[css-anchor-position-1] Clarify validation of anchor() and anchor-size() w3c#10955

Author: fantasai

css-anchor-position-1/Overview.bs

@@ -27,7 +27,7 @@ spec:css-position-3;
 	type:property; text:inset-inline-start
 spec:css-cascade-5; type:dfn; text:property
 spec:dom; type:dfn; text:shadow tree
-spec:css-align-3; type:value; for:<self-position>; text:center
+spec:css-align-3; type:value; text:center
 </pre>
 
 <pre class=anchors>
@@ -825,7 +825,8 @@ can use the <dfn>anchor()</dfn> function
 as a value in its [=inset properties=]
 to refer to the position of one or more [=anchor boxes=].
 The ''anchor()'' function resolves to a <<length>>.
-It is only valid to be used in the [=inset properties=].
+It is only allowed in the [=inset properties=]
+(and is otherwise invalid).
 
 <pre class="propdef partial">
 Name: top, left, right, bottom
@@ -908,10 +909,10 @@ The ''anchor()'' function has three arguments:
 			''anchor()/center'' is equivalent to ''50%''.
 
 * the optional <<length-percentage>> final argument is a fallback value,
-	specifying what the function should resolve to
-	if it's an [=invalid anchor function=].
+	specifying what the function should compute to
+	if it's an [=unresolvable anchor function=].
 
-An ''anchor()'' function representing a [=valid anchor function=]
+An ''anchor()'' function representing a [=resolvable anchor function=]
 resolves at [=computed value=] time
 (using [=style & layout interleaving=])
 to the <<length>> that would align the edge
@@ -1259,30 +1260,27 @@ specifically, the [=default anchor element=]:
 </div>
 
 
-Validity {#anchor-valid}
---------
+Resolution of ''anchor()'' {#anchor-valid}
+--------------------------
 
 An ''anchor()'' function is a
-<dfn lt="valid anchor function|invalid anchor function">valid anchor function</dfn>
+<dfn lt="resolvable anchor function|unresolvable anchor function">resolvable anchor function</dfn>
 only if all the following conditions are true:
 
-* It's being used in an [=inset property=]
-	on an [=absolutely positioned box=].
+* It's applied to an [=absolutely positioned box=].
 * If its <<anchor-side>> specifies a physical keyword,
-	it's being used in an [=inset property=] in that axis.
+	it's specified in an [=inset property=] applicable to that axis.
 	(For example, ''anchor()/left'' can only be used in 'left', 'right',
 	or a logical [=inset property=] in the horizontal axis.)
-* The result of determining the [=target anchor element=] is not nothing when
-	given the querying element as the element it's used on,
-	and the anchor specifier as
-	the <<anchor-name>> value specified in the function.
+* There is a [=target anchor element=]
+	for the box it's used on,
+	and the <<anchor-name>> value specified in the function.
 
 If any of these conditions are false,
-the ''anchor()'' function resolves to its specified fallback value.
+the ''anchor()'' function [=computed value|computes=] to its specified fallback value.
 If no fallback value is specified,
 it makes the declaration referencing it [=invalid at computed-value time=].
 
-
 <!-- Big Text: visibility
 
 █▌   █▌ ████  ███▌  ████ ████▌  ████ █▌    ████ █████▌ █   ▐▌
@@ -1407,7 +1405,8 @@ can use the <dfn>anchor-size()</dfn> function
 in its [=sizing properties=]
 to refer to the size of one or more [=anchor boxes=].
 The ''anchor-size()'' function resolves to a <<length>>.
-It is only valid to be used in the [=accepted @position-try properties=].
+It is only allowed in the [=accepted @position-try properties=]
+(and is otherwise invalid).
 
 The ''anchor-size()'' Function {#anchor-size-fn}
 ------------------------------
@@ -1453,24 +1452,22 @@ matches the axis of the property that ''anchor-size()'' is used in.
 (For example, ''width: anchor-size()''
 is equivalent to ''width: anchor-size(width)''.)
 
-An ''anchor-size()'' function representing a [=valid anchor-size function=]
+An ''anchor-size()'' function representing a [=resolvable anchor-size function=]
 resolves at [=computed value=] time
 (via [=style & layout interleaving=])
 to the <<length>> separating the relevant border edges
 (either left and right, or top and bottom,
 whichever is in the specified axis)
 of the [=target anchor element=].
 
-Validity {#anchor-size-valid}
---------
+Resolution of anchor-size() {#anchor-size-valid}
+---------------------------
 
 An ''anchor-size()'' function is a
-<dfn lt="valid anchor-size function|invalid anchor-size function">valid anchor-size function</dfn>
+<dfn lt="resolvable anchor-size function|unresolvable anchor-size function">resolvable anchor-size function</dfn>
 only if all the following conditions are true:
 
-* It's being used in a [=sizing property=], an [=inset property=], or a [=margin property=]
-	on an [=absolutely positioned box=].
-	<span class=note>(These are the [=accepted @position-try properties=] that allow lengths.)</span>
+* It's applied to an [=absolutely positioned box=].
 * There is a [=target anchor element=]
 	for the box it's used on,
 	and the <<anchor-name>> value specified in the function.