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Fix interference in fling-scrolling from cross-axis motion #122338

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merged 2 commits into from
Mar 17, 2023
Merged

Fix interference in fling-scrolling from cross-axis motion #122338

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286701b
Fix interference in fling-scrolling from cross-axis motion
gnprice Mar 8, 2023
1f0b23a
Merge branch 'master' into pr-scroll-clamping
Piinks Mar 17, 2023
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8 changes: 6 additions & 2 deletions packages/flutter/lib/src/gestures/drag_details.dart
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Original file line number Diff line number Diff line change
Expand Up @@ -216,14 +216,18 @@ typedef GestureDragUpdateCallback = void Function(DragUpdateDetails details);
class DragEndDetails {
/// Creates details for a [GestureDragEndCallback].
///
/// If [primaryVelocity] is non-null, its value must match one of the
/// coordinates of `velocity.pixelsPerSecond` and the other coordinate
/// must be zero.
///
/// The [velocity] argument must not be null.
DragEndDetails({
this.velocity = Velocity.zero,
this.primaryVelocity,
}) : assert(
primaryVelocity == null
|| primaryVelocity == velocity.pixelsPerSecond.dx
|| primaryVelocity == velocity.pixelsPerSecond.dy,
|| (primaryVelocity == velocity.pixelsPerSecond.dx && velocity.pixelsPerSecond.dy == 0)
|| (primaryVelocity == velocity.pixelsPerSecond.dy && velocity.pixelsPerSecond.dx == 0),
);

/// The velocity the pointer was moving when it stopped contacting the screen.
Expand Down
93 changes: 70 additions & 23 deletions packages/flutter/lib/src/gestures/monodrag.dart
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Original file line number Diff line number Diff line change
Expand Up @@ -147,6 +147,14 @@ abstract class DragGestureRecognizer extends OneSequenceGestureRecognizer {
/// The distance traveled by the pointer since the last update is provided in
/// the callback's `details` argument, which is a [DragUpdateDetails] object.
///
/// If this gesture recognizer recognizes movement on a single axis (a
/// [VerticalDragGestureRecognizer] or [HorizontalDragGestureRecognizer]),
/// then `details` will reflect movement only on that axis and its
/// [DragUpdateDetails.primaryDelta] will be non-null.
/// If this gesture recognizer recognizes movement in all directions
/// (a [PanGestureRecognizer]), then `details` will reflect movement on
/// both axes and its [DragUpdateDetails.primaryDelta] will be null.
///
/// See also:
///
/// * [allowedButtonsFilter], which decides which button will be allowed.
Expand All @@ -162,6 +170,14 @@ abstract class DragGestureRecognizer extends OneSequenceGestureRecognizer {
/// The velocity is provided in the callback's `details` argument, which is a
/// [DragEndDetails] object.
///
/// If this gesture recognizer recognizes movement on a single axis (a
/// [VerticalDragGestureRecognizer] or [HorizontalDragGestureRecognizer]),
/// then `details` will reflect movement only on that axis and its
/// [DragEndDetails.primaryVelocity] will be non-null.
/// If this gesture recognizer recognizes movement in all directions
/// (a [PanGestureRecognizer]), then `details` will reflect movement on
/// both axes and its [DragEndDetails.primaryVelocity] will be null.
///
/// See also:
///
/// * [allowedButtonsFilter], which decides which button will be allowed.
Expand Down Expand Up @@ -258,6 +274,13 @@ abstract class DragGestureRecognizer extends OneSequenceGestureRecognizer {
/// inertia, for example.
bool isFlingGesture(VelocityEstimate estimate, PointerDeviceKind kind);

/// Determines if a gesture is a fling or not, and if so its effective velocity.
///
/// A fling calls its gesture end callback with a velocity, allowing the
/// provider of the callback to respond by carrying the gesture forward with
/// inertia, for example.
DragEndDetails? _considerFling(VelocityEstimate estimate, PointerDeviceKind kind);

Offset _getDeltaForDetails(Offset delta);
double? _getPrimaryValueFromOffset(Offset value);
bool _hasSufficientGlobalDistanceToAccept(PointerDeviceKind pointerDeviceKind, double? deviceTouchSlop);
Expand Down Expand Up @@ -504,33 +527,21 @@ abstract class DragGestureRecognizer extends OneSequenceGestureRecognizer {
}

final VelocityTracker tracker = _velocityTrackers[pointer]!;
final VelocityEstimate? estimate = tracker.getVelocityEstimate();

final DragEndDetails details;
DragEndDetails? details;
final String Function() debugReport;

