cc/ipc/surface_id.mojom

// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

module cc.mojom;

// A surface ID is composed of three parts: a namespace, a local ID, and a
// nonce. The local part and nonce are allocated by the client using any scheme
// that avoids duplicates and makes IDs unguessable respectively. The namespace
// is allocated by the service and will be different for each client.
//
// The special id_namespace value 0 is equivalent to the namespace of the
// client. This can be used to create, destroy and submit frames to
// surfaces before learning the namespace and to reference other surfaces
// owned by the same client. The actual id namespace must be used to pass
// surface ids to other clients for them to reference.
struct SurfaceId {
  // A service allocated ID identifying a client.
  uint32 id_namespace;

  // An identifier allocated by the client uniquely identifying a surface within
  // a client process.
  uint32 local_id;

  // A cryptographically secure random int chosen to make the SurfaceId
  // unguessable by other clients.
  uint64 nonce;
};