Merge "Work to support saveLayer in new pipeline"
diff --git a/libs/hwui/BakedOpRenderer.cpp b/libs/hwui/BakedOpRenderer.cpp
index 4d9f9b4..94806ca 100644
--- a/libs/hwui/BakedOpRenderer.cpp
+++ b/libs/hwui/BakedOpRenderer.cpp
@@ -74,53 +74,64 @@
 #endif
 }
 
-void BakedOpRenderer::onRenderNodeOp(Info*, const RenderNodeOp&, const BakedOpState&) {
+void BakedOpRenderer::onRenderNodeOp(Info&, const RenderNodeOp&, const BakedOpState&) {
     LOG_ALWAYS_FATAL("unsupported operation");
 }
 
-void BakedOpRenderer::onBitmapOp(Info* info, const BitmapOp& op, const BakedOpState& state) {
-    info->caches.textureState().activateTexture(0); // TODO: should this be automatic, and/or elsewhere?
-    Texture* texture = info->getTexture(op.bitmap);
+void BakedOpRenderer::onBitmapOp(Info& info, const BitmapOp& op, const BakedOpState& state) {
+    info.caches.textureState().activateTexture(0); // TODO: should this be automatic, and/or elsewhere?
+    Texture* texture = info.getTexture(op.bitmap);
     if (!texture) return;
     const AutoTexture autoCleanup(texture);
 
     const int textureFillFlags = (op.bitmap->colorType() == kAlpha_8_SkColorType)
             ? TextureFillFlags::IsAlphaMaskTexture : TextureFillFlags::None;
     Glop glop;
-    GlopBuilder(info->renderState, info->caches, &glop)
+    GlopBuilder(info.renderState, info.caches, &glop)
             .setRoundRectClipState(state.roundRectClipState)
             .setMeshTexturedUnitQuad(texture->uvMapper)
             .setFillTexturePaint(*texture, textureFillFlags, op.paint, state.alpha)
             .setTransform(state.computedState.transform, TransformFlags::None)
             .setModelViewMapUnitToRectSnap(Rect(0, 0, texture->width, texture->height))
             .build();
-    info->renderGlop(state, glop);
+    info.renderGlop(state, glop);
 }
 
-void BakedOpRenderer::onRectOp(Info* info, const RectOp& op, const BakedOpState& state) {
+void BakedOpRenderer::onRectOp(Info& info, const RectOp& op, const BakedOpState& state) {
     Glop glop;
-    GlopBuilder(info->renderState, info->caches, &glop)
+    GlopBuilder(info.renderState, info.caches, &glop)
             .setRoundRectClipState(state.roundRectClipState)
             .setMeshUnitQuad()
             .setFillPaint(*op.paint, state.alpha)
             .setTransform(state.computedState.transform, TransformFlags::None)
             .setModelViewMapUnitToRect(op.unmappedBounds)
             .build();
-    info->renderGlop(state, glop);
+    info.renderGlop(state, glop);
 }
 
-void BakedOpRenderer::onSimpleRectsOp(Info* info, const SimpleRectsOp& op, const BakedOpState& state) {
+void BakedOpRenderer::onSimpleRectsOp(Info& info, const SimpleRectsOp& op, const BakedOpState& state) {
     Glop glop;
-    GlopBuilder(info->renderState, info->caches, &glop)
+    GlopBuilder(info.renderState, info.caches, &glop)
             .setRoundRectClipState(state.roundRectClipState)
             .setMeshIndexedQuads(&op.vertices[0], op.vertexCount / 4)
             .setFillPaint(*op.paint, state.alpha)
             .setTransform(state.computedState.transform, TransformFlags::None)
             .setModelViewOffsetRect(0, 0, op.unmappedBounds)
             .build();
-    info->renderGlop(state, glop);
+    info.renderGlop(state, glop);
 }
 
+void BakedOpRenderer::onBeginLayerOp(Info& info, const BeginLayerOp& op, const BakedOpState& state) {
+    LOG_ALWAYS_FATAL("unsupported operation");
+}
+
+void BakedOpRenderer::onEndLayerOp(Info& info, const EndLayerOp& op, const BakedOpState& state) {
+    LOG_ALWAYS_FATAL("unsupported operation");
+}
+
+void BakedOpRenderer::onLayerOp(Info& info, const LayerOp& op, const BakedOpState& state) {
+    LOG_ALWAYS_FATAL("unsupported operation");
+}
 
 } // namespace uirenderer
 } // namespace android
diff --git a/libs/hwui/BakedOpRenderer.h b/libs/hwui/BakedOpRenderer.h
index b8b4426..f45dbe4 100644
--- a/libs/hwui/BakedOpRenderer.h
+++ b/libs/hwui/BakedOpRenderer.h
@@ -65,7 +65,7 @@
      * These functions will perform the actual rendering of the individual operations in OpenGL,
      * given the transform/clip and other state built into the BakedOpState object passed in.
      */
-    #define BAKED_OP_RENDERER_METHOD(Type) static void on##Type(Info* info, const Type& op, const BakedOpState& state);
+    #define BAKED_OP_RENDERER_METHOD(Type) static void on##Type(Info& info, const Type& op, const BakedOpState& state);
     MAP_OPS(BAKED_OP_RENDERER_METHOD);
 };
 
diff --git a/libs/hwui/BakedOpState.h b/libs/hwui/BakedOpState.h
index e2201ca..ddb8c84 100644
--- a/libs/hwui/BakedOpState.h
+++ b/libs/hwui/BakedOpState.h
@@ -68,7 +68,7 @@
         // resolvedClipRect = intersect(parentMatrix * localClip, parentClip)
         clipRect = recordedOp.localClipRect;
         snapshot.transform->mapRect(clipRect);
-        clipRect.doIntersect(snapshot.getClipRect());
+        clipRect.doIntersect(snapshot.getRenderTargetClip());
         clipRect.snapToPixelBoundaries();
 
         // resolvedClippedBounds = intersect(resolvedMatrix * opBounds, resolvedClipRect)
diff --git a/libs/hwui/CanvasState.cpp b/libs/hwui/CanvasState.cpp
index eca71c6..6a6cc42 100644
--- a/libs/hwui/CanvasState.cpp
+++ b/libs/hwui/CanvasState.cpp
@@ -259,7 +259,7 @@
     currentTransform()->mapRect(r);
     r.snapGeometryToPixelBoundaries(snapOut);
 
-    Rect clipRect(currentClipRect());
+    Rect clipRect(currentRenderTargetClip());
     clipRect.snapToPixelBoundaries();
 
     if (!clipRect.intersects(r)) return true;
@@ -287,7 +287,7 @@
     currentTransform()->mapRect(r);
     r.roundOut(); // rounded out to be conservative
 
-    Rect clipRect(currentClipRect());
+    Rect clipRect(currentRenderTargetClip());
     clipRect.snapToPixelBoundaries();
 
     if (!clipRect.intersects(r)) return true;
diff --git a/libs/hwui/CanvasState.h b/libs/hwui/CanvasState.h
index be57f44..4709ef4 100644
--- a/libs/hwui/CanvasState.h
+++ b/libs/hwui/CanvasState.h
@@ -147,7 +147,7 @@
     void setInvisible(bool value) { mSnapshot->invisible = value; }
 
     inline const mat4* currentTransform() const { return currentSnapshot()->transform; }
-    inline const Rect& currentClipRect() const { return currentSnapshot()->getClipRect(); }
+    inline const Rect& currentRenderTargetClip() const { return currentSnapshot()->getRenderTargetClip(); }
     inline Region* currentRegion() const { return currentSnapshot()->region; }
     inline int currentFlags() const { return currentSnapshot()->flags; }
     const Vector3& currentLightCenter() const { return currentSnapshot()->getRelativeLightCenter(); }
diff --git a/libs/hwui/OpReorderer.cpp b/libs/hwui/OpReorderer.cpp
index 7c0e257..c1417c4 100644
--- a/libs/hwui/OpReorderer.cpp
+++ b/libs/hwui/OpReorderer.cpp
@@ -52,7 +52,8 @@
     const std::vector<BakedOpState*>& getOps() const { return mOps; }
 
     void dump() const {
-        ALOGD("    Batch %p, merging %d, bounds " RECT_STRING, this, mMerging, RECT_ARGS(mBounds));
+        ALOGD("    Batch %p, id %d, merging %d, count %d, bounds " RECT_STRING,
+                this, mBatchId, mMerging, mOps.size(), RECT_ARGS(mBounds));
     }
 protected:
     batchid_t mBatchId;
@@ -201,17 +202,106 @@
     Rect mClipRect;
 };
 
