## #define space osgGA

> The 'GA' in osgGA stands for 'GUI Abstraction'; the osgGA namespace provides facilities to help developers write the glue to allow the osg to work with varying window systems.

> As a cross-platform, window system-agnostic class library, the OpenSceneGraph has no direct ties to any given windowing environment. Viewers, however, must at some level interact with a window system - where Window system may refer to a windowing API, e.g. GLUT, Qt, FLTK, MFC, ...

> There is much commonality in the implementation of Viewers for varying windowing environments. E.g. most Viewers will update a Camera position in response to a mouse event, and may request that a timer be started as a result of a model being 'spun'.

> The purpose of the osgGA namespace is to centralise the common areas of this functionality. The viewer writer needs then only write a GUIEventAdapter, a GUIActionAdapter, and assemble a collection of GUIEventHandlers as appropriate for the viewer.

> Events from the windowing environment are adpated, and then fed into the GUIEventHandlers. The GUIEventHandlers analyse and take action, and make requests of the windowing environemnt via the GUIActionAdapter. The viewer writer should then honour these requests, translating them into calls to the windowing API.

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