Define the <selectedoption> element

[josepharhar]

The <selectedoption> element is part of the customizable <select> proposal: #9799

It allows authors to declaratively clone the contents of the currently selected <option> of a <select> and style it independently for use in a base appearance <select>'s button.

The timing of cloning has been discussed here:
#10520

The selectedoption element has been discussed generally here: w3c/csswg-drafts#10242

html-aria PR: w3c/html-aria#528
html-aam PR: w3c/html-aam#566

• At least two implementers are interested (and none opposed):
  • Chrome
  • …
• Tests are written and can be reviewed and commented upon at:
  • https://wpt.fyi/results/html/semantics/forms/the-select-element/customizable-select/selectedoption.tentative.html
• Implementation bugs are filed:
  • Chromium: …
  • Gecko: …
  • WebKit: …
• MDN issue is filed: …
• The top of this comment includes a clear commit message to use.

(See WHATWG Working Mode: Changes for more details.)

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/form-control-infrastructure.html ( diff )
/form-elements.html ( diff )
/index.html ( diff )
/indices.html ( diff )
/infrastructure.html ( diff )
/interactive-elements.html ( diff )

[annevk]

It seems this is missing a lot of the boilerplate that new elements normally have as well as changes to content models, indexes, etc. See also this checklist at the top of source:

 !   Adding a new element involves editing the following sections:
 !    - section for the element itself
 !    - descriptions of the element's categories
 !    - images/content-venn.svg
 !    - syntax, if it's void or otherwise special
 !    - parser, if it's not phrasing-level
 !    - rendering
 !    - obsolete section
 !    - element, attribute, content model, and interface indices

[josepharhar]

Thanks!

• I added a dl with a bunch of metadata for the element itself.
• I didn't include this element in any categories
• I didn't update the content-venn image because I didn't add it to any categories.
• I didn't update syntax or parsing because it doesn't have any special rules and I didn't implement anything in the HTML parser for this.
• I didn't update rendering because I noticed that elements like <div> and <span> don't have sections in there, and selectedoption is supposed to render like those elements.
• I didn't update the obsolete section because nothing is becoming obsolete...?
• I updated the element and interface indexes