include "draw.m";
include "prefab.m";
prefab := load Prefab Prefab->PATH;

The objects on the screen are of type Compound, each of which occupies a unique window on the display and contains objects of type Element. An Element may be a single object or a list of further Elements, to build hierarchically structured components.

Prefab defines Environ and Style types that specify the appearance of objects: their colours, fonts, backgrounds, and so on. A Style gives font and colour information, while an Environ identifies the Screen upon which the items will be displayed and the Style in which they will be drawn.

Applications should allocate Elements and Compounds only through the appropriate member functions, as described in the corresponding sections of the manual. Items created with regular Limbo definitions will not work properly. Moreover, except where indicated, applications should not modify the data members directly. Although the type definitions make data members visible, the members should usually be treated as read-only data.