Yes, it is a problem to transfer the focus from the browser (or the page) to the specific component (canvas) needing it.
I remember somebody asked a similar question a while ago, although I don't remember if a solution was given.
You probably need a small startup JavaScript snippet called after the page have been loaded, to set focus on the canvas.

Thanks for your response!    

First hit of a search javascript set focus to canvas
http://stackoverflow.com/questions/56771/how-do-you-set-focus-to-the-html5-canvas-element
The JS line should be outside of the sketch itself: you have to edit the generated HTML to apply the trick.