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chore(mobile): simplify asset page scroll (#26635)

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In order to scroll smoothly without interfering with the gesture
detector on the photo view, we have an offstate scroll view which we
defer all drags to, and then forward scroll offsets to the real scroll
controller. This works well, but it can be simpler. Instead, we can
create a custom scroll controller on a scroll view with never scrollable
physics, and then forward drag events to that, bypassing the need for a
proxy scroll controller.

Co-authored-by: Alex <alex.tran1502@gmail.com>
This commit is contained in:
Thomas 2026-03-04 16:28:55 +00:00 committed by GitHub
parent dd03c9c0a9
commit 7e9da945f6
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GPG Key ID: B5690EEEBB952194
2 changed files with 46 additions and 110 deletions
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109
mobile/lib/extensions/scroll_extensions.dart
View File

@ -33,12 +33,27 @@ class FastClampingScrollPhysics extends ClampingScrollPhysics {
);
}
class SnapScrollController extends ScrollController {
SnapScrollPosition get snapPosition => position as SnapScrollPosition;
@override
ScrollPosition createScrollPosition(ScrollPhysics physics, ScrollContext context, ScrollPosition? oldPosition) =>
SnapScrollPosition(physics: physics, context: context, oldPosition: oldPosition);
}
class SnapScrollPosition extends ScrollPositionWithSingleContext {
double snapOffset;
SnapScrollPosition({required super.physics, required super.context, super.oldPosition, this.snapOffset = 0.0});
@override
bool get shouldIgnorePointer => false;
}
class SnapScrollPhysics extends ScrollPhysics {
static const _minFlingVelocity = 700.0;
static const minSnapDistance = 30.0;
static final _spring = SpringDescription.withDampingRatio(mass: .5, stiffness: 300);
const SnapScrollPhysics({super.parent});
@override
@ -66,91 +81,21 @@ class SnapScrollPhysics extends ScrollPhysics {
}
}
return ScrollSpringSimulation(
_spring,
position.pixels,
target(position, velocity, snapOffset),
velocity,
tolerance: toleranceFor(position),
);
return ScrollSpringSimulation(spring, position.pixels, target(position, velocity, snapOffset), velocity);
}
@override
SpringDescription get spring => SpringDescription.withDampingRatio(mass: .5, stiffness: 300);
@override
bool get allowImplicitScrolling => false;
@override
bool get allowUserScrolling => false;
static double target(ScrollMetrics position, double velocity, double snapOffset) {
if (velocity > _minFlingVelocity) return snapOffset;
if (velocity < -_minFlingVelocity) return position.pixels < snapOffset ? 0.0 : snapOffset;
return position.pixels < minSnapDistance ? 0.0 : snapOffset;
}
}
class SnapScrollPosition extends ScrollPositionWithSingleContext {
double snapOffset;
SnapScrollPosition({this.snapOffset = 0.0, required super.physics, required super.context, super.oldPosition});
}
class ProxyScrollController extends ScrollController {
final ScrollController scrollController;
ProxyScrollController({required this.scrollController});
SnapScrollPosition get snapPosition => position as SnapScrollPosition;
@override
ScrollPosition createScrollPosition(ScrollPhysics physics, ScrollContext context, ScrollPosition? oldPosition) {
return ProxyScrollPosition(
scrollController: scrollController,
physics: physics,
context: context,
oldPosition: oldPosition,
);
}
@override
void dispose() {
scrollController.dispose();
super.dispose();
}
}
class ProxyScrollPosition extends SnapScrollPosition {
final ScrollController scrollController;
ProxyScrollPosition({
required this.scrollController,
required super.physics,
required super.context,
super.oldPosition,
});
@override
double setPixels(double newPixels) {
final overscroll = super.setPixels(newPixels);
if (scrollController.hasClients && scrollController.position.pixels != pixels) {
scrollController.position.forcePixels(pixels);
}
return overscroll;
}
@override
void forcePixels(double value) {
super.forcePixels(value);
if (scrollController.hasClients && scrollController.position.pixels != pixels) {
scrollController.position.forcePixels(pixels);
}
}
@override
double get maxScrollExtent => scrollController.hasClients && scrollController.position.hasContentDimensions
? scrollController.position.maxScrollExtent
: super.maxScrollExtent;
@override
double get minScrollExtent => scrollController.hasClients && scrollController.position.hasContentDimensions
? scrollController.position.minScrollExtent
: super.minScrollExtent;
@override
double get viewportDimension => scrollController.hasClients && scrollController.position.hasViewportDimension
? scrollController.position.viewportDimension
: super.viewportDimension;
}