-class NullClient: public CanvasStateClient {
-    void onViewportInitialized() override {}
-    void onSnapshotRestored(const Snapshot& removed, const Snapshot& restored) {}
-    GLuint getTargetFbo() const override { return 0; }
-};
-static NullClient sNullClient;
+// iterate back toward target to see if anything drawn since should overlap the new op
+// if no target, merging ops still interate to find similar batch to insert after
+void OpReorderer::LayerReorderer::locateInsertIndex(int batchId, const Rect& clippedBounds,
+        BatchBase** targetBatch, size_t* insertBatchIndex) const {
+    for (int i = mBatches.size() - 1; i >= 0; i--) {
+        BatchBase* overBatch = mBatches[i];
+
+        if (overBatch == *targetBatch) break;
+
+        // TODO: also consider shader shared between batch types
+        if (batchId == overBatch->getBatchId()) {
+            *insertBatchIndex = i + 1;
+            if (!*targetBatch) break; // found insert position, quit
+        }
+
+        if (overBatch->intersects(clippedBounds)) {
+            // NOTE: it may be possible to optimize for special cases where two operations
+            // of the same batch/paint could swap order, such as with a non-mergeable
+            // (clipped) and a mergeable text operation
+            *targetBatch = nullptr;
+            break;
+        }
+    }
+}
+
+void OpReorderer::LayerReorderer::deferUnmergeableOp(LinearAllocator& allocator,
+        BakedOpState* op, batchid_t batchId) {
+    OpBatch* targetBatch = mBatchLookup[batchId];
+
+    size_t insertBatchIndex = mBatches.size();
+    if (targetBatch) {
+        locateInsertIndex(batchId, op->computedState.clippedBounds,
+                (BatchBase**)(&targetBatch), &insertBatchIndex);
+    }
+
+    if (targetBatch) {
+        targetBatch->batchOp(op);
+    } else  {
+        // new non-merging batch
+        targetBatch = new (allocator) OpBatch(batchId, op);
+        mBatchLookup[batchId] = targetBatch;
+        mBatches.insert(mBatches.begin() + insertBatchIndex, targetBatch);
+    }
+}
+
+// insertion point of a new batch, will hopefully be immediately after similar batch
+// (generally, should be similar shader)
+void OpReorderer::LayerReorderer::deferMergeableOp(LinearAllocator& allocator,
+        BakedOpState* op, batchid_t batchId, mergeid_t mergeId) {
+    MergingOpBatch* targetBatch = nullptr;
+
+    // Try to merge with any existing batch with same mergeId
+    auto getResult = mMergingBatchLookup[batchId].find(mergeId);
+    if (getResult != mMergingBatchLookup[batchId].end()) {
+        targetBatch = getResult->second;
+        if (!targetBatch->canMergeWith(op)) {
+            targetBatch = nullptr;
+        }
+    }
+
+    size_t insertBatchIndex = mBatches.size();
+    locateInsertIndex(batchId, op->computedState.clippedBounds,
+            (BatchBase**)(&targetBatch), &insertBatchIndex);
+
+    if (targetBatch) {
+        targetBatch->mergeOp(op);
+    } else  {
+        // new merging batch
+        targetBatch = new (allocator) MergingOpBatch(batchId, op);
+        mMergingBatchLookup[batchId].insert(std::make_pair(mergeId, targetBatch));
+
+        mBatches.insert(mBatches.begin() + insertBatchIndex, targetBatch);
+    }
+}
+
+void OpReorderer::LayerReorderer::replayBakedOpsImpl(void* arg, BakedOpReceiver* receivers) const {
+    for (const BatchBase* batch : mBatches) {
+        // TODO: different behavior based on batch->isMerging()
+        for (const BakedOpState* op : batch->getOps()) {
+            receivers[op->op->opId](arg, *op->op, *op);
+        }
+    }
+}
+
+void OpReorderer::LayerReorderer::dump() const {
+    for (const BatchBase* batch : mBatches) {
+        batch->dump();
+    }
+}
 
 OpReorderer::OpReorderer()
-        : mCanvasState(sNullClient) {
+        : mCanvasState(*this) {
+    mLayerReorderers.emplace_back();
+    mLayerStack.push_back(0);
 }
 
+void OpReorderer::onViewportInitialized() {}
+
+void OpReorderer::onSnapshotRestored(const Snapshot& removed, const Snapshot& restored) {}
+
 void OpReorderer::defer(const SkRect& clip, int viewportWidth, int viewportHeight,
         const std::vector< sp<RenderNode> >& nodes) {
     mCanvasState.initializeSaveStack(viewportWidth, viewportHeight,
@@ -244,11 +334,11 @@
  * This allows opIds embedded in the RecordedOps to be used for dispatching to these lambdas. E.g. a
  * BitmapOp op then would be dispatched to OpReorderer::onBitmapOp(const BitmapOp&)
  */
-#define OP_RECIEVER(Type) \
+#define OP_RECEIVER(Type) \
         [](OpReorderer& reorderer, const RecordedOp& op) { reorderer.on##Type(static_cast<const Type&>(op)); },
 void OpReorderer::deferImpl(const DisplayList& displayList) {
     static std::function<void(OpReorderer& reorderer, const RecordedOp&)> receivers[] = {
-        MAP_OPS(OP_RECIEVER)
+        MAP_OPS(OP_RECEIVER)
     };
     for (const DisplayList::Chunk& chunk : displayList.getChunks()) {
         for (size_t opIndex = chunk.beginOpIndex; opIndex < chunk.endOpIndex; opIndex++) {
@@ -260,23 +350,18 @@
 
 void OpReorderer::replayBakedOpsImpl(void* arg, BakedOpReceiver* receivers) {
     ATRACE_NAME("flush drawing commands");
-    for (const BatchBase* batch : mBatches) {
-        // TODO: different behavior based on batch->isMerging()
-        for (const BakedOpState* op : batch->getOps()) {
-            receivers[op->op->opId](arg, *op->op, *op);
-        }
+    // Relay through layers in reverse order, since layers
+    // later in the list will be drawn by earlier ones
+    for (int i = mLayerReorderers.size() - 1; i >= 0; i--) {
+        mLayerReorderers[i].replayBakedOpsImpl(arg, receivers);
     }
 }
 
-BakedOpState* OpReorderer::bakeOpState(const RecordedOp& recordedOp) {
-    return BakedOpState::tryConstruct(mAllocator, *mCanvasState.currentSnapshot(), recordedOp);
-}
-
 void OpReorderer::onRenderNodeOp(const RenderNodeOp& op) {
     if (op.renderNode->nothingToDraw()) {
         return;
     }
-    mCanvasState.save(SkCanvas::kClip_SaveFlag | SkCanvas::kMatrix_SaveFlag);
+    int count = mCanvasState.save(SkCanvas::kClip_SaveFlag | SkCanvas::kMatrix_SaveFlag);
 
     // apply state from RecordedOp
     mCanvasState.concatMatrix(op.localMatrix);
@@ -285,10 +370,10 @@
 
     // apply RenderProperties state
     if (op.renderNode->applyViewProperties(mCanvasState)) {
-        // not rejected do ops...
+        // if node not rejected based on properties, do ops...
         deferImpl(op.renderNode->getDisplayList());
     }
-    mCanvasState.restore();
+    mCanvasState.restoreToCount(count);
 }
 
 static batchid_t tessellatedBatchId(const SkPaint& paint) {
@@ -298,104 +383,70 @@
 }
 
 void OpReorderer::onBitmapOp(const BitmapOp& op) {
-    BakedOpState* bakedStateOp = bakeOpState(op);
+    BakedOpState* bakedStateOp = tryBakeOpState(op);
     if (!bakedStateOp) return; // quick rejected
 
     mergeid_t mergeId = (mergeid_t) op.bitmap->getGenerationID();
     // TODO: AssetAtlas
-
-    deferMergeableOp(bakedStateOp, OpBatchType::Bitmap, mergeId);
+    currentLayer().deferMergeableOp(mAllocator, bakedStateOp, OpBatchType::Bitmap, mergeId);
 }
 
 void OpReorderer::onRectOp(const RectOp& op) {
-    BakedOpState* bakedStateOp = bakeOpState(op);
+    BakedOpState* bakedStateOp = tryBakeOpState(op);
     if (!bakedStateOp) return; // quick rejected
-    deferUnmergeableOp(bakedStateOp, tessellatedBatchId(*op.paint));
+    currentLayer().deferUnmergeableOp(mAllocator, bakedStateOp, tessellatedBatchId(*op.paint));
 }
 
 void OpReorderer::onSimpleRectsOp(const SimpleRectsOp& op) {
-    BakedOpState* bakedStateOp = bakeOpState(op);
+    BakedOpState* bakedStateOp = tryBakeOpState(op);
     if (!bakedStateOp) return; // quick rejected
-    deferUnmergeableOp(bakedStateOp, OpBatchType::Vertices);
+    currentLayer().deferUnmergeableOp(mAllocator, bakedStateOp, OpBatchType::Vertices);
 }
 
