from gi.repository import Gtk, cairo

class OwnContainer(Gtk.Container):
    def __init__(self):
        Gtk.Container.__init__(self)
        self.set_has_window(False)

        self.child_widget = None

    # own method to set child ...
    def set_child(self, child):
        if self.child_widget is not None:
            return

        self.child_widget = child
        self.child_widget.set_parent(self)

    # ... and default one
    def do_add(self, child):
        self.set_child(child)

    def do_remove(self, child):
        child.unparent()
        self.child_widget = None

    def do_get_request_mode(self):
        return Gtk.SizeRequestMode.WIDTH_FOR_HEIGHT

    # all 'preferred' methods are actually stubs and return fixed values
    # container should calculate that values according to its content
    def do_get_preferred_width(self):
        return (200, 200)

    def do_get_preferred_height(self):
        return (260,260)

    def do_get_preferred_width_for_height(self, height):
        return (200, 200)

    def do_get_preferred_height_for_width(self, width):
        return (260, 260)

    # propagate action to childs
    # Some bug occur here on window destroy, see http://stackoverflow.com/questions/21214732/custom-gtk-container-with-pygobject
    def do_forall(self , include_internals , callback):
        if self.child_widget is not None:
            callback(self.child_widget)

    # that method decides where to put child
    # implement it as you wish
    def do_size_allocate(self, allocation):
        self.set_allocation(allocation)

        if self.child_widget is not None:
            if self.child_widget.get_visible():
                print('showed')
                button_alloc = cairo.RectangleInt()

                button_alloc.x = allocation.x + 60
                button_alloc.y = allocation.y + 60

                button_alloc.width = 100
                button_alloc.height = 140

                self.child_widget.size_allocate(button_alloc)



def main():
    win = Gtk.Window()
    win.connect('destroy', Gtk.main_quit)

    container = OwnContainer()

    button = Gtk.Button('Hello')
    container.set_child(button)

    win.add(container)

    win.show_all()

    Gtk.main()

main()