[css-align-3][css-position-3] Clarify axes/directions/references of alignment properties for static positioning #7599 #7612

Author: fantasai

css-align-3/Overview.bs

@@ -1361,7 +1361,9 @@ Inline-Axis (or Main-Axis) Alignment: the 'justify-self' property</h3>
 		<tr>
 			<th>'justify-self' Axis
 			<td>
-				The block’s <a>containing block’s</a> <a>inline axis</a>.
+				The block’s <a>containing block’s</a> <a>inline axis</a>, generally.
+				The [=static position containing block=]’s [=inline axis=]
+				when determining the [=static position=].
 		<tr>
 			<th><a>Alignment Container</a>
 			<td>
@@ -1419,7 +1421,8 @@ Inline-Axis (or Main-Axis) Alignment: the 'justify-self' property</h3>
 				assuming the <a>writing mode</a> of the <a>containing block</a>.
 				If both inset properties in the relevant axis are ''left/auto'',
 				then use the box’s <a>static-position rectangle</a>
-				(i.e. set both insets to the box’s <a>static position</a>).
+				(i.e. set both insets to the box’s <a>static position</a>)
+				and assume the [=writing mode=] of the [=static position containing block=].
 		<tr>
 			<th><a>Alignment Subject</a>
 			<td>
@@ -1576,7 +1579,9 @@ Block-Axis (or Cross-Axis) Alignment: the 'align-self' property</h3>
 		<tr>
 			<th>'align-self' Axis
 			<td>
-				The box’s <a>containing block’s</a> <a>block axis</a>.
+				The box’s <a>containing block’s</a> <a>block axis</a>, generally.
+				The [=static position containing block=]’s [=block axis=]
+				when determining the [=static position=].
 		<tr>
 			<th><a>Alignment Container</a>
 			<td>
@@ -1586,7 +1591,8 @@ Block-Axis (or Cross-Axis) Alignment: the 'align-self' property</h3>
 				assuming the <a>writing mode</a> of the <a>containing block</a>.
 				If both inset properties in the relevant axis are ''left/auto'',
 				then use the box’s <a>static-position rectangle</a>
-				(i.e. set both insets to the box’s <a>static position</a>).
+				(i.e. set both insets to the box’s <a>static position</a>)
+				and assume the [=writing mode=] of the [=static position containing block=].
 		<tr>
 			<th><a>Alignment Subject</a>
 			<td>

css-position-3/Overview.bs

@@ -859,6 +859,10 @@ Resolving Automatic Insets: the “Static Position Rectangle”</h4>
 	assumes that both 'float' and 'clear' have their initial values,
 	and can require assuming a different hypothetical value
 	for 'display' as well.
+	To the extent the [=box alignment properties=] have an effect,
+	they use the [=static position containing block=]
+	as the effective [=containing block=],
+	including using its [=writing mode=] for resolving alignment axes and directions.
 	Additionally, the [=containing block=] of [=fixed positioned=] elements
 	is assumed to be the [=initial containing block=] instead of the [=viewport=],
 	and all [=scroll containers=] should be assumed