blob: c83dd1124314db938ec7f79fa055a80f6d32a5ce [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/rendering.dart';
import 'package:flutter/scheduler.dart';
import 'framework.dart';
import 'ticker_provider.dart';
/// An interface that [Scrollable] widgets implement in order to use
/// [ScrollPosition].
/// See also:
/// * [ScrollableState], which is the most common implementation of this
/// interface.
/// * [ScrollPosition], which uses this interface to communicate with the
/// scrollable widget.
abstract class ScrollContext {
/// The [BuildContext] that should be used when dispatching
/// [ScrollNotification]s.
/// This context is typically different that the context of the scrollable
/// widget itself. For example, [Scrollable] uses a context outside the
/// [Viewport] but inside the widgets created by
/// [ScrollBehavior.buildOverscrollIndicator] and [ScrollBehavior.buildScrollbar].
BuildContext? get notificationContext;
/// The [BuildContext] that should be used when searching for a [PageStorage].
/// This context is typically the context of the scrollable widget itself. In
/// particular, it should involve any [GlobalKey]s that are dynamically
/// created as part of creating the scrolling widget, since those would be
/// different each time the widget is created.
// TODO(goderbauer): Deprecate this when state restoration supports all features of PageStorage.
BuildContext get storageContext;
/// A [TickerProvider] to use when animating the scroll position.
TickerProvider get vsync;
/// The direction in which the widget scrolls.
AxisDirection get axisDirection;
/// Whether the contents of the widget should ignore [PointerEvent] inputs.
/// Setting this value to true prevents the use from interacting with the
/// contents of the widget with pointer events. The widget itself is still
/// interactive.
/// For example, if the scroll position is being driven by an animation, it
/// might be appropriate to set this value to ignore pointer events to
/// prevent the user from accidentally interacting with the contents of the
/// widget as it animates. The user will still be able to touch the widget,
/// potentially stopping the animation.
void setIgnorePointer(bool value);
/// Whether the user can drag the widget, for example to initiate a scroll.
void setCanDrag(bool value);
/// Set the [SemanticsAction]s that should be expose to the semantics tree.
void setSemanticsActions(Set<SemanticsAction> actions);
/// Called by the [ScrollPosition] whenever scrolling ends to persist the
/// provided scroll `offset` for state restoration purposes.
/// The [ScrollContext] may pass the value back to a [ScrollPosition] by
/// calling [ScrollPosition.restoreOffset] at a later point in time or after
/// the application has restarted to restore the scroll offset.
void saveOffset(double offset);