Introduce CanvasFrontend

Add a front-end to convert between "stateful" canvas
and "semi-statelss" CanvasOps. Handles tracking
save/restores, clips, and transforms, and injects
the transform on all draw ops.

Test: CanvasFrontend unit tests

Change-Id: Ifbcd14600690f10717047c50954ab54b4fc27aee

libs/hwui/Android.bp

@@ -429,6 +429,7 @@ cc_defaults {
     whole_static_libs: ["libskia"],
 
     srcs: [
+        "canvas/CanvasFrontend.cpp",
         "canvas/CanvasOpBuffer.cpp",
         "canvas/CanvasOpRasterizer.cpp",
         "pipeline/skia/SkiaDisplayList.cpp",
@@ -607,6 +608,7 @@ cc_test {
         "tests/unit/CacheManagerTests.cpp",
         "tests/unit/CanvasContextTests.cpp",
         "tests/unit/CanvasOpTests.cpp",
+        "tests/unit/CanvasFrontendTests.cpp",
         "tests/unit/CommonPoolTests.cpp",
         "tests/unit/DamageAccumulatorTests.cpp",
         "tests/unit/DeferredLayerUpdaterTests.cpp",

libs/hwui/SaveFlags.h

@@ -0,0 +1,36 @@
+/*
+ * Copyright (C) 2020 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#include <inttypes.h>
+
+// TODO: Move this to an enum class
+namespace android::SaveFlags {
+
+// These must match the corresponding Canvas API constants.
+enum {
+    Matrix = 0x01,
+    Clip = 0x02,
+    HasAlphaLayer = 0x04,
+    ClipToLayer = 0x10,
+
+    // Helper constant
+    MatrixClip = Matrix | Clip,
+};
+typedef uint32_t Flags;
+
+}  // namespace android::SaveFlags

libs/hwui/canvas/CanvasFrontend.cpp

@@ -0,0 +1,117 @@
+/*
+ * Copyright (C) 2020 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "CanvasFrontend.h"
+#include "CanvasOps.h"
+#include "CanvasOpBuffer.h"
+
+namespace android::uirenderer {
+
+CanvasStateHelper::CanvasStateHelper(int width, int height) {
+    mInitialBounds = SkIRect::MakeWH(width, height);
+    mSaveStack.emplace_back();
+    mClipStack.emplace_back().setRect(mInitialBounds);
+    mTransformStack.emplace_back();
+    mCurrentClipIndex = 0;
+    mCurrentTransformIndex = 0;
+}
+
+bool CanvasStateHelper::internalSave(SaveEntry saveEntry) {
+    mSaveStack.push_back(saveEntry);
+    if (saveEntry.matrix) {
+        // We need to push before accessing transform() to ensure the reference doesn't move
+        // across vector resizes
+        mTransformStack.emplace_back() = transform();
+        mCurrentTransformIndex += 1;
+    }
+    if (saveEntry.clip) {
+        // We need to push before accessing clip() to ensure the reference doesn't move
+        // across vector resizes
+        mClipStack.emplace_back() = clip();
+        mCurrentClipIndex += 1;
+        return true;
+    }
+    return false;
+}
+
+// Assert that the cast from SkClipOp to SkRegion::Op is valid
+static_assert(static_cast<int>(SkClipOp::kDifference) == SkRegion::Op::kDifference_Op);
+static_assert(static_cast<int>(SkClipOp::kIntersect) == SkRegion::Op::kIntersect_Op);
+static_assert(static_cast<int>(SkClipOp::kUnion_deprecated) == SkRegion::Op::kUnion_Op);
+static_assert(static_cast<int>(SkClipOp::kXOR_deprecated) == SkRegion::Op::kXOR_Op);
+static_assert(static_cast<int>(SkClipOp::kReverseDifference_deprecated) == SkRegion::Op::kReverseDifference_Op);
+static_assert(static_cast<int>(SkClipOp::kReplace_deprecated) == SkRegion::Op::kReplace_Op);
+
+void CanvasStateHelper::internalClipRect(const SkRect& rect, SkClipOp op) {
+    clip().opRect(rect, transform(), mInitialBounds, (SkRegion::Op)op, false);
+}
+
+void CanvasStateHelper::internalClipPath(const SkPath& path, SkClipOp op) {
+    clip().opPath(path, transform(), mInitialBounds, (SkRegion::Op)op, true);
+}
+
+bool CanvasStateHelper::internalRestore() {
+    // Prevent underflows
+    if (saveCount() <= 1) {
+        return false;
+    }
+
+    SaveEntry entry = mSaveStack[mSaveStack.size() - 1];
+    mSaveStack.pop_back();
+    bool needsRestorePropagation = entry.layer;
+    if (entry.matrix) {
+        mTransformStack.pop_back();
+        mCurrentTransformIndex -= 1;
+    }
+    if (entry.clip) {
+        // We need to push before accessing clip() to ensure the reference doesn't move
+        // across vector resizes
+        mClipStack.pop_back();
+        mCurrentClipIndex -= 1;
+        needsRestorePropagation = true;
+    }
+    return needsRestorePropagation;
+}
+
+SkRect CanvasStateHelper::getClipBounds() const {
+    SkIRect ibounds = clip().getBounds();
+
+    if (ibounds.isEmpty()) {
+        return SkRect::MakeEmpty();
+    }
+
+    SkMatrix inverse;
+    // if we can't invert the CTM, we can't return local clip bounds
+    if (!transform().invert(&inverse)) {
+        return SkRect::MakeEmpty();
+    }
+
+    SkRect ret = SkRect::MakeEmpty();
+    inverse.mapRect(&ret, SkRect::Make(ibounds));
+    return ret;
+}
+
+bool CanvasStateHelper::quickRejectRect(float left, float top, float right, float bottom) const {
+    // TODO: Implement
+    return false;
+}
+
+bool CanvasStateHelper::quickRejectPath(const SkPath& path) const {
+    // TODO: Implement
+    return false;
+}
+
+} // namespace android::uirenderer

