styles

Used by the Theme to determine how this node should be styled. Similar in concept to CSS's class attribute.

By convention, styles which represent the node's class, using the class name in all lower case, with underscores between words. e.g. split_pane.

Other styles begin with a period. e.g. .information.

Usually, styles are set when the node is first created, and remained unchanged thereafter.

If a style is added or removed, then all rules within the Theme are checked to see if they match this node, and all descendant nodes.