[vtkusers] Clearing a vtkImageTracerWidget

[David Doria]

I use a vtkImageTracerWidget to draw a single stroke. When I release
the left mouse button, the stroke stays drawn on the image. Now I want
to delete that stroke (during another event). If I call tracer->Off(),
the stroke disappears, but then at some point I have to turn On() the
tracer to draw another stroke, at which point the stroke reappears! I
can't find a function that will delete all of the strokes for real. I
found the ResetHandles() function and made it public just to test it
out, but it seems the logic more complicated (it crashes sometimes).

Does anyone know how to clear this widget?

Thanks,

David