[css-shadow-parts-1] Remove theme from spec

css-shadow-parts-1/Overview.bs

@@ -8,7 +8,7 @@ Work Status: exploring
 URL: http://drafts.csswg.org/css-shadow-parts/
 Editor: Tab Atkins-Bittner, Google, http://xanthir.com/contact/, w3cid 42199
 Editor: Fergal Daly, Google, fergal@chromium.org
-Abstract: This specification defines the ''::part()'' and ''::theme()'' pseudo-elements on <a>shadow hosts</a>, allowing <a>shadow hosts</a> to selectively expose chosen elements from their <a>shadow tree</a> to the outside page for styling purposes.
+Abstract: This specification defines the ''::part()'' pseudo-element on <a>shadow hosts</a>, allowing <a>shadow hosts</a> to selectively expose chosen elements from their <a>shadow tree</a> to the outside page for styling purposes.
 </pre>
 
 <pre class=link-defaults>
@@ -32,8 +32,8 @@ accidentally over-applying and making a different part of the page look wrong.
 However, this styling barrier also makes it harder for a page to interact with its components
 when it actually <em>wants</em> to do so.
 
-This specification defines the ''::part()'' and ''::theme()'' pseudo-elements,
-which allow an author to style specific, purposely exposed elements in a <a>shadow tree</a>
+This specification defines the ''::part()'' pseudo-element,
+which allows an author to style specific, purposely exposed elements in a <a>shadow tree</a>
 from the outside page's context.
 In combination with <a>custom properties</a>,
 which let the outside page pass particular values
@@ -95,25 +95,14 @@ and component users,
 should have much better performance,
 and allows for better encapsulation/API surface.
 
-Another interesting facet of using <a>custom properties</a>,
-however,
-is that inheritance doesn't stop at the first shadow tree.
-Unless explicitly blocked,
-a <a>custom property</a> inherits down thru nested trees,
-allowing authors to style deeply nested components
-as easily as they style directly-visible ones.
-The same considerations apply to this case,
-so we introduce ''::theme()'' to handle this.
-
-It's important to note that ''::part()'' and ''::theme()''
-offer <em>absolutely zero new theoretical power</em>.
-They are not a rehash of the ''>>>'' combinator,
-they're simply a more convenient and consistent syntax
+It's important to note that ''::part()''
+offers <em>absolutely zero new theoretical power</em>.
+It is not a rehash of the ''>>>'' combinator,
+it is simply a more convenient and consistent syntax
 for something authors can already do with <a>custom properties</a>.
 By separating out the explicitly "published" parts of an element
-(the <a>shadow part map</a>)
-from the sub-parts that it merely happens to contain
-(the <a>computed shadow theme map</a>),
+(the <a>shadow part map</a>
+from the sub-parts that it merely happens to contain,
 it also helps with encapsulation,
 as authors can use ''::part()'' without fear of accidental over-styling.
 
@@ -259,45 +248,15 @@ Consider a mechanism to exclude sub-parts without forwarding them.
 &lt;/script&gt;
 </pre>
 
-Exposing More Widely: the <{html-global/theme}> attribute {#theme-attr}
------------------------------------------------------------------------
-
-Issue: The theme section is intentionally a rough sketch at the moment.
-The functionality of theme can be achieved with part alone
-however it may be tedious to explicitly export parts as a theme.
-The need for theme will be better understood once part is in use.
-
-
-In addition to the [=shadow part map=],
-every [=shadow root=] has a <dfn export for="shadow root">partial shadow theme map</dfn>
-and a <dfn export for="shadow root">computed shadow theme map</dfn>
-both of which are [=ordered maps=]
-(with the same key/value shape as the [=shadow part map=]),
-and the elements in the [=shadow tree=]
-have a corresponding <dfn element-attr for=html-global>theme</dfn> attribute.
-
-The <{html-global/theme}> attribute is parsed and interpreted identically to the <{html-global/part}> attribute,
-except that it adds its entries to the [=shadow root’s=] [=partial shadow theme map=] instead.
-
-If the [=shadow root’s=] {{ShadowRoot/mode}} is {{ShadowRootMode/"closed"}},
-the [=computed shadow theme map=] is identical to the [=partial shadow theme map=].
-Otherwise,
-it's the union of the [=partial shadow theme map=]
-with the [=computed shadow theme maps=] of every [=shadow host’s=] [=shadow root=] in its [=shadow tree=].
-
-Issue(w3c/csswg-drafts#2381): Decide if theme can ever/always penetrate closed shadow roots.
-
-Selecting a Shadow Element: the ''::part()'' and ''::theme()'' pseudo-elements {#part-theme}
+Selecting a Shadow Element: the ''::part()'' pseudo-element {#part}
 ============================================================================================
 
-The <dfn selector>::part()</dfn> and <dfn selector>::theme()</dfn> pseudo-elements
-(collectively, the <dfn export>shadow-part pseudo-elements</dfn>)
-allow you to select elements that have been exposed via a <{html-global/part}> attribute.
-The syntaxes of them are:
+The <dfn selector>::part()</dfn> pseudo-element
+allows you to select elements that have been exposed via a <{html-global/part}> attribute.
+The syntax is:
 
 <pre class=prod>
     ::part() = ::part( <<ident>> )
-    ::theme() = ::theme( <<ident>> )
 </pre>
 
 The ''::part()'' pseudo-element only matches anything
@@ -316,20 +275,6 @@ Otherwise, it matches nothing.
     ''#the-button::part(label)''.
 </div>
 
-The ''::theme()'' pseudo-element is similar,
-except it can match regardless of whether the <a>originating element</a>
-is a <a>shadow host</a> or not.
-It matches the elements keyed to the specified <<ident>>
-in the <a>computed shadow theme map</a> of the <a>shadow trees</a>
-of the <a>originating element</a> or any descendants.
-
-<div class="example">
-    For example,
-    '':root::theme(label)'' matches any element with <code>part="label"</code>
-    anywhere in the entire document,
-    no  matter how deeply nested into shadow trees they are.
-</div>
-
 The <a>shadow-part pseudo-elements</a> can take additional pseudo-classes after them,
 such as ''x-button::part(label):hover'',
 but never match the <a>structural pseudo-classes</a>
@@ -347,10 +292,6 @@ but never match additional <a>shadow-part pseudo-elements</a>.
     This is because doing so would expose more structural information
     than is intended.
 
-    One can still target the nested label with a selector like
-    ''x-panel::theme(label)''.
-    However, this will also select the labels of any other buttons in the panel.
-
     If the <code>&lt;x-panel></code>'s internal confirm button had used something like
     <code>part="confirm-button, * => confirm-*"</code>
     to forward the button's internal parts up into the panel's own <a>part element map</a>,