CapturedTouchpadEventConverter: report relative axes

In the old touchpad stack, when a touchpad was captured we'd report
AXIS_RELATIVE_(X|Y) values for each finger, as offsets from the location
it had in the previous frame. When I implemented captured mode in the
new stack I didn't realize this, so the new stack introduced in Android
U doesn't report them. This causes problems for games that capture the
mouse pointer and use the relative axes for camera movement.

Bug: 330522990
Test: check the axis values using a test app
Test: $ atest inputflinger_tests:CapturedTouchpadEventConverterTest
Flag: com.android.input.flags.include_relative_axis_values_for_captured_touchpads
Change-Id: I8a1caa4c9315dd41bc712fd9467146bb608cf6f3
diff --git a/libs/input/input_flags.aconfig b/libs/input/input_flags.aconfig
index 500f7b4..ab117b8 100644
--- a/libs/input/input_flags.aconfig
+++ b/libs/input/input_flags.aconfig
@@ -164,3 +164,10 @@
   description: "Show touch and pointer indicators when mirroring a single task"
   bug: "310179437"
 }
+
+flag {
+  name: "include_relative_axis_values_for_captured_touchpads"
+  namespace: "input"
+  description: "Include AXIS_RELATIVE_X and AXIS_RELATIVE_Y values when reporting touches from captured touchpads."
+  bug: "330522990"
+}
diff --git a/services/inputflinger/reader/mapper/CapturedTouchpadEventConverter.cpp b/services/inputflinger/reader/mapper/CapturedTouchpadEventConverter.cpp
index c8e7790..dd46bbc 100644
--- a/services/inputflinger/reader/mapper/CapturedTouchpadEventConverter.cpp
+++ b/services/inputflinger/reader/mapper/CapturedTouchpadEventConverter.cpp
@@ -20,14 +20,19 @@
 #include <sstream>
 
 #include <android-base/stringprintf.h>
+#include <com_android_input_flags.h>
 #include <input/PrintTools.h>
 #include <linux/input-event-codes.h>
 #include <log/log_main.h>
 
+namespace input_flags = com::android::input::flags;
+
 namespace android {
 
 namespace {
 
+static constexpr uint32_t SOURCE = AINPUT_SOURCE_TOUCHPAD;
+
 int32_t actionWithIndex(int32_t action, int32_t index) {
     return action | (index << AMOTION_EVENT_ACTION_POINTER_INDEX_SHIFT);
 }
@@ -43,6 +48,12 @@
     return i;
 }
 
+void addRawMotionRange(InputDeviceInfo& deviceInfo, int32_t androidAxis,
+                       RawAbsoluteAxisInfo& evdevAxis) {
+    deviceInfo.addMotionRange(androidAxis, SOURCE, evdevAxis.minValue, evdevAxis.maxValue,
+                              evdevAxis.flat, evdevAxis.fuzz, evdevAxis.resolution);
+}
+
 } // namespace
 
 CapturedTouchpadEventConverter::CapturedTouchpadEventConverter(
@@ -108,8 +119,15 @@
 }
 
