[css-shadow-parts-1] Rename partmap to exposedparts and add IDL

Author: fergald

css-shadow-parts-1/Overview.bs

@@ -121,7 +121,7 @@ as authors can use ''::part()'' without fear of accidental over-styling.
 Exposing a Shadow Element: {#exposing}
 =============================================================
 Elements in a <a>shadow tree</a> may be exposed for styling by stylesheets outside the tree
-using the part and partmap attributes.
+using the part and exposedparts attributes.
 
 Each element has a <dfn export for="element">part name list</dfn>
 which is an [=ordered set=] of tokens.
@@ -133,8 +133,6 @@ with keys that are [=strings=]
 and values that are [=ordered sets=] of [=strings=]
 (part names that are selectable inside this element).
 
-Issue(w3c/csswg-drafts#2414): Document how the part name map will be exposed via IDL.
-
 Each <a>shadow root</a> can be thought of as having a <dfn export for="shadow root">part element map</dfn>
 with keys that are [=strings=]
 and values that are [=ordered sets=] of elements.
@@ -199,16 +197,16 @@ not an id or tagname.
 &lt;/script&gt;
 </pre>
 
-Forwarding a Shadow Element: the <{html-global/partmap}> attribute {#partmap-attr}
+Forwarding a Shadow Element: the <{html-global/exposedparts}> attribute {#exposedparts-attr}
 ----------------------------------------------------------------------------------
-Any element in a shadow tree can have a <dfn element-attr for=html-global>partmap</dfn> attribute.
+Any element in a shadow tree can have a <dfn element-attr for=html-global>exposedparts</dfn> attribute.
 If the element is a shadow host,
 this is used to allow styling of parts from hosts inside the <a>shadow tree</a>
 by rules outside this the <a>shadow tree</a>
 (as if they were elements in the same tree as the host,
 named by a part attribute).
 
-The partmap attribute is parsed as a comma-separated list of part mappings.
+The exposedparts attribute is parsed as a comma-separated list of part mappings.
 Each part mapping is one of:
 
 <dl class=switch>
@@ -233,7 +231,7 @@ Issue(w3c/csswg-drafts#2411): Decide whether to allow "ident1 => ident2 ident3 .
 as shorthand for "ident1 ident2, ident1 ident3, ...".
 
 Issue(w3c/csswg-drafts#2411): Decide whether to allow wild-card forwarding,
-e.g partmap="button-* buttons".
+e.g exposedparts="button-* buttons".
 Consider excluding sub-parts that have been explicitly forwarded.
 Consider a mechanism to exclude sub-parts without forwarding them.
 
@@ -243,7 +241,7 @@ Consider a mechanism to exclude sub-parts without forwarding them.
 &lt;/style&gt;
 
 &lt;template id="c-e-outer-template"&gt;
-  &lt;c-e-inner <b>partmap="innerspan textspan"</b>&gt;&lt;/c-e-inner&gt;
+  &lt;c-e-inner <b>exposedparts="innerspan textspan"</b>&gt;&lt;/c-e-inner&gt;
 &lt;/template&gt;
 
 &lt;template id="c-e-inner-template"&gt;
@@ -366,3 +364,15 @@ but never match additional <a>shadow-part pseudo-elements</a>.
     would select just the one button's label,
     ignoring any other labels.
 </div>
+
+Extensions to the {{Element}} Interface {#idl}
+==============================================
+
+We expose the `part` and `exposedparts` attributes as read/write string properties on Element.
+
+<pre class=idl>
+partial interface Element {
+  attribute DOMString part;
+  attribute DOMString exposedParts;
+};
+</pre>