Typing in the field is the filter: the forest is rebuilt to the matching
instances plus their ancestor areas and force-expanded so every match is on
screen; clearing the text restores the full forest, collapsed. Both bulk
expansions are deferred to OnAfterRenderAsync, because the TreeView only exists
once the panel has rendered.
Enter picks the first instance the operator can actually SEE — document order,
descending into a branch only when the tree reports it expanded — so with areas
collapsed it picks the first root instance, and with a filter (every branch
expanded) it degrades to plain document order. Escape closes and restores the
field text from the current selection; ArrowDown hands keyboard navigation to
the tree via a new additive TreeView.FocusFirstVisibleAsync(), which reuses the
existing roving-tabindex _focusNeedsApply path rather than adding a second
focus mechanism.
No preventDefault: Blazor's flag is all-or-nothing per element, and neither
default is harmful (Enter in a text input outside a form does nothing,
ArrowDown just moves the caret) while suppressing Tab would trap the control.
Claude-Session: https://claude.ai/code/session_01NcMG6xXdsJbmD2wYAgkK29
Joseph Doherty
621d6bfd94