libs/hwui/canvas/CanvasFrontend.h

@@ -0,0 +1,200 @@
+/*
+ * Copyright (C) 2020 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+// TODO: Can we get the dependencies scoped down more?
+#include "CanvasOps.h"
+#include "CanvasOpBuffer.h"
+#include <SaveFlags.h>
+
+#include <SkRasterClip.h>
+#include <ui/FatVector.h>
+
+#include <optional>
+
+namespace android::uirenderer {
+
+// Exists to avoid forcing all this common logic into the templated class
+class CanvasStateHelper {
+protected:
+    CanvasStateHelper(int width, int height);
+    ~CanvasStateHelper() = default;
+
+    struct SaveEntry {
+        bool clip : 1 = false;
+        bool matrix : 1 = false;
+        bool layer : 1 = false;
+    };
+
+    constexpr SaveEntry saveEntryForLayer() {
+        return {
+            .clip = true,
+            .matrix = true,
+            .layer = true,
+        };
+    }
+
+    constexpr SaveEntry flagsToSaveEntry(SaveFlags::Flags flags) {
+        return SaveEntry {
+            .clip = static_cast<bool>(flags & SaveFlags::Clip),
+            .matrix = static_cast<bool>(flags & SaveFlags::Matrix),
+            .layer = false
+        };
+    }
+
+    bool internalSave(SaveEntry saveEntry);
+    bool internalSave(SaveFlags::Flags flags) {
+        return internalSave(flagsToSaveEntry(flags));
+    }
+    void internalSaveLayer(const SkCanvas::SaveLayerRec& layerRec) {
+        internalSave({
+            .clip = true,
+            .matrix = true,
+            .layer = true
+        });
+        internalClipRect(*layerRec.fBounds, SkClipOp::kIntersect);
+    }
+
+    bool internalRestore();
+
+    void internalClipRect(const SkRect& rect, SkClipOp op);
+    void internalClipPath(const SkPath& path, SkClipOp op);
+
+    SkIRect mInitialBounds;
+    FatVector<SaveEntry, 6> mSaveStack;
+    FatVector<SkMatrix, 6> mTransformStack;
+    FatVector<SkConservativeClip, 6> mClipStack;
+
+    size_t mCurrentTransformIndex;
+    size_t mCurrentClipIndex;
+
+    const SkConservativeClip& clip() const {
+        return mClipStack[mCurrentClipIndex];
+    }
+
+    SkConservativeClip& clip() {
+        return mClipStack[mCurrentClipIndex];
+    }
+
+public:
+    int saveCount() const { return mSaveStack.size(); }
+
+    SkRect getClipBounds() const;
+    bool quickRejectRect(float left, float top, float right, float bottom) const;
+    bool quickRejectPath(const SkPath& path) const;
+
+    const SkMatrix& transform() const {
+        return mTransformStack[mCurrentTransformIndex];
+    }
+
+    SkMatrix& transform() {
+        return mTransformStack[mCurrentTransformIndex];
+    }
+
+    // For compat with existing HWUI Canvas interface
+    void getMatrix(SkMatrix* outMatrix) const {
+        *outMatrix = transform();
+    }
+
+    void setMatrix(const SkMatrix& matrix) {
+        transform() = matrix;
+    }
+
+    void concat(const SkMatrix& matrix) {
+        transform().preConcat(matrix);
+    }
+
+    void rotate(float degrees) {
+        SkMatrix m;
+        m.setRotate(degrees);
+        concat(m);
+    }
+
+    void scale(float sx, float sy) {
+        SkMatrix m;
+        m.setScale(sx, sy);
+        concat(m);
+    }
+
+    void skew(float sx, float sy) {
+        SkMatrix m;
+        m.setSkew(sx, sy);
+        concat(m);
+    }
+
+    void translate(float dx, float dy) {
+        transform().preTranslate(dx, dy);
+    }
+};
+
+// Front-end canvas that handles queries, up-front state, and produces CanvasOp<> output downstream
+template <typename CanvasOpReceiver>
+class CanvasFrontend final : public CanvasStateHelper {
+public:
+    template<class... Args>
+    CanvasFrontend(int width, int height, Args&&... args) : CanvasStateHelper(width, height),
+            mReceiver(std::forward<Args>(args)...) { }
+    ~CanvasFrontend() = default;
+
+    void save(SaveFlags::Flags flags = SaveFlags::MatrixClip) {
+        if (internalSave(flagsToSaveEntry(flags))) {
+            submit<CanvasOpType::Save>({});
+        }
+    }
+
+    void restore() {
+        if (internalRestore()) {
+            submit<CanvasOpType::Restore>({});
+        }
+    }
+
+    template <CanvasOpType T>
+    void draw(CanvasOp<T>&& op) {
+        // The front-end requires going through certain front-doors, which these aren't.
+        static_assert(T != CanvasOpType::Save, "Must use CanvasFrontend::save() call instead");
+        static_assert(T != CanvasOpType::Restore, "Must use CanvasFrontend::restore() call instead");
+
+        if constexpr (T == CanvasOpType::SaveLayer) {
+            internalSaveLayer(op.saveLayerRec);
+        }
+        if constexpr (T == CanvasOpType::SaveBehind) {
+            // Don't use internalSaveLayer as this doesn't apply clipping, it's a "regular" save
+            // But we do want to flag it as a layer, such that restore is Definitely Required
+            internalSave(saveEntryForLayer());
+        }
+        if constexpr (T == CanvasOpType::ClipRect) {
+            internalClipRect(op.rect, op.op);
+        }
+        if constexpr (T == CanvasOpType::ClipPath) {
+            internalClipPath(op.path, op.op);
+        }
+
+        submit(std::move(op));
+    }
+
+    const CanvasOpReceiver& receiver() const { return mReceiver; }
+
+private:
+    CanvasOpReceiver mReceiver;
+
+    template <CanvasOpType T>
+    void submit(CanvasOp<T>&& op) {
+        mReceiver.push_container(CanvasOpContainer(std::move(op), transform()));
+    }
+};
+
+} // namespace android::uirenderer

