Code review comment for lp:~mir-team/mir/touchspot-visualizer

Aren't touchspots just multiple cursors? (and, consquently, if cursors are a renderable, aren't touchspots just renderables too?) This interface seems to be making a distinctions. I'm okay with this approach, given that we don't require compositors to always implement a touch-spot visualization.

Will the DefaultDisplayBufferCompositor or the Scene/SurfaceStack own the TouchVisualizer object?

Oh, and also are we intending USC or unity8 to paint the touch-spots?