Gtk Searchbar with long text field and combo box

SearchBar.py

# -*- coding: utf-8 -*-

from gi.repository import Gtk, Gdk

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

    #Combo Ids from ui file
    COMBO_ALL = 0
    COMBO_TITLE = 1 
    COMBO_AUTHOR = 2

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

        builder = Gtk.Builder()
        builder.add_from_file("searchBar.ui")
        self._searchContainer = builder.get_object("searchBar")
        self.search_entry = builder.get_object("searchEntry")
        self.searchCombo = builder.get_object("searchCombo")
        self.add(self._searchContainer)

        self.show = False
        self.set_window(window, search_button)

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

    def open_search(self, widget):
        self.show_bar(widget.get_active())

    def show_bar(self, show):
        self.show = show
        if not self.show:
            self.search_entry.set_text('')
        if show:
            self.search_entry.grab_focus()
        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

searchbar.ui

<?xml version="1.0" encoding="UTF-8"?>
<interface>
<requires lib="gtk+" version="3.12"/>
    <object class="GtkToolbar" id="searchBar">
    <property name="visible">True</property>
    <property name="can_focus">False</property>
    <style>
      <class name="search-bar"/>
    </style>
    <child>
      <object class="GtkToolItem" id="tool_item">
        <property name="visible">True</property>
        <property name="can_focus">False</property>
        <child>
          <object class="GtkBox" id="tool_box">
            <property name="visible">True</property>
            <property name="can_focus">False</property>
            <property name="orientation">horizontal</property>
            <property name="halign">fill</property>
            <property name="hexpand">True</property>
            <child>
              <object class="GtkSearchEntry" id="searchEntry">
                <property name="visible">True</property>
                <property name="can_focus">True</property>
                <property name="hexpand">True</property>
                <property name="caps_lock_warning">False</property>
                <property name="margin_right">6</property>
              </object>
              <packing>
                <property name="expand">True</property>
                <property name="fill">True</property>
                <property name="position">0</property>
              </packing>
            </child>
            <child>
              <object class="GtkComboBoxText" id="searchCombo">
                <property name="visible">True</property>
                <property name="can_focus">False</property>
                <property name="active">0</property>
                <items>
                  <item id="comboAll" translatable="yes">All</item>
                  <item id="comboTitle" translatable="yes">Title</item>
                  <item id="comboAuthor" translatable="yes">Author</item>
                </items>
              </object>
              <packing>
                <property name="expand">False</property>
                <property name="fill">True</property>
                <property name="position">1</property>
              </packing>
            </child>
          </object>
        </child>
        </object>
        <packing>
            <property name="expand">True</property>
        </packing>
    </child>
    </object>
</interface>