Move MotionEvent#split implementation to native

There is already a native implementation of split in InputDispatcher.
Prevent code duplication by moving the Java impl to native. The Java
impl is not correct, because it cannot access all values like the
transforms to initialize the split event with.

Bug: 326171104
Test: atest libinput_tests
Test: atest inputflinger_tests
Change-Id: I6230b6aa0696dcfc275a5a14ab4af3d4b7bd0b45

5 files changed, 282 insertions, 69 deletions

diff --git a/include/input/Input.h b/include/input/Input.h
index a84dcfc63c..374254fc84 100644
--- a/include/input/Input.h
+++ b/include/input/Input.h
@@ -870,6 +870,10 @@ public:
 
     void copyFrom(const MotionEvent* other, bool keepHistory);
 
+    // Initialize this event by keeping only the pointers from "other" that are in splitPointerIds.
+    void splitFrom(const MotionEvent& other, std::bitset<MAX_POINTER_ID + 1> splitPointerIds,
+                   int32_t newEventId);
+
     void addSample(
             nsecs_t eventTime,
             const PointerCoords* pointerCoords);
@@ -910,6 +914,11 @@ public:
 
     static std::string actionToString(int32_t action);
 
+    static std::tuple<int32_t /*action*/, std::vector<PointerProperties>,
+                      std::vector<PointerCoords>>
+    split(int32_t action, int32_t flags, int32_t historySize, const std::vector<PointerProperties>&,
+          const std::vector<PointerCoords>&, std::bitset<MAX_POINTER_ID + 1> splitPointerIds);
+
     // MotionEvent will transform various axes in different ways, based on the source. For
     // example, the x and y axes will not have any offsets/translations applied if it comes from a
     // relative mouse device (since SOURCE_RELATIVE_MOUSE is a non-pointer source). These methods
diff --git a/include/input/InputEventBuilders.h b/include/input/InputEventBuilders.h
index 2d23b97386..c0c5e2412d 100644
--- a/include/input/InputEventBuilders.h
+++ b/include/input/InputEventBuilders.h
@@ -118,6 +118,16 @@ public:
         return *this;
     }
 
+    MotionEventBuilder& transform(ui::Transform t) {
+        mTransform = t;
+        return *this;
+    }
+
+    MotionEventBuilder& rawTransform(ui::Transform t) {
+        mRawTransform = t;
+        return *this;
+    }
+
     MotionEvent build() {
         std::vector<PointerProperties> pointerProperties;
         std::vector<PointerCoords> pointerCoords;
@@ -134,12 +144,11 @@ public:
         }
 
         MotionEvent event;
-        static const ui::Transform kIdentityTransform;
         event.initialize(InputEvent::nextId(), mDeviceId, mSource, mDisplayId, INVALID_HMAC,
                          mAction, mActionButton, mFlags, /*edgeFlags=*/0, AMETA_NONE, mButtonState,
-                         MotionClassification::NONE, kIdentityTransform,
+                         MotionClassification::NONE, mTransform,
                          /*xPrecision=*/0, /*yPrecision=*/0, mRawXCursorPosition,
-                         mRawYCursorPosition, kIdentityTransform, mDownTime, mEventTime,
+                         mRawYCursorPosition, mRawTransform, mDownTime, mEventTime,
                          mPointers.size(), pointerProperties.data(), pointerCoords.data());
         return event;
     }
@@ -156,6 +165,8 @@ private:
     int32_t mFlags{0};
     float mRawXCursorPosition{AMOTION_EVENT_INVALID_CURSOR_POSITION};
     float mRawYCursorPosition{AMOTION_EVENT_INVALID_CURSOR_POSITION};
+    ui::Transform mTransform;
+    ui::Transform mRawTransform;
 
     std::vector<PointerBuilder> mPointers;
 };
diff --git a/libs/input/Input.cpp b/libs/input/Input.cpp
index 9e0ce1db33..d58fb42f05 100644
--- a/libs/input/Input.cpp
+++ b/libs/input/Input.cpp
@@ -60,6 +60,45 @@ bool shouldDisregardOffset(uint32_t source) {
     return !isFromSource(source, AINPUT_SOURCE_CLASS_POINTER);
 }
 
