jextract wayland-client

[Jorn Vernee]

Hello Thiago,

It looks like the library you are using uses opaque types. Or, in other 
words, a type that is declared but not defined, such as:

struct Foo;

These types are not supported by jextract in the sense that the header 
file does not contain any definition for these types, so jextract also 
can't generate any code to access the fields of such a struct. This is 
not a current limitation of jextract, but a limitation imposed by the 
wayland library.

This is known as the 'opaque pointer idiom' [1]. It is a way of 
encapsulating the internals of a type, while still allowing a client to 
use it. It looks like the wayland library uses types like these in a lot 
of places. It doesn't mean that the library is unusable, it just means 
that the contents of these structs is not exposed by the library (and 
therefore /cannot/ be exposed by jextract). i.e. this is by design. You 
should still be able to use the library through the generated bindings.

I think for clarity we could perhaps change the warning message that 
jextract prints to something like:

     WARNING: Skipping wl_registry (type Declared(wl_registry) is 
declared but not defined)

HTH,
Jorn

[1]: https://en.wikipedia.org/wiki/Opaque_pointer

On 21/04/2024 18:58, Thiago Milczarek Sayão wrote:
> Hi,
>
> I'm trying to make a java wayland client (currently as a proof of 
> concept).
>
> I've attempted to generate the bindings like this:
>
> jextract --output src -t org.freedesktop.wayland.client 
> --header-class-name WlClient -lwayland-client 
>  /usr/include/wayland-client.h
>
> But the wl_xxx types seem to not be supported as it outputs:
>
> WARNING: Skipping wl_registry (type Declared(wl_registry) is not 
> supported)
>
> I've probably hit a current limitation. Is it expected to work in the 
> future?
>
> Thanks.
> -- Thiago.
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