Writing a plugin

A plugin is a JavaScript module with a default export. It can be bundled with the app (src/plugins/*) or loaded at runtime from a URL or a local file — both use exactly the same API.

export default {
  id: "my-plugin",
  name: "My plugin",
  version: "1.0.0",
  description: "What it does",

  setup(ctx) {
    // Own persisted state + model data (namespaced to this plugin)
    const slice = ctx.slice({ items: [] });

    // Declare the data shape (shown in the Registry panel)
    ctx.defineModel({ id: "item", fields: { id: "string", label: "string" } });

    // The only place state may change
    ctx.registerHandler("my-plugin/item.add", ({ payload }) => {
      slice.set((prev) => ({ items: [...prev.items, payload] }));
    });

    // A named action, optional shortcut, shown in the command palette
    ctx.registerCommand({
      id: "my-plugin.add",
      title: "My plugin: Add item",
      shortcut: "mod+i",
      event: "my-plugin/item.add",
      payload: { id: "1", label: "Hello" },
    });

    // UI into a surface: topBar | leftSidebar | rightPanel | bottomPanel | statusBar
    ctx.contribute({
      id: "panel",
      surface: "leftSidebar",
      title: "My panel",
      order: 20,
      component: () => {
        const { items } = slice.use();               // subscribe to own slice
        return items.length + " items";
      },
    });

    // A document view that work-area tabs can open
    ctx.registerView({ id: "editor", component: ({ params }) => null });

    // Replace a platform capability, e.g. a different file load/save
    ctx.provideService({
      files: {
        openTextFile: async () => ({ name: "demo.txt", contents: "from a plugin" }),
        saveTextFile: async () => ({ name: "demo.txt" }),
      },
    });

    // Observe without changing state
    ctx.on("shell/ready", (event) => console.log(event.payload));
  },

  dispose() {
    // clean up timers, listeners you created yourself
  },
};

Flow

UI action -> ctx.emit(event) -> handler -> (model change) -> slice.set -> UI refresh

UI never writes state directly. It emits an event; a handler decides what happens. Every event is visible live in the Events panel.