[css-grid-1] More precisely define effect of fit-content() limits when accommodating spanning items. w3c#4549

Author: fantasai

css-grid-1/Overview.bs

@@ -4278,8 +4278,6 @@ Resolve Intrinsic Track Sizes</h3>
 					to the [=growth limits=] of tracks with
 					a <a>max track sizing function</a> of ''max-content'',
 					to accommodate these items' <a>max-content contributions</a>.
-					However, limit the growth of any ''fit-content()'' tracks
-					by their ''fit-content()'' argument.
 			</ol>
 
 			Repeat incrementally for items with greater spans until all items have been considered.
@@ -4370,10 +4368,15 @@ Distributing Extra Space Across Spanned Tracks</h4>
 						(and continuing to grow the unfrozen tracks as needed).
 
 						For [=base sizes=],
-						the |limit| is its [=growth limit=].
+						the |limit| is its [=growth limit=],
+						  capped by its ''fit-content()'' argument if any.
 						For [=growth limits=],
-						the |limit| is infinity if it is marked as [=infinitely growable=],
-						and equal to the [=growth limit=] otherwise.
+						the |limit| is the [=growth limit=]
+						  if the [=growth limit=] is finite
+						  and the track is not [=infinitely growable=],
+						otherwise its ''fit-content()'' argument
+						  if it has a ''fit-content()'' [=track sizing function=],
+						and infinity otherwise.
 
 						Note: If the |affected size| was a <a>growth limit</a>
 						and the track is not marked [=infinitely growable=],
@@ -4400,14 +4403,16 @@ Distributing Extra Space Across Spanned Tracks</h4>
 							<li>
 								when accommodating any contribution
 								into [=growth limits=]:
-								all |affected track|s.
+								any |affected track| that has an intrinsic [=max track sizing function=].
 						</ul>
 
 						For this purpose,
 						the [=max track sizing function=] of a ''fit-content()'' track
 						is treated as ''max-content''
-						until it reaches the limit specified as the ''fit-content()'' argument,
-						after which it is treated as having a <a>fixed sizing function</a> of that argument.
+						until the track reaches the limit specified as the ''fit-content()'' argument,
+						after which its [=max track sizing function=] is treated as being
+						a <a>fixed sizing function</a> of that argument
+						(which can change which tracks continue to receive space in this step).
 
 						Note: This step prioritizes the distribution of space
 						for accommodating |size contribution|s
@@ -4805,6 +4810,55 @@ Changes since the <a href="https://www.w3.org/TR/2020/CRD-css-grid-1-20201218/">
 			<a href="#change-2016-stretch-algo">earlier change</a>
 			to better incorporate ''justify-content/stretch'' handling into the algorithm.
 			(<a href="https://github.com/w3c/csswg-drafts/issues/5966">Issue 5966</a>)
+
+		<li id="change-2020-fit-content">
+			Defined more precisely how ''fit-content()'' limits track growth
+			when accommodating spanning items.
+			(<a href="https://github.com/w3c/csswg-drafts/issues/4549">Issue 4549</a>)
+			<blockquote>
+				<p><strong>For intrinsic maximums:</strong>
+				Next [=distribute extra space=]
+				to the [=growth limits=] of tracks with
+				a <a>max track sizing function</a> of ''max-content'',
+				to accommodate these items' <a>max-content contributions</a>.
+				<del>However, limit the growth of any ''fit-content()'' tracks
+				by their ''fit-content()'' argument.</del></p>
+ 			</blockquote>
+ 			<blockquote>
+				<p><strong>Distribute |space| up to limits:</strong> [&hellip;]</p>
+
+				<p>For [=base sizes=],
+				the |limit| is its [=growth limit=]<ins>,
+				  capped by its ''fit-content()'' argument if any</ins>.
+					For [=growth limits=],
+				the |limit| is <del>infinity if it is marked as [=infinitely growable=],
+				and equal to the [=growth limit=] otherwise</del>
+				<ins>the [=growth limit=]
+				  if the [=growth limit=] is finite
+				  and the track is not [=infinitely growable=],
+				otherwise its ''fit-content()'' argument
+				  if it has a ''fit-content()'' [=track sizing function=],
+				and infinity otherwise</ins>.</p>
+			</blockquote>
+			<blockquote>
+				<p><strong>Distribute |space| beyond limits:</strong> [&hellip;]</p>
+				<ul>
+					<li>
+						when accommodating any contribution
+						into [=growth limits=]:
+						<del>all |affected track|s</del>
+						<ins>any |affected track| that has an intrinsic [=max track sizing function=]</ins>.
+				</ul>
+
+				<p>For this purpose,
+				the [=max track sizing function=] of a ''fit-content()'' track
+				is treated as ''max-content''
+				until <del>it</del> <ins>the track</ins> reaches the limit specified as the ''fit-content()'' argument,
+				after which <del>it</del> <ins>its [=max track sizing function=]</ins>
+				is treated as <del>having</del> <ins>being</ins>
+				a <a>fixed sizing function</a> of that argument
+				<ins>(which can change which tracks continue to receive space in this step)</ins>.</p>
+			</blockquote>
 	</ul>
 
 <h3 id="changes-202008">