[KPhotoAlbum] Assigning tags to groups

Johannes Zarl-Zierl johannes at zarl-zierl.at
Tue Dec 17 23:16:02 GMT 2019

Am Montag, 16. Dezember 2019, 13:59:46 CET schrieb Robert Krawitz:
> > I think it's intended that a tag can't only be member of one group, but of
> > multiple ones. E. g. "Esbjerg" can be part of "Denmark" as well as of
> > "Party Locations".

I vaguely remember some discussion how to do it best back in the day when, 
with the result that a DAG (direct acyclic graph) was the most reasonable 
implementation. I.e. it never was a tree.

> > IIRC, the original relationship display was groups on the left and members
> > on the right side, and each tag could/can be a member of each group. I
> > thought a tree view was better, as nested groups were possible but the
> > display could not show them. And thus, I wrote an algorithm translating
> > the parent-child relatinship to a tree view.
> > 
> > That was quite some time ago, so I'm not sure if I implemented it
> > correctly
> > back then (but I hope so!). But imo, definitely, it must be possible for a
> > tag to be member of multiple groups.
> The annotation dialog shows it as a tree.  One can drag and drop tags
> around in that tree, but that's a move, not a copy.  So either way, it
> needs to be consistent.

I guess the simple reason for displaying it as a tree was that a tree was a 
far better and intuitive visualization than the previous one, and Qt did not 
have a widget supporting a DAG.
To be honest, I don't know how a better visualization could even look like.

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