edde746
7e1f18f93f
Android enables Flutter semantics for any bound accessibility service, so a TV running the Projectivy Launcher (whose service only wants foreground-app events) paid for a full semantics tree on every frame that touched a node: on an Android 14 box, 2 ms per frame, ~20 ms on each spotlight swap, and a third of the navigation-time GC churn. The Android side now reports whether any enabled service can consume the tree (touch exploration, an accessibility tool, or spoken/braille/audible/ visual feedback; an empty list means UiAutomation, which reads it too), and AssistiveTechnologyService closes a SemanticsTreeGate on the app binding when none can. The gate sits under SemanticsBinding.semanticsEnabled, so the pipeline owner drops the semantics owner exactly as if the platform had turned accessibility off; explicit ensureSemantics clients (the debug handle for Maestro) always win. Re-evaluated on platform toggles, service-list changes (API 33+) and resume. Cold navigation on the box with Projectivy's service bound, 30 D-pad steps over three hubs: SEMANTICS phase 700-770 ms -> 0, UI frame max 31-37 ms -> 25 ms, GC 3.0 s -> 2.2-2.6 s.
71 lines
3.1 KiB
Dart
71 lines
3.1 KiB
Dart
import 'package:flutter/gestures.dart';
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import 'package:flutter/widgets.dart';
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import 'semantics_tree_gate.dart';
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/// Collapses a diagonal scroll signal onto the axis the viewer actually moved.
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///
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/// A wheel, trackpoint, trackball or button-scroll event expresses one-axis
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/// intent, but the host can report both axes in the same event: on Linux only
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/// touchpad-sourced scrolling becomes a pan/zoom sequence (which resolves in the
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/// gesture arena), while wheel/continuous/tilt sources arrive as a single
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/// [PointerScrollEvent] carrying whatever `dx` the device produced. A trackball
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/// or libinput button-scrolling maps pointer motion straight onto both axes, so
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/// `dx` is essentially never zero there.
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///
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/// That matters because [Scrollable] claims a scroll signal as soon as the delta
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/// along *its own* axis is non-zero, and the deepest claimant wins the
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/// [PointerSignalResolver]. One pixel of `dx` therefore hands the whole event to
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/// a horizontal hub row and the page behind it never scrolls — the Home,
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/// library Recommended and media-detail freeze reported in #2081, on exactly the
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/// screens whose viewport is covered by horizontal rows.
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///
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/// Returns [event] unchanged when it is already single-axis, so the common wheel
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/// path allocates nothing.
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PointerScrollEvent lockScrollSignalToDominantAxis(PointerScrollEvent event) {
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final Offset delta = event.scrollDelta;
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if (delta.dx == 0.0 || delta.dy == 0.0) return event;
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// Ties go to the vertical axis: pages scroll vertically, rows are the nested
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// exception, so an ambiguous event should reach the page.
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final Offset dominant = delta.dx.abs() > delta.dy.abs() ? Offset(delta.dx, 0.0) : Offset(0.0, delta.dy);
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return PointerScrollEvent(
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viewId: event.viewId,
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timeStamp: event.timeStamp,
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kind: event.kind,
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device: event.device,
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position: event.position,
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scrollDelta: dominant,
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embedderId: event.embedderId,
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onRespond: event.respond,
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);
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}
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/// Applies [lockScrollSignalToDominantAxis] to every scroll signal before it is
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/// hit-tested, which is the only place the delta can still be corrected: by the
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/// time a [Scrollable] sees the event it has already registered with the
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/// [PointerSignalResolver], and only the first (deepest) registration runs.
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///
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/// Pan/zoom events are left alone — trackpad panning is resolved by the gesture
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/// arena, which already prefers the axis the viewer moved along.
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mixin PointerScrollAxisLock on GestureBinding {
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@override
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void handlePointerEvent(PointerEvent event) {
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super.handlePointerEvent(event is PointerScrollEvent ? lockScrollSignalToDominantAxis(event) : event);
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}
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}
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/// The app's binding: installs [PointerScrollAxisLock] and [SemanticsTreeGate].
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class PlezyWidgetsBinding extends WidgetsFlutterBinding with PointerScrollAxisLock, SemanticsTreeGate {
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static bool _initialized = false;
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/// Creates the binding on first call and returns it afterwards, mirroring
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/// [WidgetsFlutterBinding.ensureInitialized].
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static WidgetsBinding ensureInitialized() {
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if (!_initialized) {
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PlezyWidgetsBinding();
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_initialized = true;
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}
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return WidgetsBinding.instance;
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}
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}
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