[vtkusers] How does one remove keypress events?

[David Cole]

The keypresses VTK handles by default are documented here:

    http://www.vtk.org/doc/release/5.10/html/classvtkInteractorStyle.html#details

(The 5.10 documentation, since that's the version you said you're using...)

The implementation for handling those keys is in the method
vtkInteractorStyle::OnChar, which is documented here:

    http://www.vtk.org/doc/release/5.10/html/classvtkInteractorStyle.html#a4357cd197cdf5c2d9ff8821cb4a50d82

The event triggering OnChar is the CharEvent, though, not the
KeyPressEvent. Try removing observers for CharEvent instead.


HTH,
David C.

On Fri, Oct 3, 2014 at 9:53 PM, Greg Schussman <greg.schussman at gmail.com> wrote:
> Hi.
>
> I'm having trouble getting rid of default keypress behavior.  I've had
> considerably less luck with the documentation/examples and with google than
> usual.
>
> I'm using python 2.6.8 and vtk-5.10.1.  I've been working from the example
> here:
>
> http://www.vtk.org/Wiki/index.php?title=VTK/Examples/Python/Interaction/MouseEventsObserver
>
> If I run that directly, it works, and hit 'w, it switches to wireframe.  I
> want to disconnect any default key handling so that eventually I can
> substitute my own.  That is, eventually, I want to make 'w' do something
> completely different.
>
> If I edit the end of that example to look like this:
>
> interactor.RemoveObservers('KeyPressEvent')  #  <-- I ADDED THIS
> interactor.RemoveObservers('LeftButtonPressEvent')
> interactor.AddObserver('LeftButtonPressEvent', DummyFunc1, 1.0)
> interactor.AddObserver('LeftButtonPressEvent', DummyFunc2, -1.0)
> interactor.Initialize()
> interactor.Start()
>
> and run again, pressing 'w' still switches to wireframe.   I was hoping that
> by removing all KeyPressEvent observers, the program would no longer respond
> to keypresses.  Why does 'w' still produce a wireframe image, and how do I
> disable 'w' (so I can override it with my own action)?
>
> In trying to debug this, I figured I'd check whether 'KeyPressEvent' really
> is the correct name.  If I go back to the original example code, and change
> the end to look like this:
>
> def keypress(obj, ev):  # <-- I ADDED THIS
>     print "keypress!"      # < -- I ADDED THIS
>
> interactor.AddObserver('KeyPressEvent', keypress)  # <-- I ADDED THIS
> interactor.RemoveObservers('LeftButtonPressEvent')
> interactor.AddObserver('LeftButtonPressEvent', DummyFunc1, 1.0)
> interactor.AddObserver('LeftButtonPressEvent', DummyFunc2, -1.0)
> interactor.Initialize()
> interactor.Start()
>
> then I see "keypress!" every time I press a key.  This tells me that
> 'KeyPressEvent' is the correct name. So I'm baffled.  I think I'm removing
> all 'KeyPressEvent' observers, yet 'w' still switches to wireframe.   What
> am I doing wrong?
>
> Many thanks for any help.
>
> Greg
>
>
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