class BufferLayer : public Layer {
    BufferInfo mBufferInfo;
    virtual void gatherBufferInfo() = 0;
}

class BufferQueueLayer : public BufferLayer {
    void gatherBufferInfo() override;
}

gatherBufferInfo() 在 BufferLayer 中定义的，在 BufferQueueLayer 中重写。它实现主要是更新 BufferLayer::BufferInfo。

void BufferLayer::gatherBufferInfo() {
    mBufferInfo.mPixelFormat =
            !mBufferInfo.mBuffer ? PIXEL_FORMAT_NONE : mBufferInfo.mBuffer->format;
    mBufferInfo.mFrameLatencyNeeded = true;
}

• 如果 mBuffer 是空，则给 mPixelFormat 设置 PIXEL_FORMAT_NONE，否则设置 mBuffer->format。
• mBuffer 是在 BufferLayer::latchBuffer() 中调用 gatherBufferInfo() 之前调用 BufferQueueLayer::updateActiveBuffer() 更新的。
• mFrameLatencyNeeded 是 true，表示 mBufferInfo 为合成已被锁定。

void BufferQueueLayer::gatherBufferInfo() {
    BufferLayer::gatherBufferInfo();

    mBufferInfo.mDesiredPresentTime = mConsumer->getTimestamp();
    mBufferInfo.mFenceTime = mConsumer->getCurrentFenceTime();
    mBufferInfo.mFence = mConsumer->getCurrentFence();
    mBufferInfo.mTransform = mConsumer->getCurrentTransform();
    mBufferInfo.mDataspace = translateDataspace(mConsumer->getCurrentDataSpace());
    mBufferInfo.mCrop = mConsumer->getCurrentCrop();
    mBufferInfo.mScaleMode = mConsumer->getCurrentScalingMode();
    mBufferInfo.mSurfaceDamage = mConsumer->getSurfaceDamage();
    mBufferInfo.mHdrMetadata = mConsumer->getCurrentHdrMetadata();
    mBufferInfo.mApi = mConsumer->getCurrentApi();
    mBufferInfo.mTransformToDisplayInverse = mConsumer->getTransformToDisplayInverse();
}