47
mobile/lib/presentation/widgets/asset_viewer/asset_page.widget.dart
View File

@ -50,8 +50,7 @@ class _AssetPageState extends ConsumerState<AssetPage> {
bool _showingDetails = false;
bool _isZoomed = false;
final _scrollController = ScrollController();
late final _proxyScrollController = ProxyScrollController(scrollController: _scrollController);
final _scrollController = SnapScrollController();
double _snapOffset = 0.0;
DragStartDetails? _dragStart;
@ -63,17 +62,17 @@ class _AssetPageState extends ConsumerState<AssetPage> {
super.initState();
_eventSubscription = EventStream.shared.listen(_onEvent);
WidgetsBinding.instance.addPostFrameCallback((_) {
if (!mounted || !_proxyScrollController.hasClients) return;
_proxyScrollController.snapPosition.snapOffset = _snapOffset;
if (!mounted || !_scrollController.hasClients) return;
_scrollController.snapPosition.snapOffset = _snapOffset;
if (_showingDetails && _snapOffset > 0) {
_proxyScrollController.jumpTo(_snapOffset);
_scrollController.jumpTo(_snapOffset);
}
});
}
@override
void dispose() {
_proxyScrollController.dispose();
_scrollController.dispose();
_scaleBoundarySub?.cancel();
_eventSubscription?.cancel();
super.dispose();
@ -88,21 +87,20 @@ class _AssetPageState extends ConsumerState<AssetPage> {
}
void _showDetails() {
if (!_proxyScrollController.hasClients || _snapOffset <= 0) return;
if (!_scrollController.hasClients || _snapOffset <= 0) return;
_viewer.setShowingDetails(true);
_proxyScrollController.animateTo(_snapOffset, duration: Durations.medium2, curve: Curves.easeOutCubic);
_scrollController.animateTo(_snapOffset, duration: Durations.medium2, curve: Curves.easeOutCubic);
}
bool _willClose(double scrollVelocity) {
if (!_proxyScrollController.hasClients || _snapOffset <= 0) return false;
final position = _proxyScrollController.position;
return _proxyScrollController.position.pixels < _snapOffset &&
SnapScrollPhysics.target(position, scrollVelocity, _snapOffset) < SnapScrollPhysics.minSnapDistance;
}
bool _willClose(double scrollVelocity) =>
_scrollController.hasClients &&
_snapOffset > 0 &&
_scrollController.position.pixels < _snapOffset &&
SnapScrollPhysics.target(_scrollController.position, scrollVelocity, _snapOffset) <
SnapScrollPhysics.minSnapDistance;
void _syncShowingDetails() {
final offset = _proxyScrollController.offset;
final offset = _scrollController.offset;
if (offset > SnapScrollPhysics.minSnapDistance) {
_viewer.setShowingDetails(true);
} else if (offset < SnapScrollPhysics.minSnapDistance - kTouchSlop) {
@ -124,8 +122,8 @@ class _AssetPageState extends ConsumerState<AssetPage> {
}
void _startProxyDrag() {
if (_proxyScrollController.hasClients && _dragStart != null) {
_drag = _proxyScrollController.position.drag(_dragStart!, () => _drag = null);
if (_scrollController.hasClients && _dragStart != null) {
_drag = _scrollController.position.drag(_dragStart!, () => _drag = null);
}
}
@ -390,22 +388,15 @@ class _AssetPageState extends ConsumerState<AssetPage> {
_snapOffset = detailsOffset - snapTarget;
if (_proxyScrollController.hasClients) {
_proxyScrollController.snapPosition.snapOffset = _snapOffset;
if (_scrollController.hasClients) {
_scrollController.snapPosition.snapOffset = _snapOffset;
}
return Stack(
children: [
Offstage(
child: SingleChildScrollView(
controller: _proxyScrollController,
physics: const SnapScrollPhysics(),
child: const SizedBox.shrink(),
),
),
SingleChildScrollView(
controller: _scrollController,
physics: const NeverScrollableScrollPhysics(),
physics: const SnapScrollPhysics(),
child: Stack(
children: [
SizedBox(