diff --git a/include/private/performance_hint_private.h b/include/private/performance_hint_private.h
index eaf3b5e..d50c5f8 100644
--- a/include/private/performance_hint_private.h
+++ b/include/private/performance_hint_private.h
@@ -17,6 +17,8 @@
 #ifndef ANDROID_PRIVATE_NATIVE_PERFORMANCE_HINT_PRIVATE_H
 #define ANDROID_PRIVATE_NATIVE_PERFORMANCE_HINT_PRIVATE_H
 
+#include <stdint.h>
+
 __BEGIN_DECLS
 
 /**
@@ -27,7 +29,7 @@
 /**
  * Hints for the session used to signal upcoming changes in the mode or workload.
  */
-enum SessionHint {
+enum SessionHint: int32_t {
     /**
      * This hint indicates a sudden increase in CPU workload intensity. It means
      * that this hint session needs extra CPU resources immediately to meet the
@@ -61,7 +63,7 @@
  * @return 0 on success
  *         EPIPE if communication with the system service has failed.
  */
-int APerformanceHint_sendHint(void* session, int hint);
+int APerformanceHint_sendHint(void* session, SessionHint hint);
 
 /**
  * Return the list of thread ids, this API should only be used for testing only.
diff --git a/libs/gui/ISurfaceComposer.cpp b/libs/gui/ISurfaceComposer.cpp
index d72f65e..b526a6c 100644
--- a/libs/gui/ISurfaceComposer.cpp
+++ b/libs/gui/ISurfaceComposer.cpp
@@ -59,15 +59,13 @@
 
     virtual ~BpSurfaceComposer();
 
-    status_t setTransactionState(const FrameTimelineInfo& frameTimelineInfo,
-                                 Vector<ComposerState>& state, const Vector<DisplayState>& displays,
-                                 uint32_t flags, const sp<IBinder>& applyToken,
-                                 InputWindowCommands commands, int64_t desiredPresentTime,
-                                 bool isAutoTimestamp,
-                                 const std::vector<client_cache_t>& uncacheBuffers,
-                                 bool hasListenerCallbacks,
-                                 const std::vector<ListenerCallbacks>& listenerCallbacks,
-                                 uint64_t transactionId) override {
+    status_t setTransactionState(
+            const FrameTimelineInfo& frameTimelineInfo, Vector<ComposerState>& state,
+            const Vector<DisplayState>& displays, uint32_t flags, const sp<IBinder>& applyToken,
+            InputWindowCommands commands, int64_t desiredPresentTime, bool isAutoTimestamp,
+            const std::vector<client_cache_t>& uncacheBuffers, bool hasListenerCallbacks,
+            const std::vector<ListenerCallbacks>& listenerCallbacks, uint64_t transactionId,
+            const std::vector<uint64_t>& mergedTransactionIds) override {
         Parcel data, reply;
         data.writeInterfaceToken(ISurfaceComposer::getInterfaceDescriptor());
 
@@ -103,6 +101,11 @@
 
         SAFE_PARCEL(data.writeUint64, transactionId);
 
+        SAFE_PARCEL(data.writeUint32, static_cast<uint32_t>(mergedTransactionIds.size()));
+        for (auto mergedTransactionId : mergedTransactionIds) {
+            SAFE_PARCEL(data.writeUint64, mergedTransactionId);
+        }
+
         if (flags & ISurfaceComposer::eOneWay) {
             return remote()->transact(BnSurfaceComposer::SET_TRANSACTION_STATE,
                     data, &reply, IBinder::FLAG_ONEWAY);
@@ -187,10 +190,16 @@
             uint64_t transactionId = -1;
             SAFE_PARCEL(data.readUint64, &transactionId);
 
+            SAFE_PARCEL_READ_SIZE(data.readUint32, &count, data.dataSize());
+            std::vector<uint64_t> mergedTransactions(count);
+            for (size_t i = 0; i < count; i++) {
+                SAFE_PARCEL(data.readUint64, &mergedTransactions[i]);
+            }
+
             return setTransactionState(frameTimelineInfo, state, displays, stateFlags, applyToken,
                                        std::move(inputWindowCommands), desiredPresentTime,
                                        isAutoTimestamp, uncacheBuffers, hasListenerCallbacks,
-                                       listenerCallbacks, transactionId);
+                                       listenerCallbacks, transactionId, mergedTransactions);
         }
         default: {
             return BBinder::onTransact(code, data, reply, flags);
diff --git a/libs/gui/SurfaceComposerClient.cpp b/libs/gui/SurfaceComposerClient.cpp
index c6c7367..0fda358 100644
--- a/libs/gui/SurfaceComposerClient.cpp
+++ b/libs/gui/SurfaceComposerClient.cpp
@@ -827,6 +827,15 @@
         SAFE_PARCEL(parcel->readUint64, &uncacheBuffers[i].id);
     }
 
+    count = static_cast<size_t>(parcel->readUint32());
+    if (count > parcel->dataSize()) {
+        return BAD_VALUE;
+    }
+    std::vector<uint64_t> mergedTransactionIds(count);
+    for (size_t i = 0; i < count; i++) {
+        SAFE_PARCEL(parcel->readUint64, &mergedTransactionIds[i]);
+    }
+
     // Parsing was successful. Update the object.
     mId = transactionId;
     mTransactionNestCount = transactionNestCount;
@@ -842,6 +851,7 @@
     mInputWindowCommands = inputWindowCommands;
     mApplyToken = applyToken;
     mUncacheBuffers = std::move(uncacheBuffers);
+    mMergedTransactionIds = std::move(mergedTransactionIds);
     return NO_ERROR;
 }
 
@@ -900,6 +910,11 @@
         SAFE_PARCEL(parcel->writeUint64, uncacheBuffer.id);
     }
 
+    SAFE_PARCEL(parcel->writeUint32, static_cast<uint32_t>(mMergedTransactionIds.size()));
+    for (auto mergedTransactionId : mMergedTransactionIds) {
+        SAFE_PARCEL(parcel->writeUint64, mergedTransactionId);
+    }
+
     return NO_ERROR;
 }
 
@@ -924,6 +939,22 @@
 }
 
 SurfaceComposerClient::Transaction& SurfaceComposerClient::Transaction::merge(Transaction&& other) {
+    while (mMergedTransactionIds.size() + other.mMergedTransactionIds.size() >
+                   MAX_MERGE_HISTORY_LENGTH - 1 &&
+           mMergedTransactionIds.size() > 0) {
+        mMergedTransactionIds.pop_back();
+    }
+    if (other.mMergedTransactionIds.size() == MAX_MERGE_HISTORY_LENGTH) {
+        mMergedTransactionIds.insert(mMergedTransactionIds.begin(),
+                                     other.mMergedTransactionIds.begin(),
+                                     other.mMergedTransactionIds.end() - 1);
+    } else if (other.mMergedTransactionIds.size() > 0u) {
+        mMergedTransactionIds.insert(mMergedTransactionIds.begin(),
+                                     other.mMergedTransactionIds.begin(),
+                                     other.mMergedTransactionIds.end());
+    }
+    mMergedTransactionIds.insert(mMergedTransactionIds.begin(), other.mId);
+
     for (auto const& [handle, composerState] : other.mComposerStates) {
         if (mComposerStates.count(handle) == 0) {
             mComposerStates[handle] = composerState;
@@ -998,12 +1029,17 @@
     mIsAutoTimestamp = true;
     clearFrameTimelineInfo(mFrameTimelineInfo);
     mApplyToken = nullptr;
+    mMergedTransactionIds.clear();
 }
 
 uint64_t SurfaceComposerClient::Transaction::getId() {
     return mId;
 }
 
+std::vector<uint64_t> SurfaceComposerClient::Transaction::getMergedTransactionIds() {
+    return mMergedTransactionIds;
+}
+
 void SurfaceComposerClient::doUncacheBufferTransaction(uint64_t cacheId) {
     sp<ISurfaceComposer> sf(ComposerService::getComposerService());
 
