Seelen UI — Resource Guidelines

Reference guide for creating and sharing resources — themes, widgets, plugins, icon packs, or wallpapers — for Seelen UI.

Table of Contents

1. What is a Resource?
2. Resource Kinds
3. Resource ID — Naming Your Resource
4. Metadata — Describing Your Resource
5. Supporting Multiple Languages
6. Extended YAML — Splitting Your Files
   • !include — embed a file as text
   • !extend — embed a YAML file
7. Folder Structure
8. Loading and Unloading Resources

1. What is a Resource?

A resource is a folder (or a single file) that you create and that Seelen UI can load to add new visuals or functionality. You write a metadata.yml file that describes your resource, and optionally other files (stylesheets, scripts, translations) that it references.

Once your resource is ready you can:

• Use it locally by placing the folder in the Seelen UI resources directory.
• Share it by publishing it to the Seelen marketplace.

2. Resource Kinds

Choose the kind that matches what you want to create:

Each kind shares the same basic structure described in this guide, and then adds its own specific fields. Separate guidelines cover each kind in detail.

3. Resource ID — Naming Your Resource

Every resource needs a unique ID. You choose this ID yourself when you create the resource. The format is:

@your-username/resource-name

Examples:

@johndoe/my-dark-theme
@johndoe/weather-widget
@acme/corporate-icons

Rules:

• Must start with @.
• Your username: 3–32 characters, letters, digits and hyphens, must start and end with a letter or digit.
• The resource name: at least 3 characters, letters, digits and hyphens, must start and end with a letter or digit.

When you publish a resource to the marketplace it gets a permanent internal ID assigned automatically. You don't need to worry about that — you always use your @username/name when writing resource files.

4. Metadata — Describing Your Resource

Every resource has a metadata block. This is the information shown in the marketplace and in the Seelen UI settings panel.

metadata:
  # Name shown in the UI (required)
  displayName: My Dark Theme

  # Short description (required)
  description: A clean dark theme for all widgets.

  # Keywords that help users find your resource
  tags:
    - dark
    - minimal
    - toolbar

  # Square preview image — 1:1 aspect ratio (optional)
  # portrait: uploaded via the Seelen website (see note below)

  # Wide promotional banner — 21:9 aspect ratio (optional)
  # banner: uploaded via the Seelen website (see note below)

  # Screenshots — 16:9 aspect ratio, as many as you want (optional)
  # screenshots: uploaded via the Seelen website (see note below)

  # Oldest Seelen UI version your resource is compatible with (optional)
  appTargetVersion: [1, 11, 0]

The only fields that are truly required are displayName and description. Everything else is optional but filling them in makes your resource look much better in the marketplace.

Images (portrait, banner, screenshots): these are uploaded directly through the Seelen website when you publish or edit your resource — you do not write URLs in metadata.yml yourself. Only images hosted on seelen.io are accepted; any other URL will be ignored and Seelen UI will display the default resource icon as the portrait instead.

5. Supporting Multiple Languages

displayName, description, and any user-visible text in your resource support multiple languages out of the box.

Simple — English only:

displayName: My Dark Theme

Localized — multiple languages:

displayName:
  en: My Dark Theme
  es: Mi Tema Oscuro
  de: Mein Dunkles Theme
  fr: Mon Thème Sombre
  pt-BR: Meu Tema Escuro

When a user's language is not in your list, Seelen UI automatically falls back to English. If you provide a language map, you must always include en.

Use whatever languages you are comfortable with. The more the better, but English alone is perfectly fine.

Automatic translation: Seelen UI ships a CLI command that fills in all the supported languages in a single translation file. Write your source language entry first, then run:

seelen-ui resource translate <path/to/file.yml>

For example, given i18n/display_name.yml with only:

en: My Dark Theme

Running the command on that file will complete it with every other language Seelen UI supports. If your source text is not in English, pass the language code explicitly:

seelen-ui resource translate i18n/display_name.yml es

Run the command once per translation file. Always review the results — machine translations can be inaccurate.

6. Extended YAML — Splitting Your Files

Resource files are written in YAML. Seelen UI extends standard YAML with two special tags that let you pull in content from other files. This keeps your main metadata.yml clean and each piece of content in its own focused file.

!include — embed a file as text

Reads a file and inserts its content as a text string.

key: !include path/to/file.ext

• The path is relative to the folder where your metadata.yml lives.
• .scss and .sass files are automatically compiled to CSS before being inserted.
• Any other file is inserted as plain text.

Typical uses:

# A theme inserting its stylesheets
styles:
  "@seelen/fancy-toolbar": !include styles/toolbar.scss
  "@seelen/weg": !include styles/weg.css

# A plugin inserting its JavaScript
plugin:
  template: !include plugin/template.js
  tooltip: !include plugin/tooltip.js

!extend — embed a YAML file

Reads another YAML file and inserts its contents as a YAML value (a map, a list, anything).

key: !extend path/to/file.yml

The most common use is splitting translations into their own files:

# metadata.yml
metadata:
  displayName: !extend i18n/display_name.yml
  description: !extend i18n/description.yml

# i18n/display_name.yml
en: My Dark Theme
es: Mi Tema Oscuro
de: Mein Dunkles Theme

After loading, the result is exactly the same as if you had written the translations inline. !extend files are themselves parsed with the same rules, so you can use !include and !extend inside them too.

When to use each:

7. Folder Structure

A resource can be a single metadata.yml file, but for anything real you will want a folder. Seelen UI looks for an entrypoint file inside the folder by checking these names in order: metadata.yml, metadata.yaml, index.yml, mod.yml, main.yml (and their .json variants).

Always name your entrypoint metadata.yml. It is the clearest and most expected name.

A typical resource folder looks like this:

my-dark-theme/
├── metadata.yml          ← entrypoint: id, metadata, kind-specific fields
├── i18n/
│   ├── display_name.yml  ← translations for the name
│   └── description.yml   ← translations for the description
└── styles/
    ├── toolbar.scss       ← styles referenced with !include
    └── weg.scss

There are no other required files or folder names — only metadata.yml is mandatory. The rest is entirely up to you, though following a consistent layout (like the one above) makes maintenance easier.

8. Loading and Unloading Resources

While developing a resource you can load it into a running Seelen UI instance directly from any folder on your machine using the CLI — no need to copy files anywhere.

Load

seelen-ui resource load <kind> <path>

• <kind> — one of: theme, widget, plugin, icon-pack, wallpaper
• <path> — absolute or relative path to the resource file or folder

Examples:

seelen-ui resource load theme ./my-dark-theme
seelen-ui resource load widget C:\Users\me\projects\my-clock
seelen-ui resource load plugin ./my-plugin/mod.yml

The resource is registered immediately and available in Seelen UI settings without restarting the app. Seelen UI must be running for this command to work.

Unload

seelen-ui resource unload <kind> <path>

Removes the resource from the registry using the same path you used to load it.

seelen-ui resource unload theme ./my-dark-theme

Loaded resources are registered for the current session. After restarting Seelen UI you will need to load them again, or install them permanently through the settings panel.