Return values in Wayland XML specification

Pekka Paalanen ppaalanen at
Wed Apr 26 07:23:59 UTC 2017

On Tue, 25 Apr 2017 23:01:25 +0100
adlo <adloconwy at> wrote:

> How are return values specified in the Wayland XML specification?


there are no return values in Wayland. The concept does not exist by
design, because it would imply synchronous requests. There are no
implicitly synchronous requests, everything is asynchronous (and

If you need a client to receive something as a reply to a request, you
need to specify an event for delivering it. There are no shortcuts for
that, because each roundtrip makes everything a tiny bit slower, and
that accumulates. Therefore one should reconsider if a roundtrip is
really necessary, or if things could be designed to be asynchronous

Not having implicitly synchronous request sending functions also allows
programs to coalesce multiple request-reply pairs into a single

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