[css-logical-1] Define inheritance of flow-relative properties. #3029

Author: fantasai

css-logical-1/Overview.bs

@@ -336,7 +336,7 @@ Flow-Relative Box Model Properties</h2>
   This shared value is determined by [=cascading=]
   the declarations of both properties together as one;
   in other words, the [=computed value=] of both properties in the pair
-  is derived from the [=specified=] value of the property declared with
+  is derived from the [=specified value=] of the property declared with
   higher priority in the CSS [=cascade=]. [[!CSS-CASCADE-3]]
 
   <p class="note">
@@ -391,9 +391,19 @@ Flow-Relative Box Model Properties</h2>
   to get the correct mapping behavior
   when changing an element’s <a>writing mode</a> from its parent.
 
-  ISSUE: There are some open questions on
-  the <a href="https://github.com/w3c/csswg-drafts/issues/3029">order of inheritance vs mapping in flow-relative properties</a>
-  and on the <a href="https://github.com/w3c/csswg-drafts/issues/3030">interaction of shorthands and logical properties</a>.
+  Inheritance of each property is from its corresponding property on the parent.
+  For example, although the [=inline-start=] margin of an''direction/rtl'' box is its right margin,
+  'margin-inline-start' on this box will inherit
+  the 'margin-inline-start' of an ''direction/ltr'' parent
+  even though that happens to be the parent’s <em>left</em> margin.
+
+  [=Shorthand properties=] that encompass both logical and physical longhands
+  (such as the 'all' shorthand)
+  set omitted values first,
+  and otherwise set the physical values last.
+  For example, ''all: inherit'' will set all of the 'margin' properties to ''inherit'',
+  but since the physical longhands are set last,
+  the child's margins will inherit from their physical counterparts in the parent.
 
 <h3 id="dimension-properties">
 Logical Height and Logical Width: