Styles

A style, an instance of the wx:style% class, parameterizes high-level display information that is common all snip classes. This includes the font, color, and alignment with which an item is drawn. A single style is attached to each snip.

Styles are hierarchical: each style is defined in terms of another style. There is a single root style -- named ``Basic'' -- from which all other styles are derived.

The difference between a base style and a derived style is encoded in a style delta (or simply delta). A delta can encode changes such as

• change the font family to X
• enlarge the font by adding Y to the point size
• toggle the boldness of the font
• change everything to match the style description Z
• etc.

The types of changes which can be described by a delta are limited, but all of the usual style derivations can be described.

Style objects are never created separately; rather, they are always be created through a style list, and instace of the wx:style-list% class. A style list manages the styles themselves -- servicing external requests to find a particular style -- as well as the hierarchical information. A global style list is available, but new style lists can be created for managing separate style hierarchies. For example, a buffer will typically have its own style list.

A new style can be defined in two ways:

• derived style -- A derived style is defined in terms of a base style and a delta. Every style (except for the root style) has a base style, even if it does not depend on the base style in any way (i.e., the delta describes fixed style parameters).

• join style -- A join style is defined in terms of two other styles: a base style and a shift style. The meaning of a join style is determined by reinterpreting the shift style; in the reinterpretation, the base style is used as the root style for the shift style.

In an edit buffer, all snips are assigned styles based on a style called ``Standard'' (unless the style is specifically set otherwise). By default, this style is unmodified from the root style.