paseo/docs/menus.md

# Menus

One engine, in `packages/app/src/components/ui/menu/`. `dropdown-menu.tsx` and `context-menu.tsx`
are wrappers over it and differ only in what opens them — a press, or a long press / right click.
Import the `DropdownMenu*` or `ContextMenu*` names as before; reach for `@/components/ui/menu`
directly only when you are building a third trigger shape.

Do not add a third menu implementation. The two that existed were byte-identical from
`computePosition` down, and the copies drifted: only one of them ever grew a sheet.

## Two presentations

`MenuRoot` picks one from form factor, never from platform — a tablet in a narrow split view
sheets the same way a phone does.

| Screen                         | Surface                         | Submenus                                           |
| ------------------------------ | ------------------------------- | -------------------------------------------------- |
| Wide                           | Popover anchored to the trigger | Flyout overlapping the row, opened by hover intent |
| Compact, `compactMode="sheet"` | Bottom sheet                    | The page is replaced in place, with a back header  |
| Compact, default               | Popover                         | Same as wide                                       |

`compactMode` defaults to `"popover"`, so adopting the sheet is per-menu. That is deliberate:
flipping every menu in the app to sheets at once is not a change anyone can review. Opt a menu in
when you have actually looked at it on a phone.

`ContextMenu` is the exception: it defaults to `compactMode="sheet"` and enables native long press.
Disable mobile triggering explicitly on draggable rows, where long press belongs to drag instead.

## When the items differ per form factor

A menu whose contents depend on what else is on screen gets one component per surface, not one
component with `isMobile` branches inside it. The workspace header menu is the example
(`packages/app/src/screens/workspace/workspace-header-menu.tsx`): compact has no tab strip, so it
carries new-tab actions, while wide leaves those to the strip's `+` menu and lists workspace
actions only. Items both surfaces share live in one component that each menu renders, from the same
callbacks, so the two can't drift.

## Selecting an item on iOS

An item that closes the menu runs its action after a fixed grace period on iOS, not immediately:
a native presenter launched while UIKit is still tearing down the surface can hang. Both surfaces
unmount the moment the menu closes, so the wait is a timer rather than the surface's own dismissal
callback — a callback fired from inside a subtree that is being removed is racing its own removal,
and it loses. Selections used to be dropped entirely for exactly that reason.

The consequence for callers: an `onSelect` on iOS runs a beat after the press. Don't add a second
delay on top of it, and don't read state that the same press mutated.

This is why a row inside a menu surface goes through `selectItem` rather than calling its handler
from its own `Pressable`. `MenuItem` is not the only row shape on the engine — `ComposerTrackRow`
is another, with its own icons and hover-revealed actions — but both hand the press to the engine
and take `closeOnSelect` to say whether choosing them ends the surface. A row that owns its press
outright leaves the surface open behind whatever it opened, and skips the iOS wait.

A row whose result opens a sheet passes `closeOnSelect={false}`: the sheet stacks over the menu
sheet and uncovers it on close, so the menu is where the user lands next. A row that opens a tab
closes, because the tab replaces the pane the menu belongs to. The subagents track asks the layout
store which one a row is (`useSubagentOpensInSheet`), since the answer changes with the layout.

## Pages

A submenu is a page, declared as data on the surface and reached by a `MenuSubTrigger` whose `id`
matches:

```tsx
<MenuSurface pages={pages} sheetTitle="Display">
  <MenuSubTrigger id="grouping" value="Project">
    Grouping
  </MenuSubTrigger>
</MenuSurface>
```

Pages are data rather than nested children because the popover renders them as _siblings_ of the
root surface — a flyout nested inside the root's box would be clipped by its `overflow: hidden`.
Declaring them separately is what lets one model drive both presentations.

`menu-navigation.ts` holds that model, and it is pure: the open flyout chain and the mobile push
stack are the same path, so the popover renders every entry in it and the sheet renders only the
last. Nothing else differs between the two.

Opening a submenu truncates the path to the depth of the trigger that opened it. Without that,
sliding the pointer across a row of triggers would stack up every flyout it passed instead of
swapping between them.

## A page that takes input

A menu page can hold a small form — `MenuTextField` is the field for it, drawn as a row's own
fill so its text lands on the same rail as the labels above it. Two things have to be true for
that page, and both are set on the page definition rather than discovered later:

- **`hoverIntent: false`.** A branch you skim is opened and closed by the pointer; a form is not.
  Without this the page opens on a pointer that was only passing through, and dismisses itself —
  draft and all — the moment your hands move to the keyboard and the mouse drifts off the flyout.
  While such a page is open, the whole surface stops closing on hover, because the parent flyout
  leads back to the same dismissal.
- **The compact presentation has to be a sheet.** `MenuTextField` resolves to
  `BottomSheetTextInput` on compact native, which reads the sheet's context and has none in a
  popover.

The sheet keeps `keyboardBehavior="interactive"`. `extend` grows a sheet to its largest snap
point, and with `enableDynamicSizing` that point is the content's own height — a short page does
not grow, and the keyboard comes up over the field you are typing into.

## Hover intent

A flyout **overlaps its parent by 5pt** rather than sitting beside it. With a gap there is a strip
of backdrop between the two that belongs to neither surface, and every pixel of it is a chance to
dismiss the menu you are reaching for. Overlapping deletes the strip; don't reintroduce the gap
and try to cover it with a longer timer.

On top of that, a flyout opens after the pointer rests ~90ms, closes ~260ms after it leaves, and
cancels its own pending close while the pointer is inside it. The grace still matters because the
pointer crosses sibling rows on the way down into the flyout.

Hover lives on a plain `View`, never on a `Pressable` — see [hover.md](hover.md), which owns that
rule. Hover only fires on web, which is exactly where flyouts exist; everywhere else the page
opens on press.

