GestureConverter: Stop flings with fake fingers
Currently, the only way to stop a fling (the scrolling that occurs due
to "momentum" after you've finished a two-finger swipe on the touchpad)
is to put two fingers down again and move them slightly. This is an
awkward gesture, compared to most platforms where you just touch the pad
again and scrolling stops.
The trouble is that there is currently no API by which we can tell apps
to stop a fling. Instead, make a fake finger at the current cursor
location, then immediately cancel it. This stops flings without side
effects (e.g. activating UI elements, inking in drawing apps, moving the
insertion point in text fields, etc.) in every app I've tried it in [0],
except for a number of issues in Google Docs, Sheets, and Slides (both
the Android apps and when opened in Chrome). We'll have to talk to the
relevant teams about this. Follow-up CLs will make an API change to make
it easier to distinguish these fling stops from actual clicks.
[0]: Calendar, Chrome [1, 2], Docs, Files, Firefox Beta [1, 2], Gmail,
Google, Keep, Maps, News, Photos, Play Store, Podcasts, Settings,
Sheets, Slides, Word, YouTube
[1]: https://www.longestjokeintheworld.com/
[2]: https://codepen.io/caraya/embed/ZyQMWd
Bug: 281106755
Test: start flings in a number of apps [0], touch the touchpad, and
check that the fling stops without causing other side effects
Change-Id: Ie8504dc047ee23b5524d5372f65adfaa75a76cd8
diff --git a/libs/input/input_flags.aconfig b/libs/input/input_flags.aconfig
index ec7a284..63f49f4 100644
--- a/libs/input/input_flags.aconfig
+++ b/libs/input/input_flags.aconfig
@@ -118,3 +118,10 @@
description: "Controls the API to provide InputDevice view behavior."
bug: "246946631"
}
+
+flag {
+ name: "enable_touchpad_fling_stop"
+ namespace: "input"
+ description: "Enable fling scrolling to be stopped by putting a finger on the touchpad again"
+ bug: "281106755"
+}
diff --git a/services/inputflinger/reader/mapper/gestures/GestureConverter.cpp b/services/inputflinger/reader/mapper/gestures/GestureConverter.cpp
index 19788ce..797ebcc 100644
--- a/services/inputflinger/reader/mapper/gestures/GestureConverter.cpp
+++ b/services/inputflinger/reader/mapper/gestures/GestureConverter.cpp
@@ -67,7 +67,8 @@
: mDeviceId(deviceId),
mReaderContext(readerContext),
mPointerController(readerContext.getPointerController(deviceId)),
- mEnablePointerChoreographer(input_flags::enable_pointer_choreographer()) {
+ mEnablePointerChoreographer(input_flags::enable_pointer_choreographer()),
+ mEnableFlingStop(input_flags::enable_touchpad_fling_stop()) {
deviceContext.getAbsoluteAxisInfo(ABS_MT_POSITION_X, &mXAxisInfo);
deviceContext.getAbsoluteAxisInfo(ABS_MT_POSITION_Y, &mYAxisInfo);
}
@@ -400,20 +401,55 @@
// ensure consistency between touchscreen and touchpad flings), so we're just using
// the "start fling" gestures as a marker for the end of a two-finger scroll
// gesture.
+ mFlingMayBeInProgress = true;
return endScroll(when, readTime);
}
break;
case GESTURES_FLING_TAP_DOWN:
if (mCurrentClassification == MotionClassification::NONE) {
- // Use the tap down state of a fling gesture as an indicator that a contact
- // has been initiated with the touchpad. We treat this as a move event with zero
- // magnitude, which will also result in the pointer icon being updated.
- // TODO(b/282023644): Add a signal in libgestures for when a stable contact has been
- // initiated with a touchpad.
- return handleMove(when, readTime, gestureStartTime,
- Gesture(kGestureMove, gesture.start_time, gesture.end_time,
- /*dx=*/0.f,
- /*dy=*/0.f));
+ if (mEnableFlingStop && mFlingMayBeInProgress) {
+ // The user has just touched the pad again after ending a two-finger scroll
+ // motion, which might have started a fling. We want to stop the fling, but
+ // unfortunately there's currently no API for doing so. Instead, send and
+ // immediately cancel a fake finger to cause the scrolling to stop and hopefully
+ // avoid side effects (e.g. activation of UI elements).
+ // TODO(b/326056750): add an API for fling stops.
