Rewrite editor selections to better handle selection and movement logic #2329
It'd be a good idea to go through this in code, rather than looking at the diff, since most of everything besides
The general idea behind this is that we need the masks to handle mouse down events, as they need to handle the drag (mousedown -> drag immediately).
I've rewritten the editor selections to use
Note that the
The general idea here is that we need the masks to handle mouse down events, as they need to handle the drag (mousedown -> drag immediately). I've rewritten the editor selections to use events, as there are some 3 different components that handle/trigger selections in different ways. 1. All selections/deselections now propagate through `HitObjectMask.Select()`/`HitObjectMask.Deselect()`. 2. Components that react to changes in the selection bind to the masks' `Selected`/`Deselected` events, and track them/change their states locally. 3. Masks provide a `SingleSelectionRequested` event which is invoked on the mouse-down event. Various components bind to this event to perform state changes locally in this scenario. 4. `DragBox` now handles all drag input locally. It triggers `Select`/`Deselect` on the masks it needs to. 5. `SelectionBox` handles the display of itself locally. 6. `SelectionBox` handles movement of groups of masks locally. 7. `HitObjectMasks` handles movement of itself locally.