Android Graphics模块中的各种State和重要类普法

引言

尼玛，这Android Graphics图形栈蛋疼啊，更新太快了。机会是每年一个版本，前进的胶布不能停啊，继续干。这边博客，我们的核心是理一理Android Graphics中各种State状态类。

这里分析的Android版本是Android 13 aosp！

一. Layer中State

先不解释，先直接上代码，后分析:

//frameworks/native/services/surfaceflinger/Layer.h//struct android::Layer::Statestruct State {Geometry active_legacy;Geometry requested_legacy;int32_t z;ui::LayerStack layerStack;uint32_t flags;uint8_t reserved[2];int32_t sequence; // changes when visible regions can changebool modified;// Crop is expressed in layer space coordinate.Rect crop;Rect requestedCrop;// the transparentRegion hint is a bit special, it's latched only// when we receive a buffer -- this is because it's "content"// dependent.Region activeTransparentRegion_legacy;Region requestedTransparentRegion_legacy;LayerMetadata metadata;// If non-null, a Surface this Surface's Z-order is interpreted relative to.wp<Layer> zOrderRelativeOf;bool isRelativeOf{false};// A list of surfaces whose Z-order is interpreted relative to ours.SortedVector<wp<Layer>> zOrderRelatives;half4 color;float cornerRadius;int backgroundBlurRadius;gui::WindowInfo inputInfo;wp<Layer> touchableRegionCrop;// dataspace is only used by BufferStateLayer and EffectLayerui::Dataspace dataspace;// The fields below this point are only used by BufferStateLayeruint64_t frameNumber;uint32_t width;uint32_t height;ui::Transform transform;uint32_t bufferTransform;bool transformToDisplayInverse;Region transparentRegionHint;std::shared_ptr<renderengine::ExternalTexture> buffer;client_cache_t clientCacheId;sp<Fence> acquireFence;std::shared_ptr<FenceTime> acquireFenceTime;HdrMetadata hdrMetadata;Region surfaceDamageRegion;int32_t api;sp<NativeHandle> sidebandStream;mat4 colorTransform;bool hasColorTransform;// pointer to background color layer that, if set, appears below the buffer state layer// and the buffer state layer's children.  Z order will be set to// INT_MINsp<Layer> bgColorLayer;// The deque of callback handles for this frame. The back of the deque contains the most// recent callback handle.std::deque<sp<CallbackHandle>> callbackHandles;bool colorSpaceAgnostic;nsecs_t desiredPresentTime = 0;bool isAutoTimestamp = true;// Length of the cast shadow. If the radius is > 0, a shadow of length shadowRadius will// be rendered around the layer.float shadowRadius;// Layer regions that are made of custom materials, like frosted glassstd::vector<BlurRegion> blurRegions;// Priority of the layer assigned by Window Manager.int32_t frameRateSelectionPriority;FrameRate frameRate;// The combined frame rate of parents / children of this layerFrameRate frameRateForLayerTree;// Set by window manager indicating the layer and all its children are// in a different orientation than the display. The hint suggests that// the graphic producers should receive a transform hint as if the// display was in this orientation. When the display changes to match// the layer orientation, the graphic producer may not need to allocate// a buffer of a different size. ui::Transform::ROT_INVALID means the// a fixed transform hint is not set.ui::Transform::RotationFlags fixedTransformHint;// The vsync info that was used to start the transactionFrameTimelineInfo frameTimelineInfo;// When the transaction was postednsecs_t postTime;sp<ITransactionCompletedListener> releaseBufferListener;// SurfaceFrame that tracks the timeline of Transactions that contain a Buffer. Only one// such SurfaceFrame exists because only one buffer can be presented on the layer per vsync.// If multiple buffers are queued, the prior ones will be dropped, along with the// SurfaceFrame that's tracking them.std::shared_ptr<frametimeline::SurfaceFrame> bufferSurfaceFrameTX;// A map of token(frametimelineVsyncId) to the SurfaceFrame that's tracking a transaction// that contains the token. Only one SurfaceFrame exisits for transactions that share the// same token, unless they are presented in different vsyncs.std::unordered_map<int64_t, std::shared_ptr<frametimeline::SurfaceFrame>>bufferlessSurfaceFramesTX;// An arbitrary threshold for the number of BufferlessSurfaceFrames in the state. Used to// trigger a warning if the number of SurfaceFrames crosses the threshold.static constexpr uint32_t kStateSurfaceFramesThreshold = 25;// Stretch effect to apply to this layerStretchEffect stretchEffect;// Whether or not this layer is a trusted overlay for inputbool isTrustedOverlay;Rect bufferCrop;Rect destinationFrame;sp<IBinder> releaseBufferEndpoint;gui::DropInputMode dropInputMode;bool autoRefresh = false;bool dimmingEnabled = true;};// These are only accessed by the main thread or the tracing thread.State mDrawingState;

