Function onFocus

packages/react-aria/src/focus/FocusScope.tsx:396–419

    };

    let onFocus: EventListener = e => {
      // If focusing an element in a child scope of the currently active scope, the child becomes active.
      // Moving out of the active scope to an ancestor is not allowed.
      if (
        (!activeScope || isAncestorScope(activeScope, scopeRef)) &&
        isElementInScope(getEventTarget(e) as Element, scopeRef.current)
      ) {
        activeScope = scopeRef;
        focusedNode.current = getEventTarget(e) as FocusableElement;
      } else if (
        shouldContainFocus(scopeRef) &&
        !isElementInChildScope(getEventTarget(e) as Element, scopeRef)
      ) {
        // If a focus event occurs outside the active scope (e.g. user tabs from browser location bar),
        // restore focus to the previously focused node or the first tabbable element in the active scope.
        if (focusedNode.current) {
          focusedNode.current.focus();
        } else if (activeScope && activeScope.current) {
          focusFirstInScope(activeScope.current);
        }
      } else if (shouldContainFocus(scopeRef)) {
        focusedNode.current = getEventTarget(e) as FocusableElement;
      }
    };

    let onBlur: EventListener = e => {
      // Firefox doesn't shift focus back to the Dialog properly without this