[css-grid-3][masonry] Exort the highest/lowest baseline across all tracks #9530

Author: fantasai

css-grid-3/Overview.bs

@@ -1033,8 +1033,8 @@ Alignment and Spacing</h2>
 	ISSUE: Should alignment in the stacking axis do something more sophisticated?
 	What should that be?
 
-<h3 id="masonry-axis-baseline-alignment">
-Baseline Alignment in the stacking axis</h3>
+<h3 id="masonry-baseline-alignment">
+Baseline Alignment</h3>
 
 	Item [=baseline alignment=] inside the [=grid axis=] tracks
 	works as usual for a regular [=grid container=],
@@ -1043,9 +1043,10 @@ Baseline Alignment in the stacking axis</h3>
 
 	[=Baseline alignment=] is not supported in the [=stacking axis=].
 	The first baseline set of the [=grid container=] in this axis
-	is generated from the [=alignment baseline=] of
-	the first [=grid item=] in the first occupied track,
-	and the last baseline set from the last [=grid item=] placed.
+	is generated from the highest [=alignment baseline=]
+	among the [=grid items=] placed first in each track,
+	and the last baseline set from the lowest [=alignment baseline=]
+	among the [=grid items=] placed last in each track.
 
 	ISSUE: We could support baseline alignment in the first row. Do we want to?
 
@@ -1482,6 +1483,8 @@ Recent Changes</h3>
 		replacing <css>masonry-flow</css> and related properties.
 		(<a href="https://github.com/w3c/csswg-drafts/issues/11480">Issue 11480</a>)
 	* Renamed <css>masonry-slack</css> to 'item-tolerance'.
+	* Tweak baseline alignment to export the highest/lowest among the first/last items of every track.
+		(<a href="https://github.com/w3c/csswg-drafts/issues/9530">Issue 9530</a>)
 
 <wpt hidden>
 alignment/masonry-align-content-001.html