这里的Layer.State主要存储了该Layer相关的数据，例如长宽，各种矩阵，阴影等。

这里有点疑问，没有看到mCurrentState这个！

二. BufferLayer中对应的BufferInfo

这个BufferInfo比较重要，主要用于将Layer的信息传递给后续的OutputLayer。

//frameworks/native/services/surfaceflinger/BufferLayer.h
class BufferLayer : public Layer {...protected:struct BufferInfo {nsecs_t mDesiredPresentTime;std::shared_ptr<FenceTime> mFenceTime;sp<Fence> mFence;uint32_t mTransform{0};ui::Dataspace mDataspace{ui::Dataspace::UNKNOWN};Rect mCrop;uint32_t mScaleMode{NATIVE_WINDOW_SCALING_MODE_FREEZE};Region mSurfaceDamage;HdrMetadata mHdrMetadata;int mApi;PixelFormat mPixelFormat{PIXEL_FORMAT_NONE};bool mTransformToDisplayInverse{false};std::shared_ptr<renderengine::ExternalTexture> mBuffer;uint64_t mFrameNumber;int mBufferSlot{BufferQueue::INVALID_BUFFER_SLOT};bool mFrameLatencyNeeded{false};};BufferInfo mBufferInfo;   ...}

三. OutputLayer对应的CompositionState

这里需要注意CompositionState对应的域空间，不要和Layer里面的搞混淆了！

//frameworks/native/services/surfaceflinger/CompositionEngine/include/compositionengine/OutputLayer.h
class OutputLayer {using CompositionState = compositionengine::impl::OutputLayerCompositionState;
}///frameworks/native/services/surfaceflinger/CompositionEngine/include/compositionengine/impl/OutputLayerCompositionState.h
namespace compositionengine::impl {//namespace android::compositionengine::impl// Note that fields that affect HW composer state may need to be mirrored into
// android::compositionengine::impl::planner::LayerState
struct OutputLayerCompositionState {// The portion of the layer that is not obscured by opaque layers on topRegion visibleRegion;// The portion of the layer that is not obscured and is also opaqueRegion visibleNonTransparentRegion;// The portion of the layer that is obscured by opaque layers on topRegion coveredRegion;// The visibleRegion transformed to output spaceRegion outputSpaceVisibleRegion;// Region cast by the layer's shadowRegion shadowRegion;// If true, client composition will be used on this outputbool forceClientComposition{false};// If true, when doing client composition, the target may need to be clearedbool clearClientTarget{false};// The display frame for this layer on this outputRect displayFrame;// The source crop for this layer on this outputFloatRect sourceCrop;// The buffer transform to use for this layer o on this output.Hwc2::Transform bufferTransform{static_cast<Hwc2::Transform>(0)};// The dataspace for this layerui::Dataspace dataspace{ui::Dataspace::UNKNOWN};// A hint to the HWC that this region is transparent and may be skipped in// order to save power.Region outputSpaceBlockingRegionHint;// Overrides the buffer, acquire fence, and display frame stored in LayerFECompositionStatestruct {std::shared_ptr<renderengine::ExternalTexture> buffer = nullptr;sp<Fence> acquireFence = nullptr;Rect displayFrame = {};ui::Dataspace dataspace{ui::Dataspace::UNKNOWN};ProjectionSpace displaySpace;Region damageRegion = Region::INVALID_REGION;Region visibleRegion;// The OutputLayer pointed to by this field will be rearranged to draw// behind the OutputLayer represented by this CompositionState and will// be visible through it. Unowned - the OutputLayer's lifetime will// outlast this.)compositionengine::OutputLayer* peekThroughLayer = nullptr;// True when this layer's blur has been cached with a previous layer, so that this layer// does not need to request blurring.// TODO(b/188816867): support blur regions too, which are less likely to be common if a// device supports cross-window blurs. Blur region support should be doable, but we would// need to make sure that layer caching works well with the blur region transform passed// into RenderEnginebool disableBackgroundBlur = false;} overrideInfo;/** HWC state*/struct Hwc {explicit Hwc(std::shared_ptr<HWC2::Layer> hwcLayer) : hwcLayer(hwcLayer) {}// The HWC Layer backing this layerstd::shared_ptr<HWC2::Layer> hwcLayer;// The most recently set HWC composition type for this layeraidl::android::hardware::graphics::composer3::Composition hwcCompositionType{aidl::android::hardware::graphics::composer3::Composition::INVALID};// The buffer cache for this layer. This is used to lower the// cost of sending reused buffers to the HWC.HwcBufferCache hwcBufferCache;// Set to true when overridden info has been sent to HW composerbool stateOverridden = false;// True when this layer was skipped as part of SF-side layer caching.bool layerSkipped = false;};// The HWC state is optional, and is only set up if there is any potential// HWC acceleration possible.std::optional<Hwc> hwc;// Debuggingvoid dump(std::string& result) const;// Timestamp for when the layer is queued for client compositionnsecs_t clientCompositionTimestamp{0};static constexpr float kDefaultWhitePointNits = 200.f;float whitePointNits = kDefaultWhitePointNits;// Dimming ratio of the layer from [0, 1]static constexpr float kDefaultDimmingRatio = 1.f;float dimmingRatio = kDefaultDimmingRatio;
};} // namespace compositionengine::impl

四 Output和Display

这里要怎么理解Output和Display呢，可以简单概括就是:

Output: 封装所有与合成输出层相关的状态

//frameworks/native/services/surfaceflinger/CompositionEngine/include/compositionengine/Output.h
namespace android {
namespace compositionengine {
class Output {
public:using OutputCompositionState = compositionengine::impl::OutputCompositionState;// Gets the raw composition state data for the output// TODO(lpique): Make this protected once it is only internally called.virtual const OutputCompositionState& getState() const = 0;// Allows mutable access to the raw composition state data for the output.// This is meant to be used by the various functions that are part of the// composition process.// TODO(lpique): Make this protected once it is only internally called.virtual OutputCompositionState& editState() = 0;auto getOutputLayersOrderedByZ() const { return OutputLayersEnumerator(*this); }    // Prepare the output, updating the OutputLayers used in the outputvirtual void prepare(const CompositionRefreshArgs&, LayerFESet&) = 0;// Presents the output, finalizing all composition detailsvirtual void present(const CompositionRefreshArgs&) = 0;// Latches the front-end layer state for each output layervirtual void updateLayerStateFromFE(const CompositionRefreshArgs&) const = 0;    
}
}// namespace compositionengine
}// namespace android

Output还有一个对应域空间android::compositionengine::impl的，它们之间的关联，暂时还没有搞清楚！

Display: 表示所有输出层最终对应的显示设备，可以有硬件合成器支持的显示设备，也可以对应虚拟显示设备

namespace android::compositionengine {
class Display : public virtual Output {
}
} // namespace android::compositionengine

五. LayerFE

按照谷歌注释的翻译意思是，定义合成引擎用于向前端层发出请求的接口！这个我的理解它主要是Layer的一个前端,主要用来处理Layer合成相关的,!表示一个"前端"Layer，跟Layer相对应，用于处理Layer在合成阶段的工作


namespace android {
namespace compositionengine {// Defines the interface used by the CompositionEngine to make requests
// of the front-end layer
class LayerFE : public virtual RefBase {// Gets the raw front-end composition state data for the layervirtual const LayerFECompositionState* getCompositionState() const = 0;}} // namespace compositionengine
} // namespace android

六 LayerFECompositionState

表示Layer的frontEnd（LayerFECompositionState）

//frameworks/native/services/surfaceflinger/CompositionEngine/include/compositionengine/LayerFECompositionState.h
/** Used by LayerFE::getCompositionState* Note that fields that affect HW composer state may need to be mirrored into* android::compositionengine::impl::planner::LayerState*/
struct LayerFECompositionState {// If set to true, forces client composition on all output layers until// the next geometry change.bool forceClientComposition{false};// TODO(b/121291683): Reorganize and rename the contents of this structure/** Visibility state*/// The filter that determines which outputs include this layerui::LayerFilter outputFilter;// If false, this layer should not be considered visiblebool isVisible{true};// True if the layer is completely opaquebool isOpaque{true};// If true, invalidates the entire visible regionbool contentDirty{false};// The alpha value for this layerfloat alpha{1.f};// Background blur in pixelsint backgroundBlurRadius{0};// The transform from layer local coordinates to composition coordinatesui::Transform geomLayerTransform;// The inverse of the layer transformui::Transform geomInverseLayerTransform;// The hint from the layer producer as to what portion of the layer is// transparent.Region transparentRegionHint;// The blend mode for this layerhal::BlendMode blendMode{hal::BlendMode::INVALID};// The bounds of the layer in layer local coordinatesFloatRect geomLayerBounds;// length of the shadow in screen spacefloat shadowRadius{0.f};// List of regions that require blurstd::vector<BlurRegion> blurRegions;StretchEffect stretchEffect;/** Geometry state*/bool isSecure{false};bool geomUsesSourceCrop{false};bool geomBufferUsesDisplayInverseTransform{false};uint32_t geomBufferTransform{0};Rect geomBufferSize;Rect geomContentCrop;Rect geomCrop;GenericLayerMetadataMap metadata;/** Per-frame content*/// The type of composition for this layeraidl::android::hardware::graphics::composer3::Composition compositionType{aidl::android::hardware::graphics::composer3::Composition::INVALID};// The buffer and related statesp<GraphicBuffer> buffer;int bufferSlot{BufferQueue::INVALID_BUFFER_SLOT};sp<Fence> acquireFence = Fence::NO_FENCE;Region surfaceDamage;uint64_t frameNumber = 0;// The handle to use for a sideband stream for this layersp<NativeHandle> sidebandStream;// If true, this sideband layer has a frame updatebool sidebandStreamHasFrame{false};// The color for this layerhalf4 color;/** Per-frame presentation state*/// If true, this layer will use the dataspace chosen for the output and// ignore the dataspace value just belowbool isColorspaceAgnostic{false};// The dataspace for this layerui::Dataspace dataspace{ui::Dataspace::UNKNOWN};// The metadata for this layerHdrMetadata hdrMetadata;// The color transformmat4 colorTransform;bool colorTransformIsIdentity{true};// True if the layer has protected contentbool hasProtectedContent{false};/** Cursor state*/// The output-independent frame for the cursorRect cursorFrame;// framerate of the layer as measured by LayerHistoryfloat fps;// The dimming flagbool dimmingEnabled{true};virtual ~LayerFECompositionState();// Debuggingvirtual void dump(std::string& out) const;
};

1.Surface的创建【Android 12】

2.Android下Layer的创建

3.onMessageRefresh