---
name: ha-frontend-gallery
description: Home Assistant frontend gallery structure, pages, demos, content, and verification. Use when changing files under gallery/, including gallery markdown, TypeScript demos, sidebar entries, mock data, page generation, or gallery builds.
---

# HA Frontend Gallery

Use this skill for all work under `gallery/`. Follow the persistent repository guidance in `AGENTS.md` and load the matching specialist skills alongside this gallery-specific guidance.

## Quick Reference

Run commands from the repository root unless noted otherwise:

```bash
gallery/script/develop_gallery  # Start the gallery development server
gallery/script/build_gallery    # Build the static gallery
yarn lint                       # ESLint, Prettier, TypeScript, and Lit checks
yarn lint:types                 # TypeScript compiler, without file arguments
```

Never run `yarn lint:types` or `tsc` with file arguments. File arguments make `tsc` ignore `tsconfig.json` and can emit `.js` files into `src/`.

## Purpose

The gallery is a developer and designer reference for Home Assistant frontend UI patterns. It documents component APIs, shows realistic Lovelace and more-info states, captures brand and copy guidance, and provides reproducible demos that are safe to inspect outside a running Home Assistant instance.

- Prefer demonstrating real production components from `src/` instead of creating gallery-only replacements.
- Keep fake state, sample data, and demo-only helpers inside `gallery/`.
- Do not move gallery stubs or demo data into production code unless a production feature explicitly needs them.
- Do not hand-edit generated output under `gallery/build/` or `gallery/dist/`.

## Structure

- `gallery/sidebar.js`: Defines gallery sections, headers, and explicit page ordering.
- `gallery/script/develop_gallery`: Wrapper for the `develop-gallery` gulp task.
- `gallery/script/build_gallery`: Wrapper for the `build-gallery` gulp task.
- `gallery/src/entrypoint.js`: Creates the `<ha-gallery>` shell.
- `gallery/src/ha-gallery.ts`: Renders the drawer, page routing, markdown descriptions, demos, edit links, and RTL toggle.
- `gallery/src/html/index.html.template`: HTML template used by the gallery build.
- `gallery/src/pages/<category>/<page>.markdown`: Optional page description and frontmatter.
- `gallery/src/pages/<category>/<page>.ts`: Optional live demo module for the same page ID.
- `gallery/src/components/`: Gallery-only demo wrappers like `demo-card`, `demo-cards`, `demo-more-info`, and `page-description`.
- `gallery/src/data/`: Fake `hass`, demo states, mock traces, and reusable sample data.
- `gallery/public/`: Static assets copied into the gallery output.

## Page Model

Gallery pages are generated by `gather-gallery-pages` in `build-scripts/gulp/gallery.js`.

- A page ID is the path under `gallery/src/pages/` without the extension, like `components/ha-button`.
- A `.markdown` file and a `.ts` file with the same page ID become one gallery page.
- A page may have only markdown, only a TypeScript demo, or both.
- Markdown can contain YAML frontmatter with `title` and optional `subtitle`.
- Markdown that contains only frontmatter contributes metadata without rendering a description block.
- TypeScript demo modules are dynamically imported for side effects when the page is opened.
- A demo module must define a custom element named `demo-${category}-${page}` with slashes replaced by hyphens, like `demo-components-ha-button` for `components/ha-button`.
- `gallery/src/ha-gallery.ts` renders that element with `dynamicElement()` based on the current page ID.

## Sidebar

Use `gallery/sidebar.js` when a page needs a visible section, section header, or deterministic ordering.

- `category` must match the first directory name under `gallery/src/pages/`.
- `header` is the section label shown in the drawer.
- `pages` is optional. When present, listed pages keep that exact order.
- Pages in a category that are not listed are appended alphabetically after the listed pages.
- New categories without a sidebar entry are appended by the generator with their category name as the header.
- If a listed page does not exist, the generator logs an error during `gather-gallery-pages`.

### Subsections

A section can group its pages under named subsections instead of one flat list. Use this for large categories where related pages should sit together.

- `subsections` is an array of `{ header, pages }`. It is mutually exclusive with a flat `pages` array on the same group.
- Each subsection `header` is a non-collapsible label rendered inside the section's expansion panel; the section stays the only collapsible level.
- Listed pages keep their per-subsection order.
- Any pages found in the category but not listed in a subsection are collected into a generated `Other` subsection, appended alphabetically. The `Other` subsection is omitted when there are no leftovers.
- A listed page that does not exist still logs an error during `gather-gallery-pages`.
- Use sentence case for subsection headers and follow the content standards below.

## Markdown Pages

Use markdown pages for explanations, design guidance, API notes, and copy standards.

- Start with frontmatter when the page needs a title or subtitle.
- Use sentence case for titles, headings, labels, and UI copy.
- Put the live example before the reference API when that makes the page easier to scan.
- Use fenced code blocks with a language tag for copyable examples.
- Keep examples short and focused on the behavior being documented.
- Prefer real component names and attributes over prose-only descriptions.
- Use Home Assistant terminology from `ha-frontend-user-facing-text`.
- For remove/delete and add/create wording, follow `gallery/src/pages/misc/remove-delete-add-create.markdown`.

Gallery markdown is documentation content and is not localized with `localize`. If demo code creates production UI strings, follow the localization and copy guidance in `ha-frontend-user-facing-text`.

## Demo Components

Use TypeScript demo pages for interactive or stateful examples.

- Import production components from `src/` using the correct relative path from the demo file.
- Import reusable gallery helpers from `gallery/src/components/` when they already model the pattern.
- Use `demo-card` and `demo-cards` for Lovelace card examples that render YAML card configs.
- Use `demo-more-info` and `demo-more-infos` for more-info dialog examples.
- Use shared mock data from `gallery/src/data/` instead of repeating large fake state objects inline.
- Show meaningful states, such as loading, unavailable, empty, error, active, inactive, and disabled when relevant.
- Check responsive behavior and the gallery RTL toggle when layout or direction-sensitive UI changes.
- Keep unavoidable casts or loose demo parsing local to the demo helper or demo page.

The gallery ESLint config allows `console` for gallery diagnostics. Do not copy that exception into production frontend code.

## Content Standards

Follow the detailed copy standards in `ha-frontend-user-facing-text`: use American English, sentence case, active voice, inclusive language, direct user-focused wording, and consistent Home Assistant terminology.

- Use `Home Assistant` in full, not `HA` or `HASS`.
- Use `integration` instead of `component` for product concepts.
- Use `Remove` for reversible disassociation and `Delete` for permanent deletion.
- Use `Add` for existing items and `Create` for something made from scratch.
- Avoid Latin abbreviations like `e.g.` and `i.e.` in prose.
- Avoid stitching sentence fragments together in production UI examples.

## Verification

- For markdown, sidebar, and page-generation changes, run `gallery/script/build_gallery`.
- For TypeScript demo or gallery shell changes, run the smallest relevant check plus `yarn lint` when practical.
- For type checking, run `yarn lint:types` without file arguments.
- For visual changes, run `gallery/script/develop_gallery` and check the affected page on desktop, narrow viewport, and RTL when relevant.
- If verification is skipped, state which command was skipped and why.
