UI schema

Normative. A declarative description of an extension's control panel. The host renders it as native widgets — Compose, SwiftUI, whatever it is. No HTML, no DOM, no React: that is precisely what keeps the standard cross-app.

Model

A panel is a JSON object with a controls array. Each control has a type, a unique key, a label, and type-specific fields. The extension reads values through the params capability; the host owns rendering and layout. UI schemas can be attached to code contributions (filters, tools) or to configurable assets (like shader).

Core controls (0.1)

type	Fields	Value
slider	min, max, step, default	number
number	min?, max?, step?, default	number
toggle	default	boolean
select	options: [{value,label}], default	option value
color	default, alpha?	RGBA
text	default, placeholder?	string
button	action	fires action on the entry
group	label, controls[]	container

Kept deliberately small so every host can render it natively. Richer controls — tone curve, gradient, conditional visibility — are candidate extensions to the schema, not part of 0.1.

Update model

• Controls update live by default: a change pushes new params and the host MAY re-run a preview.
• A button with an action is the apply/commit path for expensive operations.

Example

{
  "controls": [
    { "type": "slider", "key": "cellSize", "label": "Cell size", "min": 2, "max": 40, "step": 1, "default": 8 },
    { "type": "select", "key": "shape", "label": "Dot shape",
      "options": [{ "value": "circle", "label": "Circle" }, { "value": "square", "label": "Square" }],
      "default": "circle" },
    { "type": "color", "key": "ink", "label": "Ink", "default": "#000000", "alpha": true },
    { "type": "toggle", "key": "cmyk", "label": "CMYK separation", "default": true }
  ]
}

Open

• The expressiveness ceiling — rich enough for real tool UIs vs. renderable natively on every host. The central UI tension of the whole standard.
• Localization of labels/options; conditional show-hide; validation messages.