[css-inline-3] Add leading value to initial-letter-align to handle Tamil et al. per ILREQ. w3c#864

Author: fantasai

css-inline-3/Overview.bs

@@ -1781,7 +1781,7 @@ Alignment of Initial Letters: the 'initial-letter-align' property</h3>
 
 	<pre class="propdef" id="initial-letter-align">
 	Name: <dfn id="propdef-initial-letter-align">initial-letter-align</dfn>
-	Value: [ border-box? [ alphabetic | ideographic | hanging ]? ]!
+	Value: [ border-box? [ alphabetic | ideographic | hanging | leading ]? ]!
 	Initial: alphabetic
 	Applies to: certain inline-level boxes and <css>::first-letter</css> and inside <css>::marker</css> boxes (<a href="#first-most-inline-level">see prose</a>)
 	Inherited: yes
@@ -1794,7 +1794,8 @@ Alignment of Initial Letters: the 'initial-letter-align' property</h3>
 	used to size and position an <a>initial letter</a>.
 	Two sets of alignment points are necessary:
 	the <a>over</a> and <a>under</a> alignment points of the <a>initial letter</a>
-	are matched to corresponding <a>over</a> and <a>under</a> points of the surrounding text.
+	are matched to corresponding <a>over</a> and <a>under</a> points
+	of the [=root inline box=].
 
 	Values have the following meanings:
 
@@ -1817,6 +1818,16 @@ Alignment of Initial Letters: the 'initial-letter-align' property</h3>
 			of the surrounding text
 			to align the <a>initial letter</a>.
 
+		<dt><dfn>leading</dfn>
+		<dd>
+			Use the over/under half-leading edges
+			(i.e. [=ascent=]/[=descent=] + [=half-leading=])
+			of the surrounding text
+			to align the <a>initial letter</a>.
+
+			Note: This will essentially match the edges of the [=initial letter=]
+			to middle of the line gap above/below the first/last impacted lines.
+
 		<dt><dfn>border-box</dfn>
 		<dd>
 			Use the [=initial letter box=]’s [=line-under=] and [=line-over=] [=border edges=]
@@ -1866,10 +1877,6 @@ Alignment of Initial Letters: the 'initial-letter-align' property</h3>
 		</figure>
 	</div>
 
-	Issue: What is the proper alignment for South Asian scripts
-	that do not have the explicit hanging baseline, such as Tamil or Telugu?
-	See GitHub issue <a href="https://github.com/w3c/csswg-drafts/issues/864">864</a>
-
 	Note: The ordering of keywords in this property is fixed in case ''border-box''
 	is expanded to ''[ border-box | alphabetic | ideographic | hanging ]''
 	to allow explicitly specifying the <a>initial letter</a>’s alignment points.
@@ -2171,7 +2178,7 @@ Block-axis Positioning</h4>
 
 	* If its [=initial letter size|size=] is greater than or equal to
 		its [=initial letter sink|sink=],
-		[=the initial letter=] is positioned
+		the [=initial letter=] is positioned
 		to satisfy its <a>under</a> alignment,
 		and then shifted by
 		([=initial letter sink|sink=] - 1) &times; 'line-height' of [=containing block=]
@@ -2901,6 +2908,16 @@ A.3: Synthesizing Baselines for Atomic Inlines</h3>
 <h2 class="no-num" id="changes">
 Changes</h2>
 
+	Changes since the
+	<a href="https://www.w3.org/TR/2020/WD-css-inline-3-20200618/">18 June 2020 Working Draft</a>
+	include:
+	<ul>
+		<li>Added ''initial-letter-align/leading'' value to 'initial-letter-align'
+		to handle common practices for certain Indic scripts.
+		See <a href="https://www.w3.org/TR/ilreq/#h_scripts_without_hanging_baseline">Indic Layout Requirements</a>.
+		(<a href="https://github.com/w3c/csswg-drafts/issues/864">Issue 864</a>)
+	</ul>
+
 	Changes since the
 	<a href="https://www.w3.org/TR/2020/WD-css-inline-3-20200604/">4 June 2020 Working Draft</a>
 	include: