(cffi:defcstruct size-t
  (width :float)
  (height :float))  

The graphene:size-t structure is a data structure capable of describing a size with two components width and height of type float.

Access the coordinates with the graphene:size-width and graphene:size-height functions. Use the graphene:with-size and graphene:with-sizes macros to allocate a new graphene:size-t instance and initialize the size with values.