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Subsections

• Design Principles

Overview

The AIPS++ Display Library, or more properly the display package of AIPS++, is a sophisticated class library for static and interactive display of scientific - predominantly astronomical - data. The display package also includes an interface to Glish which is loaded on-demand into the glishtk client.¹ The highest-level component of the package - the Viewer tool - is implemented as a set of Glish scripts, and is a genuine AIPS++ tool providing display services within the AIPS++ environment for many kinds of data.

The purpose of this document is firstly to give the reader a high-level outline of the Library - an outline not possible in the framework of the AIPS++ class documentation - and secondly to give practical advice on extending the package in a number of ways, for example to work with new display devices, to display new types of data, or to display existing types of data in new ways.

Design Principles

The initial design of the Display Library was made in 1996, taking ideas from the existing AIPS++ display application AipsView, and the ATNF's suite of visualisation tools. The objective was to adopt an object-oriented approach to visualisation so that:

• the many technical and esoteric aspects of data display could be encapsulated and therefore hidden from the application (tool) programmer,
• the support of new data types and display paradigms could be implemented in very high-level classes, maximising code re-use and minimising the burden of in-depth knowledge on the part of the application programmer, and
• visualisation applications could be built up in a modular fashion, consistent with the AIPS++ paradigm.

In 1998, the Display Library design was extended to enable the construction of visualisation tools from Glish. Instead of using the AIPS++ Distributed Object (DO) system, the extension made use of the Glish proxy system, and the dynamic loading capabilities of the one existing Glish proxy - glishtk. The first Glish application created using this system - the viewer - is, nevertheless, a true AIPS++ tool which can be managed by the AIPS++ Tool Manager.