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Add non-normative notes for attributes.
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Each attribute has a "note" explanation of when it is measured, with a
link to the service-worker/HTML spec where it's being measured in
practice.

Also update the diagram to include service-worker handling.

Closes #157.
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@noamr
noamr committed Sep 27, 2021
1 parent 41e3e65 commit 76e32ca
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96 changes: 77 additions & 19 deletions index.html
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Expand Up @@ -312,6 +312,15 @@ <h3>
<li>If |workerTiming| is null, then return |this|'s prototype's `workerStart`.
<li>Return |workerTiming|'s [=service worker timing info/start time=].
</ol>
<p class="note">
Though `workerStart` is exposed in <a data-cite=
"RESOURCE-TIMING-2#dom-performanceresourcetiming">PerformanceResourceTiming</a>, it
has a different meaning in Navigation Timing, as unlike subresources, a navigation may
trigger the activation or running of a service worker.
In the context of Navigation Timing, `workerStart` returns the timestamp measured
just before the worker has been activated or started. See [[service-workers]] for
a precise definition.
</p>
</li>
<li>The `fetchStart` getter steps are to perform the following steps:
<ol>
Expand All @@ -320,6 +329,17 @@ <h3>
<li>Return |workerTiming|'s [=service worker timing info/fetch event dispatch time=].
</ol>
</li>
<p class="note">
When a [=service worker=] is used as part of the navigation, The `fetchStart` overload
holds a different meaning than the meaning in
<a data-cite="resource-timing-2#dom-performanceresourcetiming-requeststart">
<code>PerformanceResourceTiming</code></a>.
It returns the timestamp measured right before the {{FetchEvent}} is dispatched for
the [=service worker=]. The time difference between `workerStart` and `fetchStart` in
the document's navigation timing entry can be used to determine roughly how long it
took for the worker to be initialized or activated. See [[service-workers]] for
a precise definition.
</p>
</ul>
<p class="note">
Only the <a>current document</a> resource is included in the
Expand Down Expand Up @@ -379,57 +399,82 @@ <h3>

<p>A {{PerformanceNavigationTiming}} has an associated null or [=service worker timing info=]
<dfn data-dfn-for="PerformanceNavigationTiming">service worker timing</dfn>.

</p>

<p data-dfn-for='PerformanceNavigationTiming'>
The <dfn>unloadEventStart</dfn> getter steps are to return |this|'s
[=previous document unload timing=]'s [=document unload timing info/unload event start time=].
</li>
<p class="note">See <a data-cite=
"HTML/browsing-the-web.html#unloading-documents">unload event</a> for more info.</p>
</ol>
[=previous document unload timing=]'s [=document unload timing info/unload event start
time=].
<p class="note">If the previous document and the current document have the same
<a data-cite="html#concept-origin">origin</a>, this timestamp is measured immediately
before the user agent starts the <a data-cite=
"HTML/browsing-the-web.html#unloading-documents">unload</a> event
of the previous document. If there is no previous document or the
previous document has a different <a data-cite=
"html#concept-origin">origin</a> than the current document, this attribute will return
zero.
</p>
<p data-dfn-for='PerformanceNavigationTiming'>
The <dfn>unloadEventEnd</dfn> getter steps are to return |this|'s
[=previous document unload timing=]'s [=document unload timing info/unload event end time=].</li>
<p class="note">See <a data-cite=
"HTML/browsing-the-web.html#unloading-documents">unload event</a> for more info.</p>
</ol>
[=previous document unload timing=]'s
[=document unload timing info/unload event end time=].</li>
<p class="note">If the previous document and the current document have the same
<a data-cite="html#concept-origin">origin</a>, this timestamp is measured immediately
after the user agent handles the <a data-cite=
"HTML/browsing-the-web.html#unloading-documents">unload</a> event
of the previous document. If there is no previous document or the
previous document has a different <a data-cite=
"html#concept-origin">origin</a> than the current document, this attribute will return
zero.
</p>
<p data-dfn-for='PerformanceNavigationTiming'>
The <dfn>domInteractive</dfn> getter steps are to return
|this|'s [=document load timing=]'s [=document load timing info/DOM interactive time=].</p>

