[css-ruby] Define in more details how columns are sized

Author: frivoal

css-ruby-1/Overview.bs

@@ -720,22 +720,50 @@ Ruby Layout</h2>
 	This makes layout more robust,
 	but is inconsistent with how inlines behave along the inline-axis.
 
-	A [=ruby container=] (or fragment thereof)
-	measures as wide as the content of its widest level.
-	Similarly, [=ruby base boxes=] and [=ruby annotation boxes=]
-	within a [=ruby column=] have the measure of the widest content in that [=column=].
+	When 'ruby-merge' is ''ruby-merge/separate'',
+	each [=ruby column=] is sized
+	to the widest content ([=ruby base=] or [=ruby annotation=]) in that [=column=].
 	In the case of [=spanning annotations=]
-	(whether actually spanning or pretending to span per 'ruby-merge'),
-	the measures of the [=ruby annotation box=] and
-	the sum of its associated [=ruby base boxes=] must match.
-
-	How the extra space is distributed
+	(whether actually spanning or pretending to span per ''ruby-merge: merge''),
+	if the content of a [=spanning annotation=] would be wider
+	than the [=columns=] that it spans,
+	then the difference is distributed equally among the spanned [=columns=].
+	If a [=ruby segment=] contains multiple [=spanning annotations=],
+	this distribution of additional space
+	is performed starting with the [=spanning annotations=]
+	that span the least number of bases,
+	and then in increasing number of bases spanned.
+	Each [=ruby base=] and [=ruby annotation=]
+	is then sized to exactly span its column(s).
+
+	Note: If there are multiple annotations spanning the same number of bases
+	that overlap but do not coincide,
+	the distribution of space is undefined.
+	Note this is not possible with HTML markup,
+	but can happen in markup languages with explicit spanning such as in [[RUBY]].
+
+	If any [=ruby annotation=] in an [=annotation container=] with ''ruby-merge: auto''
+	is wider than its [=ruby base|base=],
+	then [=ruby annotations=] in that [=annotation container=]
+	may extend outside of their [=column=](s).
+	When they do, their influence on
+	the measure of the [=columns=] they intersect
+	is up to the User Agent,
+	provided that the [=ruby segment=] is made wide enough to fit all its content.
+
+	[=Inter-character=] annotations are interleaved between columns:
+	they factor into measurement of annotations that span both adjacent columns,
+	but are not included in either column
+	and are never affected by the sizing or positioning
+	of [=interlinear annotations=].
+
+	A [=ruby container=] measures as wide as the sum of its [=columns=].
+
+	Within these boxes,
+	how the extra space is distributed
 	when ruby content is narrower than the measure of its box
 	is specified by the 'ruby-align' property.
 
-	Issue: Should the ruby bases and annotations size to the column,
-	or size to the content?
-
 	As in other CSS layout models,
 	relative positioning, transforms, and other graphical effects
 	apply after this layout of the boxes.