[css-inline] improve definitions of initial letter wrapping

Author: dauwhe

css-inline/Overview.bs

@@ -573,41 +573,73 @@ In the <a>inline axis</a>, the position of the inline letter is given by alignin
 However, if the <a>initial letter</a> is a non-atomic inline with zero padding and borders, the UA must apply an additional negative offset on the start side of the amount necessary to optically align the first glyph to the containing block edge as it would be in normal text.
 
 
-<h4 id="initial-letter-wrapping">
-Initial Letter Wrapping</h4>
+<h3 id="initial-letter-wrapping">
+Initial Letter Wrapping</h3>
 
 <pre class="propdef">
 Name: <dfn id="propdef-initial-letter-wrap">initial-letter-wrap</dfn>
-Value: none | auto | first-line
-Initial: none
+Value: none | all | first | auto
+Initial: auto
 Applies to: <code>::first-letter</code> pseudo-elements and inline-level first child of a block container
-Inherited: no
+Inherited: yes
 Percentages: N/A
 Media: visual
 Computed value: as specified
 </pre>
 
+This property specifies whether lines impacted by an <a>initial letter</a>
+are shortened to fit the rectangular shape of the <a>initial letter</a> box
+or follow the contour of its end-edge glyph outline.
+
 <dl dfn-for=initial-letter-wrap dfn-type=value>
 <dt><dfn>none</dfn>
-<dd>No wrapping is performed.</dd>
-<dt><dfn>auto</dfn></dt>
-<dd>For each line of text impacted by the initial letter, the line box adjacent to the intial letter starts at the left-most point that touches the ink of the initial letter, plus a fixed amount of offset.</dd>
+<dd>No contour-fitting is performed:
+each impacted line is aligned flush to the end margin edge of the <a>initial letter</a>.</dd>
 
-Issue: How much offset? Based on the right side-bearing of the initial letter? That could be a problem as it's sometimes negative (see Zapfino). 
+<dt><dfn>all</dfn></dt>
+<dd>For each line of text impacted by the initial letter, the line box adjacent to the intial letter starts at the start-most point that touches the ink of the initial letter, plus the amount of the <a>initial letter</a>’s end-side border+padding+margin.</dd>
 
-<dt><dfn>first-line</dfn>
-<dd>As auto, but wrapping only performed on the first line of the block containing the initial letter.</dd>
-</dl>
 
-Issue: Rewrite for logical directions.
+<dt><dfn>first</dfn>
+<dd>Behaves as for ''all'' on the first line of the block containing the initial letter and as ''none'' on the rest.</dd>
+
+<dt><dfn>auto</dfn>
+<dd>Behaves as ''none'' if
+the <a>initial letter</a>’s end-side padding or margin is nonzero <em>or</em>
+the first <a>typographic character unit</a> after the <a>initial letter</a> belongs to Unicode General Category Zs <em>or</em>
+the last <a>typographic character unit</a> of the <a>initial letter</a>
+<ul>
+	<li>belongs to the Symbols <a>Unicode General Category</a> (<code>S</code>)
+	<li>has an <a>East Asian Width</a> property of <code>Wide</code> or <code>Fullwidth</code>
+	<li>belongs to a script that is commonly used without spaces between words.
+	(Such scripts include:
+	Cham,
+	Han,
+	Khmer,
+	Lao,
+	Thai,
+	Yi
+	)
+</ul>
+Behaves as ''first'' otherwise.
 
-Issue: Bikeshed value names. 
+Issue: Do we want to make this script-dependent? 
+
+</dl>
 
 
 Issue: Do we need anything else for scripts where this behavior is undesirable? Or is default "none" sufficient? 
 
 
-Note: If the next character after the initial letter is a whitespace character, auto and first-line compute to none, in order to avoid the initial letter appearing to be part of the subsequent word. 
+Note: If the next character after the initial letter is a whitespace character, auto and first compute to none, in order to avoid the initial letter appearing to be part of the subsequent word. 
+
+
+<figure>
+<img src="images/OpticalKerning.png" alt="optical kerning in the presence or absence of a space after the initial letter" width="200"/>
+<p class="caption">In the top paragraph, the initial letter "A" has a word space after it. In the middle paragraph, the initial letter "A" is part of a word. In this case, the first line of text should be kerned into the initial letter's area as shown in the bottom paragraph.</p>
+</figure>
+
+Issue: Edit figure to show how auto behaves in varying contexts
 
 
 <div class="example">
@@ -643,13 +675,13 @@ Text follows shape of initial letter. Each line box should just touch the ink of
 <pre>
 p::first-letter {
   initial-letter: 3;
-  initial-letter-wrap: first-line;
+  initial-letter-wrap: first;
 }
 </pre>
 
 <img alt="text wrapping around dropcap A but only on first line"  src="images/A-wraparound-first.png" width="600">
 
-Only first line is moved up against the ink of the initial letter.
+Only the first line is moved up against the ink of the initial letter.
 
 </div>
 
@@ -672,19 +704,9 @@ Only first line is moved up against the ink of the initial letter.
 
 </div>
 
-Issue: What should happen with initial letters that are concave on the (right) side? Wrapping the middle line in a three-line initial "K" can look very strange. 
 
 
-Additionally, when borders and padding are zero
-and the next <a>typographic character unit</a> after the <a>initial letter</a>
-is not a space (<a>Unicode general category</a> <code>Zs</code>),
-the UA should optically kern the first line of text into the <a>initial letter</a>’s area
-as necessary to maintain perceptual continuity of the text.
 
-<figure>
-<img src="images/OpticalKerning.png" alt="optical kerning in the presence or absence of a space after the initial letter" width="200"/>
-<p class="caption">In the top paragraph, the initial letter "A" has a word space after it. In the middle paragraph, the initial letter "A" is part of a word. In this case, the first line of text should be kerned into the initial letter's area as shown in the bottom paragraph.</p>
-</figure>
 
 <h3 id="initial-letter-paragraphs">
 Clearing Initial Letters</h3>