[Interest] [OT] Re: autosave on OSX

Till Oliver Knoll till.oliver.knoll at gmail.com
Thu Oct 25 10:02:08 CEST 2012

2012/10/25 Lincoln Ramsay <a1291762 at gmail.com>:
> ...
> If you want "Mac" document handling (including Lion autosave/versions), you
> need to use NSDocument.

Absolutely correct.

To my surprise it was unexpectedly hard to find any useful information
about that matter, e.g. a google search "lion autosave tutorial" shows
mostly desperate forum entry how to /disable/ that feature ;)

But from what I gather from the Apple docs about NSDocument itself I
think given an instance of NSDocument:


* Let the system know that you support auto-save: autosavesDrafts

* Let the system know that you support "in place" autosave: autosavesInPlace

I *think* the later, when returning YES, will tell the system that it
is fine to do "auto-saving" and replacing the original file path (if
the file was ever stored manually with "Save As" - otherwise the file
is stored at a temporary location).

Then the flag NSSaveOperationType will tell you what kind of auto-save
operation is going on (in the appropriate "save document" methods).
Notice the two newly added values (OS X 10.7)
NSAutosaveElsewhereOperation ("document has never been saved manually
by the user: no file path") and NSAutosaveInPlaceOperation ("overwrite
the existing file").

To support "Versions" you would have at least to return YES in
"preservesVersions" (and possibly support/implement other methods),
and most likely you also want to implement "duplicateDocument" etc.

At least that's what I understand so far.

"How to call Objective-C APIs from within C++" in a nutshell:

* Mix C++ and Objective-C code in Objective-C++ source files: *.mm
* You can instantiate a C++ class from within Objective-C classes,
even keep references to them and vice versa
* You can pass plain simple C types such as int, float, double from
C++ to Objective-C methods (and vice versa) without problems etc.
* But you should never go as far as inheriting an Objective-C class
from a C++ base class or vice versa ;)
* (More restrictions probably apply, but that's what I remember out of my head)
* Finally, add those Objective-C++ sources to your qmake project:

mac {

* Link with the appropriate Cocoa frameworks explicitly, if needed

Lastly, you should consider whether that "Lion auto-save" is really
such a great feature (or whether you don't want at least to provide an
option to revert to the classic "Save/Save As" approach):

"That bloody autosaving is a disaster for me. I can not work with it.
Duplicates, duplicates and duplicates all over, when needing to save
the same picture in different formats. I can't keep track of it and it
makes a huge mess which steals time. If I make a mistake my original
Jpegs gets destroyed, without any warnings."


Yes, Apple re-introduced a "kind-of Save As" operation again in
Mountain Lion 10.8 (learing from above "disasters" ;)). But from what
I know last is that it *still* also saves the original document at the
same time, too! Ouch! Hence "kind of" Save As ;)

I agree that for a certain user group this Auto Save might be a good idea.

But my own experience is that I never ever lost a document due to a
"power outtage" or any other of those "You should have saved" moments
that Phil Schiller was telling us about when they introduced that
feature (yes, I did loose documents due to application crashes! But
I'd rather not have such an app auto-save my document at the very
moment it crashes - and if it does, please don't overwrite the actual
file ;)).

But I lost more nerves when I mindlessly started to change video edits
in Final Cut Pro X, just to experiment a bit - simply to realise
moments later that -shit!- I just modified that movie which was
already good as it was! So keep pressing Undo, Undo, Undo,... (even
though I am not even sure whether FCP X is actually using that
"Autosave" feature: I think it is more of a Core Data application
which more or less immediatelly reflects all your model changes in the
underlying DB or XML files).

Or Preview: each time I double-click e.g. a PDF first dozens of other
documents I had previewed at some previous time are opened first
(auto-save goes hand-in-hand with that "application restauration
thing"), possibly even in full-screen mode. And I got the feeling that
each time I get presented another document - not the one I
double-clicked on! - in fullscreen mode! So close, close, close all
those rubbish previews first and search my actual preview document.

Even worse with the QuickTime player: want to see a movie? You have to
fight through all the previous movies you did not close previously!

I know, I know, there's some *.plist configuration entry how you can
disable this "auto-restauration" feature. But so far Text Edit,
Preview and QuickTime are the only applications I use from Apple
(besides FCP X) and I have learnt to ignore and suffer ;) All other
applications still have the good ol' Save As functionality (for now

Just my 0.02$

Cheers, Oliver

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