How do I specify constraints in Blueprint?
Is there an equivalent to
<object class="GtkConstraintLayout">
<constraints>
<constraint target="button" target-attribute="start"
relation="eq"
source="super" source-attribute="start"
constant="12"
strength="required" />
<constraint target="button" target-attribute="width"
relation="ge"
constant="250"
strength="strong" />
</constraints>
</object>
?