MainWindow.glade (Código)

<?xml version="1.0" encoding="UTF-8"?>
<!-- Generated with glade 3.38.2 -->
<interface>
    <requires lib="gtk+" version="3.24"/>
    <object class="GtkMenu" id="menu">
        <property name="visible">True</property>
        <property name="can_focus">False</property>
        <property name="rect_anchor_dx">-30</property>
        <child>
            <object class="GtkMenuItem" id="item1">
                <property name="visible">True</property>
                <property name="can_focus">False</property>
                <property name="label" translatable="yes">Item 1</property>
                <property name="use_underline">True</property>
                <signal name="activate" handler="menu_item_clicked" swapped="no"/>
            </object>
        </child>
        <child>
            <object class="GtkMenuItem" id="item2">
                <property name="visible">True</property>
                <property name="can_focus">False</property>
                <property name="label" translatable="yes">Item 2</property>
                <property name="use_underline">True</property>
                <signal name="activate" handler="menu_item_clicked" swapped="no"/>
            </object>
        </child>
        <child>
            <object class="GtkSeparatorMenuItem" id="separator">
                <property name="visible">True</property>
                <property name="can_focus">False</property>
            </object>
        </child>
        <child>
            <object class="GtkMenuItem" id="Item3">
                <property name="visible">True</property>
                <property name="can_focus">False</property>
                <property name="label" translatable="yes">Sobre</property>
                <property name="use_underline">True</property>
                <signal name="activate" handler="about" swapped="no"/>
            </object>
        </child>
    </object>
    <object class="GtkApplicationWindow" id="MainWindow">
        <property name="can_focus">False</property>
        <property name="default_width">683</property>
        <property name="default_height">384</property>
        <property name="icon">../../../assets/icons/icon.png</property>
        <child>
            <placeholder/>
        </child>
        <child type="titlebar">
            <object class="GtkHeaderBar">
                <property name="visible">True</property>
                <property name="can_focus">False</property>
                <property name="title" translatable="yes">Gtk.Menu</property>
                <property name="subtitle" translatable="yes">Gtk.Menu</property>
                <property name="show_close_button">True</property>
                <child>
                    <object class="GtkMenuButton">
                        <property name="visible">True</property>
                        <property name="can_focus">True</property>
                        <property name="receives_default">True</property>
                        <property name="popup">menu</property>
                        <child>
                            <object class="GtkImage">
                                <property name="visible">True</property>
                                <property name="can_focus">False</property>
                                <property name="icon_name">open-menu-symbolic</property>
                            </object>
                        </child>
                    </object>
                    <packing>
                        <property name="pack_type">end</property>
                    </packing>
                </child>
            </object>
        </child>
    </object>
</interface>