The Inform 6 Release notes (Inform Release Notes) mention:
A new LibraryExtensions object is defined, whose function is to act as a parent to initialisation objects created by library extensions. These objects may provide ext_initialise and/or ext_messages property routines, whose role is to help integrate the extension into a game. This is best explained by example.
Consider the SmartCantGo.h extension, which replaces “You can’t go that way” messages by the more informative “You can go only north, south and east”, and can be integrated into a game by adding a ChangeDefault(cant_go, SmartCantGo) statement to your Initialise() routine. Instead of requiring the author to make this addition, the extension could now cause it to happen automatically by defining an initialisation object as a child of LibraryExtensions, like this:
Object "(SmartCantGo)" LibraryExtensions
with ext_initialise [; ChangeDefault(cant_go, SmartCantGo); ];
Just before calling the game’s Initialise() routine, the library loops through the children — if any — of LibraryExtensions, and executes those ext_initialise properties that it finds there. The property routines can perform any appropriate setup processing that would otherwise have to be inserted into the Initialise() routine itself; for example, starting a daemon running.
A similar process takes place when displaying library messages. The library first checks whether the author has provided a LibraryMessages object to intercept the message which it is about to display. If not, it now loops through the children of LibraryExtensions, and executes ext_messages properties that it finds there. If none of those routines returns true to signal that the message has been dealt with, the standard library text is then printed in the usual way. For example, here’s how an extension might automatically intercept Inventory messages (unless the game has already handled them via LibraryMessages):
Object "(someInventoryExtension)" LibraryExtensions
with ext_messages [;
Inv: switch(lm_n) {
1: "You are empty-handed.";
2: "Your possessions include";
}
];
Note that this is an experimental feature, and may be modified or extended in the light of experience.
Is there any source for more complete documentation of this?
EDIT: I should add that the reason that I’m asking is because of the large number of other extension hooks (in addition to ext_initialise and ext_messages) that are evident in StdLib 6.12.4:
ext_afterlife
ext_afterprompt
ext_afterrestore*
ext_aftersave*
ext_amusing
ext_beforeparsing
ext_chooseobjects
ext_darktodark
ext_deathmessage
ext_gamepostroutine
ext_gamepreroutine
ext_handleglkevent*
ext_identifyglkobject*
ext_InitGlkWindow*
ext_inscope
ext_lookroutine
ext_newroom
ext_objectdoesnotfit*
ext_parsenoun
ext_parsenumber
ext_parsererror
ext_printrank
ext_printverb
ext_timepasses
ext_unknownverb
Are these mostly (except for those marked with asterisks) just alternates to their same-name entry points as found in DM4 Appendix A5? If so, why are relatively new entry points GamePrologue() and GameEpilogue() left out?