@@ -1014,7 +1050,7 @@
     status_t status = sf->setTransactionState(FrameTimelineInfo{}, composerStates, {},
                                               ISurfaceComposer::eOneWay,
                                               Transaction::getDefaultApplyToken(), {}, systemTime(),
-                                              true, {uncacheBuffer}, false, {}, generateId());
+                                              true, {uncacheBuffer}, false, {}, generateId(), {});
     if (status != NO_ERROR) {
         ALOGE_AND_TRACE("SurfaceComposerClient::doUncacheBufferTransaction - %s",
                         strerror(-status));
@@ -1189,7 +1225,8 @@
     sp<ISurfaceComposer> sf(ComposerService::getComposerService());
     sf->setTransactionState(mFrameTimelineInfo, composerStates, displayStates, flags, applyToken,
                             mInputWindowCommands, mDesiredPresentTime, mIsAutoTimestamp,
-                            mUncacheBuffers, hasListenerCallbacks, listenerCallbacks, mId);
+                            mUncacheBuffers, hasListenerCallbacks, listenerCallbacks, mId,
+                            mMergedTransactionIds);
     mId = generateId();
 
     // Clear the current states and flags
diff --git a/libs/gui/include/gui/ISurfaceComposer.h b/libs/gui/include/gui/ISurfaceComposer.h
index bd21851..7c150d5 100644
--- a/libs/gui/include/gui/ISurfaceComposer.h
+++ b/libs/gui/include/gui/ISurfaceComposer.h
@@ -116,7 +116,7 @@
             InputWindowCommands inputWindowCommands, int64_t desiredPresentTime,
             bool isAutoTimestamp, const std::vector<client_cache_t>& uncacheBuffer,
             bool hasListenerCallbacks, const std::vector<ListenerCallbacks>& listenerCallbacks,
-            uint64_t transactionId) = 0;
+            uint64_t transactionId, const std::vector<uint64_t>& mergedTransactionIds) = 0;
 };
 
 // ----------------------------------------------------------------------------
diff --git a/libs/gui/include/gui/SurfaceComposerClient.h b/libs/gui/include/gui/SurfaceComposerClient.h
index 8d2cdaf..fb57f63 100644
--- a/libs/gui/include/gui/SurfaceComposerClient.h
+++ b/libs/gui/include/gui/SurfaceComposerClient.h
@@ -419,6 +419,11 @@
                 mListenerCallbacks;
         std::vector<client_cache_t> mUncacheBuffers;
 
+        // We keep track of the last MAX_MERGE_HISTORY_LENGTH merged transaction ids.
+        // Ordered most recently merged to least recently merged.
+        static const size_t MAX_MERGE_HISTORY_LENGTH = 10u;
+        std::vector<uint64_t> mMergedTransactionIds;
+
         uint64_t mId;
 
         uint32_t mTransactionNestCount = 0;
@@ -482,6 +487,8 @@
         // The id is updated every time the transaction is applied.
         uint64_t getId();
 
+        std::vector<uint64_t> getMergedTransactionIds();
+
         status_t apply(bool synchronous = false, bool oneWay = false);
         // Merge another transaction in to this one, clearing other
         // as if it had been applied.
diff --git a/libs/gui/tests/Surface_test.cpp b/libs/gui/tests/Surface_test.cpp
index 5bc6904..096a43c 100644
--- a/libs/gui/tests/Surface_test.cpp
+++ b/libs/gui/tests/Surface_test.cpp
@@ -695,16 +695,14 @@
         mSupportsPresent = supportsPresent;
     }
 
-    status_t setTransactionState(const FrameTimelineInfo& /*frameTimelineInfo*/,
-                                 Vector<ComposerState>& /*state*/,
-                                 const Vector<DisplayState>& /*displays*/, uint32_t /*flags*/,
-                                 const sp<IBinder>& /*applyToken*/,
-                                 InputWindowCommands /*inputWindowCommands*/,
-                                 int64_t /*desiredPresentTime*/, bool /*isAutoTimestamp*/,
-                                 const std::vector<client_cache_t>& /*cachedBuffer*/,
-                                 bool /*hasListenerCallbacks*/,
-                                 const std::vector<ListenerCallbacks>& /*listenerCallbacks*/,
-                                 uint64_t /*transactionId*/) override {
+    status_t setTransactionState(
+            const FrameTimelineInfo& /*frameTimelineInfo*/, Vector<ComposerState>& /*state*/,
+            const Vector<DisplayState>& /*displays*/, uint32_t /*flags*/,
+            const sp<IBinder>& /*applyToken*/, InputWindowCommands /*inputWindowCommands*/,
+            int64_t /*desiredPresentTime*/, bool /*isAutoTimestamp*/,
+            const std::vector<client_cache_t>& /*cachedBuffer*/, bool /*hasListenerCallbacks*/,
+            const std::vector<ListenerCallbacks>& /*listenerCallbacks*/, uint64_t /*transactionId*/,
+            const std::vector<uint64_t>& /*mergedTransactionIds*/) override {
         return NO_ERROR;
     }
 
diff --git a/services/inputflinger/reader/EventHub.cpp b/services/inputflinger/reader/EventHub.cpp
index 0eb4ad2..0354164 100644
--- a/services/inputflinger/reader/EventHub.cpp
+++ b/services/inputflinger/reader/EventHub.cpp
@@ -1072,16 +1072,8 @@
     Device* device = getDeviceLocked(deviceId);
     if (device != nullptr && device->keyMap.haveKeyLayout()) {
         for (size_t codeIndex = 0; codeIndex < keyCodes.size(); codeIndex++) {
-            std::vector<int32_t> scanCodes =
-                    device->keyMap.keyLayoutMap->findScanCodesForKey(keyCodes[codeIndex]);
-
-            // check the possible scan codes identified by the layout map against the
-            // map of codes actually emitted by the driver
-            for (const int32_t scanCode : scanCodes) {
-                if (device->keyBitmask.test(scanCode)) {
-                    outFlags[codeIndex] = 1;
-                    break;
-                }
+            if (device->hasKeycodeLocked(keyCodes[codeIndex])) {
+                outFlags[codeIndex] = 1;
             }
         }
         return true;
diff --git a/services/inputflinger/reader/InputDevice.cpp b/services/inputflinger/reader/InputDevice.cpp
index 3f6d557..c8c5115 100644
--- a/services/inputflinger/reader/InputDevice.cpp
+++ b/services/inputflinger/reader/InputDevice.cpp
@@ -503,9 +503,9 @@
         classes.test(InputDeviceClass::TOUCH_MT) && !isSonyDualShock4Touchpad) {
         mappers.push_back(createInputMapper<TouchpadInputMapper>(contextPtr, readerConfig));
     } else if (classes.test(InputDeviceClass::TOUCH_MT)) {
-        mappers.push_back(createInputMapper<MultiTouchInputMapper>(contextPtr, readerConfig));
+        mappers.push_back(std::make_unique<MultiTouchInputMapper>(contextPtr, readerConfig));
     } else if (classes.test(InputDeviceClass::TOUCH)) {
-        mappers.push_back(createInputMapper<SingleTouchInputMapper>(contextPtr, readerConfig));
+        mappers.push_back(std::make_unique<SingleTouchInputMapper>(contextPtr, readerConfig));
     }
 
