Android 11 Display System源码分析（4）：SurfaceFlinger合成流程（V1）

（==文章基于 Android 11.0==）

正是由于前人的分析和总结，帮助我节约了大量的时间和精力，特别感谢，由于不喜欢图片水印，去除了水印，敬请谅解！！！

zhoujinjian.com

==源码（部分）==：

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==源码（部分）==：

一、SurfaceFlinger::onMessageInvalidate

SurfaceFlinger接收到MessageQueue::INVALIDATE消息后。

调用handlePageFlip()查看是否有刷新的必要，如果有发送刷新信号signalRefresh()。

（1）、handlePageFlip

遍历mDrawingState里面的layer是否有准备好的。如果有并且需要立即显示加入到mLayersWithQueuedFrames里面。

invalidateLayerStack

判断需要刷新的layer是否属于当前Output。

二、SurfaceFlinger::onMessageRefresh

CompositionRefreshArgs构造

获取mDrawingState每个layer的CompositionEngineLayerFE，加入到layers中

前面主要搜集需要送显的layer的情况，封装成compositionengine::CompositionRefreshArgs参数传递给CompositionEngine做进一步操作。

三、CompositionEngine->present(refreshArgs)

（1）、onPreComposition

SurfaceFlinger主要合成及调用Hal composer送显的逻辑都在这里了。

调用了layer->onPreComposition做composition前的准备。进去看没做啥实际操作。

（2）、Output::prepare

收集可见的Layers。

记得之前版本是放在SurfaceFlinger::computeVisibleRegions函数里面的。

（3）、Output::updateLayerStateFromFE

遍历每个output中的layer。调用getLayerFE().prepareCompositionState

（4）、Output::updateInfoForHwc2On1Adapter

更新colorMode，Composition状态，然后写入hwc。

将Composition模式，Color状态写入HWC。

（5）、Output::presentForHwc2On1Adapter

5.1、Output::beginFrame

Y:\home\zhoujinjian\android11_rockpi4\frameworks\native\services\surfaceflinger\CompositionEngine\src\RenderSurface.cpp
status_t RenderSurface::beginFrame(bool mustRecompose) {
    ATRACE_NAME("RenderSurface::beginFrame");
    return mDisplaySurface->beginFrame(mustRecompose);
}
Y:\home\zhoujinjian\android11_rockpi4\frameworks\native\services\surfaceflinger\DisplayHardware\FramebufferSurface.cpp
status_t FramebufferSurface::beginFrame(bool /*mustRecompose*/) {
    ATRACE_NAME("FramebufferSurface::beginFrame");
    return NO_ERROR;
}

5.2、Output::prepareFrame

Y:\home\zhoujinjian\android11_rockpi4\frameworks\native\services\surfaceflinger\CompositionEngine\src\Output.cpp
void Output::prepareFrame() {
    ATRACE_CALL();
    ALOGV(__FUNCTION__);
    ATRACE_NAME("Output::prepareFrame");

    const auto& outputState = getState();
    if (!outputState.isEnabled) {
        return;
    }

    chooseCompositionStrategy();

    mRenderSurface->prepareFrame(outputState.usesClientComposition,
                                 outputState.usesDeviceComposition);
}

void Output::chooseCompositionStrategy() {
    // The base output implementation can only do client composition
    ATRACE_NAME("Output::chooseCompositionStrategy");
    auto& outputState = editState();
    outputState.usesClientComposition = true;
    outputState.usesDeviceComposition = false;
    outputState.reusedClientComposition = false;
}
Y:\home\zhoujinjian\android11_rockpi4\frameworks\native\services\surfaceflinger\CompositionEngine\src\Display.cpp
void Display::chooseCompositionStrategy() {
    ATRACE_CALL();
    ALOGV(__FUNCTION__);
    ATRACE_NAME("Display::chooseCompositionStrategy");

    // Default to the base settings -- client composition only.
    Output::chooseCompositionStrategy();

    // If we don't have a HWC display, then we are done
    if (!mId) {
        return;
    }

    // Get any composition changes requested by the HWC device, and apply them.
    std::optional<android::HWComposer::DeviceRequestedChanges> changes;
    auto& hwc = getCompositionEngine().getHwComposer();
    if (status_t result = hwc.getDeviceCompositionChanges(*mId, anyLayersRequireClientComposition(),
                                                          &changes);
        result != NO_ERROR) {
        ALOGE("chooseCompositionStrategy failed for %s: %d (%s)", getName().c_str(), result,
              strerror(-result));
        return;
    }
    if (changes) {
        applyChangedTypesToLayers(changes->changedTypes);
        applyDisplayRequests(changes->displayRequests);
        applyLayerRequestsToLayers(changes->layerRequests);
        applyClientTargetRequests(changes->clientTargetProperty);
    }

    // Determine what type of composition we are doing from the final state
    auto& state = editState();
    state.usesClientComposition = anyLayersRequireClientComposition();
    state.usesDeviceComposition = !allLayersRequireClientComposition();
}