[typed-om] Kill CSSResourceValue and CSSURLImageValue, remove all details from CSSImageValue, so it's just an opaque handle to an image, suitable for Custom Paint. Fixes #716.

Author: tabatkins

css-typed-om/Overview.bs

@@ -14,7 +14,7 @@ Editor: Naina Raisinghani, Google, nainar@google.com, w3cid 100915
 Repository: w3c/css-houdini-drafts
 Inline Github Issues: title
 Ignored Vars: type, unit
-Ignored Terms: Drawable, paint image definition, list-valued property, list-valued property iteration, parse a CSSStyleValue, values to iterate over, CSS, PseudoElement
+Ignored Terms: Drawable, paint image definition, list-valued property, list-valued property iteration, parse a CSSStyleValue, values to iterate over, CSS, PseudoElement, style
 Markup Shorthands: markdown yes
 </pre>
 
@@ -91,6 +91,7 @@ spec:dom; type:interface;
     text:Document
     text:Element;
 spec:geometry-1; type:dfn; for:DOMMatrixReadOnly; text:stringification behavior
+spec:html; type:element; text:style
 spec:infra;
     type: dfn;
         text: list
@@ -2684,55 +2685,6 @@ The {{CSSPositionValue/x}} attribute expresses the offset from the left edge of
     </pre>
 </div>
 
-<!--
-████████  ████████  ██████   ███████  ██     ██ ████████   ██████  ████████
-██     ██ ██       ██    ██ ██     ██ ██     ██ ██     ██ ██    ██ ██
-██     ██ ██       ██       ██     ██ ██     ██ ██     ██ ██       ██
-████████  ██████    ██████  ██     ██ ██     ██ ████████  ██       ██████
-██   ██   ██             ██ ██     ██ ██     ██ ██   ██   ██       ██
-██    ██  ██       ██    ██ ██     ██ ██     ██ ██    ██  ██    ██ ██
-██     ██ ████████  ██████   ███████   ███████  ██     ██  ██████  ████████
--->
-
-{{CSSResourceValue}} objects {#resourcevalue-objects}
------------------------------------------------------
-
-<pre class='idl'>
-enum CSSResourceState {"unloaded", "loading", "loaded", "error"};
-
-[Exposed=(Window, Worker, PaintWorklet, LayoutWorklet)]
-interface CSSResourceValue : CSSStyleValue {
-    readonly attribute CSSResourceState state;
-};
-
-</pre>
-
-{{CSSResourceValue}} objects represent CSS values that may require an asynchronous network fetch
-before being usable.
-
-A {{CSSResourceValue}} is in one of the following states, as reflected in the value of the
-{{CSSResourceValue/state}} attribute:
-
-:   "unloaded"
-::  The resource is not ready and is not actively being fetched
-:   "loading"
-::  The resource is not ready, but is in the process of being fetched
-:   "loaded"
-::  The resource is ready for rendering
-:   "error"
-::  The resource can't be fetched, or the fetched resource is invalid
-
-{{CSSResourceValue}} objects that do not require network data (for example linear and radial gradients)
-are initialized with {{CSSResourceValue/state}} "loaded".
-
-<div class='example'>
-For example, images that match the <<url>> production can be used immediately, but will not result
-in a visual change until the image data is fetched. {{CSSResourceValue}} objects represent this by
-providing values that track loaded state via the {{CSSResourceState}} enum.
-</div>
-
-Issue(186): CSSResourceValues constructed within Worklets should be "unloaded".
-
 <!--
 ████ ██     ██    ███     ██████   ████████
  ██  ███   ███   ██ ██   ██    ██  ██
@@ -2748,50 +2700,50 @@ Issue(186): CSSResourceValues constructed within Worklets should be "unloaded".
 
 <pre class='idl'>
 [Exposed=(Window, Worker, PaintWorklet, LayoutWorklet)]
-interface CSSImageValue : CSSResourceValue {
-    readonly attribute double? intrinsicWidth;
-    readonly attribute double? intrinsicHeight;
-    readonly attribute double? intrinsicRatio;
-};
-
-[Exposed=(Window, Worker, PaintWorklet, LayoutWorklet),
- Constructor(USVString url)]
-interface CSSURLImageValue : CSSImageValue {
-    readonly attribute USVString url;
+interface CSSImageValue : CSSStyleValue {
 };
-
 </pre>
 
 {{CSSImageValue}} objects represent values for properties that take <<image>> productions,
 for example 'background-image', 'list-style-image', and 'border-image-source'.
 
-If the {{CSSImageValue}}'s {{CSSResourceValue/state}} is "loaded",
-and the resource has an intrinsic width, height, or aspect ratio,
-then {{CSSImageValue/intrinsicWidth}}, {{CSSImageValue/intrinsicHeight}}, and {{CSSImageValue/intrinsicRatio}} must reflect the resource's corresponding value.
-In this case, {{CSSImageValue/intrinsicWidth}} and {{CSSImageValue/intrinsicHeight}} has units `px`.
-In all other cases, the attributes must be <code>null</code>.
-
-Issue(186): Does the loading lifecycle need to be described here?
+Note: This object is intentionally opaque,
+and exposes no details of what kind of image it contains,
+or any aspect of the image.
+This is because having *something* to represent images is necessary for Custom Paint,
+but there are sufficient complexities in getting URL-handling and loading specified firmly
+that it's not realistically possible to specify in the timeline of this specification.
+This will be expanded on in future levels.
 
-{{CSSURLImageValue}} objects represent {{CSSImageValue}}s that match the <<url>> production. For these
-objects, the {{CSSURLImageValue/url}} attribute contains the URL that references the image.
+If a {{CSSImageValue}} object represents an <<image>> that involves a URL
+(such as ''url()'' or ''image()''),
+the handling of such values is identical to how CSS currently handles them.
+In particular, resolving relative URLs or fragment URLs
+has the same behavior as in normal CSS.
 
-<div algorithm>
-    The <dfn constructor for=CSSURLImageValue>CSSURLImageValue(|url|)</dfn> constructor must,
-    when called,
-    perform the following steps:
-
-    1. Return a new {{CSSURLImageValue}}
-        with its {{CSSURLImageValue/url}} internal slot
-        set to |url|.
-</div>
-
-<div algorithm="CSSURLImageValue.url">
-    The getter for the <dfn attribute for=CSSURLImageValue>url</dfn> attribute
-    of a {{CSSURLImageValue}} must return its {{CSSURLImageValue/url}} internal slot.
+<div class=example>
+    For example, relative URLs are resolved against the URL of the stylesheet they're within
+    (or the document's URL, if they're specified in a <{style}> element or <{html-global/style}> attribute).
+    This resolution doesn't happen eagerly at parse-time,
+    but at some currently-unspecified point during value computation.
+
+    Thus, if an element's style is set to ''background-image: url(foo);'',
+    and that specified value is extracted via the Typed OM
+    and then set on an element in a different document,
+    both the source and destination elements
+    will resolve the URL differently,
+    as they provide different base URLs.
+
+    On the other hand,
+    if the extracted value was a [=computed value=]
+    (from {{computedStyleMap()}}),
+    then it would already be resolved to an absolute URL,
+    and thus would act identically no matter where you later set it to.
+    (Unless it was a fragment URL,
+    which CSS treats differently and never fully resolves,
+    so it always resolves against the current document.)
 </div>
 
-Issue(159): Spec up ColorValue
 
 <!--
  ██████   ██████   ██████                ██           ███████  ██     ██