[vtkusers] Why the baggage in vtkInteractorStyle?

[Elvis Stansvik]

2016-08-09 13:51 GMT+02:00 David Cole <DLRdave at aol.com>:

> I think it's really just for convenience / laziness. It's nice to be
> able to use all the familiar keyboard shortcuts in all your simple
> little test/example VTK apps without having to customize the
> interactor style at all.
>
> It's been that way for a long long time now, and changing it would
> probably be somewhat controversial among some of the long time VTK
> developers.
>
> As with most answers to questions like this, it's just a consequence
> of the organic growth VTK has undergone over time. It probably wasn't
> really **designed** that way intentionally, it probably just sort of
> happened that way, and since it works and there is a way to do what
> you want (override, and implement everything yourself...) then nobody
> has bothered with trying to impose a more sensible design on it after
> the fact.
>

Alright, thanks for clarifying! And sorry for the sort-of pointless
question. I guess I'm so used to the way the top base classes are designed
in e.g. Qt, not imposing any particular behavior.

Elvis


>
> HTH,
> David C.
>
>
>
>
> On Tue, Aug 9, 2016 at 5:47 AM, Elvis Stansvik
> <elvis.stansvik at orexplore.com> wrote:
> > 2016-08-08 15:30 GMT+02:00 Elvis Stansvik <elvis.stansvik at orexplore.com>
> :
> >>
> >> Hi all,
> >>
> >> This is a bit of a general question about the interactor style system in
> >> VTK.
> >>
> >> Why does vtkInteractorStyle, which is described as the superclass of all
> >> interactor styles, have things functions like Dolly, Pan, Zoom et.c.?
> And
> >> why does it have keypress behaviors at all (e.g. 'j', 't', 'c', 'a',
> ...)?
> >
> >
> > I realize now that the docs are a little out of date, and that some of
> the
> > keyboard shortcuts I mention are now handled by vtkInteractorStyleSwitch.
> >
> > But I'm still wondering why vtkInteractorStyle makes so many assumptions
> > about how a subclasser wishes to implement his/her style. I would have
> > expected a more "bare bone" base class.
> >
> > Elvis
> >
> >>
> >>
> >> If it's supposed to be a general base class for interactor styles, why
> >> should it make assumptions like this about the camera movements the
> >> subclasser want to provide, and assumptions about keybindings?
> >>
> >> I'm looking for a base class to use, which is not making any such
> >> assumptions, since I want to provide a completely custom behavior,
> without
> >> having to guard myself against unwanted behavior coming from the base
> class.
> >>
> >> I've looked at, and even used vtkInteractorStyleUser, for this purpose
> >> (even if it's described as something mostly for the scripting
> languages),
> >> but I'm just wondering about the VTK design, why it was made this way?
> >>
> >> Thanks in advance,
> >> Elvis
> >
> >
> >
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