Remove playHeadMarker static reference

[michael2402]

The MapView uses a playHeadMarker.

There is a special case handling for the MarkerLayer class in addLayers().

I would like to:
Step 1:

• Convert the PlayHeadMarker to be a temporary layer
• Remove MapView#playHeadMarker
• Remove PlayHeadMarker#playHead
• Move the whole addMouseListener code to hookUpMapView()

Step 2:
Remove the need for a mouse listener:

• Allow layers and the MapMode to intercept mouse events (MouseListener + MouseMotionListener) by implementing a new interface.

We currently have 12 uses of Main.mapView.addMouseListener. We can replace all of them by this change. This will also prevent us from having layers that do not unregister their events (like NoteLayer)
(no timeframe yet)

[stoecker]

Sounds good to me.

[Don-vip]

+1

[michael2402]

I moved this further back in the pipeline because I don't see a way to do this nicely with the current infrastructure. I don't see a point in simply moving the global reference out of the map view to somewhere else - the current design does not stop the MapView from being used twice.

I would like to wait until we decide on what to do with swing data transfer. If I have enough time for it I'll ad it to the main map view.