-// iterate back toward target to see if anything drawn since should overlap the new op
-// if no target, merging ops still interate to find similar batch to insert after
-void OpReorderer::locateInsertIndex(int batchId, const Rect& clippedBounds,
-        BatchBase** targetBatch, size_t* insertBatchIndex) const {
-    for (int i = mBatches.size() - 1; i >= mEarliestBatchIndex; i--) {
-        BatchBase* overBatch = mBatches[i];
+// TODO: test rejection at defer time, where the bounds become empty
+void OpReorderer::onBeginLayerOp(const BeginLayerOp& op) {
+    mCanvasState.save(SkCanvas::kClip_SaveFlag | SkCanvas::kMatrix_SaveFlag);
+    mCanvasState.writableSnapshot()->transform->loadIdentity();
+    mCanvasState.writableSnapshot()->initializeViewport(
+            (int) op.unmappedBounds.getWidth(), (int) op.unmappedBounds.getHeight());
+    mCanvasState.writableSnapshot()->roundRectClipState = nullptr;
 
-        if (overBatch == *targetBatch) break;
+    // create a new layer, and push its index on the stack
+    mLayerStack.push_back(mLayerReorderers.size());
+    mLayerReorderers.emplace_back();
+    mLayerReorderers.back().beginLayerOp = &op;
+}
 
-        // TODO: also consider shader shared between batch types
-        if (batchId == overBatch->getBatchId()) {
-            *insertBatchIndex = i + 1;
-            if (!*targetBatch) break; // found insert position, quit
-        }
+void OpReorderer::onEndLayerOp(const EndLayerOp& /* ignored */) {
+    mCanvasState.restore();
 
-        if (overBatch->intersects(clippedBounds)) {
-            // NOTE: it may be possible to optimize for special cases where two operations
-            // of the same batch/paint could swap order, such as with a non-mergeable
-            // (clipped) and a mergeable text operation
-            *targetBatch = nullptr;
-            break;
-        }
+    const BeginLayerOp& beginLayerOp = *currentLayer().beginLayerOp;
+
+    // pop finished layer off of the stack
+    int finishedLayerIndex = mLayerStack.back();
+    mLayerStack.pop_back();
+
+    // record the draw operation into the previous layer's list of draw commands
+    // uses state from the associated beginLayerOp, since it has all the state needed for drawing
+    LayerOp* drawLayerOp = new (mAllocator) LayerOp(
+            beginLayerOp.unmappedBounds,
+            beginLayerOp.localMatrix,
+            beginLayerOp.localClipRect,
+            beginLayerOp.paint);
+    BakedOpState* bakedOpState = tryBakeOpState(*drawLayerOp);
+
+    if (bakedOpState) {
+        // Layer will be drawn into parent layer (which is now current, since we popped mLayerStack)
+        currentLayer().deferUnmergeableOp(mAllocator, bakedOpState, OpBatchType::Bitmap);
+    } else {
+        // Layer won't be drawn - delete its drawing batches to prevent it from doing any work
+        mLayerReorderers[finishedLayerIndex].clear();
+        return;
     }
 }
 
-void OpReorderer::deferUnmergeableOp(BakedOpState* op, batchid_t batchId) {
-    OpBatch* targetBatch = mBatchLookup[batchId];
-
-    size_t insertBatchIndex = mBatches.size();
-    if (targetBatch) {
-        locateInsertIndex(batchId, op->computedState.clippedBounds,
-                (BatchBase**)(&targetBatch), &insertBatchIndex);
-    }
-
-    if (targetBatch) {
-        targetBatch->batchOp(op);
-    } else  {
-        // new non-merging batch
-        targetBatch = new (mAllocator) OpBatch(batchId, op);
-        mBatchLookup[batchId] = targetBatch;
-        mBatches.insert(mBatches.begin() + insertBatchIndex, targetBatch);
-    }
-}
-
-// insertion point of a new batch, will hopefully be immediately after similar batch
-// (generally, should be similar shader)
-void OpReorderer::deferMergeableOp(BakedOpState* op, batchid_t batchId, mergeid_t mergeId) {
-    MergingOpBatch* targetBatch = nullptr;
-
-    // Try to merge with any existing batch with same mergeId
-    auto getResult = mMergingBatches[batchId].find(mergeId);
-    if (getResult != mMergingBatches[batchId].end()) {
-        targetBatch = getResult->second;
-        if (!targetBatch->canMergeWith(op)) {
-            targetBatch = nullptr;
-        }
-    }
-
-    size_t insertBatchIndex = mBatches.size();
-    locateInsertIndex(batchId, op->computedState.clippedBounds,
-            (BatchBase**)(&targetBatch), &insertBatchIndex);
-
-    if (targetBatch) {
-        targetBatch->mergeOp(op);
-    } else  {
-        // new merging batch
-        targetBatch = new (mAllocator) MergingOpBatch(batchId, op);
-        mMergingBatches[batchId].insert(std::make_pair(mergeId, targetBatch));
-
-        mBatches.insert(mBatches.begin() + insertBatchIndex, targetBatch);
-    }
-}
-
-void OpReorderer::dump() {
-    for (const BatchBase* batch : mBatches) {
-        batch->dump();
-    }
+void OpReorderer::onLayerOp(const LayerOp& op) {
+    LOG_ALWAYS_FATAL("unsupported");
 }
 
 } // namespace uirenderer
diff --git a/libs/hwui/OpReorderer.h b/libs/hwui/OpReorderer.h
index 6776a3c..73dc9af 100644
--- a/libs/hwui/OpReorderer.h
+++ b/libs/hwui/OpReorderer.h
@@ -54,19 +54,63 @@
     };
 }
 
-class OpReorderer {
+class OpReorderer : public CanvasStateClient {
+    typedef std::function<void(void*, const RecordedOp&, const BakedOpState&)> BakedOpReceiver;
+
+    /**
+     * Stores the deferred render operations and state used to compute ordering
+     * for a single FBO/layer.
+     */
+    class LayerReorderer {
+    public:
+        // iterate back toward target to see if anything drawn since should overlap the new op
+        // if no target, merging ops still iterate to find similar batch to insert after
+        void locateInsertIndex(int batchId, const Rect& clippedBounds,
+                BatchBase** targetBatch, size_t* insertBatchIndex) const;
+
+        void deferUnmergeableOp(LinearAllocator& allocator, BakedOpState* op, batchid_t batchId);
+
+        // insertion point of a new batch, will hopefully be immediately after similar batch
+        // (generally, should be similar shader)
+        void deferMergeableOp(LinearAllocator& allocator,
+                BakedOpState* op, batchid_t batchId, mergeid_t mergeId);
+
+        void replayBakedOpsImpl(void* arg, BakedOpReceiver* receivers) const;
+
+        void clear() {
+            mBatches.clear();
+        }
+
+        void dump() const;
+
+        const BeginLayerOp* beginLayerOp = nullptr;
+
+    private:
+        std::vector<BatchBase*> mBatches;
+
+        /**
+         * Maps the mergeid_t returned by an op's getMergeId() to the most recently seen
+         * MergingDrawBatch of that id. These ids are unique per draw type and guaranteed to not
+         * collide, which avoids the need to resolve mergeid collisions.
+         */
+        std::unordered_map<mergeid_t, MergingOpBatch*> mMergingBatchLookup[OpBatchType::Count];
+
+        // Maps batch ids to the most recent *non-merging* batch of that id
+        OpBatch* mBatchLookup[OpBatchType::Count] = { nullptr };
+
+    };
 public:
     OpReorderer();
+    virtual ~OpReorderer() {}
 
     // TODO: not final, just presented this way for simplicity. Layers too?
     void defer(const SkRect& clip, int viewportWidth, int viewportHeight,
             const std::vector< sp<RenderNode> >& nodes);
 
     void defer(int viewportWidth, int viewportHeight, const DisplayList& displayList);
-    typedef std::function<void(void*, const RecordedOp&, const BakedOpState&)> BakedOpReceiver;
 
