GTK scroll to newly added child in a container

I have an application that will add a Widget to an HBox, which is contained i开发者_Go百科n a ScrolledWindow. When a Widget is added, I would like the parent ScrolledWindow to scroll to the right, where the newly added Widget is. Adding the widget works just fine, my problem is:

How can I make the ScrolledWindow move when a child is added?

My Vala code looks something like:

private void addView() {
    var widget = this.createWidget();

    this.box.pack_start(widget);                   // this.box is a HBox
    widget.show_all();

    var adj = this.parent_win.get_hadjustment();   //  parent_win is a ScrolledWindow
    adj.set_value(adj.get_upper());
}

The behavior I am getting now is the adjustment will work every other double click (what signals all this). I would like for the adjustment to occur on every double click.

update I have seen this: Gtk, How to scroll at bottom of viewport list? , but there is no real definitive answer given. you mean to tell me i have to set a 1 sec timeout to scroll ?

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Use an idle callback instead of a timeout, and use the GtkContainer::add signal to get notified when a new child is added (http://developer.gnome.org/gtk/unstable/GtkContainer.html#GtkContainer-add).