A system theme schema file format includes declarations of enumerations, properties,
control parts, and control part states for providing extensible theming of the
visual appearance of a computer operating system's user interface components. Custom
theme schema files can extend the system theme schema by adding declarations of
custom enumerations, custom properties, custom control part, and custom control
part states, thereby participating in theming of the visual appearance of components
of the computer's operating system. The schema files establish the allowable form
and content of data that specifies how user interface components should be displayed
in accordance with particular themes. Themes are defined and user interface components
are displayed by the operating system in accordance with the information specified
in the schema files.
