[ui-input] Clarify intent of focus chain.
Change-Id: I4584177360e7aacdfd383a8ca14cf392a0393bdf
Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/443704
Commit-Queue: Jaeheon Yi <jaeheon@google.com>
Reviewed-by: Kyo Lee <kyol@google.com>
Reviewed-by: Filip Filmar <fmil@google.com>
diff --git a/docs/concepts/graphics/scenic/focus_chain.md b/docs/concepts/graphics/scenic/focus_chain.md
index 8a41fa6..b18c11f 100644
--- a/docs/concepts/graphics/scenic/focus_chain.md
+++ b/docs/concepts/graphics/scenic/focus_chain.md
@@ -52,15 +52,23 @@
## Focus chain: focus path in a view tree
+If we think about just the view parts of the scene graph, they form a tree
+hierarchy; we call this the view tree. Parent views have tremendous power over
+child views: the power to reposition the child's view, enforce clip boundaries
+on the child's view, hide the child's UI content, etc. Because of the inherent
+power of the view hierarchy, we use it as a basis of hierarchy outside of
+Scenic. This hierarchy, which changes dynamically based on view focusing, is
+represented with a "focus chain".
+
In a data structure sense, a focus chain is merely a vector of ViewRefs. The
canonical definition is
[fuchsia.ui.focus.FocusChain](/sdk/fidl/fuchsia.ui.focus/focus_chain.fidl).
-However, the focus chain is tied intimately to the view tree. It captures a
-snapshot of view authority, starting from the root view, walking down through
-descendants, and terminating at the focused view. It is thus ordered in amount
-of authority, from most to least. Views outside the focus chain have no
-authority.
+However, it's more than just that. The focus chain is tied intimately to the
+view tree. It captures a snapshot of view authority, starting from the root
+view, walking down through descendants, and terminating at the focused view. It
+is thus ordered in amount of authority, from most to least. Views outside the
+focus chain have no view-based authority.
Intuitively, the focus chain is the path from view tree's root node to the
focused node.
diff --git a/docs/concepts/graphics/scenic/view_ref.md b/docs/concepts/graphics/scenic/view_ref.md
index 4773035..0af1cdb 100644
--- a/docs/concepts/graphics/scenic/view_ref.md
+++ b/docs/concepts/graphics/scenic/view_ref.md
@@ -40,6 +40,13 @@
content and embedding other Views. Because we have a ViewRef for each View, we
can also think of the view tree as a tree of ViewRefs.
+In a view tree, parent views have tremendous power over child views: the power
+to reposition the child's view, enforce clip boundaries on the child's view,
+hide the child's UI content, etc. Because of the inherent power of the view
+hierarchy, we use it as a basis of hierarchy outside of Scenic. This hierarchy,
+which changes dynamically based on view focusing, is represented with a
+"[focus chain](focus_chain.md)".
+
### How is a ViewRef used?
Typically, a UI client uses a ViewRef to self-identify itself to manager-type
