[krita/video-export-rebased] libs/ui: Save to a temporary file, then copy the result over on success (fwd)

[Boudewijn Rempt]

On Tue, 16 Aug 2016, Dmitry Kazakov wrote:

> Can we somehow limit this behavior to network files only?

I would prefer not to. This also solves the issue we've seen where a
failure to save breaks the original file. In fact, this is how saving
should have been implemented already, and as I thought it had been
implemented.

You never directly overwrite an existing file, you always save to a
temporary file and then let the OS do the copy. Anything else is a bug.

> There are two problems I see:
> 
> 1) If some other application, like Blender, is waiting on Krita-edited file
> with inotify (QFileSystemWatcher), it may go crazy when we rename and
> delete the file. The inotify opject will be destroyed after that.

Did you test that, or is this just a hunch?

> 2) What if the user works with 700MiB image? It mean he needs twice the
> size of the image free space just to be able to save it. Many people will
> be unhappy with it.

But far fewer people than are currently unhappy because our unsafe saving
code breaks their files. And if the file hasn't been saved before there is 
no extra disk space needed,

> 3) What if there is not enough free space in Temp folder? The user will
> never be able to save the image? That is a dataloss bug.

Then they get an error message and can clean out their temp folder.

But they WILL NOT LOSE THEIR ORIGINAL FILE. And that is what counts. 

And as I said, this is how saving was supposed to happen anyway.
-- 
Boudewijn Rempt | http://www.krita.org, http://www.valdyas.org