libs/hwui/canvas/CanvasOpRecorder.cpp

@@ -0,0 +1,22 @@
+/*
+ * Copyright (C) 2020 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "CanvasOpRecorder.h"
+
+#include "CanvasOpBuffer.h"
+#include "CanvasOps.h"
+
+namespace android::uirenderer {}  // namespace android::uirenderer

libs/hwui/canvas/CanvasOpRecorder.h

@@ -0,0 +1,38 @@
+/*
+ * Copyright (C) 2020 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#include "hwui/Canvas.h"
+#include "CanvasOpBuffer.h"
+
+#include <vector>
+
+namespace android::uirenderer {
+
+// Interop with existing HWUI Canvas
+class CanvasOpRecorder final : /* todo: public Canvas */ {
+public:
+    // Transform ops
+private:
+    struct SaveEntry {
+
+    };
+
+    std::vector<SaveEntry> mSaveStack;
+};
+
+}  // namespace android::uirenderer

libs/hwui/hwui/Canvas.h

@@ -18,6 +18,7 @@
 
 #include <cutils/compiler.h>
 #include <utils/Functor.h>
+#include <SaveFlags.h>
 
 #include <androidfw/ResourceTypes.h>
 #include "Properties.h"
@@ -57,22 +58,6 @@ class SkiaDisplayList;
 using DisplayList = skiapipeline::SkiaDisplayList;
 }
 
-namespace SaveFlags {
-
-// These must match the corresponding Canvas API constants.
-enum {
-    Matrix = 0x01,
-    Clip = 0x02,
-    HasAlphaLayer = 0x04,
-    ClipToLayer = 0x10,
-
-    // Helper constant
-    MatrixClip = Matrix | Clip,
-};
-typedef uint32_t Flags;
-
-}  // namespace SaveFlags
-
 namespace uirenderer {
 namespace VectorDrawable {
 class Tree;