     // Joystick-like devices.
diff --git a/services/inputflinger/reader/mapper/MultiTouchInputMapper.h b/services/inputflinger/reader/mapper/MultiTouchInputMapper.h
index 1d788df..f300ee1 100644
--- a/services/inputflinger/reader/mapper/MultiTouchInputMapper.h
+++ b/services/inputflinger/reader/mapper/MultiTouchInputMapper.h
@@ -27,6 +27,8 @@
     friend std::unique_ptr<T> createInputMapper(InputDeviceContext& deviceContext,
                                                 const InputReaderConfiguration& readerConfig,
                                                 Args... args);
+    explicit MultiTouchInputMapper(InputDeviceContext& deviceContext,
+                                   const InputReaderConfiguration& readerConfig);
 
     ~MultiTouchInputMapper() override;
 
@@ -39,8 +41,6 @@
     bool hasStylus() const override;
 
 private:
-    explicit MultiTouchInputMapper(InputDeviceContext& deviceContext,
-                                   const InputReaderConfiguration& readerConfig);
     // simulate_stylus_with_touch is a debug mode that converts all finger pointers reported by this
     // mapper's touchscreen into stylus pointers, and adds SOURCE_STYLUS to the input device.
     // It is used to simulate stylus events for debugging and testing on a device that does not
diff --git a/services/inputflinger/reader/mapper/SingleTouchInputMapper.h b/services/inputflinger/reader/mapper/SingleTouchInputMapper.h
index 7726bfb..dac53cf 100644
--- a/services/inputflinger/reader/mapper/SingleTouchInputMapper.h
+++ b/services/inputflinger/reader/mapper/SingleTouchInputMapper.h
@@ -27,6 +27,8 @@
     friend std::unique_ptr<T> createInputMapper(InputDeviceContext& deviceContext,
                                                 const InputReaderConfiguration& readerConfig,
                                                 Args... args);
+    explicit SingleTouchInputMapper(InputDeviceContext& deviceContext,
+                                    const InputReaderConfiguration& readerConfig);
 
     ~SingleTouchInputMapper() override;
 
@@ -40,8 +42,6 @@
 
 private:
     SingleTouchMotionAccumulator mSingleTouchMotionAccumulator;
-    explicit SingleTouchInputMapper(InputDeviceContext& deviceContext,
-                                    const InputReaderConfiguration& readerConfig);
 };
 
 } // namespace android
diff --git a/services/inputflinger/reader/mapper/gestures/GestureConverter.cpp b/services/inputflinger/reader/mapper/gestures/GestureConverter.cpp
index fd2be5f..7eca6fa 100644
--- a/services/inputflinger/reader/mapper/gestures/GestureConverter.cpp
+++ b/services/inputflinger/reader/mapper/gestures/GestureConverter.cpp
@@ -132,7 +132,7 @@
         case kGestureTypeScroll:
             return handleScroll(when, readTime, gesture);
         case kGestureTypeFling:
-            return {handleFling(when, readTime, gesture)};
+            return handleFling(when, readTime, gesture);
         case kGestureTypeSwipe:
             return handleMultiFingerSwipe(when, readTime, 3, gesture.details.swipe.dx,
                                           gesture.details.swipe.dy);
@@ -149,7 +149,8 @@
     }
 }
 
-NotifyArgs GestureConverter::handleMove(nsecs_t when, nsecs_t readTime, const Gesture& gesture) {
+NotifyMotionArgs GestureConverter::handleMove(nsecs_t when, nsecs_t readTime,
+                                              const Gesture& gesture) {
     float deltaX = gesture.details.move.dx;
     float deltaY = gesture.details.move.dy;
     rotateDelta(mOrientation, &deltaX, &deltaY);
@@ -312,19 +313,39 @@
     return out;
 }
 
-NotifyArgs GestureConverter::handleFling(nsecs_t when, nsecs_t readTime, const Gesture& gesture) {
-    // We don't actually want to use the gestures library's fling velocity values (to ensure
-    // consistency between touchscreen and touchpad flings), so we're just using the "start fling"
-    // gestures as a marker for the end of a two-finger scroll gesture.
-    if (gesture.details.fling.fling_state != GESTURES_FLING_START ||
-        mCurrentClassification != MotionClassification::TWO_FINGER_SWIPE) {
-        return {};
+std::list<NotifyArgs> GestureConverter::handleFling(nsecs_t when, nsecs_t readTime,
+                                                    const Gesture& gesture) {
+    switch (gesture.details.fling.fling_state) {
+        case GESTURES_FLING_START:
+            if (mCurrentClassification == MotionClassification::TWO_FINGER_SWIPE) {
+                // We don't actually want to use the gestures library's fling velocity values (to
+                // ensure consistency between touchscreen and touchpad flings), so we're just using
+                // the "start fling" gestures as a marker for the end of a two-finger scroll
+                // gesture.
+                return {endScroll(when, readTime)};
+            }
+            break;
+        case GESTURES_FLING_TAP_DOWN:
+            if (mCurrentClassification == MotionClassification::NONE) {
+                // Use the tap down state of a fling gesture as an indicator that a contact
+                // has been initiated with the touchpad. We treat this as a move event with zero
+                // magnitude, which will also result in the pointer icon being updated.
+                // TODO(b/282023644): Add a signal in libgestures for when a stable contact has been
+                //  initiated with a touchpad.
+                return {handleMove(when, readTime,
+                                   Gesture(kGestureMove, gesture.start_time, gesture.end_time,
+                                           /*dx=*/0.f,
+                                           /*dy=*/0.f))};
+            }
+            break;
+        default:
+            break;
     }
 
-    return endScroll(when, readTime);
+    return {};
 }
 
-NotifyArgs GestureConverter::endScroll(nsecs_t when, nsecs_t readTime) {
+NotifyMotionArgs GestureConverter::endScroll(nsecs_t when, nsecs_t readTime) {
     const auto [xCursorPosition, yCursorPosition] = mPointerController->getPosition();
     mFakeFingerCoords[0].setAxisValue(AMOTION_EVENT_AXIS_GESTURE_SCROLL_X_DISTANCE, 0);
     mFakeFingerCoords[0].setAxisValue(AMOTION_EVENT_AXIS_GESTURE_SCROLL_Y_DISTANCE, 0);
@@ -507,14 +528,29 @@
                                                   const PointerProperties* pointerProperties,
                                                   const PointerCoords* pointerCoords,
                                                   float xCursorPosition, float yCursorPosition) {
-    return NotifyMotionArgs(mReaderContext.getNextId(), when, readTime, mDeviceId, SOURCE,
-                            mPointerController->getDisplayId(), /* policyFlags= */ POLICY_FLAG_WAKE,
-                            action, /* actionButton= */ actionButton, /* flags= */ 0,
-                            mReaderContext.getGlobalMetaState(), buttonState,
-                            mCurrentClassification, AMOTION_EVENT_EDGE_FLAG_NONE, pointerCount,
-                            pointerProperties, pointerCoords, /* xPrecision= */ 1.0f,
-                            /* yPrecision= */ 1.0f, xCursorPosition, yCursorPosition,
-                            /* downTime= */ mDownTime, /* videoFrames= */ {});
+    return {mReaderContext.getNextId(),
+            when,
+            readTime,
+            mDeviceId,
+            SOURCE,
+            mPointerController->getDisplayId(),
+            /* policyFlags= */ POLICY_FLAG_WAKE,
+            action,
+            /* actionButton= */ actionButton,
+            /* flags= */ 0,
+            mReaderContext.getGlobalMetaState(),
+            buttonState,
+            mCurrentClassification,
+            AMOTION_EVENT_EDGE_FLAG_NONE,
+            pointerCount,
+            pointerProperties,
+            pointerCoords,
+            /* xPrecision= */ 1.0f,
+            /* yPrecision= */ 1.0f,
+            xCursorPosition,
+            yCursorPosition,
+            /* downTime= */ mDownTime,
+            /* videoFrames= */ {}};
 }
 
