Does anyone have a clue as to HTML5/JavaScript/Webkit code for an x/y 
trackpad in Android Csound6?

I've been writing a tutorial for HTML5 GUIs for the latest Android Csound6 
apk's, and would like to include an example of a trackpad widget in a 
simulation of the basic built-in Android GUI. (The idea is to enable 
composers to include simple custom performance GUIs in the contest of 
"canonical" Android Csound.)

The natural candidates seem to be input=range or canvas methods, but to this 
point neither has led to a successful result. (Is it perhaps not 
possible/feasible?)

Thanks for any suggestions/code along these lines.