+ mFlingMayBeInProgress = false;
+ const auto [xCursorPosition, yCursorPosition] = mEnablePointerChoreographer
+ ? FloatPoint{0, 0}
+ : mPointerController->getPosition();
+ PointerCoords coords;
+ coords.clear();
+ coords.setAxisValue(AMOTION_EVENT_AXIS_X, xCursorPosition);
+ coords.setAxisValue(AMOTION_EVENT_AXIS_Y, yCursorPosition);
+ coords.setAxisValue(AMOTION_EVENT_AXIS_RELATIVE_X, 0);
+ coords.setAxisValue(AMOTION_EVENT_AXIS_RELATIVE_Y, 0);
+
+ std::list<NotifyArgs> out;
+ mDownTime = when;
+ out += exitHover(when, readTime, xCursorPosition, yCursorPosition);
+ // TODO(b/281106755): add a MotionClassification value for fling stops.
+ out.push_back(makeMotionArgs(when, readTime, AMOTION_EVENT_ACTION_DOWN,
+ /*actionButton=*/0, /*buttonState=*/0,
+ /*pointerCount=*/1, &coords, xCursorPosition,
+ yCursorPosition));
+ out.push_back(makeMotionArgs(when, readTime, AMOTION_EVENT_ACTION_CANCEL,
+ /*actionButton=*/0, /*buttonState=*/0,
+ /*pointerCount=*/1, &coords, xCursorPosition,
+ yCursorPosition));
+ out += enterHover(when, readTime, xCursorPosition, yCursorPosition);
+ return out;
+ } else {
+ // Use the tap down state of a fling gesture as an indicator that a contact
+ // has been initiated with the touchpad. We treat this as a move event with zero
+ // magnitude, which will also result in the pointer icon being updated.
+ // TODO(b/282023644): Add a signal in libgestures for when a stable contact has
+ // been initiated with a touchpad.
+ return handleMove(when, readTime, gestureStartTime,
+ Gesture(kGestureMove, gesture.start_time, gesture.end_time,
+ /*dx=*/0.f,
+ /*dy=*/0.f));
+ }
}
break;
default:
diff --git a/services/inputflinger/reader/mapper/gestures/GestureConverter.h b/services/inputflinger/reader/mapper/gestures/GestureConverter.h
index 07cc56c..ffab039 100644
--- a/services/inputflinger/reader/mapper/gestures/GestureConverter.h
+++ b/services/inputflinger/reader/mapper/gestures/GestureConverter.h
@@ -106,6 +106,7 @@
InputReaderContext& mReaderContext;
std::shared_ptr<PointerControllerInterface> mPointerController;
const bool mEnablePointerChoreographer;
+ const bool mEnableFlingStop;
std::optional<int32_t> mDisplayId;
FloatRect mBoundsInLogicalDisplay{};
@@ -120,6 +121,9 @@
// Whether we are currently in a hover state (i.e. a HOVER_ENTER event has been sent without a
// matching HOVER_EXIT).
bool mIsHovering = false;
+ // Whether we've received a "fling start" gesture (i.e. the end of a scroll) but no "fling tap
+ // down" gesture to match it yet.
+ bool mFlingMayBeInProgress = false;
MotionClassification mCurrentClassification = MotionClassification::NONE;
// Only used when mCurrentClassification is MULTI_FINGER_SWIPE.
diff --git a/services/inputflinger/tests/GestureConverter_test.cpp b/services/inputflinger/tests/GestureConverter_test.cpp
index 1630769..0cd0d46 100644
--- a/services/inputflinger/tests/GestureConverter_test.cpp
+++ b/services/inputflinger/tests/GestureConverter_test.cpp
@@ -47,6 +47,7 @@
} // namespace
using testing::AllOf;
+using testing::Each;
using testing::ElementsAre;
using testing::VariantWith;
@@ -1229,6 +1230,38 @@
ASSERT_TRUE(mFakePointerController->isPointerShown());
}
+TEST_F(GestureConverterTest, FlingTapDownAfterScrollStopsFling) {
+ InputDeviceContext deviceContext(*mDevice, EVENTHUB_ID);
+ input_flags::enable_touchpad_fling_stop(true);