 void CapturedTouchpadEventConverter::populateMotionRanges(InputDeviceInfo& info) const {
-    tryAddRawMotionRange(/*byref*/ info, AMOTION_EVENT_AXIS_X, ABS_MT_POSITION_X);
-    tryAddRawMotionRange(/*byref*/ info, AMOTION_EVENT_AXIS_Y, ABS_MT_POSITION_Y);
+    if (input_flags::include_relative_axis_values_for_captured_touchpads()) {
+        tryAddRawMotionRangeWithRelative(/*byref*/ info, AMOTION_EVENT_AXIS_X,
+                                         AMOTION_EVENT_AXIS_RELATIVE_X, ABS_MT_POSITION_X);
+        tryAddRawMotionRangeWithRelative(/*byref*/ info, AMOTION_EVENT_AXIS_Y,
+                                         AMOTION_EVENT_AXIS_RELATIVE_Y, ABS_MT_POSITION_Y);
+    } else {
+        tryAddRawMotionRange(/*byref*/ info, AMOTION_EVENT_AXIS_X, ABS_MT_POSITION_X);
+        tryAddRawMotionRange(/*byref*/ info, AMOTION_EVENT_AXIS_Y, ABS_MT_POSITION_Y);
+    }
     tryAddRawMotionRange(/*byref*/ info, AMOTION_EVENT_AXIS_TOUCH_MAJOR, ABS_MT_TOUCH_MAJOR);
     tryAddRawMotionRange(/*byref*/ info, AMOTION_EVENT_AXIS_TOUCH_MINOR, ABS_MT_TOUCH_MINOR);
     tryAddRawMotionRange(/*byref*/ info, AMOTION_EVENT_AXIS_TOOL_MAJOR, ABS_MT_WIDTH_MAJOR);
@@ -135,8 +153,23 @@
                                                           int32_t evdevAxis) const {
     std::optional<RawAbsoluteAxisInfo> info = mDeviceContext.getAbsoluteAxisInfo(evdevAxis);
     if (info) {
-        deviceInfo.addMotionRange(androidAxis, SOURCE, info->minValue, info->maxValue, info->flat,
-                                  info->fuzz, info->resolution);
+        addRawMotionRange(/*byref*/ deviceInfo, androidAxis, *info);
+    }
+}
+
+void CapturedTouchpadEventConverter::tryAddRawMotionRangeWithRelative(InputDeviceInfo& deviceInfo,
+                                                                      int32_t androidAxis,
+                                                                      int32_t androidRelativeAxis,
+                                                                      int32_t evdevAxis) const {
+    std::optional<RawAbsoluteAxisInfo> axisInfo = mDeviceContext.getAbsoluteAxisInfo(evdevAxis);
+    if (axisInfo) {
+        addRawMotionRange(/*byref*/ deviceInfo, androidAxis, *axisInfo);
+
+        // The largest movement we could possibly report on a relative axis is from the minimum to
+        // the maximum (or vice versa) of the absolute axis.
+        float range = axisInfo->maxValue - axisInfo->minValue;
+        deviceInfo.addMotionRange(androidRelativeAxis, SOURCE, -range, range, axisInfo->flat,
+                                  axisInfo->fuzz, axisInfo->resolution);
     }
 }
 
@@ -163,7 +196,7 @@
     std::list<NotifyArgs> out;
     std::vector<PointerCoords> coords;
     std::vector<PointerProperties> properties;
-    std::map<size_t, size_t> coordsIndexForSlotNumber;
+    std::map<size_t /*slotNumber*/, size_t /*coordsIndex*/> coordsIndexForSlotNumber;
 
     // For all the touches that were already down, send a MOVE event with their updated coordinates.
     // A convention of the MotionEvent API is that pointer coordinates in UP events match the
@@ -175,11 +208,19 @@
             // to stay perfectly still between frames, and if it does the worst that can happen is
             // an extra MOVE event, so it's not worth the overhead of checking for changes.
             coordsIndexForSlotNumber[slotNumber] = coords.size();
-            coords.push_back(makePointerCoordsForSlot(mMotionAccumulator.getSlot(slotNumber)));
+            coords.push_back(makePointerCoordsForSlot(slotNumber));
             properties.push_back({.id = pointerId, .toolType = ToolType::FINGER});
         }
         out.push_back(
                 makeMotionArgs(when, readTime, AMOTION_EVENT_ACTION_MOVE, coords, properties));
+        if (input_flags::include_relative_axis_values_for_captured_touchpads()) {
+            // For any further events we send from this sync, the pointers won't have moved relative
+            // to the positions we just reported in this MOVE event, so zero out the relative axes.
+            for (PointerCoords& pointer : coords) {
+                pointer.setAxisValue(AMOTION_EVENT_AXIS_RELATIVE_X, 0);
+                pointer.setAxisValue(AMOTION_EVENT_AXIS_RELATIVE_Y, 0);
+            }
+        }
     }
 
