Am 28.04.2010 12:26, schrieb Hannes Hirzel:
> Thank you Andreas for the writeup you put at
> 
> 'Annotations for Service Discovery'
> http://squeakingalong.wordpress.com/2010/04/27/annotations-for-service-discovery/
> [...]
> 
> --Hannes
+1

Thank you all (on- and off-list) for the pragma discussion. Now I see
that pragmas can be looked at from different angles. I believe what we
want for menus is a pragma which is like a declarative contract (see
Tobias' post).

What about organizing official system extension points via services?
A (DockingBar-)MenuBuilder is a service, a PreferenceManager is a
service, ..and so on.

Given I have build an applications that wants to use a menu service it
could implement something along this:

toggleColor
	"Toggles the background color of my singleton instance."
	<action>
	<actionScope: #UI>
	<actionCategory: #extra subCategory: #colors>
	<actionOccurence: #persistent>
	<actionName: 'Toggle Color'>
	<actionIcon: #toggleColorIcon>

	(Instance color = Color blue)
		ifTrue: [ Instance color: Color red ]
		ifFalse: [ Instance color: Color blue ].

Please read the method like this:
 This message wants to contribute an action which should be accessible
through the UI - therefore we have the annotation <action> (which is
kind of a general tag) and <actionScope: #UI> which says we want this
action be present in the UI.
(The other annotations are optional in this case!)

Pleasee note that the message basically implements its own business
stuff, but annotates some ui-things as a different plane.

The DockingBar, for example, is a way to represent UI-actions which
applications offer the user.
So a service, namely the docking bar, looks through all
service-annotations with scope: #UI. ("Ah, I (the docking bar) may offer
a menu for this message of this class").
As it is specified that this is a persistent activity (meaning: this
UIAction doesn't change too often) through <serviceOccurence:
#persistent> the docking bar decides to build a menu for this action.
(The world menu may decide different as it is better in displaying
#changing actions.)

What do you think about this approach?

- philipp