Skip to content

Add the section for children changed callback in 2022 #40

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 2 commits into from
Aug 18, 2022
Merged

Add the section for children changed callback in 2022 #40

Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
f6d67cb
Add the section for children changed callback in 2022
Aug 17, 2022
12a67a7
Add editor name
Aug 18, 2022
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
46 changes: 36 additions & 10 deletions reports/2022.html
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,10 @@
name: "Westbrook Johnson",
url: "https://westbrookjohnson.com",
},
{
name: "Alan Dávalos",
url: "https://github.com/alangdm",
},
],
github: "w3c/webcomponents-cg",
shortName: "webcomponents-cg",
Expand Down Expand Up @@ -109,7 +113,7 @@ <h3>Table of Contents</h3>
<th><a href="#children-changed-callback">Children changed callback</a></th>
<td><a href="https://github.com/WICG/webcomponents/issues/809">WICG/webcomponents#809</a></td>
<td>High</td>
<td>---</td>
<td>Uncertain</td>
</tr>
<tr>
<th><a href="#open-styling-of-shadow-roots">Open styling of shadow roots</a></th>
Expand Down Expand Up @@ -661,51 +665,73 @@ <h3>Links</h3>
<dt>Previous WCCG Report(s)</dt>
<dd><a href="https://w3c.github.io/webcomponents-cg/index.html#children-changed-callback">2021</a></dd>
<dt>GitHub issues:</dt>
<dd>---</dd>
<dd>
<ul>
<li><a href="https://github.com/WICG/webcomponents/issues/809">2019 discussion - open</a></li>
<li><a href="https://github.com/WICG/webcomponents/issues/619">December 2016 discussion - closed</a></li>
<li><a href="https://github.com/WICG/webcomponents/issues/551">August 2016 discussion regarding parsing timing - closed</a></li>
<li><a href="https://github.com/WICG/webcomponents/issues/550">August 2016 discussion - closed</a></li>
</ul>
</dd>
<dt>Browser positions:</dt>
<dd>---</dd>
<dt>Polyfills/Libraries</dt>
<dd><a href="https://github.com/WebReflection/html-parsed-element"> For the parsing behavior</a></dd>
</dl>
</section>
<section>
<h3>Description</h3>
<p>---</p>
<p>Provide a callback that triggers whenever the parser finishes parsing children or when a new child is inserted or an old child is removed.</p>
</section>
<section>
<h3>Status</h3>
<ul>
<li>---</li>
<li>Uncertain - no concrete proposal or consensus on spec</li>
</ul>
</section>
<section>
<h3>Initial API Summary/Quick API Proposal</h3>
<p>Summary or proposal based on current status; paragraph(s) and code.</p>
<p>No concrete API proposal exists so far but the discussions seem to refer to using the callback similar to the attributeChangedCallback.</p>
<p>A component using said callback would look like this:</p>
<pre class="javascript">
class ChildrenChangedCallbackSample extends HTMLElement {
childrenChangedCallback() {}
}
</pre>
</section>
<section>
<h3>Key Scenarios</h3>
<p>---</p>
<ul>
<li><strong>Children parsed</strong>: This proposal would act as a cross-browser method of detecting when a custom element's children have been fully parsed reliably.</li>
<li><strong>Children inserted/removed</strong>: This proposal would provide better ergonomics to react to insertion or removal of children nodes than using a MutationObserver.</li>
</ul>
</section>
<section>
<h3>Concerns</h3>
<ul>
<li>---</li>
<li>Too expensive to implement: this is no longer the case, all engines have mechanisms for this already</li>
<li>The addition of the parsing behavior might encourage assuming a set of initial children exists and not reacting to changes in them.</li>
</ul>
</section>
<section>
<h3>Dissenting Opinion</h3>
<ul>
<li>---</li>
<li>Some people believe using a MutationObserver is enough to cover the insertion/removal cases and want to avoid creating a duplicate similar API for custom elements. But the async nature of MutationObserver seems to cause timing issues.</li>
<li>Some other people don't want to add this API if it will only cover the use case when the parser finishes parsing children. (See the second concern)</li>
</ul>
</section>
<section>
<h3>Related Specs</h3>
<ul>
<li>---</li>
<li><a href="https://github.com/WICG/webcomponents/issues/933">slotchange event options</a></li>
</ul>
</section>
<section>
<h3>Open Questions</h3>
<ul>
<li>---</li>
<li>Should this API really cover both use cases to begin with? Arguments for both sides have been mentioned in all referenced discussions with no conclusion</li>
<li>Should this be one or two separate callback functions?</li>
<li>Would it be better to implement this behavior as <a href="https://github.com/WICG/webcomponents/issues/933">part of the slotchange event as suggested in this other issue</a>? This might lead to engine security bugs so the callback seems a better option in that regard.</li>
</ul>
</section>
</section>
Expand Down