[Wayland-bugs] [Bug 91750] Wayland may have interface bug when multi-threads programing.

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=91750

--- Comment #7 from Yujie Shen <syjman at gmail.com> ---
(In reply to Jonas Ådahl from comment #6)
> Yujie: as indirectly stated by Pekka, my example was incomplete. You would
> also need to dispatch pending events before the
> wl_display_prepare_read(display) call. This makes it, ignoring error
> handling, more or less:
> 
> 	wl_surface_attach();
> 	while (wl_display_prepare_read_queue(display, queue) < 0)
> 		wl_display_dispatch_queue_pending(display, queue);
> 	window->callback = wl_surface_frame(window->surface);
> 	wl_proxy_set_queue(window->callback,queue2);
> 	wl_callback_add_listener(window->callback, &frame_listener, window);
> 	wl_display_cancel_read(display);
> 	wl_surface_commit(window->surface);
> 
> This has the side effect that events already in the queue will be always
> dispatched before the frame is requested. This may have unwanted effects, so
> please consider whether this is Ok in your architecture. If it is not, you
> need to make sure that the above code is done after all events on the queue
> has been dispatched.

Thanks for your kindly help.
By adding 
>while (wl_display_prepare_read_queue(display, queue2) < 0)
>		wl_display_dispatch_queue_pending(display, queue2);
>wl_surface_commit(window->surface);
it works in my case.
but, I still don't understand why it requires the wl_event_queue to be empty??
I'm trying to summary the restrictions of wayland when multi-thread
programming.
May I know if you have any idea about it.

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