void SurfaceFlinger::onMessageInvalidate(int64_t vsyncId, nsecs_t expectedVSyncTime) {
    ...
    bool refreshNeeded;
    {
        mTracePostComposition = mTracing.flagIsSet(SurfaceTracing::TRACE_COMPOSITION) ||
                mTracing.flagIsSet(SurfaceTracing::TRACE_SYNC) ||
                mTracing.flagIsSet(SurfaceTracing::TRACE_BUFFERS);
        const bool tracePreComposition = mTracingEnabled && !mTracePostComposition;
        ConditionalLockGuard<std::mutex> lock(mTracingLock, tracePreComposition);

        mFrameTimeline->setSfWakeUp(vsyncId, frameStart, Fps::fromPeriodNsecs(stats.vsyncPeriod));

        refreshNeeded = handleMessageTransaction();
        refreshNeeded |= handleMessageInvalidate();
        if (tracePreComposition) {
            if (mVisibleRegionsDirty) {
                mTracing.notifyLocked("visibleRegionsDirty");
            }
        }
    }

该函数由 VSYNC 调用。

• 调用 SurfaceFlinger::handleMessageTransaction() 处理事务。
  • 遍历 mPendingTransactionQueues 把有效的加入到 mCurrentState。
  • 更新 mDrawingState。
• 调用 SurfaceFlinger::handleMessageInvalidate()。
  • 调用 SurfaceFlinger::handlePageFlip() 更新每个 layer 的 buffer。
  • 如果有可见脏区域，则调用 computeLayerBounds() 更新。

    updateCursorAsync();
    updateInputFlinger();

• updateCursorAsync() 更新每个屏幕的光标。
• updateInputFlinger() 更新每个 layer 的 WindowInfo，通知给 InputFlinger/InputDispatcher。

    refreshNeeded |= mRepaintEverything;
    if (refreshNeeded && CC_LIKELY(mBootStage != BootStage::BOOTLOADER)) {
        // Signal a refresh if a transaction modified the window state,
        // a new buffer was latched, or if HWC has requested a full
        // repaint
        if (mFrameStartTime <= 0) {
            // We should only use the time of the first invalidate
            // message that signals a refresh as the beginning of the
            // frame. Otherwise the real frame time will be
            // underestimated.
            mFrameStartTime = frameStart;
        }

        // Run the refresh immediately after invalidate as there is no point going thru the message
        // queue again, and to ensure that we actually refresh the screen instead of handling
        // other messages that were queued us already in the MessageQueue.
        mRefreshPending = true;
        onMessageRefresh();
    }
    notifyRegionSamplingThread();
}

• 如果 refreshNeeded 是 true，调用 SurfaceFlinger::onMessageRefresh() 触发合成。
• 合成成功后回调 ITransactionCompletedListener 的 onTransactionCompleted() 通知 client。

Android 13 中改名为 commit()。