local_surface_id.h | Explore in Territory

// Copyright 2017 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef COMPONENTS_VIZ_COMMON_SURFACES_LOCAL_SURFACE_ID_H_
#define COMPONENTS_VIZ_COMMON_SURFACES_LOCAL_SURFACE_ID_H_

#include <inttypes.h>

#include <compare>
#include <iosfwd>
#include <limits>
#include <string>

#include "base/tracing/protos/chrome_track_event.pbzero.h"
#include "base/unguessable_token.h"
#include "components/viz/common/viz_common_export.h"
#include "mojo/public/cpp/bindings/struct_traits.h"
#include "third_party/perfetto/include/perfetto/tracing/traced_proto.h"

namespace viz {
namespace mojom {
class LocalSurfaceIdDataView;
}

class ParentLocalSurfaceIdAllocator;
class ChildLocalSurfaceIdAllocator;

constexpr uint32_t kInvalidParentSequenceNumber = …;
constexpr uint32_t kInvalidChildSequenceNumber = …;
constexpr uint32_t kInitialParentSequenceNumber = …;
constexpr uint32_t kInitialChildSequenceNumber = …;
constexpr uint32_t kMaxParentSequenceNumber = …;
constexpr uint32_t kMaxChildSequenceNumber = …;

// This struct is the part of SurfaceId that can be modified by the client.
// LocalSurfaceId uniquely identifies a surface among the surfaces created by a
// particular client. A SurfaceId, which is FrameSinkId+LocalSurfaceId, uniquely
// identifies a surface globally across all clients.
//
// LocalSurfaceId consists of:
//
// - parent_sequence_number: This part is incremented by the embedder of the
//   client.
//
// - child_sequence_number: This part is incremented by the client itself.
//
// - embed_token: An UnguessableToken generated by the embedder. The purpose of
//   this value is to make SurfaceIds unguessable, because FrameSinkIds and
//   LocalSurfaceIds are otherwise predictable and clients might exploit this
//   fact to embed surfaces they're not allowed to. This value is generated once
//   by ParentLocalSurfaceIdAllocator and remains constant during the lifetime
//   of the embedding, even if a new LocalSurfaceId is generated for the
//   embedded client because of some change in its state (e.g. size,
//   device scale factor, etc.), or for other reasons. If a client is
//   re-parented, then the new parent allocates a new LocalSurfaceId, with a new
//   embed token, and communicates that to the embedded client.
//
// The embedder uses ParentLocalSurfaceIdAllocator to generate LocalSurfaceIds
// for the embedee. If Surface Synchronization is on, the embedee uses
// ChildLocalSurfaceIdAllocator to generate LocalSurfaceIds for itself. If
// Surface Synchronization is off, the embedee also uses
// ParentLocalSurfaceIdAllocator, as the parent doesn't generate LocalSurfaceIds
// for the child.
class VIZ_COMMON_EXPORT LocalSurfaceId { … };

VIZ_COMMON_EXPORT std::ostream& operator<<(
    std::ostream& out,
    const LocalSurfaceId& local_surface_id);

}  // namespace viz

#endif  // COMPONENTS_VIZ_COMMON_SURFACES_LOCAL_SURFACE_ID_H_
chromium/components/viz/common/surfaces/local_surface_id.h
