I did not actually measure it, so I'm not sure if it matters with respect
to performance. That said, the method that figures out what flavor of
UIManager to instantiate is a bit complex, so it may have some value.

But the real reason I did it is that the UIManager was clearly designed
with the intent of maintaining a reference to single instance while any
given user interface is in effect. This was supported by referring to
the default UIManager through a class variable. I presume the intent
was to update this variable whenever the type of user interface changed
(i.e. enter a different kind of project), although this had not yet been
implemented in our trunk image.

That approach made good sense when maintaining UIManager as a separate
package, but it did require that the default UIManager be updated
when changing projects, which actually ends up being a bit complicated
(and that may be why it never got implemented). But the UIManager
is conceptually related to Project, in the sense that a project has
a kind of user interface, and the UIManager implements the appropriate
UI requests for that kind of project. So it turns out to be simpler to
just give the Project a UIManager, and not bother with trying to keep
the value of "UIManager default" up to date when switching projects.

And last but not least, it made the class comment simpler ;-)

Dave

On Mon, May 03, 2010 at 10:24:52AM -0500, Chris Muller wrote:
> Since UIManager does not have any state, will this matter?  YAGNI?
> 
> On Sun, May 2, 2010 at 5:19 PM,  <commits at source.squeak.org> wrote:
> > David T. Lewis uploaded a new version of ToolBuilder-Kernel to project The Trunk:
> > http://source.squeak.org/trunk/ToolBuilder-Kernel-dtl.34.mcz
> >
> > ==================== Summary ====================
> >
> > Name: ToolBuilder-Kernel-dtl.34
> > Author: dtl
> > Time: 2 May 2010, 6:15:49.448 pm
> > UUID: d9bb885a-17d0-45ae-b93e-04cdf4e05a9f
> > Ancestors: ToolBuilder-Kernel-MAD.33
> >
> > Associate an instance of UIManager with each project, such that UIManager current refers to an appropriate instance for that type of project. Remove incomplete implementation of caching the current UIManager instance in class UIManager.
> >
> > Update class comment for UIManager.
> >
> > =============== Diff against ToolBuilder-Kernel-MAD.33 ===============