final VelocityEstimate? estimate = tracker.getVelocityEstimate();
if (estimate != null && isFlingGesture(estimate, tracker.kind)) {
final Velocity velocity = Velocity(pixelsPerSecond: estimate.pixelsPerSecond)
.clampMagnitude(minFlingVelocity ?? kMinFlingVelocity, maxFlingVelocity ?? kMaxFlingVelocity);
details = DragEndDetails(
velocity: velocity,
primaryVelocity: _getPrimaryValueFromOffset(velocity.pixelsPerSecond),
);
debugReport = () {
return '$estimate; fling at $velocity.';
};
if (estimate == null) {
debugReport = () => 'Could not estimate velocity.';
} else {
details = DragEndDetails(
primaryVelocity: 0.0,
);
debugReport = () {
if (estimate == null) {
return 'Could not estimate velocity.';
}
return '$estimate; judged to not be a fling.';
};
details = _considerFling(estimate, tracker.kind);
debugReport = (details != null)
? () => '$estimate; fling at ${details!.velocity}.'
: () => '$estimate; judged to not be a fling.';
}
invokeCallback<void>('onEnd', () => onEnd!(details), debugReport: debugReport);
details ??= DragEndDetails(primaryVelocity: 0.0);

invokeCallback<void>('onEnd', () => onEnd!(details!), debugReport: debugReport);
}

void _checkCancel() {
Expand Down Expand Up @@ -578,6 +589,19 @@ class VerticalDragGestureRecognizer extends DragGestureRecognizer {
return estimate.pixelsPerSecond.dy.abs() > minVelocity && estimate.offset.dy.abs() > minDistance;
}

@override
DragEndDetails? _considerFling(VelocityEstimate estimate, PointerDeviceKind kind) {
if (!isFlingGesture(estimate, kind)) {
return null;
}
final double maxVelocity = maxFlingVelocity ?? kMaxFlingVelocity;
final double dy = clampDouble(estimate.pixelsPerSecond.dy, -maxVelocity, maxVelocity);
return DragEndDetails(
velocity: Velocity(pixelsPerSecond: Offset(0, dy)),
primaryVelocity: dy,
);
}

@override
bool _hasSufficientGlobalDistanceToAccept(PointerDeviceKind pointerDeviceKind, double? deviceTouchSlop) {
return _globalDistanceMoved.abs() > computeHitSlop(pointerDeviceKind, gestureSettings);
Expand Down Expand Up @@ -620,6 +644,19 @@ class HorizontalDragGestureRecognizer extends DragGestureRecognizer {
return estimate.pixelsPerSecond.dx.abs() > minVelocity && estimate.offset.dx.abs() > minDistance;
}

@override
DragEndDetails? _considerFling(VelocityEstimate estimate, PointerDeviceKind kind) {
if (!isFlingGesture(estimate, kind)) {
return null;
}
final double maxVelocity = maxFlingVelocity ?? kMaxFlingVelocity;
final double dx = clampDouble(estimate.pixelsPerSecond.dx, -maxVelocity, maxVelocity);
return DragEndDetails(
velocity: Velocity(pixelsPerSecond: Offset(dx, 0)),
primaryVelocity: dx,
);
}

@override
bool _hasSufficientGlobalDistanceToAccept(PointerDeviceKind pointerDeviceKind, double? deviceTouchSlop) {
return _globalDistanceMoved.abs() > computeHitSlop(pointerDeviceKind, gestureSettings);
Expand Down Expand Up @@ -660,6 +697,16 @@ class PanGestureRecognizer extends DragGestureRecognizer {
&& estimate.offset.distanceSquared > minDistance * minDistance;
}

@override
DragEndDetails? _considerFling(VelocityEstimate estimate, PointerDeviceKind kind) {
if (!isFlingGesture(estimate, kind)) {
return null;
}
final Velocity velocity = Velocity(pixelsPerSecond: estimate.pixelsPerSecond)
.clampMagnitude(minFlingVelocity ?? kMinFlingVelocity, maxFlingVelocity ?? kMaxFlingVelocity);
return DragEndDetails(velocity: velocity);
}

@override
bool _hasSufficientGlobalDistanceToAccept(PointerDeviceKind pointerDeviceKind, double? deviceTouchSlop) {
return _globalDistanceMoved.abs() > computePanSlop(pointerDeviceKind, gestureSettings);
Expand Down
80 changes: 80 additions & 0 deletions packages/flutter/test/gestures/drag_test.dart
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Original file line number Diff line number Diff line change
Expand Up @@ -569,6 +569,86 @@ void main() {
expect(primaryVelocity, velocity.pixelsPerSecond.dx);
});