libs/hwui/tests/unit/CanvasFrontendTests.cpp

@@ -0,0 +1,213 @@
+/*
+ * Copyright (C) 2020 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <gtest/gtest.h>
+
+#include <canvas/CanvasFrontend.h>
+#include <canvas/CanvasOpBuffer.h>
+#include <canvas/CanvasOps.h>
+#include <canvas/CanvasOpRasterizer.h>
+
+#include <tests/common/CallCountingCanvas.h>
+
+#include "SkPictureRecorder.h"
+#include "SkColor.h"
+#include "SkLatticeIter.h"
+#include "pipeline/skia/AnimatedDrawables.h"
+#include <SkNoDrawCanvas.h>
+
+using namespace android;
+using namespace android::uirenderer;
+using namespace android::uirenderer::test;
+
+class CanvasOpCountingReceiver {
+public:
+    template <CanvasOpType T>
+    void push_container(CanvasOpContainer<T>&& op) {
+        mOpCounts[static_cast<size_t>(T)] += 1;
+    }
+
+    int operator[](CanvasOpType op) const {
+        return mOpCounts[static_cast<size_t>(op)];
+    }
+
+private:
+    std::array<int, static_cast<size_t>(CanvasOpType::COUNT)> mOpCounts;
+};
+
+TEST(CanvasFrontend, saveCount) {
+    SkNoDrawCanvas skiaCanvas(100, 100);
+    CanvasFrontend<CanvasOpCountingReceiver> opCanvas(100, 100);
+    const auto& receiver = opCanvas.receiver();
+
+    EXPECT_EQ(1, skiaCanvas.getSaveCount());
+    EXPECT_EQ(1, opCanvas.saveCount());
+
+    skiaCanvas.save();
+    opCanvas.save(SaveFlags::MatrixClip);
+    EXPECT_EQ(2, skiaCanvas.getSaveCount());
+    EXPECT_EQ(2, opCanvas.saveCount());
+
+    skiaCanvas.restore();
+    opCanvas.restore();
+    EXPECT_EQ(1, skiaCanvas.getSaveCount());
+    EXPECT_EQ(1, opCanvas.saveCount());
+
+    skiaCanvas.restore();
+    opCanvas.restore();
+    EXPECT_EQ(1, skiaCanvas.getSaveCount());
+    EXPECT_EQ(1, opCanvas.saveCount());
+
+    EXPECT_EQ(1, receiver[CanvasOpType::Save]);
+    EXPECT_EQ(1, receiver[CanvasOpType::Restore]);
+}
+
+TEST(CanvasFrontend, transform) {
+    SkNoDrawCanvas skiaCanvas(100, 100);
+    CanvasFrontend<CanvasOpCountingReceiver> opCanvas(100, 100);
+
+    skiaCanvas.translate(10, 10);
+    opCanvas.translate(10, 10);
+    EXPECT_EQ(skiaCanvas.getTotalMatrix(), opCanvas.transform());
+
+    {
+        skiaCanvas.save();
+        opCanvas.save(SaveFlags::Matrix);
+        skiaCanvas.scale(2.0f, 1.125f);
+        opCanvas.scale(2.0f, 1.125f);
+
+        EXPECT_EQ(skiaCanvas.getTotalMatrix(), opCanvas.transform());
+        skiaCanvas.restore();
+        opCanvas.restore();
+    }
+
+    EXPECT_EQ(skiaCanvas.getTotalMatrix(), opCanvas.transform());
+
+    {
+        skiaCanvas.save();
+        opCanvas.save(SaveFlags::Matrix);
+        skiaCanvas.rotate(90.f);
+        opCanvas.rotate(90.f);
+
+        EXPECT_EQ(skiaCanvas.getTotalMatrix(), opCanvas.transform());
+
+        {
+            skiaCanvas.save();
+            opCanvas.save(SaveFlags::Matrix);
+            skiaCanvas.skew(5.0f, 2.25f);
+            opCanvas.skew(5.0f, 2.25f);
+
+            EXPECT_EQ(skiaCanvas.getTotalMatrix(), opCanvas.transform());
