orca/docs/reference/plugin-declarative-ui.md

Components panels (TSX)

A components panel describes its UI as data; Orca draws it with its own controls, so it matches the app in light and dark, follows its keyboard and focus rules, and needs no HTML or CSS. Design contract: plugin-isolated-frames.md.

Manifest

{
  "execution": "sandboxed-ui",
  "engines": { "orca": ">=1.4.246" },
  "contributes": {
    "panels": [{ "id": "todos", "title": "Todos", "entry": "src/panel.tsx", "ui": "components" }]
  }
}

ui defaults to html (a web page in an isolated frame). With components, entry is an ES module: .tsx, .ts, .jsx or .mts with no build step, or a bundled .js/.mjs. ui and build-less entries arrived in Orca 1.4.246, so declare at least that in engines.orca; an older Orca then says which release the plugin needs.

Writing a panel

import { atom, read, set, update, Stack, Text, Button } from 'orca'

const count = atom('count', 0, { persist: 'plugin' })

export default function Panel() {
  return (
    <Stack gap="sm">
      <Text>Clicked {read(count)} times</Text>
      <Button onPress={() => update(count, (n) => n + 1)}>Click</Button>
      <Button variant="ghost" onPress={() => set(count, 0)}>
        Reset
      </Button>
    </Stack>
  )
}

• The default export must be a component function; it is mounted as the panel. mount(Component) does the same explicitly.
• Catalog components are imported from orca by name. They are JSX tags only, and lowercase tags such as <div> do not exist.
• Function components take props and children as in React. There are no hooks: keep state in atoms.
• Props are plain JSON data (strings, finite numbers, booleans, null, arrays, plain objects) or event handler functions. Anything else (a Date, a Map, a class instance) is reported as an error and the render is not shown.
• key works as in React. Give items of lists that reorder a key; siblings must not share one.

State

• atom(initial) holds state for this panel run.
• atom(key, initial, { persist, version, migrate }) is named, unique per plugin, and may persist: persist: 'memory' (default; this panel run, plus hot reloads in development), 'plugin' (every run of the plugin) or 'workspace' (per Orca workspace; switching workspaces swaps the values). Persisted values must be plain JSON, load before the first render, are saved shortly after they change, and live in the plugin's own data folder; no capability is needed. When the stored shape changes, bump version; migrate(stored, fromVersion) turns an older value into the new shape, and without it the atom starts from initial.
• derived(() => ...) computes from other atoms; it is read-only.
• read(atom) reads; reading while rendering subscribes the panel to it.
• set(atom, value) stores a value as is, functions included; update(atom, (previous) => next) derives the next one. Both are batched (about one render per frame) and throw while rendering.

Lifetime

The module runs while its panel is the open right-sidebar tab, including while the sidebar is collapsed or Orca's window is hidden. Switching to another tab, closing the panel, disabling the plugin or reloading it ends the run; only persisted atoms carry over to the next one.

An optional setup export runs once, after persisted atoms load and before the first render:

import { on, read, type PanelContext } from 'orca'

export function setup(ctx: PanelContext) {
  ctx.subscriptions.push(on('theme', ({ colorScheme }) => console.log(colorScheme)))
  // ctx.signal aborts, and ctx.subscriptions are disposed, when the run ends.
  // read(ctx.visible) is true while the person can see the panel.
  return () => {
    // Also runs when the run ends.
  }
}

Cleanup runs when the panel reloads or navigates; when a panel is closed its process ends with it, so do not rely on cleanup to save anything: persist it in an atom.

Talking to Orca

The orca module has the same facade as frame panels:

• host.call(method, params, { signal, timeoutMs }), typed from the host API (see plugin-host-api.md); rejections carry a code such as timeout or capability_denied. host.has(method) says whether this Orca offers a method to the panel.
• api is { major, minor } of the host API.
• env.locale is Orca's UI language, env.theme is { colorScheme } (reading it while rendering re-renders on a switch) and env.client is 'desktop'.
• shell.openExternal(url) and files.saveAs({ suggestedName, mimeType, data }) are shorthands for host.call('shell.openExternal' | 'files.saveAs', ...) and resolve with the same result. They follow the user-gesture rule below; the hidden module has no window.orca.shell or window.orca.files.
• on(event, handler) returns a Disposable. Events are typed (OrcaEvents); Orca's own panel messages are not events and on() refuses them.
• ui.catalog is a number that grows with the component catalog; ui.has(component, prop?) says whether this Orca draws a component or accepts a prop on it.

Hot reload

In a development folder, saving a file reloads the panel in place:

• Keyed atoms carry over. Persisted ones reload as always; keyed memory atoms (atom('draft', '')) are handed to the new module, so a half-typed draft or the open tab survives the save. An atom whose version changed starts from initial (migrate is not called), and so does one holding something other than plain JSON (a function, a Map). Unkeyed atom(initial) state, module variables and setup start over; setup's cleanup runs for the old module.
• A brief Reloaded mark shows in the panel's corner.
• A save that fails to load (a syntax error, an import Orca refuses, or a module that throws before its first render) keeps the last version that loaded on screen, with an inline error naming file:line:column and the message; the same line is in orca plugin logs. Until the next save loads, that last tree does not respond to clicks. The next save that loads replaces it and clears the error. Lines are your source's; a column can be off on a line that had types or JSX.

