Revert "InputReader: Clear the multi-touch state when the device is reset"

This reverts commit f8d9e440558f4dfb13ef41e23f41f30092297582.

Reason for revert: b/316593362

Test: atest inputflinger_tests
Bug: b/316593362
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:4bb0bd5eb22f87c7c39a982bc4a7e6826f224383)
Merged-In: Idfbf2091febba12c0e92a39bedb56b1058b85047
Change-Id: Idfbf2091febba12c0e92a39bedb56b1058b85047

4 files changed, 30 insertions, 106 deletions

diff --git a/services/inputflinger/reader/mapper/MultiTouchInputMapper.cpp b/services/inputflinger/reader/mapper/MultiTouchInputMapper.cpp
index 5a74a42446..2dd05f5c66 100644
--- a/services/inputflinger/reader/mapper/MultiTouchInputMapper.cpp
+++ b/services/inputflinger/reader/mapper/MultiTouchInputMapper.cpp
@@ -35,10 +35,12 @@ MultiTouchInputMapper::MultiTouchInputMapper(InputDeviceContext& deviceContext,
 MultiTouchInputMapper::~MultiTouchInputMapper() {}
 
 std::list<NotifyArgs> MultiTouchInputMapper::reset(nsecs_t when) {
-    // TODO(b/291626046): Sync the MT state with the kernel using EVIOCGMTSLOTS.
-    mMultiTouchMotionAccumulator.reset(getDeviceContext());
-    mPointerIdBits.clear();
-
+    // The evdev multi-touch protocol does not allow userspace applications to query the initial or
+    // current state of the pointers at any time. This means if we clear our accumulated state when
+    // resetting the input mapper, there's no way to rebuild the full initial state of the pointers.
+    // We can only wait for updates to all the pointers and axes. Rather than clearing the state and
+    // rebuilding the state from scratch, we work around this kernel API limitation by never
+    // fully clearing any state specific to the multi-touch protocol.
     return TouchInputMapper::reset(when);
 }
 
diff --git a/services/inputflinger/reader/mapper/accumulator/MultiTouchMotionAccumulator.cpp b/services/inputflinger/reader/mapper/accumulator/MultiTouchMotionAccumulator.cpp
index d06514acab..b0fc9035f2 100644
--- a/services/inputflinger/reader/mapper/accumulator/MultiTouchMotionAccumulator.cpp
+++ b/services/inputflinger/reader/mapper/accumulator/MultiTouchMotionAccumulator.cpp
@@ -30,29 +30,23 @@ void MultiTouchMotionAccumulator::configure(const InputDeviceContext& deviceCont
                                             size_t slotCount, bool usingSlotsProtocol) {
     mUsingSlotsProtocol = usingSlotsProtocol;
     mSlots = std::vector<Slot>(slotCount);
-    reset(deviceContext);
-}
-
-void MultiTouchMotionAccumulator::reset(const InputDeviceContext& deviceContext) {
-    resetSlots();
-
-    if (!mUsingSlotsProtocol) {
-        return;
-    }
 
-    // Query the driver for the current slot index and use it as the initial slot before we
-    // start reading events from the device.  It is possible that the current slot index will
-    // not be the same as it was when the first event was written into the evdev buffer, which
-    // means the input mapper could start out of sync with the initial state of the events in
-    // the evdev buffer. In the extremely unlikely case that this happens, the data from two
-    // slots will be confused until the next ABS_MT_SLOT event is received. This can cause the
-    // touch point to "jump", but at least there will be no stuck touches.
-    int32_t initialSlot;
-    if (const auto status = deviceContext.getAbsoluteAxisValue(ABS_MT_SLOT, &initialSlot);
-        status == OK) {
-        mCurrentSlot = initialSlot;
-    } else {
-        ALOGD("Could not retrieve current multi-touch slot index. status=%d", status);
+    mCurrentSlot = -1;
+    if (mUsingSlotsProtocol) {
+        // Query the driver for the current slot index and use it as the initial slot before we
+        // start reading events from the device.  It is possible that the current slot index will
+        // not be the same as it was when the first event was written into the evdev buffer, which
+        // means the input mapper could start out of sync with the initial state of the events in
+        // the evdev buffer. In the extremely unlikely case that this happens, the data from two
+        // slots will be confused until the next ABS_MT_SLOT event is received. This can cause the
+        // touch point to "jump", but at least there will be no stuck touches.
+        int32_t initialSlot;
+        if (const auto status = deviceContext.getAbsoluteAxisValue(ABS_MT_SLOT, &initialSlot);
+            status == OK) {
+            mCurrentSlot = initialSlot;
+        } else {
+            ALOGD("Could not retrieve current multi-touch slot index. status=%d", status);
+        }
     }
 }
 
