Treat Bluetooth-smoothened events with modified timestmaps as synthetic
Since we are modifying the timestamps of events from Bluetooth devices,
these may have unintended consequences on latency metrics. Treat these
modified events as synthetic by setting the event time equal to the read
time to give it zero read latency.
Bug: 257124950
Test: atest inputflinger_tests
Change-Id: I65288050b273e6544861af1db0aee7a42d1b246d
diff --git a/services/inputflinger/reader/mapper/CursorInputMapper.cpp b/services/inputflinger/reader/mapper/CursorInputMapper.cpp
index 5657d61..a1a2af9 100644
--- a/services/inputflinger/reader/mapper/CursorInputMapper.cpp
+++ b/services/inputflinger/reader/mapper/CursorInputMapper.cpp
@@ -300,10 +300,11 @@
mCursorScrollAccumulator.process(rawEvent);
if (rawEvent->type == EV_SYN && rawEvent->code == SYN_REPORT) {
- const nsecs_t eventTime =
+ const auto [eventTime, readTime] =
applyBluetoothTimestampSmoothening(getDeviceContext().getDeviceIdentifier(),
- rawEvent->when, mLastEventTime);
- out += sync(eventTime, rawEvent->readTime);
+ rawEvent->when, rawEvent->readTime,
+ mLastEventTime);
+ out += sync(eventTime, readTime);
mLastEventTime = eventTime;
}
return out;
diff --git a/services/inputflinger/reader/mapper/TouchCursorInputMapperCommon.h b/services/inputflinger/reader/mapper/TouchCursorInputMapperCommon.h
index 0b7ff84..d8a4d34 100644
--- a/services/inputflinger/reader/mapper/TouchCursorInputMapperCommon.h
+++ b/services/inputflinger/reader/mapper/TouchCursorInputMapperCommon.h
@@ -110,10 +110,11 @@
// coordinates result in extremely large instantaneous velocities, which can negatively impact
// user experience. To avoid this, we augment the timestamps so that subsequent event timestamps
// differ by at least a minimum delta value.
-static nsecs_t applyBluetoothTimestampSmoothening(const InputDeviceIdentifier& identifier,
- nsecs_t currentEventTime, nsecs_t lastEventTime) {
+static std::tuple<nsecs_t /*eventTime*/, nsecs_t /*readTime*/> applyBluetoothTimestampSmoothening(
+ const InputDeviceIdentifier& identifier, nsecs_t currentEventTime, nsecs_t readTime,
+ nsecs_t lastEventTime) {
if (identifier.bus != BUS_BLUETOOTH) {
- return currentEventTime;
+ return {currentEventTime, readTime};
}
// Assume the fastest rate at which a Bluetooth touch device can report input events is one
@@ -123,8 +124,14 @@
// We define a maximum smoothing time delta so that we don't generate events too far into the
// future.
constexpr static nsecs_t MAX_BLUETOOTH_SMOOTHING_DELTA = ms2ns(32);
- return std::min(std::max(currentEventTime, lastEventTime + MIN_BLUETOOTH_TIMESTAMP_DELTA),
- currentEventTime + MAX_BLUETOOTH_SMOOTHING_DELTA);
+ const nsecs_t smoothenedEventTime =
+ std::min(std::max(currentEventTime, lastEventTime + MIN_BLUETOOTH_TIMESTAMP_DELTA),
+ currentEventTime + MAX_BLUETOOTH_SMOOTHING_DELTA);
+ // If we are modifying the event time, treat this event as a synthetically generated event for
+ // latency tracking purposes and use the event time as the read time (zero read latency).
+ const nsecs_t smoothenedReadTime =
+ smoothenedEventTime != currentEventTime ? currentEventTime : readTime;
+ return {smoothenedEventTime, smoothenedReadTime};
}
} // namespace android
diff --git a/services/inputflinger/reader/mapper/TouchInputMapper.cpp b/services/inputflinger/reader/mapper/TouchInputMapper.cpp
index 8bae650..d4c2e4f 100644
--- a/services/inputflinger/reader/mapper/TouchInputMapper.cpp
+++ b/services/inputflinger/reader/mapper/TouchInputMapper.cpp
@@ -1467,8 +1467,9 @@
const RawState& last =
mRawStatesPending.size() == 1 ? mCurrentRawState : mRawStatesPending.rbegin()[1];
- next.when = applyBluetoothTimestampSmoothening(getDeviceContext().getDeviceIdentifier(), when,
- last.when);
+ std::tie(next.when, next.readTime) =
+ applyBluetoothTimestampSmoothening(getDeviceContext().getDeviceIdentifier(), when,
+ readTime, last.when);
// Assign pointer ids.
if (!mHavePointerIds) {