+int32_t resolveActionForSplitMotionEvent(
+        int32_t action, int32_t flags, const std::vector<PointerProperties>& pointerProperties,
+        const std::vector<PointerProperties>& splitPointerProperties) {
+    LOG_ALWAYS_FATAL_IF(splitPointerProperties.empty());
+    const auto maskedAction = MotionEvent::getActionMasked(action);
+    if (maskedAction != AMOTION_EVENT_ACTION_POINTER_DOWN &&
+        maskedAction != AMOTION_EVENT_ACTION_POINTER_UP) {
+        // The action is unaffected by splitting this motion event.
+        return action;
+    }
+    const auto actionIndex = MotionEvent::getActionIndex(action);
+    if (CC_UNLIKELY(actionIndex >= pointerProperties.size())) {
+        LOG(FATAL) << "Action index is out of bounds, index: " << actionIndex;
+    }
+
+    const auto affectedPointerId = pointerProperties[actionIndex].id;
+    std::optional<uint32_t> splitActionIndex;
+    for (uint32_t i = 0; i < splitPointerProperties.size(); i++) {
+        if (affectedPointerId == splitPointerProperties[i].id) {
+            splitActionIndex = i;
+            break;
+        }
+    }
+    if (!splitActionIndex.has_value()) {
+        // The affected pointer is not part of the split motion event.
+        return AMOTION_EVENT_ACTION_MOVE;
+    }
+
+    if (splitPointerProperties.size() > 1) {
+        return maskedAction | (*splitActionIndex << AMOTION_EVENT_ACTION_POINTER_INDEX_SHIFT);
+    }
+
+    if (maskedAction == AMOTION_EVENT_ACTION_POINTER_UP) {
+        return ((flags & AMOTION_EVENT_FLAG_CANCELED) != 0) ? AMOTION_EVENT_ACTION_CANCEL
+                                                            : AMOTION_EVENT_ACTION_UP;
+    }
+    return AMOTION_EVENT_ACTION_DOWN;
+}
+
 } // namespace
 
 const char* motionClassificationToString(MotionClassification classification) {
@@ -584,6 +623,28 @@ void MotionEvent::copyFrom(const MotionEvent* other, bool keepHistory) {
     }
 }
 
+void MotionEvent::splitFrom(const android::MotionEvent& other,
+                            std::bitset<MAX_POINTER_ID + 1> splitPointerIds, int32_t newEventId) {
+    // TODO(b/327503168): The down time should be a parameter to the split function, because only
+    //   the caller can know when the first event went down on the target.
+    const nsecs_t splitDownTime = other.mDownTime;
+
+    auto [action, pointerProperties, pointerCoords] =
+            split(other.getAction(), other.getFlags(), other.getHistorySize(),
+                  other.mPointerProperties, other.mSamplePointerCoords, splitPointerIds);
+
+    // Initialize the event with zero pointers, and manually set the split pointers.
+    initialize(newEventId, other.mDeviceId, other.mSource, other.mDisplayId, /*hmac=*/{}, action,
+               other.mActionButton, other.mFlags, other.mEdgeFlags, other.mMetaState,
+               other.mButtonState, other.mClassification, other.mTransform, other.mXPrecision,
+               other.mYPrecision, other.mRawXCursorPosition, other.mRawYCursorPosition,
+               other.mRawTransform, splitDownTime, other.getEventTime(), /*pointerCount=*/0,
+               pointerProperties.data(), pointerCoords.data());
+    mPointerProperties = std::move(pointerProperties);
+    mSamplePointerCoords = std::move(pointerCoords);
+    mSampleEventTimes = other.mSampleEventTimes;
+}
+
 void MotionEvent::addSample(
         int64_t eventTime,
         const PointerCoords* pointerCoords) {
@@ -934,6 +995,45 @@ std::string MotionEvent::actionToString(int32_t action) {
     return android::base::StringPrintf("%" PRId32, action);
 }
 
