Re: [libreoffice-users] PDF export checking whether the file is locked (opened) by another program before starting exporting over it

At 19:56 30/11/2014 +0100, Jaroslaw Staniek wrote:
> On Sunday, 30 November 2014, Brian Barker wrote:
> > At 13:55 30/11/2014 +0100, Jaroslaw Staniek wrote:
> > > Google for "acrobat reader file locking" and you'd notice that 
> > > this unnecessary locking is inherent issue of Windows. You're 
> > > dealing with behavior largely inherited from the MS DOS era. You 
> > > can pick other pdf reader.
> >
> > Surely that evidence falsifies your claim? If it's possible for 
> > another reader under the same operating system not to lock the 
> > file, then the locking cannot be a property of the operating 
> > system, still less of its legacy? In fact, it cannot be: just look 
> > at Windows' Notepad, which does not lock files it opens.
>
> Opening for writing locks the on Windows.

Do you mean that all Windows software capable of editing document 
files locks them? Sorry, but that is simply untrue - as I suggested. 
See http://en.wikipedia.org/wiki/Notepad_(software) : "Notepad does 
not require a lock on the file it opens, so it can open files already 
opened by other processes, users, or computers...". So this is surely 
not about any difference between operating systems? In any case, file 
locking is surely in general a Good Thing, isn't it? LibreOffice 
locks document files against opening in another instance of 
LibreOffice in its own way (under whatever operating system). The 
question here should surely be whether you want a PDF reader that is 
capable of annotation (and therefore of writing to document files), 
and if you do, how you want it to behave.

> Linux informs that the file was changed or removed if it editing it, 
> that models the real world.

So you mean that I can spend a couple of hours editing a file, only 
to discover when I try to save the result that you have been editing 
it as well, and I have the choice of either overwriting your changes 
or abandoning mine? That's not part of any "real world" I want to inhabit.

> Perhaps argument about other readers suggests that the bug should be 
> filled against the Adobe app, not LO.

Sort of. If you need just a reader, you may prefer something that 
isn't capable of editing (such as annotation) - so not Adobe Reader, 
despite its name. But the original suggestion was that LibreOffice 
should make a better fist of handling the lock when it exists.

> The wish for a special message looks for me like asking for 
> usability-wise unfortunate "solution" where LO would ask the user to 
> close the file.

Yes, just as happens in many other contexts - installing software, for example.

> In this scenario LO doesn't even know who's locking ...

Which is why it would ask the user for decision and action.

> ... and how to communicate the intent to unlock.

The suggestion is not that LibreOffice should override the lock, but 
that it should report the problem gracefully to the current user - by 
error message.

> All that made me write about core problem - pessimistic locking on 
> DOS/Windows.

I don't see how you can blame the operating system. (See above.) Oh, 
and I think you'll find that LibreOffice is not available for DOS.

> Not talking about the context - the OS - leads to situation that 
> apps on normally behaving oses show unexpected messages that really 
> make sense for Windows. Extra care is needed to avoid that.

If LibreOffice were to detect the lock, it would not see one if there 
were no lock. Why do you think it would produce a message about a 
lock it didn't detect? Do you underestimate the designers?

> I'm not studying the pdf export code of LO but proper development 
> practice is to write the new file to a temporary path, then renaming 
> it atomically. If that's true the message would appear on the very end anyway.

But it *could* establish if there was a lock at the beginning of the 
process. That's the suggestion (about which I make no comment).

Brian Barker 


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