Function pointers now go through the same argument marshalling pipeline
as normal functions.
This will enable interfaces like Efl.Ui.Format to work properly.
In general, ptr(struct) parameters behavior depends whether the
parameter has the @owned modifier or not.
If there is no @owned parameter (meaning no transfer of ownership
happens) and it is a "complex" struct, with reference type fields
(like strings), the struct is converted to the respective
<Struct>Internal struct and passed with "ref" to the DllImport'd
function. For @in parameters, after the function it returns, this
intermediate struct is converted to the public struct type and
assigned to the original parameter, updating it to the external
world.
When we have ownership transfers, the structure is copied to unmanaged
memory and given to the callee. We can't send managed memory directly as
the callee may try to free it. On the managed side, the original struct
is left to be garbage collected normally.
Lauro Moura