     /**
-     * replayBakedOps() is templated based on what class will recieve ops being replayed.
+     * replayBakedOps() is templated based on what class will receive ops being replayed.
      *
      * It constructs a lookup array of lambdas, which allows a recorded BakeOpState to use
      * state->op->opId to lookup a receiver that will be called when the op is replayed.
@@ -77,19 +121,37 @@
      */
 #define BAKED_OP_RECEIVER(Type) \
     [](void* internalArg, const RecordedOp& op, const BakedOpState& state) { \
-        StaticReceiver::on##Type(static_cast<Arg*>(internalArg), static_cast<const Type&>(op), state); \
+        StaticReceiver::on##Type(*(static_cast<Arg*>(internalArg)), static_cast<const Type&>(op), state); \
     },
     template <typename StaticReceiver, typename Arg>
-    void replayBakedOps(Arg* arg) {
+    void replayBakedOps(Arg& arg) {
         static BakedOpReceiver receivers[] = {
             MAP_OPS(BAKED_OP_RECEIVER)
         };
-        StaticReceiver::startFrame(*arg);
-        replayBakedOpsImpl((void*)arg, receivers);
-        StaticReceiver::endFrame(*arg);
+        StaticReceiver::startFrame(arg);
+        replayBakedOpsImpl((void*)&arg, receivers);
+        StaticReceiver::endFrame(arg);
     }
+
+    void dump() const {
+        for (auto&& layer : mLayerReorderers) {
+            layer.dump();
+        }
+    }
+
+    ///////////////////////////////////////////////////////////////////
+    /// CanvasStateClient interface
+    ///////////////////////////////////////////////////////////////////
+    virtual void onViewportInitialized() override;
+    virtual void onSnapshotRestored(const Snapshot& removed, const Snapshot& restored) override;
+    virtual GLuint getTargetFbo() const override { return 0; }
+
 private:
-    BakedOpState* bakeOpState(const RecordedOp& recordedOp);
+    LayerReorderer& currentLayer() { return mLayerReorderers[mLayerStack.back()]; }
+
+    BakedOpState* tryBakeOpState(const RecordedOp& recordedOp) {
+        return BakedOpState::tryConstruct(mAllocator, *mCanvasState.currentSnapshot(), recordedOp);
+    }
 
     void deferImpl(const DisplayList& displayList);
 
@@ -105,36 +167,27 @@
     void on##Type(const Type& op);
     MAP_OPS(INTERNAL_OP_HANDLER)
 
-    // iterate back toward target to see if anything drawn since should overlap the new op
-    // if no target, merging ops still iterate to find similar batch to insert after
-    void locateInsertIndex(int batchId, const Rect& clippedBounds,
-            BatchBase** targetBatch, size_t* insertBatchIndex) const;
+    // List of every deferred layer's render state. Replayed in reverse order to render a frame.
+    std::vector<LayerReorderer> mLayerReorderers;
 
-    void deferUnmergeableOp(BakedOpState* op, batchid_t batchId);
+    /*
+     * Stack of indices within mLayerReorderers representing currently active layers. If drawing
+     * layerA within a layerB, will contain, in order:
+     *  - 0 (representing FBO 0, always present)
+     *  - layerB's index
+     *  - layerA's index
+     *
+     * Note that this doesn't vector doesn't always map onto all values of mLayerReorderers. When a
+     * layer is finished deferring, it will still be represented in mLayerReorderers, but it's index
+     * won't be in mLayerStack. This is because it can be replayed, but can't have any more drawing
+     * ops added to it.
+    */
+    std::vector<size_t> mLayerStack;
 
-    // insertion point of a new batch, will hopefully be immediately after similar batch
-    // (generally, should be similar shader)
-    void deferMergeableOp(BakedOpState* op, batchid_t batchId, mergeid_t mergeId);
-
-    void dump();
-
-    std::vector<BatchBase*> mBatches;
-
-    /**
-     * Maps the mergeid_t returned by an op's getMergeId() to the most recently seen
-     * MergingDrawBatch of that id. These ids are unique per draw type and guaranteed to not
-     * collide, which avoids the need to resolve mergeid collisions.
-     */
-    std::unordered_map<mergeid_t, MergingOpBatch*> mMergingBatches[OpBatchType::Count];
-
-    // Maps batch ids to the most recent *non-merging* batch of that id
-    OpBatch* mBatchLookup[OpBatchType::Count] = { nullptr };
     CanvasState mCanvasState;
 
     // contains ResolvedOps and Batches
     LinearAllocator mAllocator;
-
-    int mEarliestBatchIndex = 0;
 };
 
 }; // namespace uirenderer
diff --git a/libs/hwui/OpenGLRenderer.cpp b/libs/hwui/OpenGLRenderer.cpp
index cd03ac4..d4f65b6 100644
--- a/libs/hwui/OpenGLRenderer.cpp
+++ b/libs/hwui/OpenGLRenderer.cpp
@@ -223,7 +223,7 @@
 void OpenGLRenderer::callDrawGLFunction(Functor* functor, Rect& dirty) {
     if (mState.currentlyIgnored()) return;
 
-    Rect clip(mState.currentClipRect());
+    Rect clip(mState.currentRenderTargetClip());
     clip.snapToPixelBoundaries();
 
     // Since we don't know what the functor will draw, let's dirty
@@ -488,7 +488,7 @@
     currentTransform()->mapRect(bounds);
 
     // Layers only make sense if they are in the framebuffer's bounds
-    bounds.doIntersect(mState.currentClipRect());
+    bounds.doIntersect(mState.currentRenderTargetClip());
     if (!bounds.isEmpty()) {
         // We cannot work with sub-pixels in this case
         bounds.snapToPixelBoundaries();
@@ -1036,7 +1036,7 @@
 }
 
 void OpenGLRenderer::dirtyLayerUnchecked(Rect& bounds, Region* region) {
-    bounds.doIntersect(mState.currentClipRect());
+    bounds.doIntersect(mState.currentRenderTargetClip());
     if (!bounds.isEmpty()) {
         bounds.snapToPixelBoundaries();
         android::Rect dirty(bounds.left, bounds.top, bounds.right, bounds.bottom);
@@ -1084,7 +1084,7 @@
                 .setMeshIndexedQuads(&mesh[0], quadCount)
                 .setFillClear()
                 .setTransform(*currentSnapshot(), transformFlags)
-                .setModelViewOffsetRect(0, 0, Rect(currentSnapshot()->getClipRect()))
+                .setModelViewOffsetRect(0, 0, Rect(currentSnapshot()->getRenderTargetClip()))
                 .build();
         renderGlop(glop, GlopRenderType::LayerClear);
 
@@ -1099,7 +1099,7 @@
 ///////////////////////////////////////////////////////////////////////////////
 
 bool OpenGLRenderer::storeDisplayState(DeferredDisplayState& state, int stateDeferFlags) {
-    const Rect& currentClip = mState.currentClipRect();
+    const Rect& currentClip = mState.currentRenderTargetClip();
     const mat4* currentMatrix = currentTransform();
 
     if (stateDeferFlags & kStateDeferFlag_Draw) {
@@ -1187,7 +1187,7 @@
 ///////////////////////////////////////////////////////////////////////////////
 
 void OpenGLRenderer::setScissorFromClip() {
-    Rect clip(mState.currentClipRect());
+    Rect clip(mState.currentRenderTargetClip());
     clip.snapToPixelBoundaries();
 
     if (mRenderState.scissor().set(clip.left, getViewportHeight() - clip.bottom,
@@ -1430,7 +1430,7 @@
             return;
         }
 
-        DeferredDisplayList deferredList(mState.currentClipRect());
+        DeferredDisplayList deferredList(mState.currentRenderTargetClip());
         DeferStateStruct deferStruct(deferredList, *this, replayFlags);
         renderNode->defer(deferStruct, 0);
 
@@ -1765,7 +1765,7 @@
     // No need to check against the clip, we fill the clip region
     if (mState.currentlyIgnored()) return;
 
-    Rect clip(mState.currentClipRect());
+    Rect clip(mState.currentRenderTargetClip());
     clip.snapToPixelBoundaries();
 
     SkPaint paint;
@@ -2030,7 +2030,7 @@
     }
     fontRenderer.setTextureFiltering(linearFilter);
 
