Created attachment 251650 [details]
screenshot of the issue

The screen size is not taken into account, while trying to identify the size of the label .  Not sure, if this is the ideal solution . 

from gtk/gtkpathbar.c

@@ -1519,7 +1523,7 @@ set_label_size_request (GtkWidget  *widg
 {
   const gchar *dir_name = get_dir_name (button_data);
   PangoLayout *layout = gtk_widget_create_pango_layout (button_data->label, dir_name);
-  gint width, height, bold_width, bold_height;
+  gint width, height, screen_width, bold_width, bold_height;
   gchar *markup;
   
   pango_layout_get_pixel_size (layout, &width, &height);
@@ -1530,8 +1534,10 @@ set_label_size_request (GtkWidget  *widg
 
   pango_layout_get_pixel_size (layout, &bold_width, &bold_height);
 
+  screen_width = gdk_screen_get_width (gtk_widget_get_screen (widget)) * 0.7;
+ 
   gtk_widget_set_size_request (widget,
-                              MAX (width, bold_width),
+                              MIN (MAX (width, bold_width),screen_width),
                               MAX (height, bold_height));
   g_object_unref (layout);
 }