D18601: Rewrite taglib writer to use property interface

[Alexander Stippich]

astippich added inline comments.

INLINE COMMENTS

> bruns wrote in taglibwriter.cpp:70
> So **iff** the rating is updated at the same time as another property, taglib has to adjust some in-memory structure twice. Obviously, for most formats this poses no problem, but for Ape/Vorbis it does?
> 
> Also, this no longer applies when you use the specific tag types for Ape/Ogg.
> 
> Writing to disk only happens when calling `file->save()`...

Not sure I understand. I would like to avoid doing `file->properties();` and `file->setProperties();` twice for those formats for which only the PropertyMap is sufficient, e.g. Ape and Ogg, to avoid doing any unnecessary work.  The beauty of Ape and Ogg in the TagLib implementation is that they solely work with the PropertyMap and do not require any special handling. See D18826 <https://phabricator.kde.org/D18826>, Ape and Ogg do not have any extra codepath at all. For writing tags, we have to be a little bit more careful, though. If writing Rating information is added to writeGenericProperties, for example Id3v2's "TXXX" tags will be polluted with these values.

REPOSITORY
  R286 KFileMetaData

REVISION DETAIL
  https://phabricator.kde.org/D18601

To: astippich, bruns, mgallien, broulik, cfeck
Cc: kde-frameworks-devel, #baloo, domson, ashaposhnikov, michaelh, astippich, spoorun, ngraham, bruns, abrahams
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