[KPhotoAlbum] Auxiliary files, again

[Johannes Zarl-Zierl]

Hi Robert,

Am Dienstag, 2. April 2019, 02:08:42 CEST schrieb Robert Krawitz:
> What I'd like to do is stack auxiliary, non-image files with real
> images, using autostack rules like the existing ones for autostacking
> imags.  This sounds straightforward enough, but I can think of
> difficulties:
> 
> * If a stack is broken by having one or more of its images removed,
>   what happens to the auxiliary files?  Do they automatically stay
>   stacked with one or another of the images, do they get dropped, or
>   what?

I think as you describe the use-case, stacks are really an orthogonal concept.

> * Checksums may not be sufficient to distinguish between auxiliary
>   files.  The odds against two auxiliary files having identical
>   contact might not be that high, particularly if the filename is not
>   stored in the auxiliary file.

Just checking with one .xmp I picked randomly, it seems that the filename is 
stored there. I don't know whether this is required for xmp files, and how it 
is for different sidecar formats.

> I'm sure there are other issues I haven't reached yet, but
> nevertheless, this kind of functionality would be extremely useful.

How about taking a different approach than the darktable "a sidecar file is an 
image" one?
One possibility would be to have the base image and to add the sidecar files 
as sub-images. That way, we could do away with checksumming for sidecar files, 
both eliminating the possible duplicate problem and avoiding incorrect 
checksums all the time because sidecar files are more likely to be modified at 
some point.
How to present this image-group in the UI is a different question, though.

Maybe we could even go further with this approach and omit the sidecar files 
from the database altogether by checking for sidecar files on demand...

Cheers,
  Johannes