TextAreaRef

Multi-line text input. Tab-owned: the browser holds the canonical value.

defaults (class-level)

field	type	default	notes
`value`	`str`	`""`	initial text seeded on mount.
`placeholder`	`str`	`""`	placeholder shown when the value is empty.
`rows`	`int`	`4`	initial visible rows; minimum height when `auto_resize` is on.
`max_length`	`int \| None`	`None`	optional hard cap on character count. `None` disables the cap.
`auto_resize`	`bool`	`False`	when true, the textarea grows with content past `rows`.

Class attributes on the python TextAreaRef. Shipped on mount under the field entry's props key and used to seed the slice. Later server -> tab writes override the slice value only; the other props are structural and stay fixed for the slot's life.

interactions

op	dir	payload	nu method	notes
`write`	server -> tab	`str`	`store`	canonical push or reset; replaces the local value.
`read`	server -> tab	request `null`; resp `str`	(via `aeval`)	request/response, correlated by `id`. resolves the live value.
`notify`	tab -> server	`null`	`changed`	emitted on commit only: blur or cmd-enter / ctrl-enter.

TextAreaRef.aeval ships a read via session.aread and returns the string. TextAreaRef.store(value) compiles to write. TextAreaRef.changed() is the standard Changed subscription.

wire payloads

// mount field entry
{"path": "HomePage.body", "type": "TextAreaRef", "props": {"value": "", "placeholder": "type here", "rows": 6, "max_length": null, "auto_resize": true}}

// server pushes a value
{"op": "write",  "ref": "HomePage.body", "payload": "line one\nline two"}

// server clears via Nu sentinel
{"op": "write",  "ref": "HomePage.body", "payload": null}

// server fetches
{"op": "read",   "ref": "HomePage.body", "payload": null, "id": "ab12"}
{"op": "read",   "ref": "HomePage.body", "payload": "line one\nline two", "id": "ab12"}

// browser commits
{"op": "notify", "ref": "HomePage.body", "payload": null}

write and read-response payloads are msgpack strings. notify and read-request payloads are msgpack nil.

renderer

web/src/refs/text-area.tsx. Native controlled <textarea> with tailwind utility classes (matches InputRef weight). When auto_resize is on, a layout effect resets height = "auto" then height = scrollHeight on every value change so the box tracks content. Plain Enter inserts a newline; cmd/ctrl-Enter commits and blurs.

edge cases

write payload is msgpack nil (Nu sentinel): slice value becomes "".
write payload is non-string: coerced via String(v); no error frame.
slot never written and no props: slice defaults to the class-level values.
max_length enforced by the browser via the maxLength attribute; None disables.
only blur and cmd/ctrl-Enter emit notify; per-keystroke edits stay local until commit.
when auto_resize is off the textarea keeps its native resize handle behavior; with auto_resize on the inline height overrides it.