-    const Rect& clip(pureTranslate ? writableSnapshot()->getClipRect() : writableSnapshot()->getLocalClip());
+    const Rect& clip(pureTranslate ? writableSnapshot()->getRenderTargetClip() : writableSnapshot()->getLocalClip());
     Rect bounds(FLT_MAX / 2.0f, FLT_MAX / 2.0f, FLT_MIN / 2.0f, FLT_MIN / 2.0f);
 
     TextDrawFunctor functor(this, x, y, pureTranslate, alpha, mode, paint);
@@ -2191,7 +2191,7 @@
     fontRenderer.setTextureFiltering(linearFilter);
 
     // TODO: Implement better clipping for scaled/rotated text
-    const Rect* clip = !pureTranslate ? nullptr : &mState.currentClipRect();
+    const Rect* clip = !pureTranslate ? nullptr : &mState.currentRenderTargetClip();
     Rect layerBounds(FLT_MAX / 2.0f, FLT_MAX / 2.0f, FLT_MIN / 2.0f, FLT_MIN / 2.0f);
 
     bool status;
diff --git a/libs/hwui/RecordedOp.h b/libs/hwui/RecordedOp.h
index a69f030..dd01637 100644
--- a/libs/hwui/RecordedOp.h
+++ b/libs/hwui/RecordedOp.h
@@ -41,7 +41,10 @@
         OP_FN(BitmapOp) \
         OP_FN(RectOp) \
         OP_FN(RenderNodeOp) \
-        OP_FN(SimpleRectsOp)
+        OP_FN(SimpleRectsOp) \
+        OP_FN(BeginLayerOp) \
+        OP_FN(EndLayerOp) \
+        OP_FN(LayerOp)
 
 // Generate OpId enum
 #define IDENTITY_FN(Type) Type,
@@ -112,6 +115,31 @@
     const size_t vertexCount;
 };
 
+/**
+ * Stateful operation! denotes the creation of an off-screen layer,
+ * and that commands following will render into it.
+ */
+struct BeginLayerOp : RecordedOp {
+    BeginLayerOp(BASE_PARAMS)
+            : SUPER(BeginLayerOp) {}
+};
+
+/**
+ * Stateful operation! Denotes end of off-screen layer, and that
+ * commands since last BeginLayerOp should be drawn into parent FBO.
+ *
+ * State in this op is empty, it just serves to signal that a layer has been finished.
+ */
+struct EndLayerOp : RecordedOp {
+    EndLayerOp()
+            : RecordedOp(RecordedOpId::EndLayerOp, Rect(0, 0), Matrix4::identity(), Rect(0, 0), nullptr) {}
+};
+
+struct LayerOp : RecordedOp {
+    LayerOp(BASE_PARAMS)
+            : SUPER(LayerOp) {}
+};
+
 }; // namespace uirenderer
 }; // namespace android
 
diff --git a/libs/hwui/RecordingCanvas.cpp b/libs/hwui/RecordingCanvas.cpp
index 3b413aa..1f113bc 100644
--- a/libs/hwui/RecordingCanvas.cpp
+++ b/libs/hwui/RecordingCanvas.cpp
@@ -73,6 +73,20 @@
 }
 
 // ----------------------------------------------------------------------------
+// CanvasStateClient implementation
+// ----------------------------------------------------------------------------
+
+void RecordingCanvas::onViewportInitialized() {
+
+}
+
+void RecordingCanvas::onSnapshotRestored(const Snapshot& removed, const Snapshot& restored) {
+    if (removed.flags & Snapshot::kFlagIsFboLayer) {
+        addOp(new (alloc()) EndLayerOp());
+    }
+}
+
+// ----------------------------------------------------------------------------
 // android/graphics/Canvas state operations
 // ----------------------------------------------------------------------------
 // Save (layer)
@@ -97,8 +111,66 @@
 
 int RecordingCanvas::saveLayer(float left, float top, float right, float bottom, const SkPaint* paint,
         SkCanvas::SaveFlags flags) {
-    LOG_ALWAYS_FATAL("TODO");
-    return 0;
+    if (!(flags & SkCanvas::kClipToLayer_SaveFlag)) {
+        LOG_ALWAYS_FATAL("unclipped layers not supported");
+    }
+    // force matrix/clip isolation for layer
+    flags |= SkCanvas::kClip_SaveFlag | SkCanvas::kMatrix_SaveFlag;
+
+
+    const Snapshot& previous = *mState.currentSnapshot();
+
+    // initialize the snapshot as though it almost represents an FBO layer so deferred draw
+    // operations will be able to store and restore the current clip and transform info, and
+    // quick rejection will be correct (for display lists)
+
+    const Rect untransformedBounds(left, top, right, bottom);
+
+    // determine clipped bounds relative to previous viewport.
+    Rect visibleBounds = untransformedBounds;
+    previous.transform->mapRect(visibleBounds);
+
+
+    visibleBounds.doIntersect(previous.getRenderTargetClip());
+    visibleBounds.snapToPixelBoundaries();
+
+    Rect previousViewport(0, 0, previous.getViewportWidth(), previous.getViewportHeight());
+    visibleBounds.doIntersect(previousViewport);
+
+    // Map visible bounds back to layer space, and intersect with parameter bounds
+    Rect layerBounds = visibleBounds;
+    Matrix4 inverse;
+    inverse.loadInverse(*previous.transform);
+    inverse.mapRect(layerBounds);
+    layerBounds.doIntersect(untransformedBounds);
+
+    int saveValue = mState.save((int) flags);
+    Snapshot& snapshot = *mState.writableSnapshot();
+
+    // layerBounds is now original bounds, but with clipped to clip
+    // and viewport to ensure it's minimal size.
+    if (layerBounds.isEmpty() || untransformedBounds.isEmpty()) {
+        // Don't bother recording layer, since it's been rejected
+        snapshot.resetClip(0, 0, 0, 0);
+        return saveValue;
+    }
+
+    snapshot.flags |= Snapshot::kFlagFboTarget | Snapshot::kFlagIsFboLayer;
+    snapshot.initializeViewport(untransformedBounds.getWidth(), untransformedBounds.getHeight());
+    snapshot.resetTransform(-untransformedBounds.left, -untransformedBounds.top, 0.0f);
+
+    Rect clip = layerBounds;
+    clip.translate(-untransformedBounds.left, -untransformedBounds.top);
+    snapshot.resetClip(clip.left, clip.top, clip.right, clip.bottom);
+    snapshot.roundRectClipState = nullptr;
+
+    addOp(new (alloc()) BeginLayerOp(
+            Rect(left, top, right, bottom),
+            *previous.transform, // transform to *draw* with
+            previous.getRenderTargetClip(), // clip to *draw* with
+            refPaint(paint)));
+
+    return saveValue;
 }
 
 // Matrix
diff --git a/libs/hwui/RecordingCanvas.h b/libs/hwui/RecordingCanvas.h
index 2179e4c..9c32b1a 100644
--- a/libs/hwui/RecordingCanvas.h
+++ b/libs/hwui/RecordingCanvas.h
@@ -52,8 +52,8 @@
 // ----------------------------------------------------------------------------
 // CanvasStateClient interface
 // ----------------------------------------------------------------------------
-    virtual void onViewportInitialized() override {}
-    virtual void onSnapshotRestored(const Snapshot& removed, const Snapshot& restored) override {}
+    virtual void onViewportInitialized() override;
+    virtual void onSnapshotRestored(const Snapshot& removed, const Snapshot& restored) override;
     virtual GLuint getTargetFbo() const override { return -1; }
 
 // ----------------------------------------------------------------------------
diff --git a/libs/hwui/RenderNode.cpp b/libs/hwui/RenderNode.cpp
index 894a2bd..351fbaa 100644
--- a/libs/hwui/RenderNode.cpp
+++ b/libs/hwui/RenderNode.cpp
@@ -929,7 +929,7 @@
     const RenderProperties& backgroundProps = backgroundOp->renderNode->properties();
     renderer.translate(backgroundProps.getTranslationX(), backgroundProps.getTranslationY());
 
-    // If the projection reciever has an outline, we mask projected content to it
+    // If the projection receiver has an outline, we mask projected content to it
     // (which we know, apriori, are all tessellated paths)
     renderer.setProjectionPathMask(alloc, projectionReceiverOutline);
 
diff --git a/libs/hwui/RenderProperties.h b/libs/hwui/RenderProperties.h
index f824cc0..abef806 100644
--- a/libs/hwui/RenderProperties.h
+++ b/libs/hwui/RenderProperties.h
@@ -203,8 +203,8 @@
         return RP_SET(mPrimitiveFields.mProjectBackwards, shouldProject);
     }
 
