onPaint called continuously on touchscreen

[sm_jamieson]

I have noticed that when I am touching the touchscreen on the module canvas, the onPaint() routine is called continuously (many times a second) even when the touch location is not changing. This does not happen with the mouse when the mouse button is pressed.

I think it might be related to the other issue I noticed when using the fixed mouse multi callbacks, see
http://www.sensomusic.org/forums/viewtopic.php?id=5267

I said this:
> 1. Using the touch screen, I am getting continuous callbacks, up to 8 per bloc, where the touch point has not moved at all, up to
> the maximum precision of "float". These can be filtered out, but it is not very efficient.

Perhaps something about the nature of the touchscreen means that the points are always changing at a very low level, like electrical "noise". But having so many mouse callbacks and calls to onPaint() does not seem correct. I know Usine may call onPaint at any time for its own reasons, but there may be a bug in the touchscreen handling lurking somewhere.