element-web/docs/theming.md

Theming Riot

Themes are a very basic way of providing simple alternative look & feels to the riot-web app via CSS & custom imagery.

They are NOT co be confused with 'skins', which describe apps which sit on top of matrix-react-sdk - e.g. in theory Riot itself is a react-sdk skin. As of Jan 2017, skins are not fully supported; riot is the only available skin.

To define a theme for Riot:

1. Pick a name, e.g. teal. at time of writing we have light and dark.
2. Fork src/skins/vector/css/themes/dark.scss to be teal.scss
3. Fork src/skins/vector/css/themes/_base.scss to be _teal.scss
4. Override variables in _teal.scss as desired. You may wish to delete ones which don't differ from _base.scss, to make it clear which are being overridden. If every single colour is being changed (as per _dark.scss) then you might as well keep them all.
5. Add the theme to the list of entrypoints in webpack.config.js
6. Add the theme to the list of themes in matrix-react-sdk's UserSettings.js
7. Sit back and admire your handywork.

In future, the assets for a theme will probably be gathered together into a single directory tree.