Created attachment 181779 [details]
patch

Been looking into improving the startup time and one thing that slows it down is the loop in `trackChanged`.

When opening Elisa `enqueueRestoredEntries` is called, 
which loops over the playlist items of the last instance to restore them, 
each item is added to `mData` and `newEntryInList` is emitted. 

After some signal/slot jumps we end up in `trackChanged` where we loop over all items of `mData`. 
This causes the startup to increase the more items are in the playlist.

One thing I thougt of is, in `enqueueRestoredEntries` when emitting `newEntryInList` also 
pass the index of item in `mData` so that we get that index in `trackChanged` thus avoiding the loop.
I implemented this in a not-so-nice way and it improves startup by a lot. 

With this change, starting Elisa while restoring a playlist with 9K items 
took 2 seconds vs 15 seconds with the loop, that's the time until the playlist is usable.

I opened this bug report because the code of `trackChanged` is very confusing
and as I don't use Elisa I'm not particularly eager to spend more time on it,
but still wanted to share this in case someone wants to look into this more.