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viewer: improved panning inertia

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This commit is contained in:
Thibault Deckers 2020-12-24 11:36:06 +09:00
parent e914188917
commit 640bb272dd
1 changed files with 43 additions and 32 deletions
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75
lib/widgets/common/magnifier/core/core.dart
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@ -19,6 +19,7 @@ class MagnifierCore extends StatefulWidget {
@required this.controller, @required this.controller,
@required this.scaleStateCycle, @required this.scaleStateCycle,
@required this.applyScale, @required this.applyScale,
this.panInertia = .2,
}) : super(key: key); }) : super(key: key);
final Widget child; final Widget child;
@ -30,6 +31,7 @@ class MagnifierCore extends StatefulWidget {
final HitTestBehavior gestureDetectorBehavior; final HitTestBehavior gestureDetectorBehavior;
final bool applyScale; final bool applyScale;
final double panInertia;
@override @override
State<StatefulWidget> createState() { State<StatefulWidget> createState() {
@ -41,6 +43,7 @@ class MagnifierCoreState extends State<MagnifierCore> with TickerProviderStateMi
Offset _startFocalPoint, _lastViewportFocalPosition; Offset _startFocalPoint, _lastViewportFocalPosition;
double _startScale, _quickScaleLastY, _quickScaleLastDistance; double _startScale, _quickScaleLastY, _quickScaleLastDistance;
bool _doubleTap, _quickScaleMoved; bool _doubleTap, _quickScaleMoved;
DateTime _lastScaleGestureDate;
AnimationController _scaleAnimationController; AnimationController _scaleAnimationController;
Animation<double> _scaleAnimation; Animation<double> _scaleAnimation;
@ -105,47 +108,55 @@ class MagnifierCoreState extends State<MagnifierCore> with TickerProviderStateMi
} }
void onScaleEnd(ScaleEndDetails details) { void onScaleEnd(ScaleEndDetails details) {
final _scale = scale;
final _position = controller.position; final _position = controller.position;
final _scale = controller.scale;
final maxScale = scaleBoundaries.maxScale; final maxScale = scaleBoundaries.maxScale;
final minScale = scaleBoundaries.minScale; final minScale = scaleBoundaries.minScale;
//animate back to maxScale if gesture exceeded the maxScale specified // animate back to min/max scale if gesture yielded a scale exceeding them
if (_scale > maxScale) { if (_scale > maxScale || _scale < minScale) {
final scaleComebackRatio = maxScale / _scale; final newScale = _scale.clamp(minScale, maxScale);
animateScale(_scale, maxScale); final newPosition = clampPosition(position: _position * newScale / _scale, scale: newScale);
final clampedPosition = clampPosition( animateScale(_scale, newScale);
position: _position * scaleComebackRatio, animatePosition(_position, newPosition);
scale: maxScale,
);
animatePosition(_position, clampedPosition);
return; return;
} }
//animate back to minScale if gesture fell smaller than the minScale specified // The gesture recognizer triggers a new `onScaleStart` every time a pointer/finger is added or removed.
if (_scale < minScale) { // Following a pinch-to-zoom gesture, a new panning gesture may start if the user does not lift both fingers at the same time,
final scaleComebackRatio = minScale / _scale; // so we dismiss such panning gestures when it looks like it followed a scaling gesture.
animateScale(_scale, minScale); final isPanning = _scale == _startScale && (DateTime.now().difference(_lastScaleGestureDate)).inMilliseconds > 100;
animatePosition(
_position,
clampPosition(
position: _position * scaleComebackRatio,
scale: minScale,
),
);
return;
}
// get magnitude from gesture velocity
final magnitude = details.velocity.pixelsPerSecond.distance;
// animate velocity only if there is no scale change and a significant magnitude // animate position only when panning without scaling
if (_startScale / _scale == 1.0 && magnitude >= 400.0) { if (isPanning) {
final direction = details.velocity.pixelsPerSecond / magnitude; final pps = details.velocity.pixelsPerSecond;
animatePosition( if (pps != Offset.zero) {
_position, final newPosition = clampPosition(position: _position + pps * widget.panInertia);
clampPosition(position: _position + direction * 100.0), final tween = Tween<Offset>(begin: _position, end: newPosition);
); const curve = Curves.easeOutCubic;
_positionAnimation = tween.animate(CurvedAnimation(parent: _positionAnimationController, curve: curve));
_positionAnimationController
..duration = _getAnimationDurationForVelocity(curve: curve, tween: tween, targetPixelPerSecond: pps)
..forward(from: 0.0);
}
} }
if (_scale != _startScale) {
_lastScaleGestureDate = DateTime.now();
}
}
Duration _getAnimationDurationForVelocity({
Cubic curve,
Tween<Offset> tween,
Offset targetPixelPerSecond,
}) {
assert(targetPixelPerSecond != Offset.zero);
// find initial animation velocity over the first 20% of the specified curve
const t = 0.2;
final animationVelocity = (tween.end - tween.begin).distance * curve.transform(t) / t;
final gestureVelocity = targetPixelPerSecond.distance;
return Duration(milliseconds: (animationVelocity / gestureVelocity * 1000).round());
} }
void onTap(TapUpDetails details) { void onTap(TapUpDetails details) {