xdg-shell: ack_configure must be strictly monotonic

Clients must send ack_configure in a strictly monotonic order wrt
received configure events. It is an error to send an ack_configure
request for a configure event which was sent prior to the last
ack_configure for that surface, or to send multiple ack_configures for
the same configure event.

Weston and wlroots already use this interpretation, however Mutter and
KWayland are more lax and allow duplicates. This clarification tightens
the spec working to explicitly encode the Weston/wlroots behaviour.

Fixes: #21

Signed-off-by: Daniel Stone <daniels@collabora.com>
3 jobs for xdg-shell-monotonic-ack-configure in 1 minute and 31 seconds (queued for 8 seconds)
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Status Name Job ID Coverage
  Review
passed check-commit #15996903

00:00:10

 
  Containers Build
passed container_build #15996904

00:00:50

 
  Test
passed test-meson #15996905

00:00:29