+std::tuple<int32_t, std::vector<PointerProperties>, std::vector<PointerCoords>> MotionEvent::split(
+        int32_t action, int32_t flags, int32_t historySize,
+        const std::vector<PointerProperties>& pointerProperties,
+        const std::vector<PointerCoords>& pointerCoords,
+        std::bitset<MAX_POINTER_ID + 1> splitPointerIds) {
+    LOG_ALWAYS_FATAL_IF(!splitPointerIds.any());
+    const auto pointerCount = pointerProperties.size();
+    LOG_ALWAYS_FATAL_IF(pointerCoords.size() != (pointerCount * (historySize + 1)));
+    const auto splitCount = splitPointerIds.count();
+
+    std::vector<PointerProperties> splitPointerProperties;
+    std::vector<PointerCoords> splitPointerCoords;
+
+    for (uint32_t i = 0; i < pointerCount; i++) {
+        if (splitPointerIds.test(pointerProperties[i].id)) {
+            splitPointerProperties.emplace_back(pointerProperties[i]);
+        }
+    }
+    for (uint32_t i = 0; i < pointerCoords.size(); i++) {
+        if (splitPointerIds.test(pointerProperties[i % pointerCount].id)) {
+            splitPointerCoords.emplace_back(pointerCoords[i]);
+        }
+    }
+    LOG_ALWAYS_FATAL_IF(splitPointerCoords.size() !=
+                        (splitPointerProperties.size() * (historySize + 1)));
+
+    if (CC_UNLIKELY(splitPointerProperties.size() != splitCount)) {
+        LOG(FATAL) << "Cannot split MotionEvent: Requested splitting " << splitCount
+                   << " pointers from the original event, but the original event only contained "
+                   << splitPointerProperties.size() << " of those pointers.";
+    }
+
+    // TODO(b/327503168): Verify the splitDownTime here once it is used correctly.
+
+    const auto splitAction = resolveActionForSplitMotionEvent(action, flags, pointerProperties,
+                                                              splitPointerProperties);
+    return {splitAction, splitPointerProperties, splitPointerCoords};
+}
+
 // Apply the given transformation to the point without checking whether the entire transform
 // should be disregarded altogether for the provided source.
 static inline vec2 calculateTransformedXYUnchecked(uint32_t source, const ui::Transform& transform,
diff --git a/libs/input/tests/InputEvent_test.cpp b/libs/input/tests/InputEvent_test.cpp
index a9655730fc..540766d66c 100644
--- a/libs/input/tests/InputEvent_test.cpp
+++ b/libs/input/tests/InputEvent_test.cpp
@@ -23,6 +23,7 @@
 #include <gtest/gtest.h>
 #include <gui/constants.h>
 #include <input/Input.h>
+#include <input/InputEventBuilders.h>
 
 namespace android {
 
@@ -31,6 +32,18 @@ static constexpr int32_t DISPLAY_ID = ADISPLAY_ID_DEFAULT;
 
 static constexpr float EPSILON = MotionEvent::ROUNDING_PRECISION;
 
