Override VelocityTracker strategy for non-differential axes only

VelocityTracker may use different strategies, depending on the system
flags. By default, the behaviour is like this:
AXIS_X -> lsq2
AXIS_Y -> lsq2
AXIS_SCROLL -> impulse

However, if we provide a specific strategy to VT, then things would
change. The new map would look like this:
AXIS_X -> provided strategy
AXIS_Y -> provided strategy
AXIS_SCROLL -> provided strategy

This works fine if the user specifies "impulse" as the desired strategy,
because impulse supports all of the axes.
However, lsq2 only works in non-differential mode.

The combination of "AXIS_SCROLL -> lsq2" is not allowed.

To fix this, we only allow the specified strategy to affect
non-differential axes.

This is fine, because currently, impulse is the only strategy that can
work in the differential mode.

To reproduce the issue:
1. Run `atest VelocityTrackerTest`. Test should pass, because the
   default strategy is being used.
2. Connect the device to internet
3. Reboot the device
4. Run `atest VelocityTrackerTest` again. Test should fail because the
   device would pick up an "lsq2" strategy value and then try to run the
   axis_scroll tests with it.

Bug: 295290374
Test: atest VelocityTrackerTest
Change-Id: I702a2a3e58db3ce2e0ff0c33122839a527eebab2

3 files changed, 19 insertions, 21 deletions

diff --git a/include/input/VelocityTracker.h b/include/input/VelocityTracker.h
index b58feac444..70d503d782 100644
--- a/include/input/VelocityTracker.h
+++ b/include/input/VelocityTracker.h
@@ -48,6 +48,7 @@ public:
         INT2 = 8,
         LEGACY = 9,
         MAX = LEGACY,
+        ftl_last = LEGACY,
     };
 
     /*
@@ -81,8 +82,6 @@ public:
     // TODO(b/32830165): support axis-specific strategies.
     VelocityTracker(const Strategy strategy = Strategy::DEFAULT);
 
-    ~VelocityTracker();
-
     /** Return true if the axis is supported for velocity tracking, false otherwise. */
     static bool isAxisSupported(int32_t axis);
 
diff --git a/libs/input/VelocityTracker.cpp b/libs/input/VelocityTracker.cpp
index 8704eee73d..116b778608 100644
--- a/libs/input/VelocityTracker.cpp
+++ b/libs/input/VelocityTracker.cpp
@@ -17,6 +17,7 @@
 #define LOG_TAG "VelocityTracker"
 
 #include <android-base/logging.h>
+#include <ftl/enum.h>
 #include <inttypes.h>
 #include <limits.h>
 #include <math.h>
@@ -148,27 +149,19 @@ static std::string matrixToString(const float* a, uint32_t m, uint32_t n, bool r
 VelocityTracker::VelocityTracker(const Strategy strategy)
       : mLastEventTime(0), mCurrentPointerIdBits(0), mOverrideStrategy(strategy) {}
 
-VelocityTracker::~VelocityTracker() {
-}
-
 bool VelocityTracker::isAxisSupported(int32_t axis) {
     return DEFAULT_STRATEGY_BY_AXIS.find(axis) != DEFAULT_STRATEGY_BY_AXIS.end();
 }
 
 void VelocityTracker::configureStrategy(int32_t axis) {
     const bool isDifferentialAxis = DIFFERENTIAL_AXES.find(axis) != DIFFERENTIAL_AXES.end();
-
-    std::unique_ptr<VelocityTrackerStrategy> createdStrategy;
-    if (mOverrideStrategy != VelocityTracker::Strategy::DEFAULT) {
-        createdStrategy = createStrategy(mOverrideStrategy, /*deltaValues=*/isDifferentialAxis);
+    if (isDifferentialAxis || mOverrideStrategy == VelocityTracker::Strategy::DEFAULT) {
+        // Do not allow overrides of strategies for differential axes, for now.
+        mConfiguredStrategies[axis] = createStrategy(DEFAULT_STRATEGY_BY_AXIS.at(axis),
+                                                     /*deltaValues=*/isDifferentialAxis);
     } else {
-        createdStrategy = createStrategy(DEFAULT_STRATEGY_BY_AXIS.at(axis),
-                                         /*deltaValues=*/isDifferentialAxis);
+        mConfiguredStrategies[axis] = createStrategy(mOverrideStrategy, /*deltaValues=*/false);
     }
-
-    LOG_ALWAYS_FATAL_IF(createdStrategy == nullptr,
-                        "Could not create velocity tracker strategy for axis '%" PRId32 "'!", axis);
-    mConfiguredStrategies[axis] = std::move(createdStrategy);
 }
 
 std::unique_ptr<VelocityTrackerStrategy> VelocityTracker::createStrategy(
@@ -216,6 +209,9 @@ std::unique_ptr<VelocityTrackerStrategy> VelocityTracker::createStrategy(
         default:
             break;
     }
+    LOG(FATAL) << "Invalid strategy: " << ftl::enum_string(strategy)
+               << ", deltaValues = " << deltaValues;
+
     return nullptr;
 }
 
@@ -272,12 +268,10 @@ void VelocityTracker::addMovement(nsecs_t eventTime, int32_t pointerId, int32_t
     mConfiguredStrategies[axis]->addMovement(eventTime, pointerId, position);
 
     if (DEBUG_VELOCITY) {
-        ALOGD("VelocityTracker: addMovement eventTime=%" PRId64 ", pointerId=%" PRId32
-              ", activePointerId=%s",
-              eventTime, pointerId, toString(mActivePointerId).c_str());
-
-        ALOGD("  %d: axis=%d, position=%0.3f, velocity=%s", pointerId, axis, position,
-              toString(getVelocity(axis, pointerId)).c_str());
+        LOG(INFO) << "VelocityTracker: addMovement axis=" << MotionEvent::getLabel(axis)
+                  << ", eventTime=" << eventTime << ", pointerId=" << pointerId
+                  << ", activePointerId=" << toString(mActivePointerId) << ", position=" << position
+                  << ", velocity=" << toString(getVelocity(axis, pointerId));
     }
 }
 
diff --git a/libs/input/tests/VelocityTracker_test.cpp b/libs/input/tests/VelocityTracker_test.cpp
index ffebff1e65..1c8ec90373 100644
--- a/libs/input/tests/VelocityTracker_test.cpp
+++ b/libs/input/tests/VelocityTracker_test.cpp
@@ -278,6 +278,11 @@ static void computeAndCheckAxisScrollVelocity(
         const std::vector<std::pair<std::chrono::nanoseconds, float>>& motions,
         std::optional<float> targetVelocity) {
     checkVelocity(computeVelocity(strategy, motions, AMOTION_EVENT_AXIS_SCROLL), targetVelocity);
+    // The strategy LSQ2 is not compatible with AXIS_SCROLL. In those situations, we should fall
+    // back to a strategy that supports differential axes.
+    checkVelocity(computeVelocity(VelocityTracker::Strategy::LSQ2, motions,
+                                  AMOTION_EVENT_AXIS_SCROLL),
+                  targetVelocity);
 }
 
 static void computeAndCheckQuadraticVelocity(const std::vector<PlanarMotionEventEntry>& motions,