Actually it looks like the problem is overlays. Maybe fingerpaint is rendered by overlay whereas touchspots use GL rendering and Mir's rapidly alternating between the two compositing methods which are never in sync.
Workaround: mir_demo_server_minimal --enable-touchspots --disable-overlays=true &
Actually it looks like the problem is overlays. Maybe fingerpaint is rendered by overlay whereas touchspots use GL rendering and Mir's rapidly alternating between the two compositing methods which are never in sync.
Workaround: mir_demo_ server_ minimal --enable-touchspots --disable- overlays= true &