Lion Resume when Closing Docs without Quitting App

Question

I'm dipping my feet into Cocoa for the first time.

Here's a simple question. OS X Lion supports Resuming of window state when an app is terminated and relaunched. Okay, good and fine.

But for document-based apps, can the same Resume feature also manage saving of window state when a document is closed and reopened later but without any quitting of the app? (In other words, can it manage each file's state persistently regardless of whether the app quits or not? Or do I have to manage it myself by saving the information in the documents' files?)

For instance, iWork '09 apps do do this sort of thing: if you close a saved document and reopen it, it will restore the window size, location, and scroller position. I don't know if it does this using Lion's Resume per se.

But, in contrast, OS X Lion's TextEdit restores windows when it is quit and restarted, but it does not remember window states when you close a document and reopen it. This makes me suspicious that using Resume without quitting might not be possible automatically (since maybe Pages keeps window states in its proprietary file format, but TextEdit doesn't since it uses plain text, RTF, HTML, etc. files).

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I don't have access to the WWDC 2011 videos yet, and neither the OS X release notes, the OS X Application Programming Guide, nor the NSWindowRestoration API docs talk about this specifically.

So the question again: automatically remembering the state of a document window after closing and reopening it without quitting the app (like iWork does)...does Lion's Restore support this?

Thanks a lot!

Answer 1

But for document-based apps, can the same Resume feature also manage saving of window state when a document is closed and reopened later but without any quitting of the app? (In other words, can it manage each file's state persistently regardless of whether the app quits or not?

Not unassisted, no.

Or do I have to manage it myself by saving the information in the documents' files?)

Or somewhere else, yes.

My untested suggestion is to try using the window-restoration protocol yourself. When closing, send yourself encodeRestorableStateWithCoder:, then stash that data in your document (or wherever you want). When opening a document, if it has restorable state information, pass it to restoreStateWithCoder:.