+            skiaCanvas.restore();
+            opCanvas.restore();
+        }
+
+        skiaCanvas.restore();
+        opCanvas.restore();
+    }
+
+    EXPECT_EQ(skiaCanvas.getTotalMatrix(), opCanvas.transform());
+}
+
+TEST(CanvasFrontend, drawOpTransform) {
+    CanvasFrontend<CanvasOpBuffer> opCanvas(100, 100);
+    const auto& receiver = opCanvas.receiver();
+
+    auto makeDrawRect = [] {
+        return CanvasOp<CanvasOpType::DrawRect>{
+            .rect = SkRect::MakeWH(50, 50),
+            .paint = SkPaint(SkColors::kBlack),
+        };
+    };
+
+    opCanvas.draw(makeDrawRect());
+
+    opCanvas.translate(10, 10);
+    opCanvas.draw(makeDrawRect());
+
+    opCanvas.save();
+    opCanvas.scale(2.0f, 4.0f);
+    opCanvas.draw(makeDrawRect());
+    opCanvas.restore();
+
+    opCanvas.save();
+    opCanvas.translate(20, 15);
+    opCanvas.draw(makeDrawRect());
+    opCanvas.save();
+    opCanvas.rotate(90.f);
+    opCanvas.draw(makeDrawRect());
+    opCanvas.restore();
+    opCanvas.restore();
+
+    // Validate the results
+    std::vector<SkMatrix> transforms;
+    transforms.reserve(5);
+    receiver.for_each([&](auto op) {
+        // Filter for the DrawRect calls; ignore the save & restores
+        // (TODO: Add a filtered for_each variant to OpBuffer?)
+        if (op->type() == CanvasOpType::DrawRect) {
+            transforms.push_back(op->transform());
+        }
+    });
+
+    EXPECT_EQ(transforms.size(), 5);
+
+    {
+        // First result should be identity
+        const auto& result = transforms[0];
+        EXPECT_EQ(SkMatrix::kIdentity_Mask, result.getType());
+        EXPECT_EQ(SkMatrix::I(), result);
+    }
+
+    {
+        // Should be translate 10, 10
+        const auto& result = transforms[1];
+        EXPECT_EQ(SkMatrix::kTranslate_Mask, result.getType());
+        SkMatrix m;
+        m.setTranslate(10, 10);
+        EXPECT_EQ(m, result);
+    }
+
+    {
+        // Should be translate 10, 10 + scale 2, 4
+        const auto& result = transforms[2];
+        EXPECT_EQ(SkMatrix::kTranslate_Mask | SkMatrix::kScale_Mask, result.getType());
+        SkMatrix m;
+        m.setTranslate(10, 10);
+        m.preScale(2.0f, 4.0f);
+        EXPECT_EQ(m, result);
+    }
+
+    {
+        // Should be translate 10, 10 + translate 20, 15
+        const auto& result = transforms[3];
+        EXPECT_EQ(SkMatrix::kTranslate_Mask, result.getType());
+        SkMatrix m;
+        m.setTranslate(30, 25);
+        EXPECT_EQ(m, result);
+    }
+
+    {
+        // Should be translate 10, 10 + translate 20, 15 + rotate 90
+        const auto& result = transforms[4];
+        EXPECT_EQ(SkMatrix::kTranslate_Mask | SkMatrix::kAffine_Mask | SkMatrix::kScale_Mask,
+                result.getType());
+        SkMatrix m;
+        m.setTranslate(30, 25);
+        m.preRotate(90.f);
+        EXPECT_EQ(m, result);
+    }
+}

