[vtkusers] vtkSeedWidget -- points always displayed in overlay?

[kent williams]

I was having nothing but trouble trying to get the vtkSeedWidget
going, and I instrumented it so I could quickly try all the
HandleRepresentation types.

What I'd like is for points to display in a 2D viewer, allow all the
normal interactions, and when I change to a different slice, the
handles disappear. When I change back to the slice, the points should
reappear.

What actually happens is this, depending on representation:

1. vtkPointHandleRepresentation2D: Points stuck at one pixel size,
regardless of zoom. Nearly invisible.  They stay visible no matter
what slice you go to.
2. vtkPointHandleRepresentation3D: Nothing shows up in my 2D viewer at all.
3. vtkPolygonalRepresentation3D -- with geometry provided by a
vtkSphereSource: Spheres display, but don't disappear if you change
slices. Points can't be selected, moved, or deleted with the mouse.
4.vtkSphereHandleRepresentation -- pretty much as case #3.

I am using vtkinria3d's vtkViewWidget2D class, and not
vtkImageViewer2, but that shouldn't cause this problem -- I though if
I used 3D, the handles would disappear when i changed slices and
reappear when i went back to the original slice.