-    bool setProjectionReceiver(bool shouldRecieve) {
-        return RP_SET(mPrimitiveFields.mProjectionReceiver, shouldRecieve);
+    bool setProjectionReceiver(bool shouldReceive) {
+        return RP_SET(mPrimitiveFields.mProjectionReceiver, shouldReceive);
     }
 
     bool isProjectionReceiver() const {
diff --git a/libs/hwui/Snapshot.h b/libs/hwui/Snapshot.h
index aeeda96..4789b33 100644
--- a/libs/hwui/Snapshot.h
+++ b/libs/hwui/Snapshot.h
@@ -158,13 +158,12 @@
     /**
      * Returns the current clip in render target coordinates.
      */
-    const Rect& getRenderTargetClip() { return mClipArea->getClipRect(); }
+    const Rect& getRenderTargetClip() const { return mClipArea->getClipRect(); }
 
     /*
      * Accessor functions so that the clip area can stay private
      */
     bool clipIsEmpty() const { return mClipArea->isEmpty(); }
-    const Rect& getClipRect() const { return mClipArea->getClipRect(); }
     const SkRegion& getClipRegion() const { return mClipArea->getClipRegion(); }
     bool clipIsSimple() const { return mClipArea->isSimple(); }
     const ClipArea& getClipArea() const { return *mClipArea; }
diff --git a/libs/hwui/microbench/OpReordererBench.cpp b/libs/hwui/microbench/OpReordererBench.cpp
index 4c8dedf..cf96d44 100644
--- a/libs/hwui/microbench/OpReordererBench.cpp
+++ b/libs/hwui/microbench/OpReordererBench.cpp
@@ -65,7 +65,7 @@
             MicroBench::DoNotOptimize(&reorderer);
 
             BakedOpRenderer::Info info(caches, renderState, 200, 200, true);
-            reorderer.replayBakedOps<BakedOpRenderer>(&info);
+            reorderer.replayBakedOps<BakedOpRenderer>(info);
         }
         StopBenchmarkTiming();
     });
diff --git a/libs/hwui/renderthread/CanvasContext.cpp b/libs/hwui/renderthread/CanvasContext.cpp
index 238cf06..f571426 100644
--- a/libs/hwui/renderthread/CanvasContext.cpp
+++ b/libs/hwui/renderthread/CanvasContext.cpp
@@ -323,7 +323,7 @@
     BakedOpRenderer::Info info(Caches::getInstance(), mRenderThread.renderState(),
             frame.width(), frame.height(), mOpaque);
     // TODO: profiler().draw(mCanvas);
-    reorderer.replayBakedOps<BakedOpRenderer>(&info);
+    reorderer.replayBakedOps<BakedOpRenderer>(info);
 
     bool drew = info.didDraw;
 
diff --git a/libs/hwui/unit_tests/OpReordererTests.cpp b/libs/hwui/unit_tests/OpReordererTests.cpp
index e1249fb..d02f89d 100644
--- a/libs/hwui/unit_tests/OpReordererTests.cpp
+++ b/libs/hwui/unit_tests/OpReordererTests.cpp
@@ -27,26 +27,69 @@
 namespace android {
 namespace uirenderer {
 
-#define UNSUPPORTED_OP(Info, Type) \
-        static void on##Type(Info*, const Type&, const BakedOpState&) { FAIL(); }
+/**
+ * Class that redirects static operation dispatch to virtual methods on a Client class.
+ *
+ * The client is recreated for every op (so data cannot be persisted between operations), but the
+ * virtual dispatch allows for default behaviors to be specified without enumerating each operation
+ * for every test.
+ *
+ * onXXXOp methods fail by default - tests should override ops they expect
+ * startFrame/endFrame do nothing by default - tests should override to intercept
+ */
+template<class CustomClient, class Arg>
+class TestReceiver {
+public:
+#define CLIENT_METHOD(Type) \
+    virtual void on##Type(Arg&, const Type&, const BakedOpState&) { FAIL(); }
+    class Client {
+    public:
+        virtual ~Client() {};
+        MAP_OPS(CLIENT_METHOD)
+
+        virtual void startFrame(Arg& info) {}
+        virtual void endFrame(Arg& info) {}
+    };
+
+#define DISPATCHER_METHOD(Type) \
+    static void on##Type(Arg& arg, const Type& op, const BakedOpState& state) { \
+        CustomClient client; client.on##Type(arg, op, state); \
+    }
+    MAP_OPS(DISPATCHER_METHOD)
+
+    static void startFrame(Arg& info) {
+        CustomClient client;
+        client.startFrame(info);
+    }
+
+    static void endFrame(Arg& info) {
+        CustomClient client;
+        client.endFrame(info);
+    }
+};
 
 class Info {
 public:
     int index = 0;
 };
 
-class SimpleReceiver {
+// Receiver class which will fail if it receives any ops
+class FailReceiver : public TestReceiver<FailReceiver, Info>::Client {};
+
+class SimpleReceiver : public TestReceiver<SimpleReceiver, Info>::Client {
 public:
-    static void onBitmapOp(Info* info, const BitmapOp& op, const BakedOpState& state) {
-        EXPECT_EQ(1, info->index++);
+    void startFrame(Info& info) override {
+        EXPECT_EQ(0, info.index++);
     }
-    static void onRectOp(Info* info, const RectOp& op, const BakedOpState& state) {
-        EXPECT_EQ(0, info->index++);
+    void onRectOp(Info& info, const RectOp& op, const BakedOpState& state) override {
+        EXPECT_EQ(1, info.index++);
     }
-    UNSUPPORTED_OP(Info, RenderNodeOp)
-    UNSUPPORTED_OP(Info, SimpleRectsOp)
-    static void startFrame(Info& info) {}
-    static void endFrame(Info& info) {}
+    void onBitmapOp(Info& info, const BitmapOp& op, const BakedOpState& state) override {
+        EXPECT_EQ(2, info.index++);
+    }
+    void endFrame(Info& info) override {
+        EXPECT_EQ(3, info.index++);
+    }
 };
 TEST(OpReorderer, simple) {
     auto dl = TestUtils::createDisplayList<RecordingCanvas>(100, 200, [](RecordingCanvas& canvas) {
@@ -54,28 +97,39 @@
         canvas.drawRect(0, 0, 100, 200, SkPaint());
         canvas.drawBitmap(bitmap, 10, 10, nullptr);
     });
-
     OpReorderer reorderer;
     reorderer.defer(200, 200, *dl);
 
     Info info;
-    reorderer.replayBakedOps<SimpleReceiver>(&info);
+    reorderer.replayBakedOps<TestReceiver<SimpleReceiver, Info>>(info);
+    EXPECT_EQ(4, info.index); // 2 ops + start + end
+}
+
+
+TEST(OpReorderer, simpleRejection) {
+    auto dl = TestUtils::createDisplayList<RecordingCanvas>(200, 200, [](RecordingCanvas& canvas) {
+        canvas.save(SkCanvas::kMatrix_SaveFlag | SkCanvas::kClip_SaveFlag);
+        canvas.clipRect(200, 200, 400, 400, SkRegion::kIntersect_Op); // intersection should be empty
+        canvas.drawRect(0, 0, 400, 400, SkPaint());
+        canvas.restore();
+    });
+    OpReorderer reorderer;
+    reorderer.defer(200, 200, *dl);
+
+    Info info;
+    reorderer.replayBakedOps<TestReceiver<FailReceiver, Info>>(info);
 }
 
 
 static int SIMPLE_BATCHING_LOOPS = 5;
-class SimpleBatchingReceiver {
+class SimpleBatchingReceiver : public TestReceiver<SimpleBatchingReceiver, Info>::Client {
 public:
-    static void onBitmapOp(Info* info, const BitmapOp& op, const BakedOpState& state) {
-        EXPECT_TRUE(info->index++ >= SIMPLE_BATCHING_LOOPS);
+    void onBitmapOp(Info& info, const BitmapOp& op, const BakedOpState& state) override {
+        EXPECT_TRUE(info.index++ >= SIMPLE_BATCHING_LOOPS);
     }
-    static void onRectOp(Info* info, const RectOp& op, const BakedOpState& state) {
-        EXPECT_TRUE(info->index++ < SIMPLE_BATCHING_LOOPS);
+    void onRectOp(Info& info, const RectOp& op, const BakedOpState& state) override {
+        EXPECT_TRUE(info.index++ < SIMPLE_BATCHING_LOOPS);
     }
-    UNSUPPORTED_OP(Info, RenderNodeOp)
-    UNSUPPORTED_OP(Info, SimpleRectsOp)
-    static void startFrame(Info& info) {}
-    static void endFrame(Info& info) {}
 };
 TEST(OpReorderer, simpleBatching) {
     auto dl = TestUtils::createDisplayList<RecordingCanvas>(200, 200, [](RecordingCanvas& canvas) {
@@ -96,15 +150,14 @@
     reorderer.defer(200, 200, *dl);
 