diff --git a/services/inputflinger/reader/mapper/accumulator/MultiTouchMotionAccumulator.h b/services/inputflinger/reader/mapper/accumulator/MultiTouchMotionAccumulator.h
index 5b55e3d599..0e3e2bb365 100644
--- a/services/inputflinger/reader/mapper/accumulator/MultiTouchMotionAccumulator.h
+++ b/services/inputflinger/reader/mapper/accumulator/MultiTouchMotionAccumulator.h
@@ -83,7 +83,6 @@ public:
         LOG_ALWAYS_FATAL_IF(index < 0 || index >= mSlots.size(), "Invalid index: %zu", index);
         return mSlots[index];
     }
-    void reset(const InputDeviceContext& deviceContext);
 
 private:
     int32_t mCurrentSlot;
diff --git a/services/inputflinger/tests/InputReader_test.cpp b/services/inputflinger/tests/InputReader_test.cpp
index e0a3e94aad..faf7012c08 100644
--- a/services/inputflinger/tests/InputReader_test.cpp
+++ b/services/inputflinger/tests/InputReader_test.cpp
@@ -10971,7 +10971,7 @@ TEST_F(MultiTouchInputMapperTest, Process_MultiTouch_WithInvalidTrackingId) {
     ASSERT_EQ(uint32_t(1), motionArgs.getPointerCount());
 }
 
-TEST_F(MultiTouchInputMapperTest, ResetClearsTouchState) {
+TEST_F(MultiTouchInputMapperTest, Reset_PreservesLastTouchState) {
     addConfigurationProperty("touch.deviceType", "touchScreen");
     prepareDisplay(ui::ROTATION_0);
     prepareAxes(POSITION | ID | SLOT | PRESSURE);
@@ -10994,36 +10994,25 @@ TEST_F(MultiTouchInputMapperTest, ResetClearsTouchState) {
     ASSERT_NO_FATAL_FAILURE(
             mFakeListener->assertNotifyMotionWasCalled(WithMotionAction(ACTION_POINTER_1_DOWN)));
 
-    // Reset the mapper. When the mapper is reset, the touch state is also cleared.
+    // Reset the mapper. When the mapper is reset, we expect the current multi-touch state to be
+    // preserved. Resetting should cancel the ongoing gesture.
     resetMapper(mapper, ARBITRARY_TIME);
     ASSERT_NO_FATAL_FAILURE(mFakeListener->assertNotifyMotionWasCalled(
             WithMotionAction(AMOTION_EVENT_ACTION_CANCEL)));
 
-    // Move the second slot pointer, and ensure there are no events, because the touch state was
-    // cleared and no slots should be in use.
+    // Send a sync to simulate an empty touch frame where nothing changes. The mapper should use
+    // the existing touch state to generate a down event.
     processPosition(mapper, 301, 302);
     processSync(mapper);
-    ASSERT_NO_FATAL_FAILURE(mFakeListener->assertNotifyMotionWasNotCalled());
-
-    // Release both fingers.
-    processId(mapper, INVALID_TRACKING_ID);
-    processSlot(mapper, FIRST_SLOT);
-    processId(mapper, INVALID_TRACKING_ID);
-    processSync(mapper);
-    ASSERT_NO_FATAL_FAILURE(mFakeListener->assertNotifyMotionWasNotCalled());
-
-    // Start a new gesture, and ensure we get a DOWN event for it.
-    processId(mapper, FIRST_TRACKING_ID);
-    processPosition(mapper, 200, 300);
-    processPressure(mapper, RAW_PRESSURE_MAX);
-    processSync(mapper);
     ASSERT_NO_FATAL_FAILURE(mFakeListener->assertNotifyMotionWasCalled(
             AllOf(WithMotionAction(AMOTION_EVENT_ACTION_DOWN), WithPressure(1.f))));
+    ASSERT_NO_FATAL_FAILURE(mFakeListener->assertNotifyMotionWasCalled(
+            AllOf(WithMotionAction(ACTION_POINTER_1_DOWN), WithPressure(1.f))));
 
