mirror of
https://github.com/dart-lang/sdk
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745f112ef6
Opt an initial batch of files under samples, samples-dev, utils, and runtime/tools/dartfuzz out of null safety in preparation for switching the flag on by default. Change-Id: Icdfd52a5a969e678a7205903332f73fe3841c223 Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/166960 Reviewed-by: Daco Harkes <dacoharkes@google.com> Commit-Queue: Leaf Petersen <leafp@google.com>
79 lines
2.3 KiB
Dart
79 lines
2.3 KiB
Dart
// Copyright (c) 2011, the Dart project authors. Please see the AUTHORS file
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// for details. All rights reserved. Use of this source code is governed by a
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// BSD-style license that can be found in the LICENSE file.
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// @dart = 2.9
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part of swarmlib;
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/**
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* The base class for UI state that intends to support browser history.
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*/
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abstract class UIState {
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/**
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* The event listener we hook to the window's "popstate" event.
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* This event is triggered by the back button or by the first page load.
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*/
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StreamSubscription _historyTracking;
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UIState();
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void startHistoryTracking() {
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stopHistoryTracking();
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bool firstEvent = true;
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var handler = EventBatch.wrap((event) {
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String state = window.location.hash;
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if (state.startsWith('#')) {
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// TODO(jimhug): Support default argument on substring.
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state = state.substring(1, state.length);
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}
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if (firstEvent && state != '') {
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// TODO(jmesserly): When loading a bookmark or refreshing, we replace
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// the app state with a clean app state so the back button works. It
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// would be better to support jumping to the previous story.
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// We'd need to do some history manipulation here and some fixes to
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// the views for this.
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window.history.replaceState(null, document.title, '#');
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} else if (state != '') {
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loadFromHistory(jsonDecode(state));
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}
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firstEvent = false;
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});
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_historyTracking = window.onPopState.listen(handler);
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}
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void stopHistoryTracking() {
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if (_historyTracking != null) {
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_historyTracking.cancel();
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}
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}
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/** Pushes a state onto the browser history stack */
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void pushToHistory() {
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if (_historyTracking == null) {
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throw 'history tracking not started';
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}
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String state = jsonEncode(toHistory());
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// TODO(jmesserly): [state] should be an Object, and we should pass it to
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// the state parameter instead of as a #hash URL. Right now we're working
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// around b/4582542.
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window.history
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.pushState(null, '${document.title}', '${document.title}#$state');
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}
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/**
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* Serialize the state to a form suitable for storing in browser history.
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*/
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Map<String, String> toHistory();
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/**
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* Load the UI state from the given [values].
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*/
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void loadFromHistory(Map<String, String> values);
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}
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