StyleScheme
Controls the appearance of class@View.
#GtkSourceStyleScheme contains all the text styles to be used in class@View and class@Buffer. For instance, it contains text styles for syntax highlighting, it may contain foreground and background color for non-highlighted text, color for the line numbers, current line highlighting, bracket matching, etc.
Style schemes are stored in XML files. The format of a scheme file is documented in the ./style-reference.html.
The two style schemes with IDs "classic" and "tango" follow more closely the GTK theme (for example for the background color).