module type Capabilities =
val name :
Name under which to register the backend.
val make :
options:string list -> float -> float -> t
create options width height must creates a new handle of
height (in units proper to the module) on which
the subsequent drawing functions operate.
options allows to
pass options to the backend (this is backend specific).
val close :
options:string list -> t -> unit
Close the handle. This function will be given the options
specified at backend creation so it can react appropriately if
some final work need to be done for some of them.