client API: be more explicit about what can be done in wakeup callbacks

Don't leave any room for interpretation.

1 files changed, 13 insertions, 5 deletions

diff --git a/libmpv/client.h b/libmpv/client.h
index bc2fff0563..f3e4d4c8c8 100644
--- a/libmpv/client.h
+++ b/libmpv/client.h
@@ -1588,11 +1588,19 @@ void mpv_wakeup(mpv_handle *ctx);
  *
  * Keep in mind that the callback will be called from foreign threads. You
  * must not make any assumptions of the environment, and you must return as
- * soon as possible. You are not allowed to call any client API functions
- * inside of the callback. In particular, you should not do any processing in
- * the callback, but wake up another thread that does all the work. It's also
- * possible that the callback is called from a thread while a mpv API function
- * is called (i.e. it can be reentrant).
+ * soon as possible (i.e. no long blocking waits). Exiting the callback through
+ * any other means than a normal return is forbidden (no throwing exceptions,
+ * no longjmp() calls). You must not change any local thread state (such as
+ * the C floating point environment).
+ *
+ * You are not allowed to call any client API functions inside of the callback.
+ * In particular, you should not do any processing in the callback, but wake up
+ * another thread that does all the work. The callback is meant strictly for
+ * notification only, and is called from arbitrary core parts of the player,
+ * that make no considerations for reentrant API use or allowing the callee to
+ * spend a lot of time doing other things. Keep in mind that it's also possible
+ * that the callback is called from a thread while a mpv API function is called
+ * (i.e. it can be reentrant).
  *
  * In general, the client API expects you to call mpv_wait_event() to receive
  * notifications, and the wakeup callback is merely a helper utility to make