 } // namespace android
diff --git a/services/inputflinger/reader/mapper/gestures/GestureConverter.h b/services/inputflinger/reader/mapper/gestures/GestureConverter.h
index 70e8fb7..b613b88 100644
--- a/services/inputflinger/reader/mapper/gestures/GestureConverter.h
+++ b/services/inputflinger/reader/mapper/gestures/GestureConverter.h
@@ -52,14 +52,16 @@
                                                       const Gesture& gesture);
 
 private:
-    [[nodiscard]] NotifyArgs handleMove(nsecs_t when, nsecs_t readTime, const Gesture& gesture);
+    [[nodiscard]] NotifyMotionArgs handleMove(nsecs_t when, nsecs_t readTime,
+                                              const Gesture& gesture);
     [[nodiscard]] std::list<NotifyArgs> handleButtonsChange(nsecs_t when, nsecs_t readTime,
                                                             const Gesture& gesture);
     [[nodiscard]] std::list<NotifyArgs> releaseAllButtons(nsecs_t when, nsecs_t readTime);
     [[nodiscard]] std::list<NotifyArgs> handleScroll(nsecs_t when, nsecs_t readTime,
                                                      const Gesture& gesture);
-    [[nodiscard]] NotifyArgs handleFling(nsecs_t when, nsecs_t readTime, const Gesture& gesture);
-    [[nodiscard]] NotifyArgs endScroll(nsecs_t when, nsecs_t readTime);
+    [[nodiscard]] std::list<NotifyArgs> handleFling(nsecs_t when, nsecs_t readTime,
+                                                    const Gesture& gesture);
+    [[nodiscard]] NotifyMotionArgs endScroll(nsecs_t when, nsecs_t readTime);
 
     [[nodiscard]] std::list<NotifyArgs> handleMultiFingerSwipe(nsecs_t when, nsecs_t readTime,
                                                                uint32_t fingerCount, float dx,
diff --git a/services/inputflinger/tests/GestureConverter_test.cpp b/services/inputflinger/tests/GestureConverter_test.cpp
index c6d541e..a723636 100644
--- a/services/inputflinger/tests/GestureConverter_test.cpp
+++ b/services/inputflinger/tests/GestureConverter_test.cpp
@@ -888,4 +888,21 @@
                       WithToolType(ToolType::FINGER)));
 }
 
+TEST_F(GestureConverterTest, FlingTapDown) {
+    InputDeviceContext deviceContext(*mDevice, EVENTHUB_ID);
+    GestureConverter converter(*mReader->getContext(), deviceContext, DEVICE_ID);
+
+    Gesture tapDownGesture(kGestureFling, ARBITRARY_GESTURE_TIME, ARBITRARY_GESTURE_TIME,
+                           /*vx=*/0.f, /*vy=*/0.f, GESTURES_FLING_TAP_DOWN);
+    std::list<NotifyArgs> args = converter.handleGesture(ARBITRARY_TIME, READ_TIME, tapDownGesture);
+
+    ASSERT_THAT(std::get<NotifyMotionArgs>(args.front()),
+                AllOf(WithMotionAction(AMOTION_EVENT_ACTION_HOVER_MOVE),
+                      WithCoords(POINTER_X, POINTER_Y), WithRelativeMotion(0.f, 0.f),
+                      WithToolType(ToolType::FINGER), WithButtonState(0), WithPressure(0.0f)));
+
+    ASSERT_NO_FATAL_FAILURE(mFakePointerController->assertPosition(POINTER_X, POINTER_Y));
+    ASSERT_TRUE(mFakePointerController->isPointerShown());
+}
+
 } // namespace android
diff --git a/services/inputflinger/tests/InputDispatcher_test.cpp b/services/inputflinger/tests/InputDispatcher_test.cpp
index 655931c..74be843 100644
--- a/services/inputflinger/tests/InputDispatcher_test.cpp
+++ b/services/inputflinger/tests/InputDispatcher_test.cpp
@@ -1564,8 +1564,7 @@
 
         // Set mouse cursor position for the most common cases to avoid boilerplate.
         if (mSource == AINPUT_SOURCE_MOUSE &&
-            !MotionEvent::isValidCursorPosition(mRawXCursorPosition, mRawYCursorPosition) &&
-            mPointers.size() == 1) {
+            !MotionEvent::isValidCursorPosition(mRawXCursorPosition, mRawYCursorPosition)) {
             mRawXCursorPosition = pointerCoords[0].getX();
             mRawYCursorPosition = pointerCoords[0].getY();
         }
@@ -1677,8 +1676,7 @@
 
         // Set mouse cursor position for the most common cases to avoid boilerplate.
         if (mSource == AINPUT_SOURCE_MOUSE &&
-            !MotionEvent::isValidCursorPosition(mRawXCursorPosition, mRawYCursorPosition) &&
-            mPointers.size() == 1) {
+            !MotionEvent::isValidCursorPosition(mRawXCursorPosition, mRawYCursorPosition)) {
             mRawXCursorPosition = pointerCoords[0].getX();
             mRawYCursorPosition = pointerCoords[0].getY();
         }
diff --git a/services/surfaceflinger/Scheduler/EventThread.cpp b/services/surfaceflinger/Scheduler/EventThread.cpp
index af9acf3..281b0ae 100644
--- a/services/surfaceflinger/Scheduler/EventThread.cpp
+++ b/services/surfaceflinger/Scheduler/EventThread.cpp
@@ -612,6 +612,15 @@
                 preferredExpectedPresentationTime + multiplier * frameInterval;
         if (expectedPresentationTime >= preferredExpectedPresentationTime +
                     scheduler::VsyncConfig::kEarlyLatchMaxThreshold.count()) {
+            if (currentIndex == 0) {
+                ALOGW("%s: Expected present time is too far in the future but no timelines are "
+                      "valid. preferred EPT=%" PRId64 ", Calculated EPT=%" PRId64
+                      ", multiplier=%" PRId64 ", frameInterval=%" PRId64 ", threshold=%" PRId64,
+                      __func__, preferredExpectedPresentationTime, expectedPresentationTime,
+                      multiplier, frameInterval,
+                      static_cast<int64_t>(
+                              scheduler::VsyncConfig::kEarlyLatchMaxThreshold.count()));
+            }
             break;
         }
 
@@ -625,6 +634,20 @@
                  .expectedPresentationTime = expectedPresentationTime};
         currentIndex++;
     }
+
+    if (currentIndex == 0) {
+        ALOGW("%s: No timelines are valid. preferred EPT=%" PRId64 ", frameInterval=%" PRId64
+              ", threshold=%" PRId64,
+              __func__, preferredExpectedPresentationTime, frameInterval,
+              static_cast<int64_t>(scheduler::VsyncConfig::kEarlyLatchMaxThreshold.count()));
+        outVsyncEventData.frameTimelines[currentIndex] =
+                {.vsyncId = generateToken(timestamp, preferredDeadlineTimestamp,
+                                          preferredExpectedPresentationTime),
+                 .deadlineTimestamp = preferredDeadlineTimestamp,
+                 .expectedPresentationTime = preferredExpectedPresentationTime};
+        currentIndex++;
+    }
+
     outVsyncEventData.frameTimelinesLength = currentIndex;
 }
 
diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index e841954..06d6ef0 100644
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -4405,7 +4405,8 @@
         const Vector<DisplayState>& displays, uint32_t flags, const sp<IBinder>& applyToken,
         InputWindowCommands inputWindowCommands, int64_t desiredPresentTime, bool isAutoTimestamp,
         const std::vector<client_cache_t>& uncacheBuffers, bool hasListenerCallbacks,
-        const std::vector<ListenerCallbacks>& listenerCallbacks, uint64_t transactionId) {
+        const std::vector<ListenerCallbacks>& listenerCallbacks, uint64_t transactionId,
+        const std::vector<uint64_t>& mergedTransactionIds) {
     ATRACE_CALL();
 