     std::vector<size_t> upSlots, downSlots;
@@ -234,6 +275,9 @@
                                      /*flags=*/cancel ? AMOTION_EVENT_FLAG_CANCELED : 0));
 
         freePointerIdForSlot(slotNumber);
+        if (input_flags::include_relative_axis_values_for_captured_touchpads()) {
+            mPreviousCoordsForSlotNumber.erase(slotNumber);
+        }
         coords.erase(coords.begin() + indexToRemove);
         properties.erase(properties.begin() + indexToRemove);
         // Now that we've removed some coords and properties, we might have to update the slot
@@ -254,7 +298,7 @@
                 : actionWithIndex(AMOTION_EVENT_ACTION_POINTER_DOWN, coordsIndex);
 
         coordsIndexForSlotNumber[slotNumber] = coordsIndex;
-        coords.push_back(makePointerCoordsForSlot(mMotionAccumulator.getSlot(slotNumber)));
+        coords.push_back(makePointerCoordsForSlot(slotNumber));
         properties.push_back(
                 {.id = allocatePointerIdToSlot(slotNumber), .toolType = ToolType::FINGER});
 
@@ -286,12 +330,22 @@
                             AMOTION_EVENT_INVALID_CURSOR_POSITION, mDownTime, /*videoFrames=*/{});
 }
 
-PointerCoords CapturedTouchpadEventConverter::makePointerCoordsForSlot(
-        const MultiTouchMotionAccumulator::Slot& slot) const {
+PointerCoords CapturedTouchpadEventConverter::makePointerCoordsForSlot(size_t slotNumber) {
+    const MultiTouchMotionAccumulator::Slot& slot = mMotionAccumulator.getSlot(slotNumber);
     PointerCoords coords;
     coords.clear();
     coords.setAxisValue(AMOTION_EVENT_AXIS_X, slot.getX());
     coords.setAxisValue(AMOTION_EVENT_AXIS_Y, slot.getY());
+    if (input_flags::include_relative_axis_values_for_captured_touchpads()) {
+        if (auto it = mPreviousCoordsForSlotNumber.find(slotNumber);
+            it != mPreviousCoordsForSlotNumber.end()) {
+            auto [oldX, oldY] = it->second;
+            coords.setAxisValue(AMOTION_EVENT_AXIS_RELATIVE_X, slot.getX() - oldX);
+            coords.setAxisValue(AMOTION_EVENT_AXIS_RELATIVE_Y, slot.getY() - oldY);
+        }
+        mPreviousCoordsForSlotNumber[slotNumber] = std::make_pair(slot.getX(), slot.getY());
+    }
+
     coords.setAxisValue(AMOTION_EVENT_AXIS_TOUCH_MAJOR, slot.getTouchMajor());
     coords.setAxisValue(AMOTION_EVENT_AXIS_TOUCH_MINOR, slot.getTouchMinor());
     coords.setAxisValue(AMOTION_EVENT_AXIS_TOOL_MAJOR, slot.getToolMajor());
diff --git a/services/inputflinger/reader/mapper/CapturedTouchpadEventConverter.h b/services/inputflinger/reader/mapper/CapturedTouchpadEventConverter.h
index 9b6df7a..d6c0708 100644
--- a/services/inputflinger/reader/mapper/CapturedTouchpadEventConverter.h
+++ b/services/inputflinger/reader/mapper/CapturedTouchpadEventConverter.h
@@ -21,6 +21,7 @@
 #include <map>
 #include <set>
 #include <string>
+#include <utility>
 #include <vector>
 
