pulsar/docs/creating-a-theme.md

Creating a Theme

Atom's interface is rendered using HTML and it's styled via LESS (a superset of CSS). Don't worry if you haven't heard of LESS before, it's just like CSS but with a few handy extensions.

Since CSS is the basis of the theming system, we can load multiple themes within Atom and they behaves just as they would on a website. Themes loaded first are overridden by themes which are loaded later (the order is controlled from within the Settings pane).

This flexibility is helpful for users which prefer a light interface with a dark syntax theme. Atom currently has interface and syntax themes but it's easy see how one might want to create their own language specific syntax theme for very specific styling.

Getting Started

To create your own theme you'll need a few things:

• A working install of Atom, so you can work on your new theme.
• A working install of git to track changes.
• And a GitHub account, so you can distribute your themes.

Themes are pretty straight forward but it's still helpful to be familiar with a few things before starting:

• LESS is a superset of CSS but it has some really handy features like variables. If you aren't familiar with its syntax take a few minutes to familiarize yourself.
• Atom uses Chrome at its core, so you can use Chrome devtools to inspect the current state of the interface. Checkout Google's extensive tutorial for a short introduction.

Creating a Minimal Syntax Theme

1. Open the Command Palette (cmd+p)
2. Search for Package Generator: Generate Theme and select it.
3. Choose a name for the folder which will contain your theme.
4. An Atom window will open with your newly created theme.
5. Open package.json and update the relevant parts.
6. Open stylesheets/colors.less to change the various colors variables which have been already been defined.
7. Open stylesheets/base.less and modify the various syntax CSS selectors that have been already been defined.
8. When you're ready update the README.md and include an example screenshot of your new theme in action.
9. Open a terminal to your new theme directory
10. Run apm link to install it locally.
11. Reload Atom (cmd-r) and your theme should now be applied.
12. To publish, initialize a git repository, push to GitHub, and run apm publish.

Interface Themes

There are only two differences between interface and syntax themes - what they target and what they provide. Interface themes only target elements which are outside of the editor and must provide a ui-variables.less file which contains all of the variables provided by the core themes. Syntax themes don't need to provide any variables to other themes and only target elements within the editor.

How to Style a Specific Element

Once you've got the basics down you'll find that there will be changes you want to make but you aren't sure how to reference an element. That's when the devtools become really useful. To open them use cmd+alt+i and switch to the Elements tab to inspect the element you're interested in.