Enabling drag destination

[Chris Vine <chris cvine freeserve co uk>]

I am making a desktop utility which will accept a text/plain drop from
another application, and then do something with it (actually all it
does is check if the dropped text appears to be a valid URL, and if so
executes wget on it).  The utility is thus relatively trivial, so I
thought it would be suitable for GTK+3's introspection bindings.

The following works fine when written in C/C++, where 'drop_box' is a
GtkEventBox:

  static GtkTargetEntry target_array[] = {
    {(char*)"STRING", 0, 0},
    {(char*)"text/plain", 0, 0}
  };
  static guint target_size = G_N_ELEMENTS(target_array);
  gtk_drag_dest_set(drop_box, GTK_DEST_DEFAULT_ALL,
                    target_array, target_size,
                    GDK_ACTION_COPY);
  g_signal_connect(drop_box, "drag_data_received",
                   G_CALLBACK(drag_data_received), this);

However, I cannot get an equivalent to this to go with gjs-1.30.0 and
gobject-introspection-1.30.0.  A naive attempt to create a
Gtk.TargetEntry object with:

  var target1 = new Gtk.TargetEntry({target: "text/plain",
                                     flags: 0,
                                     info: 0});
fails with:

  "Unable to construct boxed type TargetEntry since it has no zero-args
  <constructor>, can only wrap an existing one"

I see that Gtk.TargetEntry has a static 'new' method representing
gtk_target_entry_new(), and although calling it appears to produce
something, as follows:

  var target1 = Gtk.TargetEntry.new("text/plain", 0, 0);

any attempt to use the returned value by putting it in an array and
passing it Gtk.Widget.drag_dest_set() or to Gtk.TargetList.new()
segfaults with no explanation.

What is the correct way to enable a destination drop using gjs?

Chris