Module focus_scope 

FocusScope — a layout-transparent wrapper that declares a traversal boundary for Tab / Shift+Tab focus cycling.

Descendants’ tab_index values are scoped to the nearest enclosing FocusScope: two sibling scopes that both number their children 1, 2, 3 never interleave — each scope is an independent, ordered unit within its parent. The TraversalScopePolicy controls what Tab does at the scope’s ends:

• Continue — Tab flows out of the scope into the enclosing scope’s next member (grouping only). Use for logical regions in a continuous Tab order, e.g. dock panels.
• Cycle — Tab wraps within the scope and never leaves via keyboard. Use for modal dialogs.

// A modal dialog whose Tab order is confined to its own content:
FocusScope::new(TraversalScopePolicy::Cycle).child(dialog_body)

Do not Cycle-wrap a popover, menu or dropdown panel. Those are non-modal, and the framework dismisses a non-modal overlay when keyboard focus leaves it — which is what their ARIA patterns (Disclosure, Menu) ask for, and what keeps an open panel from sitting over the focus ring that left it. Trapping focus inside one prevents that dismissal from ever firing. A centered modal needs no wrapper at all: cycle_focus already roots traversal at the topmost centered overlay’s content.

Layout & accessibility

FocusScope imposes no layout — it reports its child’s natural size and places the child at its own bounds (like Fade). It is a structural boundary, not an AT element: the wrapped child owns its own accessibility semantics. The scope node is never itself a Tab stop (BuildContext::set_traversal_scope forces it non-focusable).

Structs

FocusScope

Wraps a child subtree and declares it a Tab traversal scope. See the module documentation for semantics.