[css-text-4] Add pretty/stable values to text-wrapper F2F discussions. #672

Author: fantasai

css-text-4/Overview.bs

@@ -178,7 +178,7 @@ Text Wrap Settings: the 'text-wrap' property</h3>
 
 	<pre class="propdef">
 	Name: text-wrap
-	Value: wrap | nowrap | balance
+	Value: wrap | nowrap | balance | stable | pretty
 	Initial: wrap
 	Applies to: <a>inline boxes</a> and <a>block containers</a>
 	Inherited: yes
@@ -199,8 +199,13 @@ Text Wrap Settings: the 'text-wrap' property</h3>
 			in order to minimize <a>inline-axis</a> overflow.
 
 			The exact algorithm is UA-defined.
-			The algorithm may consider multiple lines when making break decisions.
-			The UA may bias for speed over best layout.
+			The algorithm <em>may</em> consider multiple lines
+			when making break decisions.
+			The UA <em>may</em> bias for speed over best layout.
+			The UA <em>must not</em> attempt to even out all lines
+			(including the last) as for ''text-wrap/balance''.
+			This value selects the UA’s preferred (or most Web-compatible)
+			wrapping algorithm.
 
 		<dt><dfn>nowrap</dfn>
 		<dd>
@@ -230,9 +235,26 @@ Text Wrap Settings: the 'text-wrap' property</h3>
 			The exact algorithm is UA-defined.
 
 			UAs may treat this value as ''text-wrap/wrap'' if there are more than ten lines to balance.
-	</dl>
 
-	ISSUE: There's some discussion about whether different wrapping algorithms (higher quality vs faster) need special keywords, see <a href="https://github.com/w3c/csswg-drafts/issues/672#issuecomment-379723243">Issue 672</a>.
+		<dt><dfn>stable</dfn>
+		<dd>
+			When applied to a <a>block container</a>
+			that establishes an <a>inline formatting context</a>,
+			specifies that content on subsequent lines
+			<em>should not</em> be considered when making break decisions
+			so that when editing text any content before the cursor
+			remains stable;
+			otherwise equivalent to ''text-wrap/wrap'',
+
+		<dt><dfn>pretty</dfn>
+		<dd>
+			When applied to a <a>block container</a>
+			that establishes an <a>inline formatting context</a>,
+			specifies the UA <em>should</em> bias for better layout over speed,
+			and is expected to consider multiple lines,
+			when making break decisions.
+			Otherwise equivalent to ''text-wrap/wrap'',
+	</dl>
 
 	Regardless of the 'text-wrap' value,
 	lines always break at forced breaks:
@@ -262,24 +284,22 @@ Text Wrap Settings: the 'text-wrap' property</h3>
 
 	<!-- add a sample prioritization algorithm -->
 
-	Note: The ''text-wrap/wrap'' value is intended 
-	for speedy legacy line breaking, 
-	which has so far used first-fit/greedy algorithms 
+	Note: The ''text-wrap/wrap'' value is will typically map
+	to Web browsers’ speedy legacy line breaking,
+	which has so far used first-fit/greedy algorithms
 	that can often give sub-optimal results. 
-	UAs could experiment with better line breaking algorithms 
+	UAs can experiment with better line breaking algorithms
 	with this default value, 
-	but optimal results will probably take more time. 
-	The ''text-wrap/multi-line'' and ''text-wrap/balance'' values 
-	are intended as opt-in choices to take more time for better results. 
-	The ''text-wrap/balance'' value is intended for titles and captions, 
-	and the ''text-wrap/multi-line'' is intended for body text.
-
-	Note: Some line breaking algorithms can interact unexpectedly with editing.
-	Changing upstream line breaks on user edits can be unsettling.
-	As UAs experiment with better line breaking algorithms, 
-	we will likely need to add a property 
-	to constrain upstream changes while editing.
-
+	but as optimal results often take more time,
+	''text-wrap/pretty'' is offered as an opt-in
+	to take more time for better results.
+	The ''text-wrap/pretty'' value is intended for body text,
+	where the last line is expected to be a bit shorter than the average line;
+	the ''text-wrap/balance'' value is intended for titles and captions,
+	where equal-length lines of text tend to be preferred;
+	and the ''text-wrap/stable'' is intended for sections that are,
+	or are likely become toggled as,
+	editable.
 <h3 id="wrap-before">
 Inline breaks between boxes: the 'wrap-before'/'wrap-after' properties</h3>