gamescope-tearing-control-unstable-v1.xml

<?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>