[vtkusers] problem with vtk3DWidgets and observer order

[Dean Inglis]

Some tests on Proximal.CRU (Intel P4, Win2k, Borland shared build,
CVS as of 11:15 a.m. EST, nVIDIA GeForce4 Ti 4400)

1. start Mace.tcl: joystick mode default, behaves ok
2. 't': behaves ok
3. 'c': behaves ok
4. 'j': crash! The instruction .... referenced memory at ... The memory
could
not be read.

>1. start /VTK/Examples/GUI/Tcl/ProbingWithPlaneWidget.tcl
>2. press 'i' to activate the vtkPlaneWidget
>3. try moving one of the balls at the corner (with left mouse button)
>4. note that the ball does move, but the camera also rotates!

I get the same here.

>5. now press 't' for trackball mode, then 'j' to go back to joystick mode
>6. try moving one of the balls at the corner
>7. note that only the ball moves, not the camera; if you drag the left
mouse
>   button somewhere else though, the camera rotates: this is the desired
>   behaviour with 3DWidgets I would think.

I get the same here. That is the desired behaviour.

>8. now deactivate the vtkPlaneWidget by pressing 'i' and reactivate by
>   pressing 'i' again... we're back to bad behaviour.

I get something weirder: the plane with probe data is still visible.

Dean