 #include <android/input.h>
@@ -49,12 +50,14 @@
 private:
     void tryAddRawMotionRange(InputDeviceInfo& deviceInfo, int32_t androidAxis,
                               int32_t evdevAxis) const;
+    void tryAddRawMotionRangeWithRelative(InputDeviceInfo& deviceInfo, int32_t androidAxis,
+                                          int32_t androidRelativeAxis, int32_t evdevAxis) const;
     [[nodiscard]] std::list<NotifyArgs> sync(nsecs_t when, nsecs_t readTime);
     [[nodiscard]] NotifyMotionArgs makeMotionArgs(nsecs_t when, nsecs_t readTime, int32_t action,
                                                   const std::vector<PointerCoords>& coords,
                                                   const std::vector<PointerProperties>& properties,
                                                   int32_t actionButton = 0, int32_t flags = 0);
-    PointerCoords makePointerCoordsForSlot(const MultiTouchMotionAccumulator::Slot& slot) const;
+    PointerCoords makePointerCoordsForSlot(size_t slotNumber);
     int32_t allocatePointerIdToSlot(size_t slotNumber);
     void freePointerIdForSlot(size_t slotNumber);
 
@@ -76,8 +79,7 @@
 
     std::bitset<MAX_POINTER_ID + 1> mPointerIdsInUse;
     std::map<size_t, int32_t> mPointerIdForSlotNumber;
-
-    static constexpr uint32_t SOURCE = AINPUT_SOURCE_TOUCHPAD;
+    std::map<size_t, std::pair<float, float>> mPreviousCoordsForSlotNumber;
 };
 
 } // namespace android
diff --git a/services/inputflinger/tests/CapturedTouchpadEventConverter_test.cpp b/services/inputflinger/tests/CapturedTouchpadEventConverter_test.cpp
index f20c43c..d39ad3f 100644
--- a/services/inputflinger/tests/CapturedTouchpadEventConverter_test.cpp
+++ b/services/inputflinger/tests/CapturedTouchpadEventConverter_test.cpp
@@ -20,6 +20,7 @@
 #include <memory>
 
 #include <EventHub.h>
+#include <com_android_input_flags.h>
 #include <gtest/gtest.h>
 #include <linux/input-event-codes.h>
 #include <linux/input.h>
@@ -32,6 +33,8 @@
 #include "TestEventMatchers.h"
 #include "TestInputListener.h"
 
+namespace input_flags = com::android::input::flags;
+
 namespace android {
 
 using testing::AllOf;
@@ -47,6 +50,8 @@
             mReader(mFakeEventHub, mFakePolicy, mFakeListener),
             mDevice(newDevice()),
             mDeviceContext(*mDevice, EVENTHUB_ID) {
+        input_flags::include_relative_axis_values_for_captured_touchpads(true);
+
         const size_t slotCount = 8;
         mFakeEventHub->addAbsoluteAxis(EVENTHUB_ID, ABS_MT_SLOT, 0, slotCount - 1, 0, 0, 0);
         mAccumulator.configure(mDeviceContext, slotCount, /*usingSlotsProtocol=*/true);
@@ -126,7 +131,7 @@
 
 TEST_F(CapturedTouchpadEventConverterTest, MotionRanges_allAxesPresent_populatedCorrectly) {
     mFakeEventHub->addAbsoluteAxis(EVENTHUB_ID, ABS_MT_POSITION_X, 0, 4000, 0, 0, 45);
-    mFakeEventHub->addAbsoluteAxis(EVENTHUB_ID, ABS_MT_POSITION_Y, 0, 2500, 0, 0, 40);
+    mFakeEventHub->addAbsoluteAxis(EVENTHUB_ID, ABS_MT_POSITION_Y, -500, 2000, 0, 0, 40);
     mFakeEventHub->addAbsoluteAxis(EVENTHUB_ID, ABS_MT_TOUCH_MAJOR, 0, 1100, 0, 0, 35);
     mFakeEventHub->addAbsoluteAxis(EVENTHUB_ID, ABS_MT_TOUCH_MINOR, 0, 1000, 0, 0, 30);
     mFakeEventHub->addAbsoluteAxis(EVENTHUB_ID, ABS_MT_WIDTH_MAJOR, 0, 900, 0, 0, 25);
@@ -150,8 +155,8 @@
     const InputDeviceInfo::MotionRange* posY =
             info.getMotionRange(AMOTION_EVENT_AXIS_Y, AINPUT_SOURCE_TOUCHPAD);
     ASSERT_NE(nullptr, posY);
-    EXPECT_NEAR(0, posY->min, EPSILON);
-    EXPECT_NEAR(2500, posY->max, EPSILON);
+    EXPECT_NEAR(-500, posY->min, EPSILON);
+    EXPECT_NEAR(2000, posY->max, EPSILON);
     EXPECT_NEAR(40, posY->resolution, EPSILON);
 
