SliderRef

Numeric slider with min/max/step. Tab-owned: the browser holds the canonical value.

defaults (class-level)

field	type	default	notes
`min`	`float`	`0.0`	left bound, inclusive.
`max`	`float`	`100.0`	right bound, inclusive.
`step`	`float`	`1.0`	quantization step. Must be positive.
`value`	`float`	`0.0`	initial position seeded on mount.
`label`	`str`	`""`	text above the track; empty means no label rendered.
`show_value`	`bool`	`True`	when true, current value is rendered next to the track.

Class attributes on the python SliderRef. 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` or partial map	`store`, `store_value`, `store_min`, `store_max`, `store_step`, `store_label`, `store_show_value`	scalar replaces `value`; map merges given keys.
`read`	server -> tab	request `null`; resp `float`	(via `aeval`)	request/response correlated by `id`. resolves the live value.
`notify`	tab -> server	`null`	`changed`	emitted on slider release (pointerup, blur, Enter, arrow keyup).

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

wire payloads

// mount field entry (inside the mount payload)
{"path": "HomePage.volume", "type": "SliderRef", "props": {"min": 0.0, "max": 100.0, "step": 1.0, "value": 0.0, "label": "", "show_value": true}}

// server pushes a scalar value
{"op": "write",  "ref": "HomePage.volume", "payload": 42.0}

// server reconfigures range and value
{"op": "write",  "ref": "HomePage.volume", "payload": {"min": 0.0, "max": 1.0, "step": 0.01, "value": 0.5}}

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

// browser reports release
{"op": "notify", "ref": "HomePage.volume", "payload": null}

write scalars and read-responses are msgpack floats. write map payloads are msgpack maps with string keys. notify and read-request payloads are msgpack nil.

renderer

web/src/refs/slider.tsx. Native <input type="range"> wrapped with an optional label above and an optional value readout to the right. Tailwind utility classes; no shadcn dep. Drag updates the slice (controlled input); notify fires only on release.

slice shape

{
  type: "SliderRef",
  value: number,
  min: number,
  max: number,
  step: number,
  label: string,
  show_value: boolean,
  write: (v: unknown) => void,
  get: () => number,
}

Seeded from field.props on mount. write accepts scalar (number/nil) or partial map. get reads the live slice to avoid stale closures.

edge cases

write scalar nil (Nu sentinel): coerced to min so the input never goes uncontrolled.
write scalar non-finite (NaN, Infinity): coerced to min.
write map missing keys: untouched fields keep prior slice values.
slot never written and no props on mount: slice defaults to value=0, min=0, max=100, step=1, label="", show_value=true.
value outside [min, max]: stored as sent; the DOM clamps the visual thumb. notify reports the user-committed value.
notify debounce: emitted on pointerup, blur, Enter, and arrow keyup. No notify during continuous drag.