Overview

Windows create a basis for the MWAPI system to communicate with users, and is the focus of this chapter. The MWAPI standard defines two different types of windows: application and MTERM. Application windows, which are GUI windows, provide the basic mechanisms for eliciting user input and displaying output. MTERM windows, which provide terminal emulation, are used to allow older, non-MWAPI code to run in a window. An MTERM window is similar to a MS Window's "DOS box." The MWAPI specification also permits developers to define window types in addition to the standard types for their implementations, but since they are nonstandard they may not be portable.

The definitions that describe windows are stored as values to attribute nodes assigned to the Window SSVN (^$W). Each M process running an implementation of the MWAPI can have its own copy of ^$W to define the entities in the process. An M process can contain a maximum of thirty-one windows, with the parent of each window either a logical display or another window defined for the same process. The parent of all MTERM windows is a logical display, but the parents of application windows may not be logical displays.

A window is created upon the successful conclusion of the assignment of at least one of its attributes. The attribute values not explicitly defined when the window is being created can be implicitly defined using default values supplied by the parent, the windowing platform, or the MWAPI specification. Window creation is...