     const InputDeviceInfo::MotionRange* touchMajor =
@@ -182,8 +187,22 @@
     EXPECT_NEAR(800, toolMinor->max, EPSILON);
     EXPECT_NEAR(20, toolMinor->resolution, EPSILON);
 
-    // ...except orientation and pressure, which get scaled, and size, which is generated from other
-    // values.
+    // ...except for the relative motion axes, derived from the corresponding absolute ones:
+    const InputDeviceInfo::MotionRange* relX =
+            info.getMotionRange(AMOTION_EVENT_AXIS_RELATIVE_X, AINPUT_SOURCE_TOUCHPAD);
+    ASSERT_NE(nullptr, relX);
+    EXPECT_NEAR(-4000, relX->min, EPSILON);
+    EXPECT_NEAR(4000, relX->max, EPSILON);
+    EXPECT_NEAR(45, relX->resolution, EPSILON);
+
+    const InputDeviceInfo::MotionRange* relY =
+            info.getMotionRange(AMOTION_EVENT_AXIS_RELATIVE_Y, AINPUT_SOURCE_TOUCHPAD);
+    ASSERT_NE(nullptr, relY);
+    EXPECT_NEAR(-2500, relY->min, EPSILON);
+    EXPECT_NEAR(2500, relY->max, EPSILON);
+    EXPECT_NEAR(40, relY->resolution, EPSILON);
+
+    // ...orientation and pressure, which get scaled:
     const InputDeviceInfo::MotionRange* orientation =
             info.getMotionRange(AMOTION_EVENT_AXIS_ORIENTATION, AINPUT_SOURCE_TOUCHPAD);
     ASSERT_NE(nullptr, orientation);
@@ -198,6 +217,7 @@
     EXPECT_NEAR(1, pressure->max, EPSILON);
     EXPECT_NEAR(0, pressure->resolution, EPSILON);
 
+    // ... and size, which is generated from other values.
     const InputDeviceInfo::MotionRange* size =
             info.getMotionRange(AMOTION_EVENT_AXIS_SIZE, AINPUT_SOURCE_TOUCHPAD);
     ASSERT_NE(nullptr, size);
@@ -219,7 +239,9 @@
     // present, since it's generated from axes that aren't provided by this device).
     EXPECT_NE(nullptr, info.getMotionRange(AMOTION_EVENT_AXIS_X, AINPUT_SOURCE_TOUCHPAD));
     EXPECT_NE(nullptr, info.getMotionRange(AMOTION_EVENT_AXIS_Y, AINPUT_SOURCE_TOUCHPAD));
-    EXPECT_EQ(2u, info.getMotionRanges().size());
+    EXPECT_NE(nullptr, info.getMotionRange(AMOTION_EVENT_AXIS_RELATIVE_X, AINPUT_SOURCE_TOUCHPAD));
+    EXPECT_NE(nullptr, info.getMotionRange(AMOTION_EVENT_AXIS_RELATIVE_Y, AINPUT_SOURCE_TOUCHPAD));
+    EXPECT_EQ(4u, info.getMotionRanges().size());
 }
 
 TEST_F(CapturedTouchpadEventConverterTest, OneFinger_motionReportedCorrectly) {
@@ -235,14 +257,16 @@
 
     EXPECT_THAT(processSyncAndExpectSingleMotionArg(conv),
                 AllOf(WithMotionAction(AMOTION_EVENT_ACTION_DOWN), WithPointerCount(1u),
-                      WithCoords(50, 100), WithToolType(ToolType::FINGER)));
+                      WithCoords(50, 100), WithRelativeMotion(0, 0),
+                      WithToolType(ToolType::FINGER)));
 
     processAxis(conv, EV_ABS, ABS_MT_POSITION_X, 52);
     processAxis(conv, EV_ABS, ABS_MT_POSITION_Y, 99);
 
