protocol: Add tearing control protocol

protocol/gamescope-tearing-control-unstable-v1.xml

@@ -0,0 +1,142 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<protocol name="gamescope_tearing_control_unstable_v1">
+
+  <copyright>
+    Copyright © 2021 Xaver Hugl
+
+    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="gamescope_tearing_control_v1" version="1">
+    <description summary="protocol for tearing control">
+      This global is a factory interface, allowing clients to request
+      the compositor to use asynchronous page flips on a per-surface basis.
+
+      Graphics APIs, like EGL or Vulkan, that manage the buffer queue and
+      commits of a wl_surface themselves, are likely to be using this
+      extension internally. If a client is using such an API for a
+      wl_surface, it should not directly use this extension on that surface,
+      to avoid raising a tearing_control_exists protocol error.
+
+      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 tearing control factory object">
+        Destroy this tearing control factory object. Other objects, including
+        gamescope_surface_tearing_control_v1 objects created by this factory,
+        shall not be affected by this request.
+      </description>
+    </request>
+
+    <enum name="error">
+      <entry name="tearing_control_exists" value="0"
+             summary="the surface already has a tearing object associated"/>
+    </enum>
+
+    <request name="get_tearing_control">
+      <description summary="extend surface interface for tearing control">
+        Instantiate an interface extension for the given wl_surface to
+        request asynchronous page flips for presentation.
+
+        If the given wl_surface already has a gamescope_surface_tearing_control_v1
+        object associated, the tearing_control_exists protocol error is raised.
+      </description>
+
+      <arg name="id" type="new_id"
+           interface="gamescope_surface_tearing_control_v1"
+           summary="the new surface tearing interface id"/>
+      <arg name="surface" type="object" interface="wl_surface"
+           summary="the surface"/>
+    </request>
+  </interface>
+
+  <interface name="gamescope_surface_tearing_control_v1" version="1">
+    <description summary="per-surface tearing control request">
+      An additional interface to a wl_surface object, which allows the client
+      to hint to the compositor if and when it should use asynchronous page
+      flips for presentation.
+    </description>
+
+    <enum name="presentation_hint">
+      <description summary="presentation hint values">
+        This enum provides information for if and when submitted frames from
+        the client may be presented with tearing. The possible values are:
+
+        VSYNC:
+        Presentation should be synchronized to the vertical retrace by the
+        display hardware so that tearing doesn't happen.
+
+        VSYNC_RELAXED:
+        Presentation should be synchronized to the vertical retrace by the
+        display hardware so that tearing doesn't happen as long as the client
+        submits new frame fast enough. If a frame is late for presentation,
+        that is, if more than one vertical retrace has occurred since the last
+        commit then the compositor should use asynchronous page flips to
+        immediately present the frame. This may cause visible tearing.
+        The compositor is encouraged to send requested frame callbacks as soon
+        as possible after such a late commit to make sure clients have as much
+        time as possible to render their next frame.
+
+        ASYNC:
+        Presentation should not be synchronized to the vertical retrace,
+        committed frames are meant to be immediately presented with asynchronous
+        page flips with as little delay as possible. Tearing will be visible.
+        The compositor is encouraged to send requested frame callbacks as soon
+        as possible after every commit.
+      </description>
+      <entry name="vsync" value="0"
+             summary="tearing-free presentation"/>
+      <entry name="vsync_relaxed" value="1"
+             summary="async pageflips on missed presentation deadline"/>
+      <entry name="async" value="2"
+             summary="async pageflips for all frames"/>
+    </enum>
+
+    <request name="set_presentation_hint">
+      <description summary="set presentation hint">
+        Set the presentation hint for the associated wl_surface. See
+        presentation_hint for the description. This state is double-buffered
+        and is applied on the next wl_surface.commit.
+
+        The compositor is free to dynamically respect or ignore this hint based
+        on various conditions, including GPU capabilities and surface window
+        state.
+      </description>
+      <arg name="hint" type="uint" enum="presentation_hint"/>
+    </request>
+
+    <request name="destroy" type="destructor">
+      <description summary="destroy synchronization object">
+        Destroy this surface tearing object and remove the presentation hint.
+        The change will be applied on the next wl_surface.commit.
+      </description>
+    </request>
+  </interface>
+
+</protocol>
+

protocol/meson.build

@@ -6,6 +6,7 @@ protocols = [
 	'gamescope-xwayland',
 	'gamescope-pipewire',
 	'gamescope-input-method',
+	'gamescope-tearing-control-unstable-v1',
 ]
 
 foreach name : protocols