having a real struggle. All of the documentation that i could find is for GTK2 and the gnome dev web site is simply not good enough. 
  Now I am trying to get the selected text/item from a GtkComboBox, here is some of the code which I have tried.</p>
  
  <pre><code>  gint array =gtk_combo_box_get_active(cbox_quaity);
    //or 
    gchar *array =gtk_combo_box_get_active(cbox_quaity);
  </code></pre>
  
  <p>If i use the gint, the printout will be "0" (zero) no matter what itom of the list I select. If I use gchar, I get back "(null)". In addition, I get these warnings while compiling.</p>
  
  <pre><code>gcc -c -g -O0 -Wall -pthread -pipe src/main.c `pkg-config --cflags --libs gtk+-3.0` -o main.o
  src/main.c: In function ‘btn_start_click’:
  src/main.c:41:17: warning: initialization makes pointer from integer without a cast [-Wint-conversion]
     gchar *array =gtk_combo_box_get_active(cbox_quaity);
                   ^~~~~~~~~~~~~~~~~~~~~~~~
  gcc -o tstreamer-gtk main.o -pthread `pkg-config --cflags --libs gtk+-3.0` -export-dynamic
  </code></pre>
  
  <p>The user interface was created in glade and the combo box used a GtkListStore. Also, here is the source code of the C code:</p>
  
  <pre><code>#include &lt;gtk/gtk.h&gt;
  #include &lt;stdio.h&gt;
  
  GtkWidget *btn_start;
  GtkComboBox *cbox_quaity;
  #define MAX_WORD_SIZE 32
  
  void btn_start_click(){
  
    gint active_item = gtk_combo_box_get_active(cbox_quaity);
    printf("%d\n",active_item);
  }
  
  int main(int argc, char *argv[]){
  
    GtkBuilder *builder;
    GtkWidget *window;
  
    gtk_init(&amp;argc, &amp;argv);
  
    builder = gtk_builder_new();
    gtk_builder_add_from_file (builder, "glade/window_main.glade", NULL);
  
    window = GTK_WIDGET(gtk_builder_get_object(builder, "window_main"));
    gtk_builder_connect_signals(builder, NULL);
  
    btn_start = GTK_WIDGET(gtk_builder_get_object(builder, "btn_start"));
  
    g_object_unref(builder);
    gtk_widget_show(window);
    gtk_main();
    return 0;
  }
  
  // called when window is closed
  void on_window_main_destroy(){
    gtk_main_quit();
  }
  </code></pre>