     IPCThreadState* ipc = IPCThreadState::self();
@@ -4494,7 +4495,8 @@
                            listenerCallbacks,
                            originPid,
                            originUid,
-                           transactionId};
+                           transactionId,
+                           mergedTransactionIds};
 
     if (mTransactionTracing) {
         mTransactionTracing->addQueuedTransaction(state);
@@ -8090,7 +8092,7 @@
                 });
     }
     if (mLegacyFrontEndEnabled && !mLayerLifecycleManagerEnabled) {
-        mDrawingState.traverseInZOrder([&refreshArgs, cursorOnly, &layers](Layer* layer) {
+        auto moveSnapshots = [&layers, &refreshArgs, cursorOnly](Layer* layer) {
             if (const auto& layerFE = layer->getCompositionEngineLayerFE()) {
                 if (cursorOnly &&
                     layer->getLayerSnapshot()->compositionType !=
@@ -8101,7 +8103,22 @@
                 refreshArgs.layers.push_back(layerFE);
                 layers.emplace_back(layer, layerFE.get());
             }
-        });
+        };
+
+        if (cursorOnly || !mVisibleRegionsDirty) {
+            // for hot path avoid traversals by walking though the previous composition list
+            for (sp<Layer> layer : mPreviouslyComposedLayers) {
+                moveSnapshots(layer.get());
+            }
+        } else {
+            mPreviouslyComposedLayers.clear();
+            mDrawingState.traverseInZOrder(
+                    [&moveSnapshots](Layer* layer) { moveSnapshots(layer); });
+            mPreviouslyComposedLayers.reserve(layers.size());
+            for (auto [layer, _] : layers) {
+                mPreviouslyComposedLayers.push_back(sp<Layer>::fromExisting(layer));
+            }
+        }
     }
 
     return layers;
diff --git a/services/surfaceflinger/SurfaceFlinger.h b/services/surfaceflinger/SurfaceFlinger.h
index 8e886fb..5a6f22c 100644
--- a/services/surfaceflinger/SurfaceFlinger.h
+++ b/services/surfaceflinger/SurfaceFlinger.h
@@ -515,15 +515,13 @@
     }
 
     sp<IBinder> getPhysicalDisplayToken(PhysicalDisplayId displayId) const;
-    status_t setTransactionState(const FrameTimelineInfo& frameTimelineInfo,
-                                 Vector<ComposerState>& state, const Vector<DisplayState>& displays,
-                                 uint32_t flags, const sp<IBinder>& applyToken,
-                                 InputWindowCommands inputWindowCommands,
-                                 int64_t desiredPresentTime, bool isAutoTimestamp,
-                                 const std::vector<client_cache_t>& uncacheBuffers,
-                                 bool hasListenerCallbacks,
-                                 const std::vector<ListenerCallbacks>& listenerCallbacks,
-                                 uint64_t transactionId) override;
+    status_t setTransactionState(
+            const FrameTimelineInfo& frameTimelineInfo, Vector<ComposerState>& state,
+            const Vector<DisplayState>& displays, uint32_t flags, const sp<IBinder>& applyToken,
+            InputWindowCommands inputWindowCommands, int64_t desiredPresentTime,
+            bool isAutoTimestamp, const std::vector<client_cache_t>& uncacheBuffers,
+            bool hasListenerCallbacks, const std::vector<ListenerCallbacks>& listenerCallbacks,
+            uint64_t transactionId, const std::vector<uint64_t>& mergedTransactionIds) override;
     void bootFinished();
     virtual status_t getSupportedFrameTimestamps(std::vector<FrameEvent>* outSupported) const;
     sp<IDisplayEventConnection> createDisplayEventConnection(
@@ -1184,6 +1182,11 @@
     std::unordered_set<sp<Layer>, SpHash<Layer>> mLayersWithBuffersRemoved;
     // Tracks layers that need to update a display's dirty region.
     std::vector<sp<Layer>> mLayersPendingRefresh;
+    // Sorted list of layers that were composed during previous frame. This is used to
+    // avoid an expensive traversal of the layer hierarchy when there are no
+    // visible region changes. Because this is a list of strong pointers, this will
+    // extend the life of the layer but this list is only updated in the main thread.
+    std::vector<sp<Layer>> mPreviouslyComposedLayers;
 
     BootStage mBootStage = BootStage::BOOTLOADER;
 
diff --git a/services/surfaceflinger/Tracing/TransactionProtoParser.cpp b/services/surfaceflinger/Tracing/TransactionProtoParser.cpp
index 19334e3..dafdc8a 100644
--- a/services/surfaceflinger/Tracing/TransactionProtoParser.cpp
+++ b/services/surfaceflinger/Tracing/TransactionProtoParser.cpp
@@ -69,6 +69,13 @@
     for (auto& displayState : t.displays) {
         proto.mutable_display_changes()->Add(std::move(toProto(displayState)));
     }
+
+    proto.mutable_merged_transaction_ids()->Reserve(
+            static_cast<int32_t>(t.mergedTransactionIds.size()));
+    for (auto& mergedTransactionId : t.mergedTransactionIds) {
+        proto.mutable_merged_transaction_ids()->Add(mergedTransactionId);
+    }
+
     return proto;
 }
 
diff --git a/services/surfaceflinger/TransactionState.h b/services/surfaceflinger/TransactionState.h
index 62a7dfd..7132a59 100644
--- a/services/surfaceflinger/TransactionState.h
+++ b/services/surfaceflinger/TransactionState.h
@@ -56,7 +56,8 @@
                      int64_t desiredPresentTime, bool isAutoTimestamp,
                      std::vector<uint64_t> uncacheBufferIds, int64_t postTime,
                      bool hasListenerCallbacks, std::vector<ListenerCallbacks> listenerCallbacks,
-                     int originPid, int originUid, uint64_t transactionId)
+                     int originPid, int originUid, uint64_t transactionId,
+                     std::vector<uint64_t> mergedTransactionIds)
           : frameTimelineInfo(frameTimelineInfo),
             states(std::move(composerStates)),
             displays(displayStates),
@@ -71,7 +72,8 @@
             listenerCallbacks(listenerCallbacks),
             originPid(originPid),
             originUid(originUid),
-            id(transactionId) {}
+            id(transactionId),
+            mergedTransactionIds(std::move(mergedTransactionIds)) {}
 
     // Invokes `void(const layer_state_t&)` visitor for matching layers.
     template <typename Visitor>
@@ -131,6 +133,7 @@
     int originUid;
     uint64_t id;
     bool sentFenceTimeoutWarning = false;
+    std::vector<uint64_t> mergedTransactionIds;
 };
 
