Since version 1.13.0 of Atom, the syntax highlighting style rules don't get applied in the preview window. This appears to be due to the fact that Atom has changed how it applies CSS, according to this deprecation warning:
Starting from Atom v1.13.0, the contents of atom-text-editor elements are no longer encapsulated within a shadow DOM boundary. This means you should stop using :host and ::shadow pseudo-selectors, and prepend all your syntax selectors with syntax--
Atom version: 1.15.0 (installed from official package)
Description
Since version 1.13.0 of Atom, the syntax highlighting style rules don't get applied in the preview window. This appears to be due to the fact that Atom has changed how it applies CSS, according to this deprecation warning:
Screenshots