NumberInputRef

Single-line numeric input with min/max/step and stepper buttons. Tab-owned: the browser holds the canonical value.

defaults (class-level)

field	type	default	notes
`label`	`str`	`""`	label rendered above the input. empty means no label node.
`placeholder`	`str`	`""`	passed to `<input placeholder=...>`.
`min`	`float \| None`	`None`	lower bound. clamped on commit if set. omitted from `<input min>` when None.
`max`	`float \| None`	`None`	upper bound. clamped on commit if set. omitted from `<input max>` when None.
`step`	`float`	`1.0`	passed to `<input step>` and drives stepper button delta.
`default`	`float`	`0.0`	initial value seeded into the slice on mount. mirrored to slice key `value`.

Class attributes on the python NumberInputRef. Shipped on mount under the field entry's props key and used to seed the slice. Later server -> tab writes override slice fields.

interactions

op	dir	payload	nu method	notes
`write`	server -> tab	`float` (scalar) or partial map	`store`, `store_value`, `store_min`, `store_max`, `store_step`, `store_label`	scalar replaces `value`; map merges any subset of `{value, min, max, step, label}`.
`read`	server -> tab	request `null`; resp `float`	(via `aeval`)	request/response correlated by `id`.
`notify`	tab -> server	`null`	`changed`	emitted on commit (blur, Enter, stepper click).

NumberInputRef.aeval ships a read via session.aread and returns the number. NumberInputRef.store(value) compiles to write (scalar form when only value is passed, map form when other kwargs are present). NumberInputRef.changed() is the standard Changed subscription.

wire payloads

// mount field entry (inside the mount payload)
{"path": "HomePage.qty", "type": "NumberInputRef",
 "props": {"label": "quantity", "placeholder": "0",
           "min": 0.0, "max": 100.0, "step": 1.0, "default": 0.0}}

// server pushes just a value (scalar shortcut)
{"op": "write",  "ref": "HomePage.qty", "payload": 42.0}

// server adjusts bounds + value together (map form)
{"op": "write",  "ref": "HomePage.qty",
 "payload": {"value": 5.0, "min": 0.0, "max": 10.0, "step": 0.5}}

// server sets just the label
{"op": "write",  "ref": "HomePage.qty", "payload": {"label": "count"}}

// server fetches
{"op": "read",   "ref": "HomePage.qty", "payload": null,  "id": "ab12"}
{"op": "read",   "ref": "HomePage.qty", "payload": 42.0,  "id": "ab12"}

// browser tells server the user committed
{"op": "notify", "ref": "HomePage.qty", "payload": null}

write scalar payload is a msgpack float (or nil -> coerced to the slice's effective floor: min if set else 0). write map payload is a msgpack map with any subset of {value, min, max, step, label}. read-response is a msgpack float. notify and read-request payloads are msgpack nil.

renderer

web/src/refs/number-input.tsx. A <label> block wrapping the optional label span above a flex row: a [-] button, a native <input type="number">, a [+] button. Tailwind utility classes; no shadcn dep. Stepper buttons mutate the local slice by +/- step (clamped) then commit. <input> commit fires notify on blur and on Enter (Enter also blurs the input). Browser clamps the value to [min, max] on commit if either bound is set.

slice shape

{
  type: "NumberInputRef",
  value: number,
  min: number | null,
  max: number | null,
  step: number,
  label: string,
  placeholder: string,
  write: (v: unknown) => void,
  get: () => number,
}

Seeded from field.props on mount: value = props.default, plus min, max, step, label, placeholder. write accepts scalar (number/nil) or partial map. get reads the live slice to avoid stale closures.

edge cases

write scalar nil: coerced to min if set, else 0.
write scalar non-finite (NaN, Infinity): coerced to min if set, else 0.
write map min: null or max: null: clears that bound.
min and max both None: no clamping; raw input value is committed.
value below min on commit: clamped up to min.
value above max on commit: clamped down to max.
slot never written and no props on mount: slice defaults to value=0, min=null, max=null, step=1, label="", placeholder="".
empty label: label span omitted.
stepper buttons at bounds: still emit a commit; clamp keeps value within range. no disabled state in v0.1.0.
user types a non-numeric string: native <input type="number"> rejects; slice keeps last valid number.

non-goals

no integer-only variant (use step=1 and accept floats on the wire).
no per-keystroke notify; only commit (blur, Enter, stepper) notifies.
no validation messages or invalid state styling.
no readonly / disabled flags.
no unit suffix / prefix decoration.
no scientific notation toggle.