The behavior and interaction of the two General preference pane checkboxes, "Ask to keep changes when closing documents" and "Close windows when quitting an application", are so complicated that I knew there was a danger of my missing something; and sure enough, I did. The book implies (p. 126) that closing a document and quitting the application are the same action; but that's true only if "Close windows" is checked. If "Close windows" is unchecked (Resume is on), quitting just autosaves and quits, with no dialog - even if "Ask to keep changes" is checked. In other words, when Resume is on ("Close windows" is unchecked), Apple is drawing a distinction between closing windows explicitly (e.g., by clicking the Close button) and quitting; and I didn't quite draw that same distinction clearly enough.

The reason I was confused is that "Close windows when quitting an application" effectively conflates two quite different things. On the one hand, it has to do with Resume (what should happen the next time the application is launched). On the other hand, it dictates whether quitting should count as closing the open documents, thus eliciting the close-window behavior specified by "Ask to keep changes when closing documents". It would have been much clearer if Apple had provided three checkboxes:

• Ask to keep changes when closing documents

• Quitting an application closes documents first

• Restore an application's windows the next time it launches

(You could argue, and presumably Apple does argue, that the second two are intimately related; but that is not the same as making them identical, as Apple as done.)

Another thing I didn't point out is that if you close multiple edited windows simultaneously, by quitting when both checkboxes are checked, you get the old familiar Cocoa dialog that saying: "You have [multiple] documents with unconfirmed changes. Do you want to review these changes before quitting?"

I've now written a lengthy TidBITS article describing the Mountain Lion changes to the Modern Document Model, covering these points and more.

—Posted by Matt Neuburg on July 30, 2012