Moodbar caching

[Nikhil Marathe]

Hi,

In ref. to bug https://bugs.kde.org/show_bug.cgi?id=260839 and
MoodbarManager implementation
I think the caching approach needs to be redefined. MoodbarManager
aggressively caches even for the
'existence' of a .mood file. Now Nikolaj's commit message from a long
long time ago :)
https://projects.kde.org/projects/extragear/multimedia/amarok/repository/revisions/bc7d0ce3888b2b367489cd9882b5e16c60b53bfe
says the cache should periodically expire.
Now I can't think of any simple or time based caching strategy that
could satisfy every use case.
I am proposing an alternative strategy of 'cache only if .mood exists'.

 Which means that when a .mood file is NOT FOUND:
     the next time a check is requested (hasMoodbar()), we CHECK IF
THE FILE EXISTS by hitting disk.
 When a .mood file IS FOUND:
     we stick it into the cache saying we do have the moodfile

This way, bugs like 260839 get resolved. Before I start implementing
the change, I just
wanted to know what is the worst case scenario. AFAIK this should not
hit the disk more
than once on track changes, and perhaps 10-15 times on initial startup
if the user has enabled moodbar drawing in the playlist view too.
Should we go ahead and reduce the amount of caching?

Regards,
Nikhil