<p class="note">See <a data-cite=
"HTML/dom.html#current-document-readiness">document readiness</a> for more info.
<p class="note">This timestamp is measured before the user agent sets the
<a data-cite="HTML/dom.html#current-document-readiness">current document readiness</a> to
<a data-cite="HTML/parsing.html#the-end">"interactive"</a>.
</p>
<p data-dfn-for='PerformanceNavigationTiming'>
The <dfn>domContentLoadedEventStart</dfn> getter steps are to return |this|'s
[=document load timing=]'s
[=document load timing info/DOM content loaded event start time=].</p>
<p class="note">See <a data-cite=
"HTML/parsing.html#the-end:event-domcontentloaded">DOMContentLoaded</a> for more info.
</p>
<p class="note">This timestamp is measured before the user agent dispatches the
<a data-cite="HTML/parsing.html#the-end:event-domcontentloaded">DOMContentLoaded</a>
event.
</p>
<p data-dfn-for='PerformanceNavigationTiming'>
The <dfn>domContentLoadedEventEnd</dfn> getter steps are to return
|this|'s [=document load timing=]'s
[=document load timing info/DOM content loaded event end time=].</p>
<p class="note">See <a data-cite=
"HTML/parsing.html#the-end:event-domcontentloaded">DOMContentLoaded
event</a> completes.
<p class="note">This timestamp is measured after the user agent completes handling of the
<a data-cite="HTML/parsing.html#the-end:event-domcontentloaded">DOMContentLoaded</a>
event.
</p>
<p data-dfn-for='PerformanceNavigationTiming'>
The <dfn>domComplete</dfn> getter steps are to return
|this|'s [=document load timing=]'s [=document load timing info/DOM complete time=].
<p class="note">See <a data-cite=
"HTML/dom.html#current-document-readiness">document readiness</a> for more info.
<p class="note">This timestamp is measured before the user agent sets the
<a data-cite="HTML/dom.html#current-document-readiness">current document readiness</a> to
<a data-cite="HTML/parsing.html#the-end">"complete"</a>. See <a data-cite=
"HTML/dom.html#current-document-readiness">document readiness</a> for a precise
definition.
</p>
<p data-dfn-for='PerformanceNavigationTiming'>
The <dfn>loadEventStart</dfn> getter steps are to return
|this|'s [=document load timing=]'s [=document load timing info/load event start time=].</p>
</p>
<p class="note">This timestamp is measured before the user agent dispatches the
<a data-cite="HTML/parsing.html#the-end:event-event-load">load</a> event for the document.
</p>
<p data-dfn-for='PerformanceNavigationTiming'>
The <dfn>loadEventEnd</dfn> getter steps are to return
|this|'s [=document load timing=]'s [=document load timing info/load event end time=].</p>
</p>
<p class="note">This timestamp is measured after the user agent completes handling the
<a data-cite="HTML/parsing.html#the-end:event-event-load">load</a> event for the document.
</p>
<p data-dfn-for='PerformanceNavigationTiming'>
The <dfn>type</dfn> getter steps are to run the |this|'s [=navigation type=].
</p>
Expand Down Expand Up @@ -538,6 +583,19 @@ <h3>
<img src="timestamp-diagram.svg" alt="Navigation Timing attributes"
style='width: 100%'>
</figure>
<figure title='Timing attributes with service worker'>
<figcaption>
This figure illustrates the timing attributes defined by the
{{PerformanceNavigationTiming}} interface, when a [=service worker=] is used as part of
the fetch. Attributes in
parenthesis indicate that they may not be available for navigations
involving documents from different <a data-cite=
"html#concept-origin" title='origin'>origins</a>.
</figcaption>
<!-- Source: https://docs.google.com/document/d/1I7XGNJ57Qgjkg9pL11s7MK7zGEcwAgdNj1W5f7NKbW8/ -->
<img src="timestamp-diagram-sw.svg" alt="Navigation Timing attributes with Service Worker"
style='width: 100%'>
</figure>
</section>
</section>
<section id="marking-navigation-timing">
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1 change: 1 addition & 0 deletions timestamp-diagram-sw.svg
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