+static constexpr auto POINTER_0_DOWN =
+        AMOTION_EVENT_ACTION_POINTER_DOWN | (0 << AMOTION_EVENT_ACTION_POINTER_INDEX_SHIFT);
+
+static constexpr auto POINTER_1_DOWN =
+        AMOTION_EVENT_ACTION_POINTER_DOWN | (1 << AMOTION_EVENT_ACTION_POINTER_INDEX_SHIFT);
+
+static constexpr auto POINTER_0_UP =
+        AMOTION_EVENT_ACTION_POINTER_UP | (0 << AMOTION_EVENT_ACTION_POINTER_INDEX_SHIFT);
+
+static constexpr auto POINTER_1_UP =
+        AMOTION_EVENT_ACTION_POINTER_UP | (1 << AMOTION_EVENT_ACTION_POINTER_INDEX_SHIFT);
+
 class BaseTest : public testing::Test {
 protected:
     static constexpr std::array<uint8_t, 32> HMAC = {0,  1,  2,  3,  4,  5,  6,  7,  8,  9,  10,
@@ -554,6 +567,145 @@ TEST_F(MotionEventTest, CopyFrom_DoNotKeepHistory) {
     ASSERT_EQ(event.getX(0), copy.getX(0));
 }
 
+TEST_F(MotionEventTest, SplitPointerDown) {
+    MotionEvent event = MotionEventBuilder(POINTER_1_DOWN, AINPUT_SOURCE_TOUCHSCREEN)
+                                .downTime(ARBITRARY_DOWN_TIME)
+                                .pointer(PointerBuilder(/*id=*/4, ToolType::FINGER).x(4).y(4))
+                                .pointer(PointerBuilder(/*id=*/6, ToolType::FINGER).x(6).y(6))
+                                .pointer(PointerBuilder(/*id=*/8, ToolType::FINGER).x(8).y(8))
+                                .build();
+
+    MotionEvent splitDown;
+    std::bitset<MAX_POINTER_ID + 1> splitDownIds{};
+    splitDownIds.set(6, true);
+    splitDown.splitFrom(event, splitDownIds, /*eventId=*/42);
+    ASSERT_EQ(splitDown.getAction(), AMOTION_EVENT_ACTION_DOWN);
+    ASSERT_EQ(splitDown.getPointerCount(), 1u);
+    ASSERT_EQ(splitDown.getPointerId(0), 6);
+    ASSERT_EQ(splitDown.getX(0), 6);
+    ASSERT_EQ(splitDown.getY(0), 6);
+
+    MotionEvent splitPointerDown;
+    std::bitset<MAX_POINTER_ID + 1> splitPointerDownIds{};
+    splitPointerDownIds.set(6, true);
+    splitPointerDownIds.set(8, true);
+    splitPointerDown.splitFrom(event, splitPointerDownIds, /*eventId=*/42);
+    ASSERT_EQ(splitPointerDown.getAction(), POINTER_0_DOWN);
+    ASSERT_EQ(splitPointerDown.getPointerCount(), 2u);
+    ASSERT_EQ(splitPointerDown.getPointerId(0), 6);
+    ASSERT_EQ(splitPointerDown.getX(0), 6);
+    ASSERT_EQ(splitPointerDown.getY(0), 6);
+    ASSERT_EQ(splitPointerDown.getPointerId(1), 8);
+    ASSERT_EQ(splitPointerDown.getX(1), 8);
+    ASSERT_EQ(splitPointerDown.getY(1), 8);
+
+    MotionEvent splitMove;
+    std::bitset<MAX_POINTER_ID + 1> splitMoveIds{};
+    splitMoveIds.set(4, true);
+    splitMove.splitFrom(event, splitMoveIds, /*eventId=*/43);
+    ASSERT_EQ(splitMove.getAction(), AMOTION_EVENT_ACTION_MOVE);
+    ASSERT_EQ(splitMove.getPointerCount(), 1u);
+    ASSERT_EQ(splitMove.getPointerId(0), 4);
+    ASSERT_EQ(splitMove.getX(0), 4);
+    ASSERT_EQ(splitMove.getY(0), 4);
+}
+
+TEST_F(MotionEventTest, SplitPointerUp) {
+    MotionEvent event = MotionEventBuilder(POINTER_0_UP, AINPUT_SOURCE_TOUCHSCREEN)
+                                .downTime(ARBITRARY_DOWN_TIME)
+                                .pointer(PointerBuilder(/*id=*/4, ToolType::FINGER).x(4).y(4))
+                                .pointer(PointerBuilder(/*id=*/6, ToolType::FINGER).x(6).y(6))
