GtkArrow and the align properties use different methods (float vs int)
to center the arrow. If the size of the arrow is odd, this will cause a
rendering that differs by half a pixel. So we request an even size for
both the arrow and the container and everything works out.
<interface>
<!-- interface-requires gtk+ 3.0 -->
<object class="GtkWindow" id="window1">
+ <property name="width_request">160</property>
<property name="can_focus">False</property>
<property name="type">popup</property>
<child>
</child>
<child>
<object class="GtkArrow" id="arrow3">
+ <property name="width_request">16</property>
<property name="visible">True</property>
<property name="can_focus">False</property>
<property name="hexpand">True</property>
<interface>
<!-- interface-requires gtk+ 3.0 -->
<object class="GtkWindow" id="window1">
+ <property name="width_request">160</property>
<property name="can_focus">False</property>
<property name="type">popup</property>
<child>
</child>
<child>
<object class="GtkArrow" id="arrow3">
+ <property name="width_request">16</property>
<property name="visible">True</property>
<property name="can_focus">False</property>
<property name="halign">center</property>