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 https://perfetto.dev/ 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. * https://github.com/KDAB/GammaRay 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
