Dropdown Menu

Base Dropdown Menu is a compound action-menu opened by a Trigger. Root owns visibility, request arbitration, collection order, entry policy, and shared facts; transient active navigation never becomes persistent selection.

The canonical family contains one Root, at most one Trigger and Content, and up to 100 Items. All visibility changes—methods, Trigger activation, dismissal, and Item commit—enter Root’s openChange request channel.

Root accepts open, defaultOpen, disabled, closeOnItemCommit, openEntry, and openEntryValue. It exposes open state, collection facts, and openDropdown(), close(), toggle(), and requestOpen(). Controlled mode retains owner-provided open until new input arrives.

Content composes overlay, transition, collection navigation, typeahead, and anchor positioning. Item accepts value, textValue, disabled, and closeOnCommit; it exposes active/interaction facts and emits select. Closing clears transient active state, so reopening follows the new entry policy instead of restoring a false “selection.”

This family represents actions or functions opened by a button. It must not disguise ordinary navigation, arbitrary forms, or persistent selection as a menu. Group, Label, Separator, Checkbox Item, Radio Item, and Submenu are not current Base guarantees.

The stable 0.2.0 package exports @proto.ui/prototypes-base/dropdown. The CLI component ID is base-dropdown and generates Root, Trigger, Content, and Item. T-BASE-DROPDOWN-MENU-0001 maps the family criteria to packages/prototypes/base/test/dropdown.test.ts; the preview runs through the Web Component, React, and Vue adapters.

P-BASE-DROPDOWN-MENU and its Trigger, Content, and Item entities are draft. Published package availability does not promote them to active guarantees.

• P-BASE-DROPDOWN-MENU
• Parts: Trigger, Content, Item
• Dropdown source
• Dropdown evidence
• Styled projection: Brutalist Dropdown Menu