wayland-protocols/unstable/vsync-feedback/vsync-feedback-unstable-v1.xml

<?xml version="1.0" encoding="UTF-8"?>
<protocol name="vsync_feedback_unstable_v1">

  <copyright>
    Copyright 2016 The Chromium Authors

    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>

  <description summary="Protocol for providing vertical synchronization timing">
    This protocol specifies a set of interfaces used to inform the client about
    vertical synchronization timing in a precise way and without unnecessary
    overhead.

    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 version number in the protocol is removed and
    the interface version number is reset.
  </description>

  <interface name="zcr_vsync_feedback_v1" version="1">
    <description summary="Protocol for providing vertical synchronization timing">
      The global interface that allows clients to subscribe for vertical
      synchronization timing data for given wl_output.
    </description>

    <request name="destroy" type="destructor">
      <description summary="destroy vsync feedback object">
        Destroy this vsync feedback object. Existing vsync timing objects shall
        not be affected by this request.
      </description>
    </request>

    <request name="get_vsync_timing">
      <description summary="get vsync timing object for given wl_output">
        Create a new vsync timing object that represents a subscription to
        vertical synchronization timing updates of given wl_output object.

        The newly created object will immediately signal an update to notify
        the subscriber of initial timing parameters.
      </description>
      <arg name="id" type="new_id" interface="zcr_vsync_timing_v1" summary="the new vsync timing interface id"/>
      <arg name="output" type="object" interface="wl_output" summary="the wl_output object to subscribe for timings of" allow-null="true"/>
    </request>
  </interface>

  <interface name="zcr_vsync_timing_v1" version="1">
    <request name="destroy" type="destructor">
      <description summary="destroy vsync timing object">
        Destroy this vsync timing object.
      </description>
    </request>

    <event name="update">
      <description summary="vsync timing updated">
        Notifies client that vertical synchronization timing of given wl_output
        has changed.

        Timing information consists of two data, timebase and interval. Timebase
        is an absolute timestamp of the vsync event that caused the timing to
        change. Interval is a period of time between subsequent vsync events.

        The unit of all above mentioned time values shall be microseconds and
        absolute timestamps should match the realm of the primary system
        monotonic counter, i.e. the POSIX clock_gettime(CLOCK_MONOTONIC). Data
        type of both values is defined to be a 64-bit unsigned integer, but
        since the biggest unsigned integer datatype defined by the Wayland
        protocol is the 32-bit uint, both timebase and interval are split into
        most significant and least significant part, suffixed by "_h" and "_l"
        respectively.
      </description>
      <arg name="timebase_l" type="uint" summary="new vsync timebase (lower 32 bits)"/>
      <arg name="timebase_h" type="uint" summary="new vsync timebase (upper 32 bits)"/>
      <arg name="interval_l" type="uint" summary="new vsync interval (lower 32 bits)"/>
      <arg name="interval_h" type="uint" summary="new vsync interval (upper 32 bits)"/>
    </event>
  </interface>

</protocol>