368. A focus by name reaches the popup it came from

Date: 2026-09-17

Status

Accepted. Closes book/src/TODO.md’s “A select tree=#true has no typeahead”.

Context

The TODO entry said a flat select’s open list reads letters on the capture phase (ADR-0246) and a tree in the same panel did not. It framed the gap as a design question: whether a prefix search descends into collapsed branches, and what it means to match a node nobody can see.

tree had already answered that when its keyboard was finished: its typeahead matches visible rows only and moves the focus without choosing (ADR-0209). The select’s panel did not stand in the way either. SelectList has no list-level typeahead for a tree, so a letter reaches the focused tree row.

Reproducing it found the cause somewhere else. A tree moves its typeahead by asking host.focus("tree-" + id). A popup’s element tree is built with the window’s Launcher as its host, and Launcher.focus asked only the window’s router, which has no such row. The letter arrived, the tree found its match, and the focus request landed in the wrong window and did nothing. Anything in a popup that focuses by name had the same defect.

A second, smaller one: a tree select opened on its first row whatever it held, because chosenId only knew option rows.

Decision

Host.focus(id) tries the open popups, topmost first, before the window, and a tree select opens on its chosen row.

• Popup.focusById asks the popup’s own router. Launcher.focus walks the open popups from the topmost down and returns at the first that finds the id, then asks the window. Topmost wins for the reason a key goes to it.
• SelectState.chosenTreeRow names tree-<value> when the value is a root and so is on screen when the list opens; otherwise the popup focuses its first row as before.

Consequences

• A select’s tree list takes a typeahead over its visible rows, which is the same behaviour a standalone tree has.
• A value inside a collapsed branch still opens the list on the first row; expanding a path to reveal it is a separate decision.
• An id present in both a popup and the window resolves to the popup. Ids are meant to be unique per window, and a popup is a window.