 } // namespace android
diff --git a/services/surfaceflinger/fuzzer/surfaceflinger_fuzzer.cpp b/services/surfaceflinger/fuzzer/surfaceflinger_fuzzer.cpp
index ce4d18f..80943b5 100644
--- a/services/surfaceflinger/fuzzer/surfaceflinger_fuzzer.cpp
+++ b/services/surfaceflinger/fuzzer/surfaceflinger_fuzzer.cpp
@@ -185,11 +185,12 @@
     bool hasListenerCallbacks = mFdp.ConsumeBool();
     std::vector<ListenerCallbacks> listenerCallbacks{};
     uint64_t transactionId = mFdp.ConsumeIntegral<uint64_t>();
+    std::vector<uint64_t> mergedTransactionIds{};
 
     mTestableFlinger.setTransactionState(FrameTimelineInfo{}, states, displays, flags, applyToken,
                                          InputWindowCommands{}, desiredPresentTime, isAutoTimestamp,
-                                         {}, hasListenerCallbacks, listenerCallbacks,
-                                         transactionId);
+                                         {}, hasListenerCallbacks, listenerCallbacks, transactionId,
+                                         mergedTransactionIds);
 }
 
 void SurfaceFlingerFuzzer::setDisplayStateLocked() {
diff --git a/services/surfaceflinger/fuzzer/surfaceflinger_fuzzers_utils.h b/services/surfaceflinger/fuzzer/surfaceflinger_fuzzers_utils.h
index 5c152b5..42b3879 100644
--- a/services/surfaceflinger/fuzzer/surfaceflinger_fuzzers_utils.h
+++ b/services/surfaceflinger/fuzzer/surfaceflinger_fuzzers_utils.h
@@ -737,19 +737,18 @@
         return mFlinger->mTransactionHandler.mPendingTransactionQueues;
     }
 
-    auto setTransactionState(const FrameTimelineInfo& frameTimelineInfo,
-                             Vector<ComposerState>& states, const Vector<DisplayState>& displays,
-                             uint32_t flags, const sp<IBinder>& applyToken,
-                             const InputWindowCommands& inputWindowCommands,
-                             int64_t desiredPresentTime, bool isAutoTimestamp,
-                             const std::vector<client_cache_t>& uncacheBuffers,
-                             bool hasListenerCallbacks,
-                             std::vector<ListenerCallbacks>& listenerCallbacks,
-                             uint64_t transactionId) {
+    auto setTransactionState(
+            const FrameTimelineInfo& frameTimelineInfo, Vector<ComposerState>& states,
+            const Vector<DisplayState>& displays, uint32_t flags, const sp<IBinder>& applyToken,
+            const InputWindowCommands& inputWindowCommands, int64_t desiredPresentTime,
+            bool isAutoTimestamp, const std::vector<client_cache_t>& uncacheBuffers,
+            bool hasListenerCallbacks, std::vector<ListenerCallbacks>& listenerCallbacks,
+            uint64_t transactionId, const std::vector<uint64_t>& mergedTransactionIds) {
         return mFlinger->setTransactionState(frameTimelineInfo, states, displays, flags, applyToken,
                                              inputWindowCommands, desiredPresentTime,
                                              isAutoTimestamp, uncacheBuffers, hasListenerCallbacks,
-                                             listenerCallbacks, transactionId);
+                                             listenerCallbacks, transactionId,
+                                             mergedTransactionIds);
     }
 
     auto flushTransactionQueues() {
diff --git a/services/surfaceflinger/layerproto/transactions.proto b/services/surfaceflinger/layerproto/transactions.proto
index 2c4eb10..b0cee9b 100644
--- a/services/surfaceflinger/layerproto/transactions.proto
+++ b/services/surfaceflinger/layerproto/transactions.proto
@@ -100,6 +100,7 @@
     uint64 transaction_id = 6;
     repeated LayerState layer_changes = 7;
     repeated DisplayState display_changes = 8;
+    repeated uint64 merged_transaction_ids = 9;
 }
 
 // Keep insync with layer_state_t
diff --git a/services/surfaceflinger/tests/unittests/CompositionTest.cpp b/services/surfaceflinger/tests/unittests/CompositionTest.cpp
index 6ca21bd..e8a9cfe 100644
--- a/services/surfaceflinger/tests/unittests/CompositionTest.cpp
+++ b/services/surfaceflinger/tests/unittests/CompositionTest.cpp
@@ -680,6 +680,9 @@
                 NativeHandle::create(reinterpret_cast<native_handle_t*>(DEFAULT_SIDEBAND_STREAM),
                                      false);
         test->mFlinger.setLayerSidebandStream(layer, stream);
+        auto& layerDrawingState = test->mFlinger.mutableLayerDrawingState(layer);
+        layerDrawingState.crop =
+                Rect(0, 0, SidebandLayerProperties::HEIGHT, SidebandLayerProperties::WIDTH);
     }
 
     static void setupHwcSetSourceCropBufferCallExpectations(CompositionTest* test) {
@@ -814,6 +817,7 @@
         Mock::VerifyAndClear(test->mComposer);
 
         test->mFlinger.mutableDrawingState().layersSortedByZ.add(layer);
+        test->mFlinger.mutableVisibleRegionsDirty() = true;
     }
 
     static void cleanupInjectedLayers(CompositionTest* test) {
@@ -822,6 +826,7 @@
 
         test->mDisplay->getCompositionDisplay()->clearOutputLayers();
         test->mFlinger.mutableDrawingState().layersSortedByZ.clear();
+        test->mFlinger.mutablePreviouslyComposedLayers().clear();
 
         // Layer should be unregistered with scheduler.
         test->mFlinger.commit();
diff --git a/services/surfaceflinger/tests/unittests/TestableSurfaceFlinger.h b/services/surfaceflinger/tests/unittests/TestableSurfaceFlinger.h
index 3a8e2ff..833984f 100644
--- a/services/surfaceflinger/tests/unittests/TestableSurfaceFlinger.h
+++ b/services/surfaceflinger/tests/unittests/TestableSurfaceFlinger.h
@@ -483,19 +483,18 @@
         return mFlinger->mTransactionHandler.mPendingTransactionCount.load();
     }
 
-    auto setTransactionState(const FrameTimelineInfo& frameTimelineInfo,
-                             Vector<ComposerState>& states, const Vector<DisplayState>& displays,
-                             uint32_t flags, const sp<IBinder>& applyToken,
-                             const InputWindowCommands& inputWindowCommands,
-                             int64_t desiredPresentTime, bool isAutoTimestamp,
-                             const std::vector<client_cache_t>& uncacheBuffers,
-                             bool hasListenerCallbacks,
-                             std::vector<ListenerCallbacks>& listenerCallbacks,
-                             uint64_t transactionId) {
+    auto setTransactionState(
+            const FrameTimelineInfo& frameTimelineInfo, Vector<ComposerState>& states,
+            const Vector<DisplayState>& displays, uint32_t flags, const sp<IBinder>& applyToken,
+            const InputWindowCommands& inputWindowCommands, int64_t desiredPresentTime,
+            bool isAutoTimestamp, const std::vector<client_cache_t>& uncacheBuffers,
+            bool hasListenerCallbacks, std::vector<ListenerCallbacks>& listenerCallbacks,
+            uint64_t transactionId, const std::vector<uint64_t>& mergedTransactionIds) {
         return mFlinger->setTransactionState(frameTimelineInfo, states, displays, flags, applyToken,
                                              inputWindowCommands, desiredPresentTime,
                                              isAutoTimestamp, uncacheBuffers, hasListenerCallbacks,
-                                             listenerCallbacks, transactionId);
+                                             listenerCallbacks, transactionId,
+                                             mergedTransactionIds);
     }
 
