A custom searchbar in Gtk and python

I wanted the following features from my searchbar:

1. It should be in place where the toolbar is in a window.
2. It should not be visible always only when the user wants to search something.
3. It should popup as soon as the user starts typing in the window
4. It should popup when user presses ctrl+F.
5. It should hide itself and the search should get invalidated when user presses escape.
6. It should be toggleable through a button.
7. It should associate to a window.

Now the searchbar that i wrote has a few requirements or a design paradigm if you must:

1. The window has to implement its own refilter() function which is called when a search term changes. This should call a refresh of the filter function on the all the views that the search applies to.
2. The window implements its own filter functions on its views.

Here is the code:

from gi.repository import Gtk, GLib, Gdk


class Searchbar(Gtk.Revealer):
    __gtype_name__ = 'Searchbar'

    def __init__(self, window=None, search_button=None):
        Gtk.Revealer.__init__(self)

        self._searchContainer = Gtk.Box(orientation=Gtk.Orientation.HORIZONTAL,
                                        halign=Gtk.Align.CENTER)

        self._search_entry = Gtk.SearchEntry(max_width_chars=45)
        self._search_entry.connect("search-changed", self.on_search_changed)
        self._search_entry.show()
        self._searchContainer.add(self._search_entry)

        self._searchContainer.show_all()
        toolbar = Gtk.Toolbar()
        toolbar.get_style_context().add_class("search-bar")
        toolbar.show()
        self.add(toolbar)

        item = Gtk.ToolItem()
        item.set_expand(True)
        item.show()
        toolbar.insert(item, 0)
        item.add(self._searchContainer)

        self.window = window
        self.search_button = search_button
        self.show = False

    def on_search_changed(self, widget):
        self.window.refilter(self._search_entry.get_text())

    def set_window(self, window, search_button):
        self.window = window
        self.search_button = search_button
        self.window.connect("key-press-event", self._on_key_press)
        self.window.connect_after("key-press-event", self._after_key_press)

    def show_bar(self, show):
        self.show = show
        if not self.show:
            self._search_entry.set_text('')
        self.set_reveal_child(show)

    def toggle_bar(self):
        self.show_bar(not self.get_child_revealed())

    def _on_key_press(self, widget, event):
        keyname = Gdk.keyval_name(event.keyval)

        if keyname == 'Escape' and self.search_button.get_active():
            if self._search_entry.is_focus():
                self.search_button.set_active(False)
            else:
                self._search_entry.grab_focus()
            return True

        if event.state & Gdk.ModifierType.CONTROL_MASK:
            if keyname == 'f':
                self.search_button.set_active(True)
                return True

        return False

    def _after_key_press(self, widget, event):
        if (not self.search_button.get_active() or
                not self._search_entry.is_focus()):
            if self._search_entry.im_context_filter_keypress(event):
                self.search_button.set_active(True)
                self._search_entry.grab_focus()

                # Text in entry is selected, deselect it
                l = self._search_entry.get_text_length()
                self._search_entry.select_region(l, l)

                return True

        return False

For more info go to https://github.com/coala-analyzer/coala and look for the branch wip/udayan/gui2