<div dir="ltr"><div class="gmail_default" style="font-size:small">I found a solution, but my offer to send a pull request adding wl_object_get_class() and wl_object_get_id() still stands. Let me know! To recap, my key question was: "The wl_protocol_logger API exposes a wl_object struct. How can I get the object class and ID from a wl_object?" To answer my own question: wl_object is actually declared here, behind an #ifndef: <a href="https://gitlab.freedesktop.org/wayland/wayland/-/blob/69633202180acce9d0d5ab4037d80291c71b2307/src/wayland-server.h#L58">https://gitlab.freedesktop.org/wayland/wayland/-/blob/69633202180acce9d0d5ab4037d80291c71b2307/src/wayland-server.h#L58</a> The declaration is deprecated, though. I'm using it anyway for now, but I think accessor functions would be better so that I can treat wl_object as opaque. I'm happy to contribute if desired. Best regards, Chloe</div></div> <div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Tue, Apr 16, 2024 at 10:56 AM Chloe Pelling <<a href="mailto:cpelling@google.com">cpelling@google.com</a>> wrote: </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Hi, I'm attempting to use the wl_protocol_logger API to replicate the functionality of WAYLAND_DEBUG=1 in my project, but logging to <a href="https://perfetto.dev/" rel="noreferrer" target="_blank">https://perfetto.dev/</a> rather than stderr. I'm having some trouble decoding message arguments of type object, since `wl_object` is an opaque struct and there doesn't appear to be a "blessed" way to interrogate it. In particular, there's no API to access `wl_object::id`. Am I missing something? Would a patch adding wl_object_get_id() and wl_object_get_class() functions be welcome? Here's what I've figured out so far: * Decoding the arguments requires inspecting the wl_argument unions in `wl_protocol_logger_message::arguments`, according to the type indications in `wl_protocol_logger_message::message->signature`. * Object arguments are denoted by "o" in the signature, indicating we should examine `wl_argument::o` of type wl_object. * wl_object is an opaque struct, and there are no wl_object_get_class() or wl_object_get_id() functions. * I can work around the lack of wl_object_get_class() by inspecting wl_protocol_logger_message::message->types[i] for argument wl_protocol_logger_message::arguments[i]. However, no such workaround exists to retrieve the wl_object's id. * <a href="https://github.com/KDAB/GammaRay" rel="noreferrer" target="_blank">https://github.com/KDAB/GammaRay</a> works around this problem by casting wl_argument::o to wl_resource* and using wl_resource_get_class() and wl_resource_get_id(). * This works because wl_resource's first member is wl_object, and wl_resource_get_class() and wl_resource_get_id() are implemented only by accessing that first member. * While comments in wl_resource indicate that the struct layout cannot be changed. It's unclear if that will be true forever. * There is no guarantee that wl_resource_get_class() and wl_resource_get_id() won't start accessing members of wl_resource other than `object`. If they did, this technique could cause invalid memory access due to overflowing the size of wl_object. I believe these are my current options: A) Cast wl_object* to wl_resource* like GammaRay does. I'm uncomfortable with this, for the reasons above. B) Copy the definition of `struct wl_object` from wayland-private.h into my project and access `id` directly. This might be safer than (A) in practice, but I still don't like it. C) Submit a patch adding wl_object_get_class() and wl_object_get_id() accessor functions. Have I missed something? Any advice would be helpful. Best regards, Chloe </blockquote></div>