Merge branch 'vrr' into 'main'

RFC: Add zwp_vrr_v1

See merge request wayland/wayland-protocols!44

unstable/vrr/README

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+Variable refresh rate protocol
+
+Maintainers:
+Alexandros Frantzis <alexandros.frantzis@collabora.com>

unstable/vrr/vrr-unstable-v1.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<protocol name="zwp_vrr_unstable_v1">
+
+  <copyright>
+    Copyright 2020 Collabora, Ltd
+
+    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="zwp_vrr_v1" version="1">
+    <description summary="protocol for variable refresh rate">
+      This global is a factory interface, allowing clients to request
+      variable refresh rate (VRR) support on a per-surface basis.
+
+      Variable refresh rate mechanisms allow outputs to vary their frame
+      timings in order to optimally accommodate frame submissions that
+      occur at irregular rates, or rates that don't match the configured
+      rate of the these outputs.
+
+      Warning! The protocol described in this file is experimental and
+      backward incompatible changes may be made. Backward compatible changes
+      may be added together with the corresponding interface version bump.
+      Backward incompatible changes are done by bumping the version number in
+      the protocol and interface names and resetting the interface version.
+      Once the protocol is to be declared stable, the 'z' prefix and the
+      version number in the protocol and interface names are removed and the
+      interface version number is reset.
+    </description>
+
+    <request name="destroy" type="destructor">
+      <description summary="destroy explicit synchronization factory object">
+        Destroy this VRR factory object. Other objects, including
+        zwp_surface_vrr_v1 objects created by this factory, shall not
+        be affected by this request.
+      </description>
+    </request>
+
+    <enum name="error">
+      <entry name="vrr_exists" value="0"
+             summary="the surface already has a VRR object associated"/>
+    </enum>
+
+    <request name="get_vrr">
+      <description summary="extend surface interface for VRR">
+        Instantiate an interface extension for the given wl_surface to
+        provide VRR support.
+
+        If the given wl_surface already has a VRR object associated, the
+        vrr_exists protocol error is raised.
+      </description>
+
+      <arg name="id" type="new_id"
+           interface="zwp_surface_vrr_v1"
+           summary="the new surface VRR interface id"/>
+      <arg name="surface" type="object" interface="wl_surface"
+           summary="the surface"/>
+    </request>
+  </interface>
+
+  <interface name="zwp_surface_vrr_v1" version="1">
+    <description summary="per-surface VRR support">
+      The existence of this object is a hint to the compositor to employ
+      a variable refresh rate mechanism to optimize frame presentations
+      for the associated surface, when possible. This is typically useful
+      when frame submissions on the associated surface may be irregular,
+      or regular at a rate different from the configured refresh rate of
+      the output they are presented on.
+
+      The compositor is free to dynamically respect or ignore this hint
+      during the lifetime of this object based on various conditions,
+      including display capabilities and surface window state.
+
+      The existence of this object additionally implies that the client
+      is able to handle irregular frame timings that may result from
+      the employment of a variable refresh rate mechanism.
+    </description>
+
+    <request name="destroy" type="destructor">
+      <description summary="destroy synchronization object">
+        Destroy this surface VRR object and remove all hints and
+        implications that are described in the interface description.
+      </description>
+    </request>
+  </interface>
+
+</protocol>