Dropdown Menu

1// Base UI base dropdown-menu — runs on @octanejs/base-ui's `Menu`. Class strings come from the
2// maintainer-supplied radix source; every difference below was verified by rendering the primitive
3// and reading the DOM, not inferred.
4//
5// PART TREE. Radix's `Content` is one element; Base UI splits positioning out, exactly as this
6// base's popover already does:
7//
8//     radix     Root > Portal > Content
9//     Base UI   Root > Portal > Positioner > Popup      (Positioner owns align/sideOffset)
10//
11// THREE CSS VARIABLES ARE RENAMED. Radix publishes per-component names; Base UI's Positioner
12// publishes generic ones, and a utility pointing at a variable nothing sets silently does nothing:
13//
14//     --radix-dropdown-menu-content-available-height  ->  --available-height
15//     --radix-dropdown-menu-trigger-width             ->  --anchor-width
16//     --radix-dropdown-menu-content-transform-origin  ->  --transform-origin
17//
18// THE SUBMENU TRIGGER'S OPEN ATTRIBUTE DIFFERS. Base UI marks an open trigger with
19// `data-popup-open` (triggerOpenStateMapping), not the `data-open` the popup itself carries — so
20// radix's `data-open:bg-accent` on the sub-trigger would never match and an open submenu's parent
21// row would not stay highlighted.
22//
23// WHAT DOES CARRY OVER UNCHANGED, and is worth recording because it looks like it should not:
24// radix styles item highlight with `focus:`, which works here because Base UI moves REAL DOM focus
25// onto the highlighted item (checked by driving ArrowDown and reading document.activeElement) as
26// well as publishing `data-highlighted`. `data-side`, `data-align`, `data-open`, `data-closed` and
27// `data-disabled` are all emitted with the same spellings radix uses.
28//
29// TWO PARTS ARE PLAIN HOST ELEMENTS ON PURPOSE:
30//   - `Label` is a `<div>`, NOT `Menu.GroupLabel`. That part calls useMenuGroupRootContext and
31//     THROWS "MenuGroupContext is missing" outside a `Menu.Group`, while shadcn's label is
32//     routinely used standalone. Same trap as `Field.Label`, which already shipped as a crash once.
33//   - `Separator` is a `<div>`, because the Menu namespace has no Separator part at all (its
34//     sibling ContextMenu does). The radix classes are pure styling, so nothing is lost.
35// POSITIONING PROPS BELONG TO THE POSITIONER, NOT THE POPUP. Radix has one `Content` element that
36// takes them all; Base UI splits positioning into its own layer, so anything forwarded to `Popup`
37// … truncated