Cross-tab picking

pick is cross-tab only: url is required. The extension opens that URL in a new tab, the user picks there, and the selector is routed back to your tab.

Why cross-tab

A web page can already inspect its own DOM, so same-tab picking isn't something an extension needs to provide. The thing a page can't do is ask the user to point at an element on another tab or origin and get the selector back — browsers isolate origins. That cross-tab/cross-origin hop is exactly what the extension bridges, and the reason pick requires a url.

(For picking on the page you're already on, use the toolbar — that's the human, same-tab path.)

The flow

your tab (source)                         target tab (params.url)
  op.pick({ url })
   → extension opens the URL  ───────────►  picker runs there
                                            user hovers / clicks / confirms
   selector routed back  ◄───────────────  result
  pick() resolves                          focus returns to your tab

• The target tab is not closed when the pick finishes — the user (and a later pick) can keep it.
• Focus returns to the source tab on finish.

Reusing the target tab with key

key is an opaque string identifying "which task" a pick is for. A follow-up pick with the same key reuses the existing target tab instead of opening a new one; with no key, reuse is decided by host/URL alone. It's compared for equality and never interpreted.

Helpers

• isTargetOpen() — whether the target tab opened by your tab is still open (useful for showing "target page is open/closed" state).
• activateSelf() — bring your own tab to the foreground (a page can't focus its own background tab; only the extension can, and only the calling tab — never another).