     auto setTransactionStateInternal(TransactionState& transaction) {
@@ -605,6 +604,7 @@
     auto& mutablePhysicalDisplays() { return mFlinger->mPhysicalDisplays; }
     auto& mutableDrawingState() { return mFlinger->mDrawingState; }
     auto& mutableGeometryDirty() { return mFlinger->mGeometryDirty; }
+    auto& mutableVisibleRegionsDirty() { return mFlinger->mVisibleRegionsDirty; }
     auto& mutableMainThreadId() { return mFlinger->mMainThreadId; }
     auto& mutablePendingHotplugEvents() { return mFlinger->mPendingHotplugEvents; }
     auto& mutableTexturePool() { return mFlinger->mTexturePool; }
@@ -616,6 +616,7 @@
     auto& mutableHwcPhysicalDisplayIdMap() { return getHwComposer().mPhysicalDisplayIdMap; }
     auto& mutablePrimaryHwcDisplayId() { return getHwComposer().mPrimaryHwcDisplayId; }
     auto& mutableActiveDisplayId() { return mFlinger->mActiveDisplayId; }
+    auto& mutablePreviouslyComposedLayers() { return mFlinger->mPreviouslyComposedLayers; }
 
     auto& mutableActiveDisplayRotationFlags() {
         return SurfaceFlinger::sActiveDisplayRotationFlags;
diff --git a/services/surfaceflinger/tests/unittests/TransactionApplicationTest.cpp b/services/surfaceflinger/tests/unittests/TransactionApplicationTest.cpp
index 6a641b3..afb8efb 100644
--- a/services/surfaceflinger/tests/unittests/TransactionApplicationTest.cpp
+++ b/services/surfaceflinger/tests/unittests/TransactionApplicationTest.cpp
@@ -73,6 +73,7 @@
         FrameTimelineInfo frameTimelineInfo;
         std::vector<client_cache_t> uncacheBuffers;
         uint64_t id = static_cast<uint64_t>(-1);
+        std::vector<uint64_t> mergedTransactionIds;
         static_assert(0xffffffffffffffff == static_cast<uint64_t>(-1));
     };
 
@@ -108,7 +109,7 @@
                                      transaction.applyToken, transaction.inputWindowCommands,
                                      transaction.desiredPresentTime, transaction.isAutoTimestamp,
                                      transaction.uncacheBuffers, mHasListenerCallbacks, mCallbacks,
-                                     transaction.id);
+                                     transaction.id, transaction.mergedTransactionIds);
 
         // If transaction is synchronous, SF applyTransactionState should time out (5s) wating for
         // SF to commit the transaction. If this is animation, it should not time out waiting.
@@ -135,7 +136,7 @@
                                      transaction.applyToken, transaction.inputWindowCommands,
                                      transaction.desiredPresentTime, transaction.isAutoTimestamp,
                                      transaction.uncacheBuffers, mHasListenerCallbacks, mCallbacks,
-                                     transaction.id);
+                                     transaction.id, transaction.mergedTransactionIds);
 
         nsecs_t returnedTime = systemTime();
         EXPECT_LE(returnedTime, applicationSentTime + TRANSACTION_TIMEOUT);
@@ -166,7 +167,7 @@
                                      transactionA.applyToken, transactionA.inputWindowCommands,
                                      transactionA.desiredPresentTime, transactionA.isAutoTimestamp,
                                      transactionA.uncacheBuffers, mHasListenerCallbacks, mCallbacks,
-                                     transactionA.id);
+                                     transactionA.id, transactionA.mergedTransactionIds);
 
         // This thread should not have been blocked by the above transaction
         // (5s is the timeout period that applyTransactionState waits for SF to
@@ -181,7 +182,7 @@
                                      transactionB.applyToken, transactionB.inputWindowCommands,
                                      transactionB.desiredPresentTime, transactionB.isAutoTimestamp,
                                      transactionB.uncacheBuffers, mHasListenerCallbacks, mCallbacks,
-                                     transactionB.id);
+                                     transactionB.id, transactionB.mergedTransactionIds);
 
         // this thread should have been blocked by the above transaction
         // if this is an animation, this thread should be blocked for 5s
@@ -218,7 +219,8 @@
                                  transactionA.displays, transactionA.flags, transactionA.applyToken,
                                  transactionA.inputWindowCommands, transactionA.desiredPresentTime,
                                  transactionA.isAutoTimestamp, transactionA.uncacheBuffers,
-                                 mHasListenerCallbacks, mCallbacks, transactionA.id);
+                                 mHasListenerCallbacks, mCallbacks, transactionA.id,
+                                 transactionA.mergedTransactionIds);
 
     auto& transactionQueue = mFlinger.getTransactionQueue();
     ASSERT_FALSE(transactionQueue.isEmpty());
@@ -238,7 +240,8 @@
                                  transactionA.displays, transactionA.flags, transactionA.applyToken,
                                  transactionA.inputWindowCommands, transactionA.desiredPresentTime,
                                  transactionA.isAutoTimestamp, transactionA.uncacheBuffers,
-                                 mHasListenerCallbacks, mCallbacks, transactionA.id);
+                                 mHasListenerCallbacks, mCallbacks, transactionA.id,
+                                 transactionA.mergedTransactionIds);
 
     auto& transactionQueue = mFlinger.getTransactionQueue();
     ASSERT_FALSE(transactionQueue.isEmpty());
@@ -251,7 +254,8 @@
     mFlinger.setTransactionState(empty.frameTimelineInfo, empty.states, empty.displays, empty.flags,
                                  empty.applyToken, empty.inputWindowCommands,
                                  empty.desiredPresentTime, empty.isAutoTimestamp,
-                                 empty.uncacheBuffers, mHasListenerCallbacks, mCallbacks, empty.id);
+                                 empty.uncacheBuffers, mHasListenerCallbacks, mCallbacks, empty.id,
+                                 empty.mergedTransactionIds);
 
     // flush transaction queue should flush as desiredPresentTime has
     // passed
@@ -388,7 +392,8 @@
                                               transaction.desiredPresentTime,
                                               transaction.isAutoTimestamp, {}, systemTime(),
                                               mHasListenerCallbacks, mCallbacks, getpid(),
-                                              static_cast<int>(getuid()), transaction.id);
+                                              static_cast<int>(getuid()), transaction.id,
+                                              transaction.mergedTransactionIds);
             mFlinger.setTransactionStateInternal(transactionState);
         }
         mFlinger.flushTransactionQueues();
@@ -1083,4 +1088,137 @@
     EXPECT_EQ(transactionsReadyToBeApplied.front().id, 42u);
 }
 
