Managing UI Geometry: 1 Geometry Manager Overview

The GEOS geometry manager is an algorithmic mechanism which interacts directly with the UI to position and size objects of all types. The geometry manager automatically manages all generic objects through interactions with the specific UI library; you can also use it to manage your visible object trees.

The Geometry Manager is what makes the generic UI possible: Since geometry of UI objects (size and position) is determined by the UI at run-time, generic UI objects do not have to be explicitly defined with certain geometry. With this feature, a specific UI library can set up the UI geometry as it wants.

Your first interaction with the geometry manager will be when you build a generic object tree for your UI. Most hints applied to an object are signals to the geometry manager about how the object should be positioned, sized, or otherwise placed on the screen. These hints are all defined in GenClass , the topmost generic object class, so they are available (though not necessarily useful) to all types of generic objects.

This chapter first describes the features of the geometry manager and how the mechanism fits into the GEOS system as a whole (later in this section). Then it discusses how to manage generic UI objects (using a dialog box as an example) in Arranging Your Generic Objects . For the hints you can apply to window objects, see Positioning and Sizing Windows . For descriptions of managing the geometry of visible object trees and composites, see the VisClass chapter.

Geometry Manager Features

How Geometry Is Managed

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