Ubuntu – Swift syntax highlighting in gedit

You can at least add file extensions in the html syntax coloring scheme by editing html.lang in /usr/share/gtksourceview-2.0/language-specs/ as a super user. So say you want to add HTML syntax highlighting to cfm files, you'd change this

<property name="globs">*.html;*.htm</property>

(default html.lang) into this

<property name="globs">*.html;*.htm;*.cfm</property>

I do not know why your original julia.lang file is not working since you're not showing the source, but the one you based on matlab.lang will not work because there's no context inside <definitions> with the same id you mentioned for <language>.

Basically, you're saying the id of this language is julia, but there is no context with that id being defined. So find <context id="matlab" (line 149 of the current HEAD), and change it to julia.

A lang file is usually organized as a bunch of individual contexts for the language features being highlighted, which are then grouped in the end into a main block with the same id as the language, and references to the other contexts.