The Extensions gallery

Slate ships with controls, charts and tables built in. Extensions add the rest: 3-D globes, computer algebra, diagram languages, domain widgets. The gallery is where you find them and install them, without leaving the notebook.

Open it with ⌘K → Extensions, or ☰ → 🧩 Extensions.

Finding something

The left column lists everything in the curated registry. Three things narrow it:

• Search matches the name, tagline and description.

• Category chips (visualization, controls, math, …) filter to one kind of thing.

• All / Installed / Updates switch what the list is about — everything available, only what this notebook already has, or only what has a newer version waiting.

Those last three are views over one list rather than separate screens, so an extension you've installed is the same card in the same place, just with a different action on it.

Listings vary in how much their authors have filled in. Some carry a tagline, screenshots and a starter snippet; others show only the description harvested from their README. A sparse card isn't a worse package, only a quieter one.

What a card tells you

Alongside the description you may find:

• Provides — the concrete things the extension adds, as its author listed them: @bind controls, cell toolbar buttons, ⌘K commands, output renderers.

• Getting started — the few lines that put it to work.

• Example notebook — a runnable demo in the extension's own repository.

Installing

Install adds the package to this notebook's environment, exactly as the Packages panel would. The notebook is paused while its worker resolves and precompiles — minutes, for something with a large dependency stack — then the cells re-run.

Two things are worth knowing before you click.

Installing doesn't activate it. A package has to be loaded with using, so after a successful install the gallery offers to drop a starter cell in for you. Accepting is the fastest route from "installed" to "working". If you decline, add using ThePackage yourself.

The first install also adds a registry. Extensions come from a package registry that sits alongside Julia's General registry, and adding one affects every project on your machine, not just this notebook. The gallery says so before doing it, and the button reads Add registry & install rather than Install. It's a one-time step; later installs don't repeat it.

On a notebook running in a region, the registry is added to the remote depot — the one that notebook actually resolves against.

Keeping up to date

An installed extension whose registry version has moved on is flagged with an amber update badge, and the Updates view collects them.

The card shows the move it will make — 0.1.2 → 0.1.3 — and Update performs it, re-running the notebook afterwards. An extension inherited from the enclosing project is updated there rather than in the notebook's own environment.

Update information is only as fresh as the catalog, which is cached for several hours so that opening the gallery doesn't hit the network every time. Check for updates at the bottom refetches it immediately.

When you're offline

The gallery still opens. It falls back to the last catalog it fetched, and failing that to the registry already in your Julia depot — which knows every extension's name and version, just not its description or screenshots. The footer says which of the three you're looking at, so an empty or sparse list is never ambiguous.

What an extension can add

Once loaded, an extension isn't confined to a corner of the UI. It can contribute:

• @bind controls that behave like the built-in ones

• Output renderers, so returning one of its values from a cell draws something

• Cell toolbar buttons on every cell's header

• ⌘K commands, badged with the package name — so typing that name in the palette shows everything it added, which is the quickest way to find your way around something you just installed

• Markdown fence renderers, so a fenced block in prose renders through it

Where they come from

The registry is curated: an extension is listed because it was registered there. Installing one runs an ordinary Pkg.add, and the package is ordinary Julia code with the same access to your machine as anything else you install. Treat it with the same judgement.

Both the registry and the catalog the gallery reads are configurable, so you can point it at a fork or a mirror. A "catalog" object in slate.json takes url, registry and registry_url (equivalently KAIMONSLATE_CATALOG_URL, KAIMONSLATE_CATALOG_REGISTRY and KAIMONSLATE_CATALOG_REGISTRY_URL, with slate.json winning over the environment). The defaults are the SlateRegistry catalog and its GitHub repository.

If you want to publish your own, see Writing an Extension for the code and Listing an Extension for getting it onto the shelf. Registering the package is the only requirement to be listed.