RFC008 - Enumerating attributes#
OfxMesh structure can contain arbitrary attributes and an effect can retrieve them by name (since RFC012).
However, an effect has no way of exploring attributes that it did not expect. This is however needed when effects is in theory able to forward any attribute it receives as input. A property
kOfxMeshPropAttributeCount exists but there is no way of getting an attribute by index rather than by name.