[css-inline-3] Actually define behavior on inline boxes. #3955

Author: fantasai

css-inline-3/Overview.bs

@@ -710,7 +710,7 @@ Line Sizing Containment: the 'line-sizing' property</h3>
 	or "don't pay attention to me".
 
 <h3 id="leading-trim-property">
-Leading Control: the 'leading-trim-over' and 'leading-trim-under' properties and 'leading-trim' shorthand</h3>
+Leading Control</h3>
 
 	ISSUE: This is a rough draft of a proposal,
 	and is likely to change significantly
@@ -803,6 +803,9 @@ Leading Control: the 'leading-trim-over' and 'leading-trim-under' properties and
 		</figure>
 	</div>
 
+<h4 id="leading-trim-over">
+Trimming Spacing Above: the 'leading-trim-over' property</h4>
+
 	<pre class="propdef">
 	Name: leading-trim-over
 	Value: normal | text | cap | ex | ideographic | ideographic-ink
@@ -813,58 +816,57 @@ Leading Control: the 'leading-trim-over' and 'leading-trim-under' properties and
 	Computed value: the specified keyword
 	</pre>
 
-	The 'leading-trim-over' property trims
+	On [=block containers=],
+	the 'leading-trim-over' property trims
 	the <a>line-over</a> side of the first line box in the block container
-	to better match the box’s content edge to its text content.
+	to the specified metric of its [=root inline box=]
+	to better match the box’s [=content edge=] to its text content.
 	The property affects only the <a>first formatted line</a> of the block container;
 	if there is no such line, it has no effect.
+
+	On [=inline boxes=],
+	it trims the [=line-over=] side of the box,
+	matching its [=content edge=] to the specified metric.
+
 	Values have the following meanings:
 
 	<dl dfn-for="leading-trim-over, leading-trim" dfn-type=value>
 		<dt><dfn>normal</dfn>
 		<dd>
-			Half-leading is applied over the first line,
-			just as for every other line.
+			Half-leading is applied over the first line of the [=block container=],
+			just as for every other line
+			and no trimming occurs.
+			(When applied to [=block containers=],
+			all other values trim this half-leading.)
 
 		<dt><dfn>text</dfn>
 		<dd>
-			Half-leading is not applied over the first line;
-			the top of the line box is set to
-			the text-top metric
+			Trim to the text-top metric
 			(the metric used for ''vertical-align: text-top''
 			and the [=line-over=] [=content edge=]
-			as defined in [[CSS2]])
-			of the root inline box.
+			as defined in [[CSS2]]).
 
 		<dt><dfn>cap</dfn>
 		<dd>
-			Half-leading is not applied over the first line;
-			the top of the line box is set to
-			the cap-height metric
-			of the root inline box.
+			Trim to the cap-height metric.
 
 		<dt><dfn>ex</dfn>
 		<dd>
-			Half-leading is not applied over the first line;
-			the top of the line box is set to
-			the ex-height metric
-			of the root inline box.
+			Trim to the ex-height metric.
 
 		<dt><dfn>ideographic</dfn>
 		<dd>
-			Half-leading is not applied over the first line;
-			the top of the line box is set to
-			the ideographic top (<code>idtp</code>) metric
-			of the root inline box.
+			Trim to the ideographic top (<code>idtp</code>) metric.
 
 		<dt><dfn>ideographic-ink</dfn>
 		<dd>
-			Half-leading is not applied over the first line;
-			the top of the line box is set to
-			the ideographic character face top (<code>icft</code>) metric
-			of the root inline box.
+			Trim to the ideographic character face top (<code>icft</code>) metric.
 	</dl>
 
+
+<h4 id="leading-trim-under">
+Trimming Spacing Below: the 'leading-trim-under' property</h4>
+
 	<pre class="propdef">
 	Name: leading-trim-under
 	Value: normal | text | alphabetic | ideographic | ideographic-ink
@@ -875,51 +877,53 @@ Leading Control: the 'leading-trim-over' and 'leading-trim-under' properties and
 	Computed value: the specified keyword
 	</pre>
 
-	The 'leading-trim-over' property trims
+	On [=block containers=],
+	the 'leading-trim-over' property trims
 	the <a>line-over</a> side of the first line box in the block container
-	to better match the box’s content edge to its text content.
-	The property affects only the <a>first formatted line</a> of the block container;
+	to the specified metric of its [=root inline box=]
+	to better match the box’s [=content edge=] to its text content.
+	The property affects only the last formatted line of the block container;
 	if there is no such line, it has no effect.
+
+	On [=inline boxes=],
+	it trims the [=line-under=] side of the box,
+	matching its [=content edge=] to the specified metric.
+
 	Values have the following meanings:
 
 	<dl dfn-for="leading-trim-under" dfn-type=value>
 		<dt><dfn>normal</dfn>
 		<dd>
-			Half-leading is applied over the first line,
-			just as for every other line.
+			Half-leading is applied under the last line of the [=block container=],
+			just as for every other line
+			and no trimming occurs.
+			(When applied to [=block containers=],
+			all other values trim this half-leading.)
 
 		<dt><dfn>text</dfn>
 		<dd>
-			Half-leading is not applied over the first line;
-			the top of the line box is set to
-			the text-bottom metric
+			Trim to the text-bottom metric
 			(the metric used for ''vertical-align: text-bottom''
 			and the [=line-under=] [=content edge=]
-			as defined in [[CSS2]])
-			of the root inline box.
+			as defined in [[CSS2]]).
 
 		<dt><dfn>alphabetic</dfn>
 		<dd>
-			Half-leading is not applied over the first line;
-			the top of the line box is set to
-			the alphabetic baseline metric
-			of the root inline box.
+			Trim to the alphabetic baseline metric.
 
 		<dt><dfn>ideographic</dfn>
 		<dd>
-			Half-leading is not applied over the first line;
-			the top of the line box is set to
-			the ideographic bottom (<code>ideo</code>) metric
-			of the root inline box.
+			Trim to the ideographic bottom (<code>ideo</code>) metric.
 
 		<dt><dfn>ideographic-ink</dfn>
 		<dd>
-			Half-leading is not applied over the first line;
-			the top of the line box is set to
-			the ideographic character face top (<code>icfb</code>) metric
-			of the root inline box.
+			Trim to the ideographic character face top (<code>icfb</code>) metric.
 	</dl>
 
+
+<h4 id="leading-trim-over">
+Trimming Spacing Above and Below: the 'leading-trim' shorthand</h4>
+
 	<pre class="propdef">
 	Name: leading-trim
 	Value: normal | text | cap | ex | ideographic | ideographic-ink