[css-anchor-position-1] Make it clearer that base styles are part of the position options list #13268

Author: tabatkins

css-anchor-position-1/Overview.bs

@@ -1503,12 +1503,12 @@ or being positioned partially off screen.
 
 To ameliorate this, an [=absolutely positioned=] box
 can use the 'position-try-fallbacks' property
-to specify additional [=position options=]
+to specify additional <dfn>position options</dfn>
 (variant sets of positioning/alignment properties
 generated from the box's existing styles,
 or specified in ''@position-try'' rules)
 that the UA can try if the box overflows its initial position.
-Each is applied to the box,
+Each [=position option=] is applied to the box,
 one by one in the order specified by 'position-try-order',
 and the first that doesn't cause the box
 to overflow its [=containing block=]
@@ -1562,25 +1562,27 @@ Applies to: [=absolutely positioned boxes=]
 Animation type: discrete
 </pre>
 
-This property provides a list of alternate positioning styles
-to try when the [=absolutely positioned box=]
-overflows its [=inset-modified containing block=].
-This <dfn export>position options list</dfn>
-initially contains a single [=position option=]
-generated from the element's <dfn export local-lt="base style">fallback base styles</dfn>,
-i.e. the [=computed values|computed styles=] without applying 'position-try-fallbacks'.
+This property provides a list of additional, alternative [=position options=]
+to try in order to prevent the [=absolutely positioned box=]
+from overflowing its [=inset-modified containing block=].
 
-Each comma-separated entry in the list is a separate option:
+Each comma-separated entry in the list is a separate [=position option=]:
 either the name of a ''@position-try'' block,
-or a <<try-tactic>> representing an automatic transformation of the box's existing computed style.
+or a <<try-tactic>> representing an automatic transformation
+of the box's existing computed style (its <dfn export local-lt="base style">fallback base styles</dfn>).
+Together with the [=fallback base styles=],
+these options form the <dfn export>position options list</dfn>
+from which the effective style is chosen,
+see [[#fallback-apply]].
 
 Values have the following meanings:
 
 <dl dfn-type=value dfn-for=position-try-fallbacks>
 	: <dfn>none</dfn>
 	::
 		The property has no effect;
-		the box's [=position options list=] is empty.
+		the box's [=position options list=]
+		consists only of the [=fallback base styles=].
 
 	: <dfn><<dashed-ident>></dfn>
 	::
@@ -1596,8 +1598,8 @@ Values have the following meanings:
 	::
 		Automatically creates a [=position option=]
 		by [=executing a try-tactic|executing the specified try tactic=]
-		to the box's [=base styles=],
-		then adding the constructed [=position option=]
+		on the box's [=base styles=],
+		then adding this constructed [=position option=]
 		to the box's [=position options list=].
 
 		<pre class=prod>
@@ -1684,10 +1686,10 @@ Inherited: no
 Animation Type: discrete
 </pre>
 
-This property allows an element to sort its [=position options=]
-by the available space they define,
-if it's more important for the box to have as much space as possible
-rather than strictly following the order declared in 'position-try-fallbacks'.
+This property allows an element to sort its [=position option list=]
+by the available space they produce.
+This allows the box to prioritize having more layout space
+over strictly following the order declared in 'position-try-fallbacks'.
 
 <pre class=prod>
 <dfn type><<try-size>></dfn> = most-width | most-height | most-block-size | most-inline-size
@@ -1845,11 +1847,10 @@ The ''@position-try'' Rule {#fallback-rule}
 -------------------------------
 
 The <dfn>@position-try</dfn> rule
-defines a <dfn>position option</dfn>
-with a given name,
+defines a [=position option=] with a given name,
 specifying one or more sets of positioning properties
 that can be applied to a box
-via 'position-try-fallbacks',
+via 'position-try-fallbacks'.
 
 The syntax of the ''@position-try'' rule is:
 
@@ -1862,10 +1863,10 @@ The syntax of the ''@position-try'' rule is:
 The <<dashed-ident>> specified in the prelude
 is the rule's name.
 If multiple ''@position-try'' rules are declared with the same name,
-they [=cascade=] the same as ''@keyframe'' rules do.
+they [=cascade=] (overriding each other) the same as ''@keyframes'' rules do.
 
-The ''@position-try'' rule only <dfn export lt="accepted @position-try properties">accepts</dfn>
-the following [=properties=]:
+The ''@position-try'' rule only accepts
+the following <dfn export>accepted @position-try properties</dfn>:
 
 * [=inset properties=]
 * [=margin properties=]