[css-grid-1][css-grid-2] Fix auto minimum size to better handle percentage specified and maximum sizes. w3c#6278

Author: fantasai

css-grid-1/Overview.bs

@@ -1332,6 +1332,11 @@ Automatic Minimum Size of Grid Items</h3>
 
 	In all cases, the size suggestion is additionally clamped by the [=maximum size=] in the affected axis,
 	if it's definite.
+	If the item is a [[css-sizing-3#min-content-zero|compressible replaced element]],
+	the size suggestion is clamped
+	by both the [=maximum size=] and the [=preferred size=], whichever are definite,
+	with their indefinite percentages resolved for this purpose against zero
+    (and therefore considered definite).
 
 	Note: The argument to ''fit-content()'' does <em>not</em> clamp
 	the [=content-based minimum size=] in the same way as a
@@ -1358,6 +1363,12 @@ Automatic Minimum Size of Grid Items</h3>
 			converted through the aspect ratio.
 			It is otherwise undefined.
 
+			If the item’s has a [=preferred size=] or [=maximum size=]
+			in the relevant axis,
+			the [=transferred size suggestion=] is capped by those sizes,
+			resolving any indefinite percentages in these sizes
+			against zero for this purpose.
+
 		<dt><dfn>content size suggestion</dfn>
 		<dd>
 			The <a>content size suggestion</a> is
@@ -4761,6 +4772,44 @@ Changes since the <a href="https://www.w3.org/TR/2020/CRD-css-grid-1-20201218/">
 			via 'aspect-ratio'. [[CSS-SIZING-4]]
 			(<a href="https://github.com/w3c/csswg-drafts/issues/6069">Issue 6069</a>)
 
+		<li id="change-2020-auto-min-compressible">
+			Defined that percentages on the [=preferred size=] and the [=maximum size=]
+			of compressible replaced elements
+			are resolved against zero and used to clamp the [=content-based minimum size=],
+			so that their [=automatic minimum size=]
+			is not larger than their [=min-content contribution=].
+			(<a href="https://github.com/w3c/csswg-drafts/issues/6278">Issue #6278</a>)
+			<blockquote>
+				<p>In all cases, the size suggestion is additionally clamped by the [=maximum size=] in the affected axis,
+				if it's definite.
+				<ins>If the item is a [[css-sizing-3#min-content-zero|compressible replaced element]],
+				the size suggestion is clamped by both the [=maximum size=] and the [=preferred size=],
+				whichever are definite,
+				with their indefinite percentages resolved for this purpose against zero
+				(and therefore considered definite).</ins></p>
+			</blockquote>
+
+		<li id="change-2020-auto-min-transferred-clamp">
+			Defined that percentages on the [=preferred size=] and the [=maximum size=]
+			always clamp the [=transferred size suggestion=]
+			so that it is strictly weaker than any size constraints
+			applied natively to that axis.
+			(<a href="https://github.com/w3c/csswg-drafts/issues/6278">Issue #6278</a>)
+			<blockquote>
+				<p>If the item has a [=preferred aspect ratio=]
+				and its [=preferred size=] in the opposite axis is <a>definite</a>,
+				then the <a>transferred size suggestion</a> is that size
+				(clamped by the opposite-axis [=minimum size|minimum=] and [=maximum sizes=] if they are <a>definite</a>),
+				converted through the aspect ratio.
+				It is otherwise undefined.</p>
+
+				<p><ins>If the item’s has a [=preferred size=] or [=maximum size=]
+				in the relevant axis,
+				the [=transferred size suggestion=] is capped by those sizes,
+				resolving any indefinite percentages in these sizes
+				against zero for this purpose.</ins></p>
+			</blockquote>
+
 		<li id="change-2020-auto-margins">
 			Made [[#auto-margins]] normative and tightened up wording,
 			since some aspects of this behavior were not otherwise defined elsewhere.

css-grid-2/Overview.bs

@@ -1378,6 +1378,11 @@ Automatic Minimum Size of Grid Items</h3>
 
 	In all cases, the size suggestion is additionally clamped by the [=maximum size=] in the affected axis,
 	if it's definite.
+	If the item is a [[css-sizing-3#min-content-zero|compressible replaced element]],
+	the size suggestion is clamped
+	by both the [=maximum size=] and the [=preferred size=], whichever are definite,
+	with their indefinite percentages resolved for this purpose against zero
+    (and therefore considered definite).
 
 	Note: The argument to ''fit-content()'' does <em>not</em> clamp
 	the [=content-based minimum size=] in the same way as a
@@ -1404,6 +1409,12 @@ Automatic Minimum Size of Grid Items</h3>
 			converted through the aspect ratio.
 			It is otherwise undefined.
 
+			If the item’s has a [=preferred size=] or [=maximum size=]
+			in the relevant axis,
+			the [=transferred size suggestion=] is capped by those sizes,
+			resolving any indefinite percentages in these sizes
+			against zero for this purpose.
+
 		<dt><dfn>content size suggestion</dfn>
 		<dd>
 			The <a>content size suggestion</a> is
@@ -5406,6 +5417,44 @@ Changes since the <a href="https://www.w3.org/TR/2020/CRD-css-grid-2-20201218/">
 			via 'aspect-ratio'. [[CSS-SIZING-4]]
 			(<a href="https://github.com/w3c/csswg-drafts/issues/6069">Issue 6069</a>)
 
+		<li id="change-2020-auto-min-compressible">
+			Defined that percentages on the [=preferred size=] and the [=maximum size=]
+			of compressible replaced elements
+			are resolved against zero and used to clamp the [=content-based minimum size=],
+			so that their [=automatic minimum size=]
+			is not larger than their [=min-content contribution=].
+			(<a href="https://github.com/w3c/csswg-drafts/issues/6278">Issue #6278</a>)
+			<blockquote>
+				<p>In all cases, the size suggestion is additionally clamped by the [=maximum size=] in the affected axis,
+				if it's definite.
+				<ins>If the item is a [[css-sizing-3#min-content-zero|compressible replaced element]],
+				the size suggestion is clamped by both the [=maximum size=] and the [=preferred size=],
+				whichever are definite,
+				with their indefinite percentages resolved for this purpose against zero
+				(and therefore considered definite).</ins></p>
+			</blockquote>
+
+		<li id="change-2020-auto-min-transferred-clamp">
+			Defined that percentages on the [=preferred size=] and the [=maximum size=]
+			always clamp the [=transferred size suggestion=]
+			so that it is strictly weaker than any size constraints
+			applied natively to that axis.
+			(<a href="https://github.com/w3c/csswg-drafts/issues/6278">Issue #6278</a>)
+			<blockquote>
+				<p>If the item has a [=preferred aspect ratio=]
+				and its [=preferred size=] in the opposite axis is <a>definite</a>,
+				then the <a>transferred size suggestion</a> is that size
+				(clamped by the opposite-axis [=minimum size|minimum=] and [=maximum sizes=] if they are <a>definite</a>),
+				converted through the aspect ratio.
+				It is otherwise undefined.</p>
+
+				<p><ins>If the item’s has a [=preferred size=] or [=maximum size=]
+				in the relevant axis,
+				the [=transferred size suggestion=] is capped by those sizes,
+				resolving any indefinite percentages in these sizes
+				against zero for this purpose.</ins></p>
+			</blockquote>
+
 		<li id="change-2020-auto-margins">
 			Made [[#auto-margins]] normative and tightened up wording,
 			since some aspects of this behavior were not otherwise defined elsewhere.