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// 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/unguessable_token.h"
#include "components/viz/common/viz_common_export.h"
#include "mojo/public/cpp/bindings/struct_traits.h"
namespace perfetto {
template <typename MessageType>
class TracedProto;
namespace protos::pbzero {
class LocalSurfaceId;
}
} // namespace perfetto
namespace viz {
namespace mojom {
class LocalSurfaceIdDataView;
}
class ParentLocalSurfaceIdAllocator;
class ChildLocalSurfaceIdAllocator;
constexpr uint32_t kInvalidParentSequenceNumber = 0;
constexpr uint32_t kInvalidChildSequenceNumber = 0;
constexpr uint32_t kInitialParentSequenceNumber = 1;
constexpr uint32_t kInitialChildSequenceNumber = 1;
constexpr uint32_t kMaxParentSequenceNumber =
std::numeric_limits<uint32_t>::max();
constexpr uint32_t kMaxChildSequenceNumber =
std::numeric_limits<uint32_t>::max();
// 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 {
public:
constexpr LocalSurfaceId()
: parent_sequence_number_(kInvalidParentSequenceNumber),
child_sequence_number_(kInvalidChildSequenceNumber) {}
constexpr LocalSurfaceId(const LocalSurfaceId& other) = default;
constexpr LocalSurfaceId& operator=(const LocalSurfaceId& other) = default;
constexpr LocalSurfaceId(uint32_t parent_sequence_number,
const base::UnguessableToken& embed_token)
: parent_sequence_number_(parent_sequence_number),
child_sequence_number_(kInitialChildSequenceNumber),
embed_token_(embed_token) {}
constexpr LocalSurfaceId(uint32_t parent_sequence_number,
uint32_t child_sequence_number,
const base::UnguessableToken& embed_token)
: parent_sequence_number_(parent_sequence_number),
child_sequence_number_(child_sequence_number),
embed_token_(embed_token) {}
static constexpr LocalSurfaceId MaxSequenceId() {
return LocalSurfaceId(kMaxParentSequenceNumber, kMaxChildSequenceNumber,
base::UnguessableToken());
}
constexpr bool is_valid() const {
return parent_sequence_number_ != kInvalidParentSequenceNumber &&
child_sequence_number_ != kInvalidChildSequenceNumber &&
!embed_token_.is_empty();
}
constexpr uint32_t parent_sequence_number() const {
return parent_sequence_number_;
}
constexpr uint32_t child_sequence_number() const {
return child_sequence_number_;
}
constexpr const base::UnguessableToken& embed_token() const {
return embed_token_;
}
// The |embed_trace_id| is used as the id for trace events associated with
// embedding this LocalSurfaceId.
uint64_t embed_trace_id() const { return persistent_hash() << 1; }
// The |submission_trace_id| is used as the id for trace events associated
// with submission of a CompositorFrame to a surface with this LocalSurfaceId.
uint64_t submission_trace_id() const { return (persistent_hash() << 1) | 1; }
friend std::strong_ordering operator<=>(const LocalSurfaceId&,
const LocalSurfaceId&) = default;
// This implementation is fast and appropriate for a hash table lookup.
// However the hash differs per process, and is inappropriate for tracing.
size_t hash() const;
// This implementation is slow and not appropriate for a hash table lookup.
// However the hash is consistent across processes and can be used for
// tracing.
size_t persistent_hash() const;
std::string ToString() const;
// Returns whether this LocalSurfaceId was generated after |other|. In the
// case where both `this` and `other` have advanced separate sequences, then
// this will return false.
bool IsNewerThan(const LocalSurfaceId& other) const;
// Returns whether this LocalSurfaceId was generated after |other|. In the
// case where both `this` and `other` have advanced separate sequences, then
// this will return false. In the case where `embed_token_` has changed, this
// will return true.
bool IsNewerThanOrEmbeddingChanged(const LocalSurfaceId& other) const;
// Returns whether this LocalSurfaceId was generated after |other| or equal to
// it.
bool IsSameOrNewerThan(const LocalSurfaceId& other) const;
// Returns the smallest valid LocalSurfaceId with the same embed token as this
// LocalSurfaceID.
LocalSurfaceId ToSmallestId() const;
using TraceProto = perfetto::protos::pbzero::LocalSurfaceId;
void WriteIntoTrace(perfetto::TracedProto<TraceProto> proto) const;
private:
friend struct mojo::StructTraits<mojom::LocalSurfaceIdDataView,
LocalSurfaceId>;
friend class ParentLocalSurfaceIdAllocator;
friend class ChildLocalSurfaceIdAllocator;
uint32_t parent_sequence_number_;
uint32_t child_sequence_number_;
base::UnguessableToken embed_token_;
};
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_
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