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Jun 17, 2021
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Specify event.signal #119

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33 changes: 24 additions & 9 deletions spec.bs
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Original file line number Diff line number Diff line change
Expand Up @@ -470,7 +470,7 @@ interface AppHistoryNavigateEvent : Event {
readonly attribute boolean canRespond;
readonly attribute boolean userInitiated;
readonly attribute boolean hashChange;
// readonly attribute AbortSignal signal;
readonly attribute AbortSignal signal;
readonly attribute FormData? formData;
readonly attribute any info;

Expand All @@ -483,7 +483,7 @@ dictionary AppHistoryNavigateEventInit : EventInit {
boolean canRespond = false;
boolean userInitiated = false;
boolean hashChange = false;
// required AbortSignal signal;
required AbortSignal signal;
FormData? formData = null;
any info = null;
};
Expand Down Expand Up @@ -523,14 +523,12 @@ enum AppHistoryNavigationType {
<p>True if this navigation is a <a spec="HTML" lt="navigate to a fragment">fragment navigation</a>; false otherwise.
</dd>

<!--
<dt><code><var ignore>event</var> . {{AppHistoryNavigateEvent/signal}}</code>
<dd>
<p>An {{AbortSignal}} which will become aborted if the navigation gets canceled, e.g. by the user pressing their browser's "Stop" button, or another higher-priority navigation interrupting this one.

<p>The expected pattern is for developers to pass this along to any async operations, such as {{WindowOrWorkerGlobalScope/fetch()}}, which they perform as part of handling this navigation.
</dd>
-->

<dt><code><var ignore>event</var> . {{AppHistoryNavigateEvent/formData}}</code>
<dd>
Expand All @@ -552,7 +550,7 @@ enum AppHistoryNavigationType {
</dd>
</dl>

The <dfn attribute for="AppHistoryNavigateEvent">navigationType</dfn>, <dfn attribute for="AppHistoryNavigateEvent">destination</dfn>, <dfn attribute for="AppHistoryNavigateEvent">canRespond</dfn>, <dfn attribute for="AppHistoryNavigateEvent">userInitiated</dfn>, <dfn attribute for="AppHistoryNavigateEvent">hashChange</dfn><!--, <dfn attribute for="AppHistoryNavigateEvent">signal</dfn>-->, <dfn attribute for="AppHistoryNavigateEvent">formData</dfn>, and <dfn attribute for="AppHistoryNavigateEvent">info</dfn> getter steps are to return the value that the corresponding attribute was initialized to.
The <dfn attribute for="AppHistoryNavigateEvent">navigationType</dfn>, <dfn attribute for="AppHistoryNavigateEvent">destination</dfn>, <dfn attribute for="AppHistoryNavigateEvent">canRespond</dfn>, <dfn attribute for="AppHistoryNavigateEvent">userInitiated</dfn>, <dfn attribute for="AppHistoryNavigateEvent">hashChange</dfn>, <dfn attribute for="AppHistoryNavigateEvent">signal</dfn>, <dfn attribute for="AppHistoryNavigateEvent">formData</dfn>, and <dfn attribute for="AppHistoryNavigateEvent">info</dfn> getter steps are to return the value that the corresponding attribute was initialized to.

An {{AppHistoryNavigateEvent}} has the following associated values which are only conditionally used:

Expand Down Expand Up @@ -675,7 +673,7 @@ The <dfn attribute for="AppHistoryDestination">sameDocument</dfn> getter steps a
1. Let |result| be the result of [=dispatching=] |event| at |appHistory|.
1. Set |appHistory|'s [=AppHistory/ongoing navigate event=] to null.
1. If |appHistory|'s [=relevant global object=]'s [=active Document=] is not [=Document/fully active=], then:
1. [=Synchronously finalize with an aborted navigation error=] for |appHistory|.
1. [=Synchronously finalize with an aborted navigation error=] given |appHistory| and |event|'s {{AppHistoryNavigateEvent/signal}}.
1. Return false.

<p class="note">This can occur if an event listener disconnected the <{iframe}> corresponding to [=this=]'s [=relevant global object=].</p>
Expand All @@ -699,17 +697,19 @@ The <dfn attribute for="AppHistoryDestination">sameDocument</dfn> getter steps a
1. Set |appHistory|'s [=AppHistory/navigate method call serialized state=] to null.