Installed plugins remount from scratch on an update; only persisted atoms carry over.

No build step

Orca transpiles .tsx, .ts, .jsx and .mts files when the panel loads, so a plugin ships its source and no dist/ folder: edit, save, and the panel hot reloads.

• Types are stripped and JSX compiles for orca (automatic runtime). Lines are kept, so an error's file:line in orca plugin logs is the line in your source; an inline source map covers columns in DevTools (orca plugin dev inspect).
• Relative imports resolve to exact files: ./todos finds todos.tsx, todos.ts, todos.jsx, todos.js, then todos/index.*, and ./todos.js finds todos.ts as TypeScript expects.
• Only orca, orca/* and relative files can be imported. A bare package such as react fails with an error naming the file and the import: copy the package's ESM files into the plugin and import them by relative path, or bundle (below).
• Transpiling is syntax only: it never type-checks. Each source file is capped at 1 MiB and 2 s of transpiling, which runs off Orca's main thread.
• TypeScript features that need type information to compile, such as const enum across files and export =, are not supported; isolatedModules in the generated tsconfig flags them.

Types: orca plugin types . writes Orca's typings and a tsconfig to .orca/types/ (orca plugin dev load refreshes them), and .orca/ ignores itself in Git. Extend it:

{ "extends": "./.orca/types/tsconfig.json", "include": ["src"] }

Then npx tsc -p . type-checks. orca plugin create <dir> --template components scaffolds all of this. examples/plugins/hello-tsx is a complete sample.

Bundling instead

A bundled .js entry still works, for example to use npm packages. orca is provided by Orca at runtime, so leave it out of the bundle:

esbuild src/panel.tsx --bundle --format=esm --jsx=automatic --jsx-import-source=orca \
  --external:orca --external:'orca/*' --outfile=dist/panel.js

/** @jsx h */ with import { h, Fragment } from 'orca' (classic jsxFactory) also works when you bundle. examples/plugins/hello-components has a build script.

Testing

orca plugin test [dir] runs the plugin's *.test.ts(x) files in plain Node, with no Orca window: Node's built-in runner (node:test), or the plugin's own vitest when it has one installed. orca and orca/testing resolve to the files this Orca ships, and the plugin's sources are transpiled and resolved exactly as Orca loads them, so a test runs the code Orca runs. The exit code is the runner's.

import { assert, mount, test } from 'orca/testing'
import * as panel from './panel'

test('adds a task', async () => {
  const view = await mount(panel, { persisted: { plugin: { todos: [] } } })

  await view.type({ label: 'New task' }, 'Ship it', { submit: true })

  assert.ok(view.find({ role: 'button', text: /Ship it/ }))
  assert.deepEqual(view.persisted.plugin.todos, [{ id: 1, title: 'Ship it', done: false }])
  assert.deepEqual(view.errors, [])
  await view.unmount()
})

• orca/testing also exports Node's test, describe, beforeEach, afterEach and strict assert, so tests type-check without @types/node. With vitest, use vitest's own test and expect.
• mount(module | Component, options) boots the panel with the real runtime (persisted atoms, setup, then the first render) and resolves once it has drawn. Options: host, theme, locale, visible, panelId, and persisted ({ plugin, workspace } by atom key; stored(value, version) for a value an older version wrote, to test migrate). Each mount starts every atom from its initial value; one panel is mounted at a time.
• Find with find(query) (the innermost match, or null) and findAll(query). A query matches on any of type, role, text, label (a control's label, a list item's or card's title) and testId (the element's key); text and label match exactly or by RegExp.
• Act with press, type(el, text, { replace?, submit? }), submit, toggle and select(el, value), on an element or a query. Each act resolves once the panel has settled: its renders, its host calls and its persisted writes. valueOf(el) is what Orca shows in an Input, Switch or Select, with the same edit protocol as Orca.
• Inspect tree() (plain data for snapshots, handlers shown as [handler]), errors (what the panel threw, with its stack, and renders Orca would refuse), warnings (props and components Orca would drop) and persisted. emit('theme', ...), setVisible, rerender and settled drive the rest; unmount() ends the run, running setup cleanup.
• mockHost({ capabilities, results }) stands in for Orca's host. It refuses what Orca refuses, with the same error codes: a method panels cannot call, a capability the manifest does not declare (capabilities default to the manifest's), bad params, and shell.openExternal or files.saveAs without a press first (each press grants one). results maps a method to a value or to a function of its params, which may throw hostError(code); calls and callsOf(method) record every call. The stationary-control rule for gestures is not simulated.

orca plugin check [dir] validates the plugin like orca plugin validate, then renders every components panel once against mockHost() and reports what the panel threw (with file:line), layouts Orca would refuse, and props it would drop. Both commands run the plugin's code on your machine with your full access, outside Orca's sandbox, so run them only on code you trust. They use the node on PATH when it is 20.6 or newer (the first with module.register), else the Node built into Orca, so authors need no Node install.

