Return values in Wayland XML specification

[Pekka Paalanen]

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

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

Hi,

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
ordered).

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
instead.

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


Thanks,
pq
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