GTK焦点链

Currently I'm working on a pyGTK3 application for which I want to set the focus chain. When using the code below (simplified version) something interesting happens GTK focuses correctly on the first button but on tab nothing happens.

At first I thought this was caused by GTK not knowing the chain, but then I tried shift+tab which resulted in the last element of the chain get the focus which is correct. Yet another shift+tab doesn't move the focus away from the last button.

所以我认为我的代码有问题，我需要手动更新链顺序吗？或者我错过了什么？

class Screen(Gtk.Grid):
  def __init__(self, parent, core, video_widget):
    Gtk.Grid.__init__(self)

    # adds the control buttons
    self.controls = load_controls(self)

    self.set_focus_chain((self.controls.play, self.controls.backward, self.controls.recording))

为了设置容器内元素的焦点链，需要首先将父级的焦点链设置到容器。从那里需要设置容器的焦点链。

因此代码需要如下：

# Points Gtk toward the container first
self.set_focus_chain([self.controls]) 

# Sets the focus chain inside the container
self.controls.set_focus_chain((self.controls.play, self.controls.backward, self.controls.recording, self.controls.end_inspection))

所以看来GTK只允许针对子代的焦点链，因此需要用户设置一条焦点链来将焦点链设置给孙子。