/// Drag the pointer at the given velocity, and return the details
/// the recognizer passes to onEnd.
///
/// This method will mutate `recognizer.onEnd`.
DragEndDetails performDragToEnd(GestureTester tester, DragGestureRecognizer recognizer, Offset pointerVelocity) {
late DragEndDetails actual;
recognizer.onEnd = (DragEndDetails details) {
actual = details;
};
final TestPointer pointer = TestPointer();
final PointerDownEvent down = pointer.down(Offset.zero);
recognizer.addPointer(down);
tester.closeArena(pointer.pointer);
tester.route(down);
tester.route(pointer.move(pointerVelocity * 0.025, timeStamp: const Duration(milliseconds: 25)));
tester.route(pointer.move(pointerVelocity * 0.050, timeStamp: const Duration(milliseconds: 50)));
tester.route(pointer.up(timeStamp: const Duration(milliseconds: 50)));
return actual;
}

testGesture('Clamp max pan velocity in 2D, isotropically', (GestureTester tester) {
final PanGestureRecognizer recognizer = PanGestureRecognizer();
addTearDown(recognizer.dispose);

void checkDrag(Offset pointerVelocity, Offset expectedVelocity) {
final DragEndDetails actual = performDragToEnd(tester, recognizer, pointerVelocity);
expect(actual.velocity.pixelsPerSecond, offsetMoreOrLessEquals(expectedVelocity, epsilon: 0.1));
expect(actual.primaryVelocity, isNull);
}

checkDrag(const Offset( 400.0, 400.0), const Offset( 400.0, 400.0));
checkDrag(const Offset( 2000.0, -2000.0), const Offset( 2000.0, -2000.0));
checkDrag(const Offset(-8000.0, -8000.0), const Offset(-5656.9, -5656.9));
checkDrag(const Offset(-8000.0, 6000.0), const Offset(-6400.0, 4800.0));
checkDrag(const Offset(-9000.0, 0.0), const Offset(-8000.0, 0.0));
checkDrag(const Offset(-9000.0, -1000.0), const Offset(-7951.1, - 883.5));
checkDrag(const Offset(-1000.0, 9000.0), const Offset(- 883.5, 7951.1));
checkDrag(const Offset( 0.0, 9000.0), const Offset( 0.0, 8000.0));
});

testGesture('Clamp max vertical-drag velocity vertically', (GestureTester tester) {
final VerticalDragGestureRecognizer recognizer = VerticalDragGestureRecognizer();
addTearDown(recognizer.dispose);

void checkDrag(Offset pointerVelocity, double expectedVelocity) {
final DragEndDetails actual = performDragToEnd(tester, recognizer, pointerVelocity);
expect(actual.primaryVelocity, moreOrLessEquals(expectedVelocity, epsilon: 0.1));
expect(actual.velocity.pixelsPerSecond.dx, 0.0);
expect(actual.velocity.pixelsPerSecond.dy, actual.primaryVelocity);
}

checkDrag(const Offset( 500.0, 400.0), 400.0);
checkDrag(const Offset( 3000.0, -2000.0), -2000.0);
checkDrag(const Offset(-9000.0, -9000.0), -8000.0);
checkDrag(const Offset(-9000.0, 0.0), 0.0);
checkDrag(const Offset(-9000.0, 1000.0), 1000.0);
checkDrag(const Offset(-1000.0, -9000.0), -8000.0);
checkDrag(const Offset( 0.0, -9000.0), -8000.0);
});

testGesture('Clamp max horizontal-drag velocity horizontally', (GestureTester tester) {
final HorizontalDragGestureRecognizer recognizer = HorizontalDragGestureRecognizer();
addTearDown(recognizer.dispose);

void checkDrag(Offset pointerVelocity, double expectedVelocity) {
final DragEndDetails actual = performDragToEnd(tester, recognizer, pointerVelocity);
expect(actual.primaryVelocity, moreOrLessEquals(expectedVelocity, epsilon: 0.1));
expect(actual.velocity.pixelsPerSecond.dx, actual.primaryVelocity);
expect(actual.velocity.pixelsPerSecond.dy, 0.0);
}

checkDrag(const Offset( 500.0, 400.0), 500.0);
checkDrag(const Offset( 3000.0, -2000.0), 3000.0);
checkDrag(const Offset(-9000.0, -9000.0), -8000.0);
checkDrag(const Offset(-9000.0, 0.0), -8000.0);
checkDrag(const Offset(-9000.0, 1000.0), -8000.0);
checkDrag(const Offset(-1000.0, -9000.0), -1000.0);
checkDrag(const Offset( 0.0, -9000.0), 0.0);
});

testGesture('Synthesized pointer events are ignored for velocity tracking', (GestureTester tester) {
final HorizontalDragGestureRecognizer drag = HorizontalDragGestureRecognizer() ..dragStartBehavior = DragStartBehavior.down;
addTearDown(drag.dispose);
Expand Down