blob: b23f3e743ee2242934e8f4b4ab3a3b192216fd5a [file] [log] [blame]
// Copyright 2017 The Chromium 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 'arena.dart';
import 'binding.dart';
class _CombiningGestureArenaEntry implements GestureArenaEntry {
_CombiningGestureArenaEntry(this._combiner, this._member);
final _CombiningGestureArenaMember _combiner;
final GestureArenaMember _member;
@override
void resolve(GestureDisposition disposition) {
_combiner._resolve(_member, disposition);
}
}
class _CombiningGestureArenaMember extends GestureArenaMember {
_CombiningGestureArenaMember(this._owner, this._pointer);
final GestureArenaTeam _owner;
final List<GestureArenaMember> _members = <GestureArenaMember>[];
final int _pointer;
bool _resolved = false;
GestureArenaMember _winner;
GestureArenaEntry _entry;
@override
void acceptGesture(int pointer) {
assert(_pointer == pointer);
assert(_winner != null || _members.isNotEmpty);
_close();
_winner ??= _members[0];
for (GestureArenaMember member in _members) {
if (member != _winner)
member.rejectGesture(pointer);
}
_winner.acceptGesture(pointer);
}
@override
void rejectGesture(int pointer) {
assert(_pointer == pointer);
_close();
for (GestureArenaMember member in _members)
member.rejectGesture(pointer);
}
void _close() {
assert(!_resolved);
_resolved = true;
final _CombiningGestureArenaMember combiner = _owner._combiners.remove(_pointer);
assert(combiner == this);
}
GestureArenaEntry _add(int pointer, GestureArenaMember member) {
assert(!_resolved);
assert(_pointer == pointer);
_members.add(member);
_entry ??= GestureBinding.instance.gestureArena.add(pointer, this);
return new _CombiningGestureArenaEntry(this, member);
}
void _resolve(GestureArenaMember member, GestureDisposition disposition) {
if (_resolved)
return;
if (disposition == GestureDisposition.rejected) {
_members.remove(member);
member.rejectGesture(_pointer);
if (_members.isEmpty)
_entry.resolve(disposition);
} else {
assert(disposition == GestureDisposition.accepted);
_winner ??= member;
_entry.resolve(disposition);
}
}
}
/// A group of [GestureArenaMember] objects that are competing as a unit in the
/// [GestureArenaManager].
///
/// Normally, a recognizer competes directly in the [GestureArenaManager] to
/// recognize a sequence of pointer events as a gesture. With a
/// [GestureArenaTeam], recognizers can compete in the arena in a group with
/// other recognizers.
///
/// When gesture recognizers are in a team together, then once there are no
/// other competing gestures in the arena, the first gesture to have been added
/// to the team automatically wins, instead of the gestures continuing to
/// compete against each other.
///
/// For example, [Slider] uses this to support both a
/// [HorizontalDragGestureRecognizer] and a [TapGestureRecognizer], but without
/// the drag recognizer having to wait until the user has dragged outside the
/// slop region of the tap gesture before triggering. Since they compete as a
/// team, as soon as any other recognizers are out of the arena, the drag
/// recognizer wins, even if the user has not actually dragged yet. On the other
/// hand, if the tap can win outright, before the other recognizers are taken
/// out of the arena (e.g. if the slider is in a vertical scrolling list and the
/// user places their finger on the touch surface then lifts it, so that neither
/// the horizontal nor vertical drag recognizers can claim victory) the tap
/// recognizer still actually wins, despite being in the team.
///
/// To assign a gesture recognizer to a team, set
/// [OneSequenceGestureRecognizer.team] to an instance of [GestureArenaTeam].
class GestureArenaTeam {
final Map<int, _CombiningGestureArenaMember> _combiners = <int, _CombiningGestureArenaMember>{};
/// Adds a new member to the arena on behalf of this team.
///
/// Used by [GestureRecognizer] subclasses that wish to compete in the arena
/// using this team.
///
/// To assign a gesture recognizer to a team, see
/// [OneSequenceGestureRecognizer.team].
GestureArenaEntry add(int pointer, GestureArenaMember member) {
final _CombiningGestureArenaMember combiner = _combiners.putIfAbsent(
pointer, () => new _CombiningGestureArenaMember(this, pointer));
return combiner._add(pointer, member);
}
}