Pitch scale

This is the fist chunk of commits, that fixes the scale jump issue of the pitch knob. 
https://bugs.launchpad.net/mixxx/+bug/1258617
The code is still a bit ugly because it still uses the old pitch adjust CO internally but it works. 
I am working on a solution where we just pass pitch and tempo to the scalers, which will clean up the code.
Yes, you are right, this case is not handled. Can you help fixing it?
I think there is also something wrong with the beat sync in this case.
I have tested with three decks.
* 4. playing fist.
* 3. play and sync lock -> syncs with 4
* stop 3.
* 2. load an press sync
* 2. syncs with 3. even if is is stopped.
This seams to be reasonable from the programmatic point of view, but 
might not be what the user expect.



Am 20.12.2014 um 17:25 schrieb Owen Williams:
>
> In src/engine/keycontrol.cpp 
> <https://github.com/mixxxdj/mixxx/pull/415#discussion-diff-22142353>:
>
> >      double dFileKey = m_pFileKey->get();
> > -    slotFileKeyChanged(dFileKey);
> > +    updateKeyCOs(dFileKey, KeyUtils::powerOf2ToOctaveChange(pitchTweakRatio));
> > +
> > +    //qDebug() << "KeyControl::slotPitchChanged 2" << m_pitchRatio << m_speedSliderPitchRatio;
> >  }
> >
> >  void KeyControl::slotSyncKey(double v) {
>
> oh you're right, it's inherited from engine control, so it should be fine.
>
> Can you add a test to confirm that the same decks are picked in the 
> following case: with two decks, one of which has SYNC_ENABLED, the key 
> should sync to the deck with SYNC_ENABLED. I think that case is not 
> handled right now.
>
> —
> Reply to this email directly or view it on GitHub 
> <https://github.com/mixxxdj/mixxx/pull/415/files#r22142353>.
>