Limit number of simultaneous drags

[AppyMike]

What could be improved

Specifically looking at DragCallbacks and the ability to have it so that only 1 (or n) draggable component(s) can be dragged at one time. Think of a chess board and only being allowed to move 1 piece rather than multiple at the same time.

Why should this be improved

This is currently possible to implement by manually keeping track of the current component being dragged and then returning from void onDragUpdate(DragUpdateEvent event). However, I imagine this is something that is implemented quite a lot and so would be nice for flame to handle it internally, making everything simpler.

Any risks?

None that I can forsee. Defaults should be provided to keep the behaviour as it is now and have the feature as "opt-in".

More information

My original question on SO

[spydon]

I think we should create a new dispatcher and new mixin for this, because single drags could be combined with scale events too, which isn't possible in a nice way with the multi-drag dispatcher.