+                                .pointer(PointerBuilder(/*id=*/8, ToolType::FINGER).x(8).y(8))
+                                .build();
+
+    MotionEvent splitUp;
+    std::bitset<MAX_POINTER_ID + 1> splitUpIds{};
+    splitUpIds.set(4, true);
+    splitUp.splitFrom(event, splitUpIds, /*eventId=*/42);
+    ASSERT_EQ(splitUp.getAction(), AMOTION_EVENT_ACTION_UP);
+    ASSERT_EQ(splitUp.getPointerCount(), 1u);
+    ASSERT_EQ(splitUp.getPointerId(0), 4);
+    ASSERT_EQ(splitUp.getX(0), 4);
+    ASSERT_EQ(splitUp.getY(0), 4);
+
+    MotionEvent splitPointerUp;
+    std::bitset<MAX_POINTER_ID + 1> splitPointerUpIds{};
+    splitPointerUpIds.set(4, true);
+    splitPointerUpIds.set(8, true);
+    splitPointerUp.splitFrom(event, splitPointerUpIds, /*eventId=*/42);
+    ASSERT_EQ(splitPointerUp.getAction(), POINTER_0_UP);
+    ASSERT_EQ(splitPointerUp.getPointerCount(), 2u);
+    ASSERT_EQ(splitPointerUp.getPointerId(0), 4);
+    ASSERT_EQ(splitPointerUp.getX(0), 4);
+    ASSERT_EQ(splitPointerUp.getY(0), 4);
+    ASSERT_EQ(splitPointerUp.getPointerId(1), 8);
+    ASSERT_EQ(splitPointerUp.getX(1), 8);
+    ASSERT_EQ(splitPointerUp.getY(1), 8);
+
+    MotionEvent splitMove;
+    std::bitset<MAX_POINTER_ID + 1> splitMoveIds{};
+    splitMoveIds.set(6, true);
+    splitMoveIds.set(8, true);
+    splitMove.splitFrom(event, splitMoveIds, /*eventId=*/43);
+    ASSERT_EQ(splitMove.getAction(), AMOTION_EVENT_ACTION_MOVE);
+    ASSERT_EQ(splitMove.getPointerCount(), 2u);
+    ASSERT_EQ(splitMove.getPointerId(0), 6);
+    ASSERT_EQ(splitMove.getX(0), 6);
+    ASSERT_EQ(splitMove.getY(0), 6);
+    ASSERT_EQ(splitMove.getPointerId(1), 8);
+    ASSERT_EQ(splitMove.getX(1), 8);
+    ASSERT_EQ(splitMove.getY(1), 8);
+}
+
+TEST_F(MotionEventTest, SplitPointerUpCancel) {
+    MotionEvent event = MotionEventBuilder(POINTER_1_UP, AINPUT_SOURCE_TOUCHSCREEN)
+                                .downTime(ARBITRARY_DOWN_TIME)
+                                .pointer(PointerBuilder(/*id=*/4, ToolType::FINGER).x(4).y(4))
+                                .pointer(PointerBuilder(/*id=*/6, ToolType::FINGER).x(6).y(6))
+                                .pointer(PointerBuilder(/*id=*/8, ToolType::FINGER).x(8).y(8))
+                                .addFlag(AMOTION_EVENT_FLAG_CANCELED)
+                                .build();
+
+    MotionEvent splitUp;
+    std::bitset<MAX_POINTER_ID + 1> splitUpIds{};
+    splitUpIds.set(6, true);
+    splitUp.splitFrom(event, splitUpIds, /*eventId=*/42);
+    ASSERT_EQ(splitUp.getAction(), AMOTION_EVENT_ACTION_CANCEL);
+    ASSERT_EQ(splitUp.getPointerCount(), 1u);
+    ASSERT_EQ(splitUp.getPointerId(0), 6);
+    ASSERT_EQ(splitUp.getX(0), 6);
+    ASSERT_EQ(splitUp.getY(0), 6);
+}
+
+TEST_F(MotionEventTest, SplitPointerMove) {
+    MotionEvent event = MotionEventBuilder(AMOTION_EVENT_ACTION_MOVE, AINPUT_SOURCE_TOUCHSCREEN)
+                                .downTime(ARBITRARY_DOWN_TIME)
+                                .pointer(PointerBuilder(/*id=*/4, ToolType::FINGER).x(4).y(4))
+                                .pointer(PointerBuilder(/*id=*/6, ToolType::FINGER).x(6).y(6))
