This needs us to expose a bit of implementation detail, but this seems
to be the cleanest way without an API change.
The specific problem is that pa_mainloop_api_once() needs to first
create a defer event and then set its destroy callback. If the defer
event is completed before the callback is set, an assert will be
trigerred.
void (*quit)(pa_mainloop_api*a, int retval);
};
-/** Run the specified callback function once from the main loop using an anonymous defer event. */
+/** Run the specified callback function once from the main loop using an anonymous defer event. Note that this performs
+ * multiple mainloop operations non-atomically. If, for example, you are using a \pa_threaded_mainloop, you will need to
+ * take the mainloop lock before this call. */
void pa_mainloop_api_once(pa_mainloop_api*m, void (*callback)(pa_mainloop_api*m, void *userdata), void *userdata);
PA_C_DECL_END