[vtk-developers] 3D Widget changes

[Will Schroeder]

Hi Folks-

After conferring with the design maestro (Ken) and looking your feedback, 
I've reworked the 3D widgets.

One thing we realized is that these family of things have different 
characteristics: while they all listen for events from 
vtkRenderWindowInteractor, some have a representation in 3D space (and 
require an indication of where to be placed), some may not have a 
representation or may be window based (e.g., probing, selection or 
measuring in the window), and vtkInteractorStyles are actually a type of 
these things and should be part of the framework.

We've added a new superclass: vtkInteractorObserver. It has a 
SetInteractor() method. It observes the keypress and delete events invoked 
by the render window interactor. The keypress activation value for a widget 
is now 'i' (although this can be programmed). vtkInteractorObserver has the 
state ivar Enabled. All subclasses must have the SetEnabled(int) method. 
Convenience methods like On(), Off(), EnabledOn(), and EnabledOff() are 
available. The state of the interactor observer is obtained using 
GetEnabled(). The SetEnabled(1) method adds observers to watch the 
interactor (appropriate to the particular interactor observer) ; 
SetEnabled(0) removes the observers . There are two new events: EnableEvent 
and DisableEvent which are invoked by the SetEnabled() method.

Things that require placement in space (with PlaceWidget()) are subclasses 
of vtk3DWidget, which inherits from vtkInteractorObserver. The vtkBoxWidget 
and vtkLineWidget inherit from vtk3DWidget.

Interactor styles will become a subclass of vtkInteractorObserver. They 
should remain backward compatible. We are looking to creating a general 
solution so that the wrapper languages (Tcl, Python. Java) can be cleanly 
interfaced with this stuff.

I still have a list of others things that people suggested, I'll get to 
them soon. Sebastien suggested creating a separate Widgets/ directory. It's 
a good idea, but I want to hold off for a bit to see how all this settles out.

Please give feedback and suggestions. We want to get this right, its going 
to be used pretty heavily in VTK.

Will