commit-timing-v1: Add new protocol

Add a new protocol for adding timestamps to wayland surface state to
allow deferring processing until later.

Signed-off-by: Derek Foreman <derek.foreman@collabora.com>

meson.build

@@ -41,6 +41,7 @@ unstable_protocols = {
 }
 
 staging_protocols = {
+	'commit-timing': ['v1'],
 	'content-type': ['v1'],
 	'cursor-shape': ['v1'],
 	'drm-lease': ['v1'],

staging/commit-timing/README

+Commit Timing Protocol
+
+Maintainers:
+Derek Foreman <derek.foreman@collabora.com> (@derekf)

staging/commit-timing/commit-timing-v1.xml

+<?xml version="1.0" encoding="UTF-8"?>
+<protocol name="commit_timing_v1">
+
+  <copyright>
+    Copyright © 2023 Valve Corporation
+
+    Permission is hereby granted, free of charge, to any person obtaining a
+    copy of this software and associated documentation files (the "Software"),
+    to deal in the Software without restriction, including without limitation
+    the rights to use, copy, modify, merge, publish, distribute, sublicense,
+    and/or sell copies of the Software, and to permit persons to whom the
+    Software is furnished to do so, subject to the following conditions:
+
+    The above copyright notice and this permission notice (including the next
+    paragraph) shall be included in all copies or substantial portions of the
+    Software.
+
+    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+    THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+    FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+    DEALINGS IN THE SOFTWARE.
+  </copyright>
+
+  <interface name="wp_commit_timing_manager_v1" version="1">
+    <description summary="commit timing">
+      When a compositor latches on to new content updates it will check for
+      any number of requirements of the available content updates (such as
+      fences of all buffers being signalled) to consider the update ready.
+
+      This protocol provides a method for adding a time constraint to surface
+      content. This constraint indicates to the compositor that a content
+      update should be presented as closely as possible to, but not before,
+      a specified time.
+
+      This protocol does not change the Wayland property that content
+      updates are applied in the order they are received, even when some
+      content updates contain timestamps and others do not.
+
+      To provide timestamps, this global factory interface must be used to
+      acquire a wp_commit_timing_v1 object for a surface, which may then be
+      used to provide timestamp information for commits.
+
+      Warning! The protocol described in this file is currently in the testing
+      phase. Backward compatible changes may be added together with the
+      corresponding interface version bump. Backward incompatible changes can
+      only be done by creating a new major version of the extension.
+    </description>
+    <enum name="error">
+      <entry name="commit_timer_exists" value="0"
+             summary="commit timer already exists for surface"/>
+    </enum>
+
+    <request name="destroy" type="destructor">
+      <description summary="unbind from the commit timing interface">
+        Informs the server that the client will no longer be using
+        this protocol object. Existing objects created by this object
+        are not affected.
+      </description>
+    </request>
+
+    <request name="get_timer">
+      <description summary="request commit timer interface for surface">
+        Establish a timing controller for a surface.
+
+        Only one commit timer can be created for a surface, or a
+        commit_timer_exists protocol error will be generated.
+      </description>
+      <arg name="id" type="new_id" interface="wp_commit_timer_v1"/>
+      <arg name="surface" type="object" interface="wl_surface"/>
+    </request>
+  </interface>
+
+  <interface name="wp_commit_timer_v1" version="1">
+    <description summary="Surface commit timer">
+      An object to set a time constraint for a content update on a surface.
+    </description>
+
+    <enum name="error">
+      <entry name="invalid_timestamp" value="0"
+             summary="timestamp contains an invalid value"/>
+      <entry name="timestamp_exists" value="1"
+             summary="timestamp exists"/>
+      <entry name="surface_destroyed" value="2"
+             summary="the associated surface no longer exists"/>
+    </enum>
+
+    <request name="set_timestamp">
+      <description summary="Specify time the following commit takes effect">
+        Provide a timing constraint for a surface content update.
+
+        A set_timestamp request may be made before a wl_surface.commit to
+        tell the compositor that the content is intended to be presented
+        as closely as possible to, but not before, the specified time.
+        The time is in the domain of the compositor's presentation clock.
+
+        An invalid_timestamp error will be generated for invalid tv_nsec.
+
+        If a timestamp already exists on the surface, a timestamp_exists
+        error is generated.
+
+        Requesting set_timestamp after the commit_timer object's surface is
+        destroyed will generate a "surface_destroyed" error.
+      </description>
+      <arg name="tv_sec_hi" type="uint"
+           summary="high 32 bits of the seconds part of target time"/>
+      <arg name="tv_sec_lo" type="uint"
+           summary="low 32 bits of the seconds part of target time"/>
+      <arg name="tv_nsec" type="uint"
+           summary="nanoseconds part of target time"/>
+    </request>
+
+    <request name="destroy" type="destructor">
+      <description summary="Destroy the timer">
+        Informs the server that the client will no longer be using
+        this protocol object.
+
+        Existing timing constraints are not affected by the destruction.
+      </description>
+    </request>
+  </interface>
+</protocol>