Version 5.0 The LEDA User Manual

17.8 Geometry Windows ( GeoWin )
1. Definition
An instance of data type GeoWin is an editor for sets of geometric objects. It can
be used for the visualization of result and progression of geometric algorithms. GeoWin
provides an interactive interface and a programming interface to visualize and manipulate
geometric objects and data structures.
Sets of geometric objects are maintained in so-called scenes.
Scenes
Scenes are instances of the various scene data types supported by GeoWin. They are used
to store collections of geometric objects and attributes of the objects and collections.
Furthermore the scene classes have to provide functionality for GeoWin to handle the
geometric objects of a scene.
Each scene stores geometric objects in a container (a LEDA-list or STL-list). We call
these geometric objects stored in a container of a scene the contents of a scene. The scenes
and their contents can be manipulated by the interactive interface and the programming
interface of GeoWin.
With every scene a set of attributes is associated. Most of them describe the visual
representation of the scene, for instance the boundary- and fill-color of the objects, the
visibility of the scene,... .
We use the type geo scene as the scene item type of GeoWin; it may be helpful to view
it as pointers to scenes.
We distinguish the following types of scene classes:
1. Edit Scenes (type GeoEditScene)
where CONTAINER is the type of the scene’s container storing the contents of the
scene, for instance list. These scenes can be edited by the user through the
interactive interface of GeoWin. Note that edit scenes have some special features.
An important feature is the possibility to select objects through the interactive
interface. These selected objects have special attributes, see the table of scene
attributes.
2. Result Scenes (type GeoResultScene)
These scenes are not independently editable by the user. The contents of result
scenes is computed by a user-defined update function or update object executing a
geometric algorithm. This recomputation of the scene contents will be done every
time when another scene (this other scene we call the input scene of the result scene)