     Info info;
-    reorderer.replayBakedOps<SimpleBatchingReceiver>(&info);
+    reorderer.replayBakedOps<TestReceiver<SimpleBatchingReceiver, Info>>(info);
     EXPECT_EQ(2 * SIMPLE_BATCHING_LOOPS, info.index); // 2 x loops ops, because no merging (TODO: force no merging)
 }
 
-class RenderNodeReceiver {
+class RenderNodeReceiver : public TestReceiver<RenderNodeReceiver, Info>::Client {
 public:
-    UNSUPPORTED_OP(Info, BitmapOp)
-    static void onRectOp(Info* info, const RectOp& op, const BakedOpState& state) {
-        switch(info->index++) {
+    void onRectOp(Info& info, const RectOp& op, const BakedOpState& state) override {
+        switch(info.index++) {
         case 0:
             EXPECT_EQ(Rect(0, 0, 200, 200), state.computedState.clippedBounds);
             EXPECT_EQ(SK_ColorDKGRAY, op.paint->getColor());
@@ -117,10 +170,6 @@
             FAIL();
         }
     }
-    UNSUPPORTED_OP(Info, RenderNodeOp)
-    UNSUPPORTED_OP(Info, SimpleRectsOp)
-    static void startFrame(Info& info) {}
-    static void endFrame(Info& info) {}
 };
 TEST(OpReorderer, renderNode) {
     sp<RenderNode> child = TestUtils::createNode<RecordingCanvas>(10, 10, 110, 110, [](RecordingCanvas& canvas) {
@@ -151,22 +200,17 @@
     reorderer.defer(SkRect::MakeWH(200, 200), 200, 200, nodes);
 
     Info info;
-    reorderer.replayBakedOps<RenderNodeReceiver>(&info);
+    reorderer.replayBakedOps<TestReceiver<RenderNodeReceiver, Info>>(info);
 }
 
-class ClippedReceiver {
+class ClippedReceiver : public TestReceiver<ClippedReceiver, Info>::Client {
 public:
-    static void onBitmapOp(Info* info, const BitmapOp& op, const BakedOpState& state) {
-        EXPECT_EQ(0, info->index++);
+    void onBitmapOp(Info& info, const BitmapOp& op, const BakedOpState& state) override {
+        EXPECT_EQ(0, info.index++);
         EXPECT_EQ(Rect(10, 20, 30, 40), state.computedState.clippedBounds);
         EXPECT_EQ(Rect(10, 20, 30, 40), state.computedState.clipRect);
         EXPECT_TRUE(state.computedState.transform.isIdentity());
     }
-    UNSUPPORTED_OP(Info, RectOp)
-    UNSUPPORTED_OP(Info, RenderNodeOp)
-    UNSUPPORTED_OP(Info, SimpleRectsOp)
-    static void startFrame(Info& info) {}
-    static void endFrame(Info& info) {}
 };
 TEST(OpReorderer, clipped) {
     sp<RenderNode> node = TestUtils::createNode<RecordingCanvas>(0, 0, 200, 200, [](RecordingCanvas& canvas) {
@@ -182,8 +226,106 @@
             200, 200, nodes);
 
     Info info;
-    reorderer.replayBakedOps<ClippedReceiver>(&info);
+    reorderer.replayBakedOps<TestReceiver<ClippedReceiver, Info>>(info);
 }
 
+
+class SaveLayerSimpleReceiver : public TestReceiver<SaveLayerSimpleReceiver, Info>::Client {
+public:
+    void onRectOp(Info& info, const RectOp& op, const BakedOpState& state) override {
+        EXPECT_EQ(0, info.index++);
+        EXPECT_EQ(Rect(10, 10, 190, 190), op.unmappedBounds);
+        EXPECT_EQ(Rect(0, 0, 180, 180), state.computedState.clippedBounds);
+        EXPECT_EQ(Rect(0, 0, 180, 180), state.computedState.clipRect);
+
+        Matrix4 expectedTransform;
+        expectedTransform.loadTranslate(-10, -10, 0);
+        EXPECT_MATRIX_APPROX_EQ(expectedTransform, state.computedState.transform);
+    }
+    void onLayerOp(Info& info, const LayerOp& op, const BakedOpState& state) override {
+        EXPECT_EQ(1, info.index++);
+        EXPECT_EQ(Rect(10, 10, 190, 190), state.computedState.clippedBounds);
+        EXPECT_EQ(Rect(0, 0, 200, 200), state.computedState.clipRect);
+        EXPECT_TRUE(state.computedState.transform.isIdentity());
+    }
+};
+TEST(OpReorderer, saveLayerSimple) {
+    auto dl = TestUtils::createDisplayList<RecordingCanvas>(200, 200, [](RecordingCanvas& canvas) {
+        canvas.saveLayerAlpha(10, 10, 190, 190, 128, SkCanvas::kClipToLayer_SaveFlag);
+        canvas.drawRect(10, 10, 190, 190, SkPaint());
+        canvas.restore();
+    });
+
+    OpReorderer reorderer;
+    reorderer.defer(200, 200, *dl);
+
+    Info info;
+    reorderer.replayBakedOps<TestReceiver<SaveLayerSimpleReceiver, Info>>(info);
+    EXPECT_EQ(2, info.index);
 }
+
+
+// saveLayer1 {rect1, saveLayer2 { rect2 } } will play back as rect2, rect1, layerOp2, layerOp1
+class SaveLayerNestedReceiver : public TestReceiver<SaveLayerNestedReceiver, Info>::Client {
+public:
+    void onRectOp(Info& info, const RectOp& op, const BakedOpState& state) override {
+        const int index = info.index++;
+        if (index == 0) {
+            EXPECT_EQ(Rect(0, 0, 400, 400), op.unmappedBounds); // inner rect
+        } else if (index == 1) {
+            EXPECT_EQ(Rect(0, 0, 800, 800), op.unmappedBounds); // outer rect
+        } else { FAIL(); }
+    }
+    void onLayerOp(Info& info, const LayerOp& op, const BakedOpState& state) override {
+        const int index = info.index++;
+        if (index == 2) {
+            EXPECT_EQ(Rect(0, 0, 400, 400), op.unmappedBounds); // inner layer
+        } else if (index == 3) {
+            EXPECT_EQ(Rect(0, 0, 800, 800), op.unmappedBounds); // outer layer
+        } else { FAIL(); }
+    }
+};
+TEST(OpReorderer, saveLayerNested) {
+    auto dl = TestUtils::createDisplayList<RecordingCanvas>(800, 800, [](RecordingCanvas& canvas) {
+        canvas.saveLayerAlpha(0, 0, 800, 800, 128, SkCanvas::kClipToLayer_SaveFlag);
+        {
+            canvas.drawRect(0, 0, 800, 800, SkPaint());
+            canvas.saveLayerAlpha(0, 0, 400, 400, 128, SkCanvas::kClipToLayer_SaveFlag);
+            {
+                canvas.drawRect(0, 0, 400, 400, SkPaint());
+            }
+            canvas.restore();
+        }
+        canvas.restore();
+    });
+
+    OpReorderer reorderer;
+    reorderer.defer(800, 800, *dl);
+
+    Info info;
+    reorderer.replayBakedOps<TestReceiver<SaveLayerNestedReceiver, Info>>(info);
+    EXPECT_EQ(4, info.index);
 }
+
+TEST(OpReorderer, saveLayerContentRejection) {
+    auto dl = TestUtils::createDisplayList<RecordingCanvas>(200, 200, [](RecordingCanvas& canvas) {
+        canvas.save(SkCanvas::kMatrix_SaveFlag | SkCanvas::kClip_SaveFlag);
+        canvas.clipRect(200, 200, 400, 400, SkRegion::kIntersect_Op);
+        canvas.saveLayerAlpha(200, 200, 400, 400, 128, SkCanvas::kClipToLayer_SaveFlag);
+
+        // draw within save layer may still be recorded, but shouldn't be drawn
+        canvas.drawRect(200, 200, 400, 400, SkPaint());
+
+        canvas.restore();
+        canvas.restore();
+    });
+    OpReorderer reorderer;
+    reorderer.defer(200, 200, *dl);
+    Info info;
+
+    // should see no ops, even within the layer, since the layer should be rejected
+    reorderer.replayBakedOps<TestReceiver<FailReceiver, Info>>(info);
+}
+
+} // namespace uirenderer
+} // namespace android
diff --git a/libs/hwui/unit_tests/RecordingCanvasTests.cpp b/libs/hwui/unit_tests/RecordingCanvasTests.cpp
index ce25fc6..c023123 100644
--- a/libs/hwui/unit_tests/RecordingCanvasTests.cpp
+++ b/libs/hwui/unit_tests/RecordingCanvasTests.cpp
@@ -24,11 +24,11 @@
 namespace uirenderer {
 