     EXPECT_THAT(processSyncAndExpectSingleMotionArg(conv),
                 AllOf(WithMotionAction(AMOTION_EVENT_ACTION_MOVE), WithPointerCount(1u),
-                      WithCoords(52, 99), WithToolType(ToolType::FINGER)));
+                      WithCoords(52, 99), WithRelativeMotion(2, -1),
+                      WithToolType(ToolType::FINGER)));
 
     processAxis(conv, EV_ABS, ABS_MT_TRACKING_ID, -1);
     processAxis(conv, EV_KEY, BTN_TOUCH, 0);
@@ -255,8 +279,9 @@
                             VariantWith<NotifyMotionArgs>(
                                     WithMotionAction(AMOTION_EVENT_ACTION_UP))));
     EXPECT_THAT(args,
-                Each(VariantWith<NotifyMotionArgs>(AllOf(WithCoords(52, 99), WithPointerCount(1u),
-                                                         WithToolType(ToolType::FINGER)))));
+                Each(VariantWith<NotifyMotionArgs>(
+                        AllOf(WithCoords(52, 99), WithRelativeMotion(0, 0), WithPointerCount(1u),
+                              WithToolType(ToolType::FINGER)))));
 }
 
 TEST_F(CapturedTouchpadEventConverterTest, OneFinger_touchDimensionsPassedThrough) {
@@ -507,13 +532,13 @@
 
     EXPECT_THAT(processSyncAndExpectSingleMotionArg(conv),
                 AllOf(WithMotionAction(AMOTION_EVENT_ACTION_DOWN), WithPointerCount(1u),
-                      WithCoords(51, 100)));
+                      WithCoords(51, 100), WithRelativeMotion(0, 0)));
 
     processAxis(conv, EV_ABS, ABS_MT_POSITION_X, 52);
 
     EXPECT_THAT(processSyncAndExpectSingleMotionArg(conv),
                 AllOf(WithMotionAction(AMOTION_EVENT_ACTION_MOVE), WithPointerCount(1u),
-                      WithCoords(52, 100)));
+                      WithCoords(52, 100), WithRelativeMotion(1, 0)));
 }
 
 TEST_F(CapturedTouchpadEventConverterTest, FingerArrivingAfterPalm_onlyFingerReported) {
@@ -553,7 +578,7 @@
 
     EXPECT_THAT(processSyncAndExpectSingleMotionArg(conv),
                 AllOf(WithMotionAction(AMOTION_EVENT_ACTION_MOVE), WithPointerCount(1u),
-                      WithCoords(98, 148)));
+                      WithCoords(98, 148), WithRelativeMotion(-2, -2)));
 }
 
 TEST_F(CapturedTouchpadEventConverterTest, FingerAndFingerTurningIntoPalm_partiallyCancelled) {
@@ -660,7 +685,8 @@
 
     EXPECT_THAT(processSyncAndExpectSingleMotionArg(conv),
                 AllOf(WithMotionAction(AMOTION_EVENT_ACTION_DOWN), WithPointerCount(1u),
-                      WithCoords(50, 100), WithToolType(ToolType::FINGER)));
+                      WithCoords(50, 100), WithRelativeMotion(0, 0),
+                      WithToolType(ToolType::FINGER)));
 