+                                .pointer(PointerBuilder(/*id=*/8, ToolType::FINGER).x(8).y(8))
+                                .transform(ui::Transform(ui::Transform::ROT_90, 100, 100))
+                                .rawTransform(ui::Transform(ui::Transform::FLIP_H, 50, 50))
+                                .build();
+
+    MotionEvent splitMove;
+    std::bitset<MAX_POINTER_ID + 1> splitMoveIds{};
+    splitMoveIds.set(4, true);
+    splitMoveIds.set(8, true);
+    splitMove.splitFrom(event, splitMoveIds, /*eventId=*/42);
+    ASSERT_EQ(splitMove.getAction(), AMOTION_EVENT_ACTION_MOVE);
+    ASSERT_EQ(splitMove.getPointerCount(), 2u);
+    ASSERT_EQ(splitMove.getPointerId(0), 4);
+    ASSERT_EQ(splitMove.getX(0), event.getX(0));
+    ASSERT_EQ(splitMove.getY(0), event.getY(0));
+    ASSERT_EQ(splitMove.getRawX(0), event.getRawX(0));
+    ASSERT_EQ(splitMove.getRawY(0), event.getRawY(0));
+    ASSERT_EQ(splitMove.getPointerId(1), 8);
+    ASSERT_EQ(splitMove.getX(1), event.getX(2));
+    ASSERT_EQ(splitMove.getY(1), event.getY(2));
+    ASSERT_EQ(splitMove.getRawX(1), event.getRawX(2));
+    ASSERT_EQ(splitMove.getRawY(1), event.getRawY(2));
+}
+
 TEST_F(MotionEventTest, OffsetLocation) {
     MotionEvent event;
     initializeEventWithHistory(&event);
diff --git a/services/inputflinger/dispatcher/InputDispatcher.cpp b/services/inputflinger/dispatcher/InputDispatcher.cpp
index 8858f0caec..bedb681366 100644
--- a/services/inputflinger/dispatcher/InputDispatcher.cpp
+++ b/services/inputflinger/dispatcher/InputDispatcher.cpp
@@ -4268,72 +4268,13 @@ void InputDispatcher::synthesizePointerDownEventsForConnectionLocked(
 std::unique_ptr<MotionEntry> InputDispatcher::splitMotionEvent(
         const MotionEntry& originalMotionEntry, std::bitset<MAX_POINTER_ID + 1> pointerIds,
         nsecs_t splitDownTime) {
-    ALOG_ASSERT(pointerIds.any());
-
-    uint32_t splitPointerIndexMap[MAX_POINTERS];
-    std::vector<PointerProperties> splitPointerProperties;
-    std::vector<PointerCoords> splitPointerCoords;
-
-    uint32_t originalPointerCount = originalMotionEntry.getPointerCount();
-    uint32_t splitPointerCount = 0;
-
-    for (uint32_t originalPointerIndex = 0; originalPointerIndex < originalPointerCount;
-         originalPointerIndex++) {
-        const PointerProperties& pointerProperties =
-                originalMotionEntry.pointerProperties[originalPointerIndex];
-        uint32_t pointerId = uint32_t(pointerProperties.id);
-        if (pointerIds.test(pointerId)) {
-            splitPointerIndexMap[splitPointerCount] = originalPointerIndex;
-            splitPointerProperties.push_back(pointerProperties);
-            splitPointerCoords.push_back(originalMotionEntry.pointerCoords[originalPointerIndex]);
-            splitPointerCount += 1;
-        }
-    }
-
-    if (splitPointerCount != pointerIds.count()) {
-        // This is bad.  We are missing some of the pointers that we expected to deliver.
-        // Most likely this indicates that we received an ACTION_MOVE events that has
-        // different pointer ids than we expected based on the previous ACTION_DOWN
-        // or ACTION_POINTER_DOWN events that caused us to decide to split the pointers