+TEST(TransactionHandlerTest, TransactionsKeepTrackOfDirectMerges) {
+    SurfaceComposerClient::Transaction transaction1, transaction2, transaction3, transaction4;
+
+    uint64_t transaction2Id = transaction2.getId();
+    uint64_t transaction3Id = transaction3.getId();
+    EXPECT_NE(transaction2Id, transaction3Id);
+
+    transaction1.merge(std::move(transaction2));
+    transaction1.merge(std::move(transaction3));
+
+    EXPECT_EQ(transaction1.getMergedTransactionIds().size(), 2u);
+    EXPECT_EQ(transaction1.getMergedTransactionIds()[0], transaction3Id);
+    EXPECT_EQ(transaction1.getMergedTransactionIds()[1], transaction2Id);
+}
+
+TEST(TransactionHandlerTest, TransactionsKeepTrackOfIndirectMerges) {
+    SurfaceComposerClient::Transaction transaction1, transaction2, transaction3, transaction4;
+
+    uint64_t transaction2Id = transaction2.getId();
+    uint64_t transaction3Id = transaction3.getId();
+    uint64_t transaction4Id = transaction4.getId();
+    EXPECT_NE(transaction2Id, transaction3Id);
+    EXPECT_NE(transaction2Id, transaction4Id);
+    EXPECT_NE(transaction3Id, transaction4Id);
+
+    transaction4.merge(std::move(transaction2));
+    transaction4.merge(std::move(transaction3));
+
+    EXPECT_EQ(transaction4.getMergedTransactionIds().size(), 2u);
+    EXPECT_EQ(transaction4.getMergedTransactionIds()[0], transaction3Id);
+    EXPECT_EQ(transaction4.getMergedTransactionIds()[1], transaction2Id);
+
+    transaction1.merge(std::move(transaction4));
+
+    EXPECT_EQ(transaction1.getMergedTransactionIds().size(), 3u);
+    EXPECT_EQ(transaction1.getMergedTransactionIds()[0], transaction4Id);
+    EXPECT_EQ(transaction1.getMergedTransactionIds()[1], transaction3Id);
+    EXPECT_EQ(transaction1.getMergedTransactionIds()[2], transaction2Id);
+}
+
+TEST(TransactionHandlerTest, TransactionMergesAreCleared) {
+    SurfaceComposerClient::Transaction transaction1, transaction2, transaction3;
+
+    transaction1.merge(std::move(transaction2));
+    transaction1.merge(std::move(transaction3));
+
+    EXPECT_EQ(transaction1.getMergedTransactionIds().size(), 2u);
+
+    transaction1.clear();
+
+    EXPECT_EQ(transaction1.getMergedTransactionIds().empty(), true);
+}
+
+TEST(TransactionHandlerTest, TransactionMergesAreCapped) {
+    SurfaceComposerClient::Transaction transaction;
+    std::vector<uint64_t> mergedTransactionIds;
+
+    for (uint i = 0; i < 20u; i++) {
+        SurfaceComposerClient::Transaction transactionToMerge;
+        mergedTransactionIds.push_back(transactionToMerge.getId());
+        transaction.merge(std::move(transactionToMerge));
+    }
+
+    // Keeps latest 10 merges in order of merge recency
+    EXPECT_EQ(transaction.getMergedTransactionIds().size(), 10u);
+    for (uint i = 0; i < 10u; i++) {
+        EXPECT_EQ(transaction.getMergedTransactionIds()[i],
+                  mergedTransactionIds[mergedTransactionIds.size() - 1 - i]);
+    }
+}
+
+TEST(TransactionHandlerTest, KeepsMergesFromMoreRecentMerge) {
+    SurfaceComposerClient::Transaction transaction1, transaction2, transaction3;
+    std::vector<uint64_t> mergedTransactionIds1, mergedTransactionIds2, mergedTransactionIds3;
+    uint64_t transaction2Id = transaction2.getId();
+    uint64_t transaction3Id = transaction3.getId();
+
+    for (uint i = 0; i < 20u; i++) {
+        SurfaceComposerClient::Transaction transactionToMerge;
+        mergedTransactionIds1.push_back(transactionToMerge.getId());
+        transaction1.merge(std::move(transactionToMerge));
+    }
+
+    for (uint i = 0; i < 5u; i++) {
+        SurfaceComposerClient::Transaction transactionToMerge;
+        mergedTransactionIds2.push_back(transactionToMerge.getId());
+        transaction2.merge(std::move(transactionToMerge));
+    }
+
+    transaction1.merge(std::move(transaction2));
+    EXPECT_EQ(transaction1.getMergedTransactionIds().size(), 10u);
+    EXPECT_EQ(transaction1.getMergedTransactionIds()[0], transaction2Id);
+    for (uint i = 0; i < 5u; i++) {
+        EXPECT_EQ(transaction1.getMergedTransactionIds()[i + 1u],
+                  mergedTransactionIds2[mergedTransactionIds2.size() - 1 - i]);
+    }
+    for (uint i = 0; i < 4u; i++) {
+        EXPECT_EQ(transaction1.getMergedTransactionIds()[i + 6u],
+                  mergedTransactionIds1[mergedTransactionIds1.size() - 1 - i]);
+    }
+
+    for (uint i = 0; i < 20u; i++) {
+        SurfaceComposerClient::Transaction transactionToMerge;
+        mergedTransactionIds3.push_back(transactionToMerge.getId());
+        transaction3.merge(std::move(transactionToMerge));
+    }
+
+    transaction1.merge(std::move(transaction3));
+    EXPECT_EQ(transaction1.getMergedTransactionIds().size(), 10u);
+    EXPECT_EQ(transaction1.getMergedTransactionIds()[0], transaction3Id);
+    for (uint i = 0; i < 9u; i++) {
+        EXPECT_EQ(transaction1.getMergedTransactionIds()[i + 1],
+                  mergedTransactionIds3[mergedTransactionIds3.size() - 1 - i]);
+    }
+}
+
+TEST(TransactionHandlerTest, CanAddTransactionWithFullMergedIds) {
+    SurfaceComposerClient::Transaction transaction1, transaction2;
+    for (uint i = 0; i < 20u; i++) {
+        SurfaceComposerClient::Transaction transactionToMerge;
+        transaction1.merge(std::move(transactionToMerge));
+    }
+
+    EXPECT_EQ(transaction1.getMergedTransactionIds().size(), 10u);
+
+    auto transaction1Id = transaction1.getId();
+    transaction2.merge(std::move(transaction1));
+    EXPECT_EQ(transaction2.getMergedTransactionIds().size(), 10u);
+    auto mergedTransactionIds = transaction2.getMergedTransactionIds();
+    EXPECT_TRUE(std::count(mergedTransactionIds.begin(), mergedTransactionIds.end(),
+                           transaction1Id) > 0);
+}
+
 } // namespace android
diff --git a/services/surfaceflinger/tests/unittests/TransactionTracingTest.cpp b/services/surfaceflinger/tests/unittests/TransactionTracingTest.cpp
index 82aac7e..92411a7 100644
--- a/services/surfaceflinger/tests/unittests/TransactionTracingTest.cpp
+++ b/services/surfaceflinger/tests/unittests/TransactionTracingTest.cpp
@@ -67,8 +67,14 @@
         ASSERT_EQ(actualProto.transactions().size(),
                   static_cast<int32_t>(expectedTransactions.size()));
         for (uint32_t i = 0; i < expectedTransactions.size(); i++) {
-            EXPECT_EQ(actualProto.transactions(static_cast<int32_t>(i)).pid(),
-                      expectedTransactions[i].originPid);
+            const auto expectedTransaction = expectedTransactions[i];
+            const auto protoTransaction = actualProto.transactions(static_cast<int32_t>(i));
+            EXPECT_EQ(protoTransaction.transaction_id(), expectedTransaction.id);
+            EXPECT_EQ(protoTransaction.pid(), expectedTransaction.originPid);
+            for (uint32_t i = 0; i < expectedTransaction.mergedTransactionIds.size(); i++) {
+                EXPECT_EQ(protoTransaction.merged_transaction_ids(static_cast<int32_t>(i)),
+                          expectedTransaction.mergedTransactionIds[i]);
+            }
         }
     }
 
@@ -92,6 +98,7 @@
         TransactionState transaction;
         transaction.id = i;
         transaction.originPid = static_cast<int32_t>(i);
+        transaction.mergedTransactionIds = std::vector<uint64_t>{i + 100, i + 102};
         transactions.emplace_back(transaction);
         mTracing.addQueuedTransaction(transaction);
     }