<p class="note">This ensures that any call to {{AppHistory/navigate()|appHistory.navigate()}} which triggered this algorithm does not overwrite the [=session history entry/app history state=] of the [=session history/current entry=] for cross-document navigations.
1. Otherwise, [=synchronously finalize with an aborted navigation error=] for |appHistory|.
1. Otherwise, [=synchronously finalize with an aborted navigation error=] given |appHistory| and |event|'s {{AppHistoryNavigateEvent/signal}}.
1. Return |result|.
</div>

<!-- TODO hook this up to the stop button etc. For now it just centralizes the ways a couple ways a navigate event handler can cause an abort. -->
<div algorithm>
To <dfn>synchronously finalize with an aborted navigation error</dfn> for an {{AppHistory}} |appHistory|:
To <dfn>synchronously finalize with an aborted navigation error</dfn> given an {{AppHistory}} |appHistory| and an {{AbortSignal}} |signal|:

1. Set |appHistory|'s [=AppHistory/navigate method call serialized state=] to null.

<p class="note">This ensures that any call to {{AppHistory/navigate()|appHistory.navigate()}} which triggered this algorithm does not overwrite the [=session history entry/app history state=] of the [=session history/current entry=] for aborted navigations.
1. [=AbortSignal/Signal abort=] on |signal|.

<p class="note">This might do nothing, if |signal| was previously aborted by <a>cancel any ongoing `navigate` event</a>.</p>
1. [=Queue a microtask=] on |appHistory|'s [=relevant agent=]'s [=agent/event loop=] to perform the following steps:
1. Let |error| be a [=new=] "{{AbortError}}" {{DOMException}}, created in |appHistory|'s [=relevant Realm=].
1. [=Fire an event=] named {{AppHistory/navigateerror}} at |appHistory| using {{ErrorEvent}}, with {{ErrorEvent/error}} initialized to |error|, {{ErrorEvent/message}} initialized to the value of |error|'s {{DOMException/message}} property, {{ErrorEvent/filename}} initialized to the empty string, and {{ErrorEvent/lineno}} and {{ErrorEvent/colno}} initialized to 0.
Expand All @@ -722,6 +722,9 @@ The <dfn attribute for="AppHistoryDestination">sameDocument</dfn> getter steps a
1. If |appHistory|'s [=AppHistory/ongoing navigate event=] is non-null, then:
1. Set |appHistory|'s [=AppHistory/ongoing navigate event=]'s [=Event/canceled flag=] to true.
1. Set |appHistory|'s [=AppHistory/ongoing navigate event=] to null.
1. [=AbortSignal/Signal abort=] on |appHistory|'s [=AppHistory/ongoing navigate event=]'s {{AppHistoryNavigateEvent/signal}}.

<p class="note">Because this cancels the event, this will eventually lead to the <a>inner `navigate` event firing algorithm</a> calling [=synchronously finalize with an aborted navigation error=] once the event firing process completes. However, we want to [=AbortSignal/signal abort=] on the relevant {{AppHistoryNavigateEvent/signal|event.signal}} right away.
</div>

<!-- Remember to modify pushState()/replaceState() to use this, when we eventually move to the HTML Standard. -->
Expand Down Expand Up @@ -1090,3 +1093,15 @@ Potentially update the <a spec="HTML">traverse the history</a> algorithm to cons
</div>

<p class="note">We do not [=AppHistory/update the entries=] when initially <a spec="HTML">creating a new browsing context</a>, as we intentionally don't want to include the initial `about:blank` {{Document}} in any app history entry list.

<h2 id="other-patches">Other patches</h2>

<h3 id="cancel-navigation">Canceling navigation</h3>

The existing HTML specification discusses canceling a navigation in a few places. However, the process is not very well-defined. We may be able to make it more rigorous, after the <a href="https://github.com/whatwg/html/issues/5767">session history rewrite</a> lands.

<div algorithm="navigation canceling patch">
The main addition of app history is that any time navigation of a given [=browsing context=] |bc| is canceled, the user agent must <a>cancel any ongoing `navigate` event</a> for |bc|'s [=browsing context/active window=]'s [=Window/app history=].
</div>

<p class="note">This includes navigation cancelation induced by the <a spec="HTML">stop document loading</a> algorithm, which is invoked by user interface elements such as a stop button and by {{Window/stop()|window.stop()}}.</p>