-        // in this way.
-        ALOGW("Dropping split motion event because the pointer count is %d but "
-              "we expected there to be %zu pointers.  This probably means we received "
-              "a broken sequence of pointer ids from the input device: %s",
-              splitPointerCount, pointerIds.count(), originalMotionEntry.getDescription().c_str());
-        return nullptr;
-    }
-
-    int32_t action = originalMotionEntry.action;
-    int32_t maskedAction = action & AMOTION_EVENT_ACTION_MASK;
-    if (maskedAction == AMOTION_EVENT_ACTION_POINTER_DOWN ||
-        maskedAction == AMOTION_EVENT_ACTION_POINTER_UP) {
-        int32_t originalPointerIndex = MotionEvent::getActionIndex(action);
-        const PointerProperties& pointerProperties =
-                originalMotionEntry.pointerProperties[originalPointerIndex];
-        uint32_t pointerId = uint32_t(pointerProperties.id);
-        if (pointerIds.test(pointerId)) {
-            if (pointerIds.count() == 1) {
-                // The first/last pointer went down/up.
-                action = maskedAction == AMOTION_EVENT_ACTION_POINTER_DOWN
-                        ? AMOTION_EVENT_ACTION_DOWN
-                        : (originalMotionEntry.flags & AMOTION_EVENT_FLAG_CANCELED) != 0
-                                ? AMOTION_EVENT_ACTION_CANCEL
-                                : AMOTION_EVENT_ACTION_UP;
-            } else {
-                // A secondary pointer went down/up.
-                uint32_t splitPointerIndex = 0;
-                while (pointerId != uint32_t(splitPointerProperties[splitPointerIndex].id)) {
-                    splitPointerIndex += 1;
-                }
-                action = maskedAction |
-                        (splitPointerIndex << AMOTION_EVENT_ACTION_POINTER_INDEX_SHIFT);
-            }
-        } else {
-            // An unrelated pointer changed.
-            action = AMOTION_EVENT_ACTION_MOVE;
-        }
-    }
+    const auto& [action, pointerProperties, pointerCoords] =
+            MotionEvent::split(originalMotionEntry.action, originalMotionEntry.flags,
+                               /*historySize=*/0, originalMotionEntry.pointerProperties,
+                               originalMotionEntry.pointerCoords, pointerIds);
 
+    // TODO(b/327503168): Move this check inside MotionEvent::split once all callers handle it
+    //   correctly.
     if (action == AMOTION_EVENT_ACTION_DOWN && splitDownTime != originalMotionEntry.eventTime) {
         logDispatchStateLocked();
         LOG_ALWAYS_FATAL("Split motion event has mismatching downTime and eventTime for "
@@ -4361,7 +4302,7 @@ std::unique_ptr<MotionEntry> InputDispatcher::splitMotionEvent(
                                           originalMotionEntry.yPrecision,
                                           originalMotionEntry.xCursorPosition,
                                           originalMotionEntry.yCursorPosition, splitDownTime,
-                                          splitPointerProperties, splitPointerCoords);
+                                          pointerProperties, pointerCoords);
 
     return splitMotionEntry;
 }