-The callback is expected to return 1 if it consumed the message properly.
-This semantic may be troublesome since it really differs from the one used
-in the main() function, but this allows to build callback stacks. It is
-perfectly valid to register several callbacks to a given message. When a
-message arrives, it is passed to the firstly-registered callback. If the
-callback returns 1 (or any other "true" value), it means that it consumed
-the message, which is discarded. If the callback returns 0, the message is
-passed to the next callback of the stack, and so on. At the end, if no
-callback returned 1, an error message is generated.
+The callback is expected to return 0 if everything went well, which is the
+same semantic than the "main()" function. You can also build stacks of
+callbacks. It is perfectly valid to register several callbacks to a given
+message. When a message arrives, it is passed to the firstly-registered
+callback. If the callback returns 0, it means that it consumed the message,
+which is discarded. If the callback returns 1 (or any other "true" value),
+the message is passed to the next callback of the stack, and so on. At the
+end, if no callback returned 0, an exception is raised.