## Item states

`selected` and `active` are different questions and must not be merged.

| Prop       | Means                      | Draws                     |
| ---------- | -------------------------- | ------------------------- |
| `selected` | This is the chosen value   | A check, and nothing else |
| `active`   | This row's submenu is open | The fill, and no check    |

`selected` also announces itself as `aria-checked`, so a multi-select page is audible as the list
of on/off things it is.

A selected row does **not** get a background. A check and a fill are two separate claims about the
same state, and showing both makes a chosen row compete with the row the pointer is actually on.
`showSelectedCheck` moves the check to a reserved leading column when a group needs to stay
aligned whether ticked or not; otherwise it sits at the trailing edge and the leading slot is free
for the option's icon.

Give options icons; leave the root rows without them. The root is labels and their current values,
and a column of icons there is decoration competing with the values you actually came to read.

## Surface details

- The hover fill is **inset from the surface's edges and rounded** — a chip inside the menu, not a
  band across it. The inset is taken _out of_ the row, never added to it: padding gives up what
  margin takes, so labels sit at the same 13pt they always did. Insetting by growing the row is how
  the menu ends up taller than it started.
- **A row is as tall as what is driving it** — 28pt for a pointer, 40pt below `md` for a thumb. The
  split is on breakpoint, not on `presentation`: the compact popover that `compactMode` defaults to
  is worked with a thumb just as a sheet is, and sizing off the sheet would leave it at the desktop
  height. `md` is where `useIsCompactFormFactor` divides, so row height and the popover/sheet choice
  turn over together.
- The desktop height only holds because the label's `lineHeight` is pinned — 18 line + 8 padding +
  2 border is exactly 28. Leave it to the platform and content outgrows `minHeight`, which then does
  nothing. Compact is the other way round: `minHeight` leads and the label centres in it.
- **A row owns its fill; `MenuPage` owns the spacing between rows.** The vertical inset above the
  first row and below the last, and the gap between rows, are the page's — one knob each,
  `MENU_ROW_GAP` being the one a redesign turns. A row that carried vertical margin would be
  serving both at once, and since margins don't collapse it would land as one unit at the edges and
  two between rows, so shrinking the gap would eat the inset with it. Horizontal inset does stay on
  the row: there is one left edge and one right edge, so nothing is doubling up.
- `MenuPage` is also what provides a page's depth, so the popover and the sheet cannot disagree
  about what a page is. Every entry point goes through it — root, flyout, pushed sheet page.
- The gap reaches a page's **direct children**. A group of rows wrapped in a `View` of its own drops
  out of it; at the current gap of zero there is nothing to lose, but anything above zero wants that
  wrapper to carry the page style too.
- The separator is the one row-level thing that asks for vertical space of its own, and now that
  rows carry none, that is still one number controlling one gap. It takes no horizontal margin and
  the page has no horizontal padding, so the rule runs the full width of the surface.
- Separators use `borderAccent`, the same colour the surface outlines itself with. `border` sits
  between `surface1` and `surface2`, which put it within a hair of the hover fill and made
  separators disappear against a hovered row.

## When a decision earns a submenu

Put a decision behind a submenu when its options are not the point — the current _value_ is. The
root row then reads as the answer (`Grouping  Project ›`) and costs one line instead of one line
per option. A menu whose every option is on screen at once does not survive its third decision.

Independent toggles stay on their page as a checkmark list. A pick-one group can share that page
below a `MenuSeparator`; make selecting the checked row clear it, so "none" doesn't need a row of
its own.

## Gotchas

- **Released height.** Reanimated's web entering animation leaves an inline height snapshot on
  the surface. `AnchoredSurface` clears it, and a `revision` prop re-clears it when content
  identity changes — a pushed page taller than the one it replaced is clipped without that.
- **Animate only once placed.** The same snapshot carries top/left, and Reanimated writes it back
  750ms after mount. `AnchoredSurface` remounts the surface when its position resolves so the
  entering animation never ends at the off-screen measuring position; on a slow machine that
  write moved the open menu back off-screen.
- **Sheets size to content.** `enableDynamicSizing`, not fixed snap points. A pushed page is
  rarely the height of the page before it.
- **The sheet's content is teleported out of the menu's subtree**, so `MenuSheetSurface` rebuilds
  both menu contexts through the sheet's `contextBridge`. Providing them around the modal puts
  them on the wrong side of the portal and every item inside throws. Gotcha 7 in
  [floating-panels.md](floating-panels.md).
- **One overlay per menu.** Submenus render inside their parent's layer and paint no second
  backdrop, so there is exactly one `Modal` on native no matter how deep the menu goes.
- **Sheet stacking and backdrop dismissal belong to `IsolatedBottomSheetModal`.** Menus only
  request a backdrop opacity. See [floating-panels.md](floating-panels.md#gotcha-6--bottom-sheet-refs-are-not-lifecycle-truth).
- **A menu closes when its panel leaves the screen.** `MenuSurface` closes the menu when its
  retained panel goes inactive. Hiding the surface alone leaves the open state behind, and the
  menu would reappear with the panel on the next tab switch.
- **Retained panels own visibility.** The shared menu surface unmounts when its panel becomes
  inactive. An async action can navigate before its menu closes; a hidden panel must not leave a
  portal backdrop blocking the destination. On web the chat suspends one commit after it goes
  inactive, and that inactive commit is where the surface unmounts.
- Anchoring, flipping, and edge clamping live in `components/ui/anchor.ts`, shared with the hover
  card, and are unit-tested. Fix positioning bugs there, not at a call site.
- Everything else about floating surfaces on Android — Portal/Modal escape, lifecycle gates,
  status-bar offset, the open flash — is in [floating-panels.md](floating-panels.md).