[css-inline-3] Draft up some kind of line-sizing proposal so we have something to talk about. #3199

Author: fantasai

css-inline-3/Overview.bs

@@ -7,7 +7,7 @@
 Title: CSS Inline Layout Module Level 3
 Shortname: css-inline
 Level: 3
-Status: WD
+Status: ED
 Work Status: Revising
 Group: csswg
 TR: https://www.w3.org/TR/css-inline-3/
@@ -298,8 +298,8 @@ Alignment Shift: the 'baseline-shift' longhand
 
 	Issue: We would prefer to remove this, and are looking for feedback from SVG user agents as to whether it's necessary.
 
-<h4 id="line-height-property">
-Line Spacing: the 'line-height' propertyh4>
+<h3 id="line-height-property">
+Line Spacing: the 'line-height' propertyh3>
 
 	
 	Name: line-height
@@ -324,6 +324,100 @@ Line Spacing: the 'line-height' property
 	See also href="https://github.com/w3c/csswg-drafts/issues/3118">Issue 3118
 	and Issue 2165.
 
+
+Line Sizing Containment: the 'line-sizing' property
+
+	
+	Name: line-sizing
+	Value: quirks-behavior | current-behavior | better-behavior | box-model-behavior | absolute-behavior
+	Initial: current-behavior
+	Applies to: block containers? inline boxes?
+	Inherited: yes
+	Percentages: N/A
+	Computed value: the specified keyword
+	
+
+	ISSUE: This is a rought draft of a proposal, and has not yet been approved by the CSSWG.
+	Many variants have been included to promote discussion of possible behaviors;
+	not all of them are expected to be kept.
+	See discussion in Issue 3199, Hyatt's message, and dbaron's proposal.
+	Also all the keywords are expected to be renamed.
+
+	This property controls the method by which line boxes are sized,
+	and thus the spacing between lines of text.
+
+	Values have the following meanings:
+
+	
+		quirks-behavior
+		
+			Line boxes are sized, and content positioned within them,
+			as defined in [[!CSS2]] except that
+			any inline box fragment
+			that has zero borders and padding and
+			that does not directly contain text or preserved white space [[!CSS-TEXT-3]]
+			is ignored for this purpose.
+
+		current-behavior
+		
+			Line boxes are sized, and content positioned within them,
+			as defined in [[!CSS2]].
+
+			Note: In this model, vertical rhythm is broken
+			any time there is a change in font metrics within a paragraph.
+
+		better-behavior
+		
+			Line boxes are sized, and content positioned within them,
+			as defined in [[!CSS2]],
+			except that positive half-leading is not applied
+			to any box other than the root inline box.
+
+			Note: This will give consistent line spacing
+			as long as there is some amount of leading added,
+			such that the half-leading on the root inline
+			is large enough to accommodate the unleaded ascent of its descendants.
+			The line box will grow to accommodate
+			content that would otherwise overflow,
+			avoiding overlap between lines.
+
+		box-model-behavior
+		
+			Line boxes are sized to fit the root inline box
+			and its half-leading,
+			as well as the outer edges of any inline-level descendants
+			in the same inline formatting context.
+			Positive half-leading is not applied to any other inline box;
+			negative half-leading is applied as negative margins
+			to inline boxes whose block-axis margins, borders, and padding
+			are zero.
+
+			Note: This mode is similar to ''better-behavior'',
+			but re-uses the familiar margin/border/padding box model
+			of controlling spacing.
+			However to ensure that 'line-height' < 1 behaves as expected,
+			the default case (no margin/border/padding)
+			needs to apply negative leading to such inlines.
+
+		absolute-behavior
+		
+			Line boxes are sized to fit the root inline box
+			and its half-leading;
+			no other boxes are considered.
+			Inline-level content may overflow the line box
+			and overlap adjacent lines
+			if it extends higher or lower
+			than the edges of the root inline box’s leading.
+	
+
+	ISSUE: Should this property apply to block containers or to inline boxes?
+	In the latter case, an individual inline could say "pay attention to me"
+	or "don't pay attention to me".
+
+	ISSUE: Need better names. Maybe `loose | normal | strict | absolute`?
+	Maybe `quirks | legacy | normal | absolute`?
+	Something else?
+
 
 Drawing Inline Boxes