     ASSERT_NO_FATAL_FAILURE(mFakeListener->assertNotifyMotionWasNotCalled());
 }
 
-TEST_F(MultiTouchInputMapperTest, ResetClearsTouchStateWithNoPointersDown) {
+TEST_F(MultiTouchInputMapperTest, Reset_PreservesLastTouchState_NoPointersDown) {
     addConfigurationProperty("touch.deviceType", "touchScreen");
     prepareDisplay(ui::ROTATION_0);
     prepareAxes(POSITION | ID | SLOT | PRESSURE);
@@ -11151,66 +11140,6 @@ TEST_F(MultiTouchInputMapperTest, Process_WhenConfigDisabled_ShouldNotShowDirect
     ASSERT_FALSE(fakePointerController->isPointerShown());
 }
 
-TEST_F(MultiTouchInputMapperTest, SimulateKernelBufferOverflow) {
-    addConfigurationProperty("touch.deviceType", "touchScreen");
-    prepareDisplay(ui::ROTATION_0);
-    prepareAxes(POSITION | ID | SLOT | PRESSURE);
-    MultiTouchInputMapper& mapper = constructAndAddMapper<MultiTouchInputMapper>();
-
-    // First finger down.
-    processId(mapper, FIRST_TRACKING_ID);
-    processPosition(mapper, 100, 200);
-    processPressure(mapper, RAW_PRESSURE_MAX);
-    processSync(mapper);
-    ASSERT_NO_FATAL_FAILURE(mFakeListener->assertNotifyMotionWasCalled(
-            WithMotionAction(AMOTION_EVENT_ACTION_DOWN)));
-
-    // Assume the kernel buffer overflows, and we get a SYN_DROPPED event.
-    // This will reset the mapper, and thus also reset the touch state.
-    process(mapper, ARBITRARY_TIME, READ_TIME, EV_SYN, SYN_DROPPED, 0);
-    resetMapper(mapper, ARBITRARY_TIME);
-    ASSERT_NO_FATAL_FAILURE(mFakeListener->assertNotifyMotionWasCalled(
-            WithMotionAction(AMOTION_EVENT_ACTION_CANCEL)));
-
-    // Since the touch state was reset, it doesn't know which slots are active, so any movements
-    // are ignored.
-    processPosition(mapper, 101, 201);
-    processSync(mapper);
-
-    ASSERT_NO_FATAL_FAILURE(mFakeListener->assertNotifyMotionWasNotCalled());
-
-    // Second finger goes down. This is the first active finger, so we get a DOWN event.
-    processSlot(mapper, SECOND_SLOT);
-    processId(mapper, SECOND_TRACKING_ID);
-    processPosition(mapper, 400, 500);
-    processPressure(mapper, RAW_PRESSURE_MAX);
-    processSync(mapper);
-
-    ASSERT_NO_FATAL_FAILURE(mFakeListener->assertNotifyMotionWasCalled(
-            WithMotionAction(AMOTION_EVENT_ACTION_DOWN)));
-
-    // First slot is still ignored, only the second one is active.
-    processSlot(mapper, FIRST_SLOT);
-    processPosition(mapper, 102, 202);
-    processSlot(mapper, SECOND_SLOT);
-    processPosition(mapper, 401, 501);
-    processSync(mapper);
-
-    ASSERT_NO_FATAL_FAILURE(mFakeListener->assertNotifyMotionWasCalled(
-            WithMotionAction(AMOTION_EVENT_ACTION_MOVE)));
-
-    // Both slots up, so we get the UP event for the active pointer.
-    processSlot(mapper, FIRST_SLOT);
-    processId(mapper, INVALID_TRACKING_ID);
-    processSlot(mapper, SECOND_SLOT);
-    processId(mapper, INVALID_TRACKING_ID);
-    processSync(mapper);
-
-    ASSERT_NO_FATAL_FAILURE(
-            mFakeListener->assertNotifyMotionWasCalled(WithMotionAction(AMOTION_EVENT_ACTION_UP)));
-    ASSERT_NO_FATAL_FAILURE(mFakeListener->assertNotifyMotionWasNotCalled());
-}
-
 // --- MultiTouchInputMapperTest_ExternalDevice ---
 
 class MultiTouchInputMapperTest_ExternalDevice : public MultiTouchInputMapperTest {