Это может быть не совсем то, что вы просили, но это был бы один из способов сделать это.
Сохраните это в файле и откройте его на поляне, чтобы просмотреть конструкцию GUI.
<?xml version="1.0" encoding="UTF-8"?>
<!-- Generated with glade 3.22.1 -->
<interface>
<requires lib="gtk+" version="3.20"/>
<object class="GtkPopover" id="popover1">
<property name="can_focus">False</property>
<child>
<object class="GtkBox">
<property name="visible">True</property>
<property name="can_focus">False</property>
<property name="orientation">vertical</property>
<child>
<object class="GtkBox">
<property name="visible">True</property>
<property name="can_focus">False</property>
<child>
<object class="GtkButton">
<property name="label" translatable="yes">Zoom</property>
<property name="visible">True</property>
<property name="can_focus">True</property>
<property name="receives_default">True</property>
</object>
<packing>
<property name="expand">False</property>
<property name="fill">True</property>
<property name="position">0</property>
</packing>
</child>
<child>
<object class="GtkSpinButton">
<property name="visible">True</property>
<property name="can_focus">True</property>
</object>
<packing>
<property name="expand">False</property>
<property name="fill">True</property>
<property name="position">1</property>
</packing>
</child>
<child>
<placeholder/>
</child>
</object>
<packing>
<property name="expand">False</property>
<property name="fill">True</property>
<property name="position">0</property>
</packing>
</child>
<child>
<object class="GtkLabel">
<property name="visible">True</property>
<property name="can_focus">False</property>
<property name="label" translatable="yes">Print</property>
</object>
<packing>
<property name="expand">False</property>
<property name="fill">True</property>
<property name="position">1</property>
</packing>
</child>
<child>
<object class="GtkLabel">
<property name="visible">True</property>
<property name="can_focus">False</property>
<property name="label" translatable="yes">More</property>
</object>
<packing>
<property name="expand">False</property>
<property name="fill">True</property>
<property name="position">2</property>
</packing>
</child>
<child>
<object class="GtkBox">
<property name="visible">True</property>
<property name="can_focus">False</property>
<property name="homogeneous">True</property>
<child>
<object class="GtkButton">
<property name="label" translatable="yes">Cut</property>
<property name="visible">True</property>
<property name="can_focus">True</property>
<property name="receives_default">True</property>
</object>
<packing>
<property name="expand">False</property>
<property name="fill">True</property>
<property name="position">0</property>
</packing>
</child>
<child>
<object class="GtkButton">
<property name="label" translatable="yes">Copy</property>
<property name="visible">True</property>
<property name="can_focus">True</property>
<property name="receives_default">True</property>
</object>
<packing>
<property name="expand">False</property>
<property name="fill">True</property>
<property name="position">1</property>
</packing>
</child>
<child>
<object class="GtkButton">
<property name="label" translatable="yes">Paste</property>
<property name="visible">True</property>
<property name="can_focus">True</property>
<property name="receives_default">True</property>
</object>
<packing>
<property name="expand">False</property>
<property name="fill">True</property>
<property name="position">2</property>
</packing>
</child>
</object>
<packing>
<property name="expand">False</property>
<property name="fill">True</property>
<property name="position">3</property>
</packing>
</child>
</object>
</child>
</object>
<object class="GtkWindow">
<property name="can_focus">False</property>
<child>
<placeholder/>
</child>
<child>
<object class="GtkBox">
<property name="visible">True</property>
<property name="can_focus">False</property>
<property name="orientation">vertical</property>
<child>
<object class="GtkMenuButton">
<property name="visible">True</property>
<property name="can_focus">True</property>
<property name="receives_default">True</property>
<property name="popover">popover1</property>
<child>
<placeholder/>
</child>
</object>
<packing>
<property name="expand">False</property>
<property name="fill">True</property>
<property name="position">0</property>
</packing>
</child>
<child>
<placeholder/>
</child>
<child>
<placeholder/>
</child>
</object>
</child>
</object>
</interface>