[css-overflow-3][css-overflow-4] Allow overflow-clip-edge to take negative lengths, and apply (shrinking only) to scrollable boxes. #11355 #10745

Author: tabatkins

css-overflow-3/Overview.bs

@@ -484,7 +484,7 @@ Managing Overflow: the 'overflow-x', 'overflow-y', and 'overflow' properties</h3
 		<dt><dfn>hidden</dfn>
 		<dd>
 			This value indicates that
-			the box’s content is clipped to its [=padding box=]
+			the box’s content is clipped to its [=overflow clip edge=]
 			and that the UA must not provide any scrolling user interface
 			to view the content outside the clipping region,
 			nor allow scrolling by direct intervention of the user,
@@ -510,12 +510,12 @@ Managing Overflow: the 'overflow-x', 'overflow-y', and 'overflow' properties</h3
 			the element to establish a new formatting context.
 
 			Note: Authors who also want the box to establish a formatting context
-			may use ''display: flow-root'' together with ''overflow: clip''.
+			can use ''display: flow-root'' together with ''overflow: clip''.
 
 		<dt><dfn>scroll</dfn>
 		<dd>
 			This value indicates that
-			the content is clipped to the [=padding box=],
+			the content is clipped to the [=overflow clip edge=],
 			but can be scrolled into view
 			(and therefore the box is a <a>scroll container</a>).
 			Furthermore, if the user agent uses a scrolling mechanism
@@ -623,7 +623,7 @@ Expanding Clipping Bounds: the 'overflow-clip-margin' property</h3>
 
 	<pre class=propdef>
 	Name: overflow-clip-margin
-	Value: <<visual-box>> || <<length [0,∞]>>
+	Value: <<visual-box>> || <<length>>
 	Initial: ''0px''
 	Inherited: no
 	Applies to: boxes to which 'overflow' applies
@@ -632,10 +632,8 @@ Expanding Clipping Bounds: the 'overflow-clip-margin' property</h3>
 	</pre>
 
 	This property defines the <dfn export>overflow clip edge</dfn> of the box,
-	i.e. precisely <em>how far</em> outside its bounds
-	the box’s content is allowed to paint
-	before being clipped
-	by effects (such as ''overflow: clip'', above)
+	i.e. precisely where the box's content is allowed to paint
+	before being clipped by effects (such as ''overflow: clip'', above)
 	that are defined to clip to the box’s [=overflow clip edge=].
 
 	Values are defined as follows:
@@ -649,12 +647,12 @@ Expanding Clipping Bounds: the 'overflow-clip-margin' property</h3>
 			If omitted,
 			defaults to ''overflow-clip-margin/padding-box''.
 
-		: <dfn><<length [0,∞]>></dfn>
+		: <dfn><<length>></dfn>
 		::
 			The specified offset dictates
 			how much the [=overflow clip edge=] is expanded from
-			the specified box edge
-			Negative values are invalid.
+			the specified box edge.
+			Negative values indicate insets, instead.
 			Defaults to zero if omitted.
 	</dl>
 
@@ -666,9 +664,14 @@ Expanding Clipping Bounds: the 'overflow-clip-margin' property</h3>
 	and [[css-backgrounds-3#shadow-shape]],
 	noting in particular the formula for outsets beyond the [=border edge=].
 
-	Note: This property has no effect on boxes
-	with ''overflow: hidden'' or ''overflow: scroll'',
-	which are not defined to use the [=overflow clip edge=].
+	If the box is a [=scroll container=],
+	the [=overflow clip edge=] is clamped to stay within the element's [=padding box=].
+	(This does not affect the [=computed value|computed=] or [=used value=] of this property.)
+
+	Note: This property was previously defined to only affect ''overflow: clip''.
+	It now also affects [=scroll containers=],
+	but only to shrink the clipping edge.
+
 
 <h3 id="overflow-propagation">
 Overflow Viewport Propagation</h3>

css-overflow-4/Overview.bs

@@ -216,11 +216,11 @@ Managing Overflow: the 'overflow-x', 'overflow-y', and 'overflow' properties</h3
 	is still being worked out.
 
 <h3 id="overflow-clip-margin">
-Expanding Clipping Bounds: the 'overflow-clip-margin-*' properties</h3>
+Changing Clipping Bounds: the 'overflow-clip-margin-*' properties</h3>
 
 	<pre class="propdef shorthand">
 	Name: overflow-clip-margin-top, overflow-clip-margin-right, overflow-clip-margin-bottom, overflow-clip-margin-left, overflow-clip-margin-block-start, overflow-clip-margin-inline-start, overflow-clip-margin-block-end, overflow-clip-margin-inline-end
-	Value: <<visual-box>> || <<length [0,∞]>>
+	Value: <<visual-box>> || <<length>>
 	Initial: ''0px''
 	Inherited: no
 	Logical property group: overflow-clip-margin
@@ -231,7 +231,7 @@ Expanding Clipping Bounds: the 'overflow-clip-margin-*' properties</h3>
 
 	<pre class="propdef shorthand">
 	Name: overflow-clip-margin, overflow-clip-margin-inline, overflow-clip-margin-block
-	Value: <<visual-box>> || <<length [0,∞]>>
+	Value: <<visual-box>> || <<length>>
 	Initial: ''0px''
 	Inherited: no
 	Applies to: boxes to which 'overflow' applies
@@ -262,12 +262,12 @@ Expanding Clipping Bounds: the 'overflow-clip-margin-*' properties</h3>
 			ISSUE(7144): Application of 'overflow-clip-margin' to [=replaced elements=]
 			is still being worked out.
 
-		: <dfn><<length [0,∞]>></dfn>
+		: <dfn><<length>></dfn>
 		::
 			The specified offset dictates
 			how much the [=overflow clip edge=] is expanded from
-			the specified box edge
-			Negative values are invalid.
+			the specified box edge.
+			Negative values shrink the box, instead.
 			Defaults to zero if omitted.
 	</dl>
 
@@ -279,10 +279,6 @@ Expanding Clipping Bounds: the 'overflow-clip-margin-*' properties</h3>
 	and [[css-backgrounds-3#shadow-shape]],
 	noting in particular the formula for outsets beyond the [=border edge=].
 
-	Note: This property has no effect on boxes
-	with ''overflow: hidden'' or ''overflow: scroll'',
-	which are not defined to use the [=overflow clip edge=].
-
 
 <h2 id="auto-ellipsis">
 Automatic Ellipses</h2>