[digiKam-users] Odd problem with tags, a sort of 'ghost' tag

[Chris Green]

Gilles Caulier <caulier.gilles at gmail.com> wrote:
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> 
> 2018-09-27 18:10 GMT+02:00 Chris Green <cl at isbd.net>:
> 
> > meku <digikam at meku.org> wrote:
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> > >
> > > That the image shows up when using the left sidebar but not the tags
> > filter
> > > suggests to me that your Tags tree is in an inconsistent state.
> > >
> > > Depending on your Digikam version and database backend this can happen
> > when
> > > creating or deleting Tags. I haven't confirmed if the Digikam maintenance
> > > tool will correct this inconsistency, personally I use a script that will
> > > rebuild the Tree when this happens.
> > >
> >
> > Yes, I suspect that tag handling is not as robust as it might be.
> > What does your "script that will rebuild the Tree" actually do?
> >
> > Going on from that can anyone tell me which Tag modification actions
> > write to the database and which write to the image metadata?  ... and
> > why doesn't Digikam always write to both?
> >
> 
> This is the legacy of the project (started in 2001, don't forget).
> 
> Some people want store in both, some other just in database (and never
> touch original image).
> 
> The last one is the default workflow.
> 
> The complexity of the metadata hub (it's called like this in source code)
> is to be able to handle all case with tags, written from DK, outside, from
> another application (welcome interroperabilty), manage all kind of file
> formats, handle XMP side car, must support multi-threading.
> 
> All low level operations are delegate to Exiv2 library.
> 
> For tags, and multiple selection of items with different tags already
> assigned, we need to process a good merging, without lost anything,
> depending of tags list changes.
> 
> The maintenance is also tedious, especially to synchronize DB to image and
> vis-versa.
> 
> So, if you think that "tag handling is not as robust as it might be", well
> you welcome to take the train in source code and to improve it. The game is
> not so simple to manage, if you list all input conditions and all output
> states from the box.
> 
Yes, sorry, I realise it's (very) complex.  Apart from anything else
the lack of standards etc. mean that everything is much more difficult
than it might be.

However it would be really nice to have a simple on/off for where
metadata is written.  E.g. a set of radio buttons in the Digikam
settings as follows:-

    X - Write metadata to database
    X - Write metadata to images
    X - Write metadata to database and images

The complexity of where to write (as in which exif/iptc/xmp fields) a
particular item doesn't really affect the above three possible settings.

-- 
Chris Green
·