struct QueueBufferOutput : public Flattenable<QueueBufferOutput> {
    QueueBufferOutput() = default;

    // Moveable.
    QueueBufferOutput(QueueBufferOutput&& src) = default;
    QueueBufferOutput& operator=(QueueBufferOutput&& src) = default;
    // Not copyable.
    QueueBufferOutput(const QueueBufferOutput& src) = delete;
    QueueBufferOutput& operator=(const QueueBufferOutput& src) = delete;

    // Flattenable protocol
    static constexpr size_t minFlattenedSize();
    size_t getFlattenedSize() const;
    size_t getFdCount() const;
    status_t flatten(void*& buffer, size_t& size, int*& fds, size_t& count) const;
    status_t unflatten(void const*& buffer, size_t& size, int const*& fds, size_t& count);

    uint32_t width{0};
    uint32_t height{0};
    uint32_t transformHint{0};
    uint32_t numPendingBuffers{0};
    uint64_t nextFrameNumber{0};
    FrameEventHistoryDelta frameTimestamps;
    bool bufferReplaced{false};
    int maxBufferCount{0};
};

QueueBufferOutput 定义在 IGraphicBufferProducer.h 中，它是 BufferQueueProducer::queueBuffer() 的输出。