from preamble:

"Change Set:		Hooker-nk
Date:			13 March 2001
Author:			Ned Konz

This implements a global registry for general-purpose
additions of behavior without having to edit code.
For instance, the method changes in the MenuMorph class
in this change set allow one to intercept calls to the various
menu construction functions and add new menu items without
having to edit menu construction code.

However, this can be used to intercept calls to any method.

Lookup of hooks is by category (typically a Symbol, like
#menuAdditions), tag (an arbitrary object, often a Symbol), calling
class (exact match, no inheritance), and calling selector.

For instance, if we want to catch calls from A>>a to B>>b or C>>c, we
would add the line

	self callHooksInCategory: #myCategory.

to both B>>b and C>>c.

Then we would register a global hook using

Object addHook: [ :cat :tag :mc1 :mc2 | 'actions here' ]
			named: #someName
			inCategory: #myCategory
			fromClass: A
			selector: #a.

When callHooksInCategory: call is made from A>>a to either B>>b or C>>c
(or any other method that calls self callHooksInCategory: #myCategory),
the block given in the registry call above will get called with:
	cat		#myCategory
	tag		#someName
	mc1		A>>a method context (not a copy!!)
	mc2		B>>b or C>>c method context (not a copy!!)

Because mc1 and mc2 are real block contexts, you can skip further
execution by using something like:

	thisContext terminateTo: mc2 sender

in your block (in this case, the rest of B>>b or C>>c would be skipped).

Look at Object class>>hookExample1 for an example of adding
an item to the World Menu.

Look at Object class>>hookExample2 for an example of adding
an item to the World Menu, and skipping another one using the
terminateTo: trick.
"!
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