[vtk-developers] Widgets within Widgets & vtkHandleWidget

[Andrew Dolgert]

Hi John,

By suggesting different families of widgets, do you think they should be
different subclasses?  Are the geometric and controller families of
widgets different in their interfaces?  Each widget presents a visual
representation of its own kind of data.  Any client object will need to
know which widget it is using and which data it is looking for.  Maybe
all the geometric widgets can present their data as a vtkCell?

You have discerned two good categories which indicate different widget
complexity; how would the different families present more convenient
interfaces to their client objects?

There is a Presentation-Abstraction-Control pattern in "A System of
Patterns" by Buschmann et al. that suggests a way to construct user
interfaces from associations of independent agents.  It's not exactly
what we want to do, but the discussion is good.  One of their
suggestions is to create a separate object for each thing the user can
manipulate.  It also acknowledges that, as Will said, you have to hook
up callbacks to your child controls carefully.  Maybe part of our task
with widgets is to make communication among the child and parent
controls more sure by augmenting the vtkInteractorObserver technique.

- Drew