wayland-server: wl_callback.done events not flushning properly about wayland-rs HOT 2 CLOSED

wayland-rs uses its own scanner for code generation, and so directly plugs in the lower-level API of libwayland

Thanks that makes sense

You mentioned weston-subsurfaces, this program uses OpenGL to draw part of its content, and the GL drivers use their own internal event queue.

Good point, I think something related to this is going wrong. Turns out I can reproduce this with sway as well, so closing since it's not a wayland-rs issue

from wayland-rs.

[...] doesn't actually trigger a call to the system libwaylands wl_callback_send_done.

This is 100% intentional, this part of libwayland's API is not really the "real" API of the library, but rather scanner generated code that is bundled in libwayland. wayland-rs uses its own scanner for code generation, and so directly plugs in the lower-level API of libwayland.

Now, this whole thing seems like a potential red herring, if libwayland-server logs that it sends the events, then that means that it sends the event. I suspect this is likely a symptom of some other issue. If the client use multiple event queues, then it can be that it processes events out of order (and thus logs them out of order). delete_id events are special though, because while all other events are internally enqueued by libwayland-client, the delete_id events are processed (and logged) as soon as they are read from the socket. So it is not rare to see in the client log delete_id events being processed before events that were actually sent earlier by the server.

You mentioned weston-subsurfaces, this program uses OpenGL to draw part of its content, and the GL drivers use their own internal event queue. So my guess would be that the app freezes at some point inside the GL code (maybe waiting for another resource to be released?). A way to make sure of that would be to spin a debugger and see where exactly the app ends up blocked.

Or similarly, does the issue also occurs with non-GL apps?

from wayland-rs.