blob: 6636f077a4ad480c25d040d15f31a8c9109133c6 [file] [log] [blame]
// Copyright 2014 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
import 'package:flutter/foundation.dart';
import 'events.dart';
/// The callback to register with a [PointerSignalResolver] to express
/// interest in a pointer signal event.
typedef PointerSignalResolvedCallback = void Function(PointerSignalEvent event);
bool _isSameEvent(PointerSignalEvent event1, PointerSignalEvent event2) {
return (event1.original ?? event1) == (event2.original ?? event2);
/// An resolver for pointer signal events.
/// Objects interested in a [PointerSignalEvent] should register a callback to
/// be called if they should handle the event. The resolver's purpose is to
/// ensure that the same pointer signal is not handled by multiple objects in
/// a hierarchy.
/// Pointer signals are immediate, so unlike a gesture arena it always resolves
/// at the end of event dispatch. The first callback registered will be the one
/// that is called.
class PointerSignalResolver {
PointerSignalResolvedCallback _firstRegisteredCallback;
PointerSignalEvent _currentEvent;
/// Registers interest in handling [event].
void register(PointerSignalEvent event, PointerSignalResolvedCallback callback) {
assert(event != null);
assert(callback != null);
assert(_currentEvent == null || _isSameEvent(_currentEvent, event));
if (_firstRegisteredCallback != null) {
_currentEvent = event;
_firstRegisteredCallback = callback;
/// Resolves the event, calling the first registered callback if there was
/// one.
/// Called after the framework has finished dispatching the pointer signal
/// event.
void resolve(PointerSignalEvent event) {
if (_firstRegisteredCallback == null) {
assert(_currentEvent == null);
assert(_isSameEvent(_currentEvent, event));
try {
} catch (exception, stack) {
InformationCollector collector;
assert(() {
collector = () sync* {
yield DiagnosticsProperty<PointerSignalEvent>('Event', event, style: DiagnosticsTreeStyle.errorProperty);
return true;
exception: exception,
stack: stack,
library: 'gesture library',
context: ErrorDescription('while resolving a PointerSignalEvent'),
informationCollector: collector
_firstRegisteredCallback = null;
_currentEvent = null;