Catalog

Props are semantic: tones, sizes and gaps, never class names, styles or colours. Colour has one vocabulary, tone: neutral accent success warning danger.

Component	Props	Children
Stack	gap (none xs sm md lg), align (start center end stretch)	any
Row	gap, align, justify (start center end between), wrap	any
Text	tone, muted, size (xs sm md), weight (regular medium semibold), truncate	text, Text Link Code Badge
Heading	level (1–3, below the panel title)	as Text
Button	variant (solid outline ghost), tone, size, icon, disabled, onPress()	text
IconButton	icon and label (required; the label is its name and tooltip), variant, tone, size, disabled, onPress()	none
Badge	tone	text
Card	title, description	any
List	label	ListItem only
ListItem	title, description, icon, current, disabled, onPress()	any; no controls with onPress
Input	label (required), labelHidden, value, defaultValue, placeholder, type (text search password), maxLength, invalid, disabled, onChange(value), onSubmit(value)	none
Switch	label (required), checked, defaultChecked, disabled, onChange(checked)	none
Select	label (required), labelHidden, value, defaultValue, placeholder, options ({ value, label, disabled? }[]), disabled, onChange(value)	none
Separator	orientation (horizontal vertical)	none
Progress	label (required), labelHidden, value (0–100)	none
Spinner	label (required), labelHidden	none
EmptyState	title (required), description, icon	actions
Link	href (https:, http:, mailto:; opened in the OS browser), onPress()	text
Code	block	text

labelHidden keeps the label as the control's accessible name without showing it.

Icons are the same names a manifest panel's icon takes, for example add delete edit refresh search settings check close info warning error open-external copy download play stop more filter branch file folder terminal agent link rocket database; see IconName in the typings. Any other name shows a neutral fallback glyph.

Forward compatibility: an unknown prop or enum value is dropped (Orca logs a warning once), and an unknown component, or one missing a required prop, is drawn as a neutral placeholder, so a panel built for a newer Orca still shows the rest of its UI. Only structural problems (a ListItem outside a List, a Stack inside Text, duplicate keys, controls inside a pressable ListItem) and the limits below refuse a render.

Import only the components your minimum supported Orca exports. orca is a real ES module, so a named import it lacks (import { Carousel } from 'orca' on an older Orca) is a link error: the whole panel module fails to load, rather than getting undefined. For a component newer than your minimum, check ui.has() and create it by name with h; an Orca that does not know it draws the placeholder:

import { h, ui, Text } from 'orca'

const gallery = ui.has('Carousel') ? (
  h('Carousel', { label: 'Shots' })
) : (
  <Text muted>Update Orca to see the gallery.</Text>
)

Inputs

Orca owns what the person types, so a re-render never drops characters and Enter submits exactly what is on screen. onChange(value) reports each edit; onSubmit(value) fires on Enter.

• defaultValue seeds an uncontrolled field.
• value controls it. Once your panel has handled the person's latest edit, the value you render is what the field shows, including a reset to the same value it had before ('' after submit). A render that your panel made before handling their latest keystrokes does not touch their text.
• value without onChange makes the field read-only. Switch (checked/defaultChecked) and Select (value/defaultValue) work the same way.

A handler that throws (or rejects) is reported in a banner attributed to your plugin; the panel keeps its last good render.

Limits

A render is refused, and the last good one kept, beyond 5000 nodes, depth 64, about 512 KiB of data, 16 KiB per text, 1 KiB per label prop, 32 props per node or 500 Select options.

User gestures

host.call('shell.openExternal' | 'files.saveAs') needs a user gesture, and only a press on Orca's own controls counts (the hidden module never has one of its own). A press on a Button, IconButton, ListItem or Link grants one call within 1 s, but only when that control has been stationary for 500 ms: the same place in the tree, the same label and target, and the same position on screen. Anything that moves it (including a sibling growing above it) restarts the wait, so a panel cannot slide a control under the pointer just before a click. Scrolling the panel does not count as a move.

A Link follows the same rule before anything happens: a press on an unsettled Link neither opens its href nor runs its onPress. When a Link has both, the href open uses the press, and onPress runs without granting a second gesture.

Isolation

The module runs in a hidden, sandboxed guest of the plugin's own partition, with the same isolation as frame panels: no network (requests outside the plugin's own files are cancelled; Electron 43 still resolves dns-prefetch hostnames), no Node, no popups, no DOM the person sees. It reaches Orca only through host.call, on, and the UI it renders. Components panels need the desktop app: browser clients (orca serve in a web browser) show that instead of the panel.