 static void playbackOps(const DisplayList& displayList,
-        std::function<void(const RecordedOp&)> opReciever) {
+        std::function<void(const RecordedOp&)> opReceiver) {
     for (const DisplayList::Chunk& chunk : displayList.getChunks()) {
         for (size_t opIndex = chunk.beginOpIndex; opIndex < chunk.endOpIndex; opIndex++) {
             RecordedOp* op = displayList.getOps()[opIndex];
-            opReciever(*op);
+            opReceiver(*op);
         }
     }
 }
@@ -109,5 +109,123 @@
     ASSERT_EQ(2, count); // two draws observed
 }
 
+TEST(RecordingCanvas, saveLayerSimple) {
+    auto dl = TestUtils::createDisplayList<RecordingCanvas>(200, 200, [](RecordingCanvas& canvas) {
+        canvas.saveLayerAlpha(10, 20, 190, 180, 128, SkCanvas::kARGB_ClipLayer_SaveFlag);
+        canvas.drawRect(10, 20, 190, 180, SkPaint());
+        canvas.restore();
+    });
+    int count = 0;
+    playbackOps(*dl, [&count](const RecordedOp& op) {
+        Matrix4 expectedMatrix;
+        switch(count++) {
+        case 0:
+            EXPECT_EQ(RecordedOpId::BeginLayerOp, op.opId);
+            // TODO: add asserts
+            break;
+        case 1:
+            EXPECT_EQ(RecordedOpId::RectOp, op.opId);
+            EXPECT_EQ(Rect(0, 0, 180, 160), op.localClipRect);
+            EXPECT_EQ(Rect(10, 20, 190, 180), op.unmappedBounds);
+            expectedMatrix.loadTranslate(-10, -20, 0);
+            EXPECT_MATRIX_APPROX_EQ(expectedMatrix, op.localMatrix);
+            break;
+        case 2:
+            EXPECT_EQ(RecordedOpId::EndLayerOp, op.opId);
+            // TODO: add asserts
+            break;
+        default:
+            FAIL();
+        }
+    });
+    EXPECT_EQ(3, count);
 }
+
+TEST(RecordingCanvas, saveLayerViewportCrop) {
+    auto dl = TestUtils::createDisplayList<RecordingCanvas>(200, 200, [](RecordingCanvas& canvas) {
+        // shouldn't matter, since saveLayer will clip to its bounds
+        canvas.clipRect(-1000, -1000, 1000, 1000, SkRegion::kReplace_Op);
+
+        canvas.saveLayerAlpha(100, 100, 300, 300, 128, SkCanvas::kARGB_ClipLayer_SaveFlag);
+        canvas.drawRect(0, 0, 400, 400, SkPaint());
+        canvas.restore();
+    });
+    int count = 0;
+    playbackOps(*dl, [&count](const RecordedOp& op) {
+        if (count++ == 1) {
+            Matrix4 expectedMatrix;
+            EXPECT_EQ(RecordedOpId::RectOp, op.opId);
+
+            // recorded clip rect should be intersection of
+            // viewport and saveLayer bounds, in layer space
+            EXPECT_EQ(Rect(0, 0, 100, 100), op.localClipRect);
+            EXPECT_EQ(Rect(0, 0, 400, 400), op.unmappedBounds);
+            expectedMatrix.loadTranslate(-100, -100, 0);
+            EXPECT_MATRIX_APPROX_EQ(expectedMatrix, op.localMatrix);
+        }
+    });
+    EXPECT_EQ(3, count);
 }
+
+TEST(RecordingCanvas, saveLayerRotateUnclipped) {
+    auto dl = TestUtils::createDisplayList<RecordingCanvas>(200, 200, [](RecordingCanvas& canvas) {
+        canvas.save(SkCanvas::kMatrix_SaveFlag | SkCanvas::kClip_SaveFlag);
+        canvas.translate(100, 100);
+        canvas.rotate(45);
+        canvas.translate(-50, -50);
+
+        canvas.saveLayerAlpha(0, 0, 100, 100, 128, SkCanvas::kARGB_ClipLayer_SaveFlag);
+        canvas.drawRect(0, 0, 100, 100, SkPaint());
+        canvas.restore();
+
+        canvas.restore();
+    });
+    int count = 0;
+    playbackOps(*dl, [&count](const RecordedOp& op) {
+        if (count++ == 1) {
+            Matrix4 expectedMatrix;
+            EXPECT_EQ(RecordedOpId::RectOp, op.opId);
+
+            // recorded rect doesn't see rotate, since recorded relative to saveLayer bounds
+            EXPECT_EQ(Rect(0, 0, 100, 100), op.localClipRect);
+            EXPECT_EQ(Rect(0, 0, 100, 100), op.unmappedBounds);
+            expectedMatrix.loadIdentity();
+            EXPECT_MATRIX_APPROX_EQ(expectedMatrix, op.localMatrix);
+        }
+    });
+    EXPECT_EQ(3, count);
+}
+
+TEST(RecordingCanvas, saveLayerRotateClipped) {
+    auto dl = TestUtils::createDisplayList<RecordingCanvas>(200, 200, [](RecordingCanvas& canvas) {
+        canvas.save(SkCanvas::kMatrix_SaveFlag | SkCanvas::kClip_SaveFlag);
+        canvas.translate(100, 100);
+        canvas.rotate(45);
+        canvas.translate(-200, -200);
+
+        // area of saveLayer will be clipped to parent viewport, so we ask for 400x400...
+        canvas.saveLayerAlpha(0, 0, 400, 400, 128, SkCanvas::kARGB_ClipLayer_SaveFlag);
+        canvas.drawRect(0, 0, 400, 400, SkPaint());
+        canvas.restore();
+
+        canvas.restore();
+    });
+    int count = 0;
+    playbackOps(*dl, [&count](const RecordedOp& op) {
+        if (count++ == 1) {
+            Matrix4 expectedMatrix;
+            EXPECT_EQ(RecordedOpId::RectOp, op.opId);
+
+            // ...and get about 58.6, 58.6, 341.4 341.4, because the bounds are clipped by
+            // the parent 200x200 viewport, but prior to rotation
+            EXPECT_RECT_APPROX_EQ(Rect(58.57864, 58.57864, 341.42136, 341.42136), op.localClipRect);
+            EXPECT_EQ(Rect(0, 0, 400, 400), op.unmappedBounds);
+            expectedMatrix.loadIdentity();
+            EXPECT_MATRIX_APPROX_EQ(expectedMatrix, op.localMatrix);
+        }
+    });
+    EXPECT_EQ(3, count);
+}
+
+} // namespace uirenderer
+} // namespace android
diff --git a/libs/hwui/unit_tests/TestUtils.h b/libs/hwui/unit_tests/TestUtils.h
index 80d83a2..99ecc9b 100644
--- a/libs/hwui/unit_tests/TestUtils.h
+++ b/libs/hwui/unit_tests/TestUtils.h
@@ -31,6 +31,12 @@
 #define EXPECT_MATRIX_APPROX_EQ(a, b) \
     EXPECT_TRUE(TestUtils::matricesAreApproxEqual(a, b))
 
+#define EXPECT_RECT_APPROX_EQ(a, b) \
+    EXPECT_TRUE(MathUtils::areEqual(a.left, b.left) \
+            && MathUtils::areEqual(a.top, b.top) \
+            && MathUtils::areEqual(a.right, b.right) \
+            && MathUtils::areEqual(a.bottom, b.bottom));
+
 class TestUtils {
 public:
     static bool matricesAreApproxEqual(const Matrix4& a, const Matrix4& b) {