* 仕様書

[REFS[
- [2] [CITE@en[DOM Standard]] ([TIME[2016-04-26 17:13:41 +09:00]] 版) <https://dom.spec.whatwg.org/#concept-element-custom-element-state>
]REFS]

* 要素の[F[カスタム要素状態]]

[3] [[要素]]は、[DFN[[F[[RUBYB[[[カスタム要素状態]]]@en[custom element state]]]]]]を持ちます。
[F[カスタム要素状態]]は、 [CODE[undefined]], [CODE[failed]],
[CODE[uncustomized]], [CODE[custom]]
のいずれかです。 [SRC[>>2]]

[5] [[要素]]の[F[カスタム要素状態]]は、[[要素の作成]]や[[要素の格上げ]]や
[CODE(DOMi)@en[HTMLElement]] [[コンストラクター]]や[[養子化]]で設定されます。

* 要素の[F[定義済み]]性

[4] [[要素]]の[F[カスタム要素状態]]が [CODE[uncustomized]] か [CODE[custom]]
のとき、[[要素]]は[DFN[[F[[RUBYB[[[定義済み]]]@en[defined]]]]]]であるといいます [SRC[>>2]]。

* 歴史

[1] [CITE@en[Add custom elements to HTML · whatwg/html@6e7eaa4]]
([TIME[2016-04-26 18:23:38 +09:00]] 版)
<https://github.com/whatwg/html/commit/6e7eaa4bd2912965fd83766f99f984f249531f3a>

[6] [CITE@en[Don't set custom element state redundantly]]
( ([[domenic]]著, [TIME[2016-05-24 17:15:10 +09:00]]))
<https://github.com/whatwg/dom/commit/d077da16b7fc307fc51820dbe541f6cf0b088115>

[7] [CITE@en[Un-customify adopted elements]]
( ([[domenic]]著, [TIME[2016-06-01 20:24:12 +09:00]]))
<https://github.com/whatwg/dom/commit/e417f9f4ca5aa16f11b8e04378f8c3425554b0fd>

[8] [CITE@en[Set the stage for preventing double custom element constructor calls]]
([[domenic]]著, [TIME[2016-07-19 02:13:14 +09:00]])
<https://github.com/whatwg/dom/commit/539e45214f682797f4fa022815a08b6f044e1240>

[9] [CITE@en['''['''selectors-4''']''' :defined · Issue #2258 · w3c/csswg-drafts]]
([TIME[2019-06-03 20:26:08 +09:00]])
<https://github.com/w3c/csswg-drafts/issues/2258>

[10] [CITE@en[Which standard defines :defined · Issue #665 · w3c/webcomponents]]
([TIME[2019-06-03 20:26:27 +09:00]])
<https://github.com/w3c/webcomponents/issues/665>

[11] [CITE@en[Remove the data-dfn-type attribute for the :defined pseudo-class by isaacdurazo · Pull Request #4433 · whatwg/html · GitHub]]
([TIME[2020-05-14 11:43:35 +09:00]])
<https://github.com/whatwg/html/pull/4433>