B. The GWindows Core

Since version .7, GWindows has been centered around a "core" system. The GWindows Core is simply a mechanism to allow modular libraries to share the Glk entry points of the inform library. GREX, GWindows, and GSound all use GWindows Core Modules. As a result, GWindows and GSound may be used separately, or in tandem (GREX, though modular, relies heavly on GWindows primitives, and cannot be used alone).

Anyone wishing to write a GWindows Core Module may do so. Even casual users may find a small GWindows Core Module easier to use than the GWindows Glk entrypoints.

A GWindows Core Module inherits from the class GWin_Module, which is defined in gcore.h. The following properties apply to a GWin_Module:

• prepare() - This is called the first time the core is invoked. It can do any preliminary setup it likes.
• init(x) - This is called whenever InitGlkWindow(x) is invoked
• identify(phase,type,ref,rock) - Called by IdentifyGlkObject
• update() - Called whenever DrawStatusLine is called.
• event_handler(x,ev,abortres) - Called by HandleGlkEvent
• number - If provided, this should be the version number of the module (as any printable)
• Unless the general attribute is set, the game banner will be augmented with the short name of the module and its version number

Programs which use the GWindows Core, but not GWindows itself must also include the GWindows Core Definitions file, gcdefs.h before including the parser.

The Core replaces DrawStatusLine. You will have to provide your own status line via an update() method if you use it.

• Chapter 9
• Appendix B
• Table of Contents