Why This Document?

This document (whose browsable version is accessible by using your browser's "File→Open File" on /opt/graphics/common/doc/GAG/Web/index.html) was created to fill a need that became evident as Hewlett-Packard began to offer multiple Application Programmer Interfaces (APIs). The situation was this: As HP created one API — say, Starbase — particular aspects of graphical operation were noted and diligently explained in the Starbase documentation. However, some of these aspects were not unique to Starbase, they pertained to graphics operation in general: they applied to all of our APIs. Therefore, those users who had HP-PHIGS would be encountering some of the same graphical questions that were already well-documented in the Starbase documentation. But HP-PHIGS users wouldn't necessarily have the Starbase documentation. Are they just out of luck? The same situation occurred with HP PEX.

Our dilemma was this: do we copy the general-graphics explanations that already existed in the Starbase documentation, into the documentation for the other APIs as well? This would mean two, three, or even more virtually identical copies of the same explanations in different places, requiring similar changes in each whenever new capabilities or devices were introduced. And if all documents containing these similar explanations were not reprinted simultaneously, "current" documents for the various APIs might contradict each other.

A more elegant solution is: this document. While the API-specific documents still contain most of their previous contents, the general graphical information — common to all APIs — was moved here. Examples include:

The above topics, and others as well, are good candidates for a common area. With this approach, only one copy of the common information need exist, and revisions can happen in a more timely manner, and at less risk of contradicting other documents.