libs/hwui/tests/unit/CanvasOpTests.cpp

@@ -16,6 +16,7 @@
 
 #include <gtest/gtest.h>
 
+#include <canvas/CanvasFrontend.h>
 #include <canvas/CanvasOpBuffer.h>
 #include <canvas/CanvasOps.h>
 #include <canvas/CanvasOpRasterizer.h>
@@ -26,6 +27,7 @@
 #include "SkColor.h"
 #include "SkLatticeIter.h"
 #include "pipeline/skia/AnimatedDrawables.h"
+#include <SkNoDrawCanvas.h>
 
 using namespace android;
 using namespace android::uirenderer;
@@ -78,6 +80,21 @@ struct MockOp<MockTypes::Lifecycle> {
 
 using MockBuffer = OpBuffer<MockTypes, MockOpContainer>;
 
+class CanvasOpCountingReceiver {
+public:
+    template <CanvasOpType T>
+    void push_container(CanvasOpContainer<T>&& op) {
+        mOpCounts[static_cast<size_t>(T)] += 1;
+    }
+
+    int operator[](CanvasOpType op) const {
+        return mOpCounts[static_cast<size_t>(op)];
+    }
+
+private:
+    std::array<int, static_cast<size_t>(CanvasOpType::COUNT)> mOpCounts;
+};
+
 template<typename T>
 static int countItems(const T& t) {
     int count = 0;
@@ -614,4 +631,35 @@ TEST(CanvasOp, immediateRendering) {
     rasterizer.draw(op);
     EXPECT_EQ(1, canvas->drawRectCount);
     EXPECT_EQ(1, canvas->sumTotalDrawCalls());
+}
+
+TEST(CanvasOp, frontendSaveCount) {
+    SkNoDrawCanvas skiaCanvas(100, 100);
+    CanvasFrontend<CanvasOpCountingReceiver> opCanvas(100, 100);
+    const auto& receiver = opCanvas.receiver();
+
+    EXPECT_EQ(1, skiaCanvas.getSaveCount());
+    EXPECT_EQ(1, opCanvas.saveCount());
+
+    skiaCanvas.save();
+    opCanvas.save(SaveFlags::MatrixClip);
+    EXPECT_EQ(2, skiaCanvas.getSaveCount());
+    EXPECT_EQ(2, opCanvas.saveCount());
+
+    skiaCanvas.restore();
+    opCanvas.restore();
+    EXPECT_EQ(1, skiaCanvas.getSaveCount());
+    EXPECT_EQ(1, opCanvas.saveCount());
+
+    skiaCanvas.restore();
+    opCanvas.restore();
+    EXPECT_EQ(1, skiaCanvas.getSaveCount());
+    EXPECT_EQ(1, opCanvas.saveCount());
+
+    EXPECT_EQ(1, receiver[Op::Save]);
+    EXPECT_EQ(1, receiver[Op::Restore]);
+}
+
+TEST(CanvasOp, frontendTransform) {
+
 }