+ GestureConverter converter(*mReader->getContext(), deviceContext, DEVICE_ID);
+ converter.setDisplayId(ADISPLAY_ID_DEFAULT);
+
+ Gesture scrollGesture(kGestureScroll, ARBITRARY_GESTURE_TIME, ARBITRARY_GESTURE_TIME, 0, -10);
+ std::list<NotifyArgs> args =
+ converter.handleGesture(ARBITRARY_TIME, READ_TIME, ARBITRARY_TIME, scrollGesture);
+ Gesture flingGesture(kGestureFling, ARBITRARY_GESTURE_TIME, ARBITRARY_GESTURE_TIME, 1, 1,
+ GESTURES_FLING_START);
+ args = converter.handleGesture(ARBITRARY_TIME, READ_TIME, ARBITRARY_TIME, flingGesture);
+
+ Gesture tapDownGesture(kGestureFling, ARBITRARY_GESTURE_TIME, ARBITRARY_GESTURE_TIME,
+ /*vx=*/0.f, /*vy=*/0.f, GESTURES_FLING_TAP_DOWN);
+ args = converter.handleGesture(ARBITRARY_TIME, READ_TIME, ARBITRARY_TIME, tapDownGesture);
+ ASSERT_THAT(args,
+ ElementsAre(VariantWith<NotifyMotionArgs>(
+ WithMotionAction(AMOTION_EVENT_ACTION_HOVER_EXIT)),
+ VariantWith<NotifyMotionArgs>(
+ WithMotionAction(AMOTION_EVENT_ACTION_DOWN)),
+ VariantWith<NotifyMotionArgs>(
+ WithMotionAction(AMOTION_EVENT_ACTION_CANCEL)),
+ VariantWith<NotifyMotionArgs>(
+ AllOf(WithMotionAction(AMOTION_EVENT_ACTION_HOVER_ENTER),
+ WithMotionClassification(MotionClassification::NONE)))));
+ ASSERT_THAT(args,
+ Each(VariantWith<NotifyMotionArgs>(AllOf(WithCoords(POINTER_X, POINTER_Y),
+ WithToolType(ToolType::FINGER),
+ WithDisplayId(ADISPLAY_ID_DEFAULT)))));
+}
+
TEST_F(GestureConverterTest, Tap) {
// Tap should produce button press/release events
InputDeviceContext deviceContext(*mDevice, EVENTHUB_ID);
@@ -2717,6 +2750,38 @@
WithButtonState(0), WithPressure(0.0f), WithDisplayId(ADISPLAY_ID_DEFAULT)));
}
+TEST_F(GestureConverterTestWithChoreographer, FlingTapDownAfterScrollStopsFling) {
+ InputDeviceContext deviceContext(*mDevice, EVENTHUB_ID);
+ input_flags::enable_touchpad_fling_stop(true);
+ GestureConverter converter(*mReader->getContext(), deviceContext, DEVICE_ID);
+ converter.setDisplayId(ADISPLAY_ID_DEFAULT);
+
+ Gesture scrollGesture(kGestureScroll, ARBITRARY_GESTURE_TIME, ARBITRARY_GESTURE_TIME, 0, -10);
+ std::list<NotifyArgs> args =
+ converter.handleGesture(ARBITRARY_TIME, READ_TIME, ARBITRARY_TIME, scrollGesture);
+ Gesture flingGesture(kGestureFling, ARBITRARY_GESTURE_TIME, ARBITRARY_GESTURE_TIME, 1, 1,
+ GESTURES_FLING_START);
+ args = converter.handleGesture(ARBITRARY_TIME, READ_TIME, ARBITRARY_TIME, flingGesture);
+
+ Gesture tapDownGesture(kGestureFling, ARBITRARY_GESTURE_TIME, ARBITRARY_GESTURE_TIME,
+ /*vx=*/0.f, /*vy=*/0.f, GESTURES_FLING_TAP_DOWN);
+ args = converter.handleGesture(ARBITRARY_TIME, READ_TIME, ARBITRARY_TIME, tapDownGesture);
+ ASSERT_THAT(args,
+ ElementsAre(VariantWith<NotifyMotionArgs>(
+ WithMotionAction(AMOTION_EVENT_ACTION_HOVER_EXIT)),
+ VariantWith<NotifyMotionArgs>(
+ WithMotionAction(AMOTION_EVENT_ACTION_DOWN)),
+ VariantWith<NotifyMotionArgs>(
+ WithMotionAction(AMOTION_EVENT_ACTION_CANCEL)),
+ VariantWith<NotifyMotionArgs>(
+ AllOf(WithMotionAction(AMOTION_EVENT_ACTION_HOVER_ENTER),
+ WithMotionClassification(MotionClassification::NONE)))));
+ ASSERT_THAT(args,
+ Each(VariantWith<NotifyMotionArgs>(AllOf(WithCoords(0, 0),
+ WithToolType(ToolType::FINGER),
+ WithDisplayId(ADISPLAY_ID_DEFAULT)))));
+}
+
TEST_F(GestureConverterTestWithChoreographer, Tap) {
// Tap should produce button press/release events
InputDeviceContext deviceContext(*mDevice, EVENTHUB_ID);