     processAxis(conv, EV_ABS, ABS_MT_SLOT, 0);
     processAxis(conv, EV_ABS, ABS_MT_POSITION_X, 52);
@@ -678,13 +704,16 @@
                 ElementsAre(VariantWith<NotifyMotionArgs>(
                                     AllOf(WithMotionAction(AMOTION_EVENT_ACTION_MOVE),
                                           WithPointerCount(1u), WithCoords(52, 99),
+                                          WithRelativeMotion(2, -1),
                                           WithToolType(ToolType::FINGER))),
                             VariantWith<NotifyMotionArgs>(
                                     AllOf(WithMotionAction(
                                                   AMOTION_EVENT_ACTION_POINTER_DOWN |
                                                   1 << AMOTION_EVENT_ACTION_POINTER_INDEX_SHIFT),
                                           WithPointerCount(2u), WithPointerCoords(0, 52, 99),
+                                          WithPointerRelativeMotion(0, 0, 0),
                                           WithPointerCoords(1, 250, 200),
+                                          WithPointerRelativeMotion(1, 0, 0),
                                           WithPointerToolType(0, ToolType::FINGER),
                                           WithPointerToolType(1, ToolType::FINGER)))));
 
@@ -700,14 +729,17 @@
     std::list<NotifyArgs> args = processSync(conv);
     EXPECT_THAT(args,
                 ElementsAre(VariantWith<NotifyMotionArgs>(
-                                    WithMotionAction(AMOTION_EVENT_ACTION_MOVE)),
-                            VariantWith<NotifyMotionArgs>(WithMotionAction(
-                                    AMOTION_EVENT_ACTION_POINTER_UP |
-                                    0 << AMOTION_EVENT_ACTION_POINTER_INDEX_SHIFT))));
+                                    AllOf(WithMotionAction(AMOTION_EVENT_ACTION_MOVE),
+                                          WithPointerRelativeMotion(1, 5, 2))),
+                            VariantWith<NotifyMotionArgs>(
+                                    AllOf(WithMotionAction(
+                                                  AMOTION_EVENT_ACTION_POINTER_UP |
+                                                  0 << AMOTION_EVENT_ACTION_POINTER_INDEX_SHIFT),
+                                          WithPointerRelativeMotion(1, 0, 0)))));
     EXPECT_THAT(args,
                 Each(VariantWith<NotifyMotionArgs>(
                         AllOf(WithPointerCount(2u), WithPointerCoords(0, 52, 99),
-                              WithPointerCoords(1, 255, 202),
+                              WithPointerRelativeMotion(0, 0, 0), WithPointerCoords(1, 255, 202),
                               WithPointerToolType(1, ToolType::FINGER),
                               WithPointerToolType(0, ToolType::FINGER)))));
 
@@ -723,9 +755,69 @@
                                     WithMotionAction(AMOTION_EVENT_ACTION_UP))));
     EXPECT_THAT(args,
                 Each(VariantWith<NotifyMotionArgs>(AllOf(WithPointerCount(1u), WithCoords(255, 202),
+                                                         WithPointerRelativeMotion(1, 0, 0),
                                                          WithToolType(ToolType::FINGER)))));
 }
 
+TEST_F(CapturedTouchpadEventConverterTest, RelativeMotionAxesClearedForNewFingerInSlot) {
+    CapturedTouchpadEventConverter conv = createConverter();
+    // Put down one finger.
+    processAxis(conv, EV_ABS, ABS_MT_SLOT, 0);
+    processAxis(conv, EV_ABS, ABS_MT_TRACKING_ID, 1);
+    processAxis(conv, EV_ABS, ABS_MT_POSITION_X, 50);
+    processAxis(conv, EV_ABS, ABS_MT_POSITION_Y, 100);
+
+    processAxis(conv, EV_KEY, BTN_TOUCH, 1);
+    processAxis(conv, EV_KEY, BTN_TOOL_FINGER, 1);
+
+    EXPECT_THAT(processSyncAndExpectSingleMotionArg(conv),
+                AllOf(WithMotionAction(AMOTION_EVENT_ACTION_DOWN), WithPointerCount(1u),
+                      WithCoords(50, 100), WithRelativeMotion(0, 0)));
+
+    // Move it in negative X and Y directions.
+    processAxis(conv, EV_ABS, ABS_MT_POSITION_X, 47);
+    processAxis(conv, EV_ABS, ABS_MT_POSITION_Y, 97);
+
+    EXPECT_THAT(processSyncAndExpectSingleMotionArg(conv),
+                AllOf(WithMotionAction(AMOTION_EVENT_ACTION_MOVE), WithCoords(47, 97),
+                      WithRelativeMotion(-3, -3)));
+
+    // Lift it.
+    processAxis(conv, EV_ABS, ABS_MT_TRACKING_ID, -1);
+    processAxis(conv, EV_KEY, BTN_TOUCH, 0);
+    processAxis(conv, EV_KEY, BTN_TOOL_FINGER, 0);
+
+    std::list<NotifyArgs> args = processSync(conv);
+    EXPECT_THAT(args,
+                ElementsAre(VariantWith<NotifyMotionArgs>(
+                                    WithMotionAction(AMOTION_EVENT_ACTION_MOVE)),
+                            VariantWith<NotifyMotionArgs>(
+                                    WithMotionAction(AMOTION_EVENT_ACTION_UP))));
+    EXPECT_THAT(args,
+                Each(VariantWith<NotifyMotionArgs>(AllOf(WithCoords(47, 97),
+                                                         WithRelativeMotion(0, 0),
+                                                         WithPointerCount(1u)))));
+
+    // Put down another finger using the same slot. Relative axis values should be cleared.
+    processAxis(conv, EV_ABS, ABS_MT_TRACKING_ID, 2);
+    processAxis(conv, EV_ABS, ABS_MT_POSITION_X, 60);
+    processAxis(conv, EV_ABS, ABS_MT_POSITION_Y, 60);
+
+    processAxis(conv, EV_KEY, BTN_TOUCH, 1);
+    processAxis(conv, EV_KEY, BTN_TOOL_FINGER, 1);
+
+    EXPECT_THAT(processSyncAndExpectSingleMotionArg(conv),
+                AllOf(WithMotionAction(AMOTION_EVENT_ACTION_DOWN), WithPointerCount(1u),
+                      WithCoords(60, 60), WithRelativeMotion(0, 0)));
+
+    processAxis(conv, EV_ABS, ABS_MT_POSITION_X, 64);
+    processAxis(conv, EV_ABS, ABS_MT_POSITION_Y, 58);
+
+    EXPECT_THAT(processSyncAndExpectSingleMotionArg(conv),
+                AllOf(WithMotionAction(AMOTION_EVENT_ACTION_MOVE), WithPointerCount(1u),
+                      WithCoords(64, 58), WithRelativeMotion(4, -2)));
+}
+
 // Pointer IDs max out at 31, and so must be reused once a touch is lifted to avoid running out.
 TEST_F(CapturedTouchpadEventConverterTest, PointerIdsReusedAfterLift) {
     CapturedTouchpadEventConverter conv = createConverter();
diff --git a/services/inputflinger/tests/TestEventMatchers.h b/services/inputflinger/tests/TestEventMatchers.h
index cfedc6e..f3be041 100644
--- a/services/inputflinger/tests/TestEventMatchers.h
+++ b/services/inputflinger/tests/TestEventMatchers.h
@@ -654,6 +654,15 @@
     return argX == x && argY == y;
 }
 
+MATCHER_P3(WithPointerRelativeMotion, pointer, x, y,
+           "InputEvent with specified relative motion for pointer") {
+    const auto argX = arg.pointerCoords[pointer].getAxisValue(AMOTION_EVENT_AXIS_RELATIVE_X);
+    const auto argY = arg.pointerCoords[pointer].getAxisValue(AMOTION_EVENT_AXIS_RELATIVE_Y);
+    *result_listener << "expected pointer " << pointer << " to have relative motion (" << x << ", "
+                     << y << "), but got (" << argX << ", " << argY << ")";
+    return argX == x && argY == y;
+}
+
 MATCHER_P3(WithGestureOffset, dx, dy, epsilon,
            "InputEvent with specified touchpad gesture offset") {
     const auto argGestureX = arg.pointerCoords[0].getAxisValue(AMOTION_EVENT_AXIS_GESTURE_X_OFFSET);