[vtkusers] Catching arrow keys in linux

[David Doria]

On Fri, Jan 22, 2010 at 3:47 PM, David Gobbi <david.gobbi at gmail.com> wrote:

> It's failing because you are doing this:
>
>  rwi->GetKeySym() == "Up"
>
> Throw in a strcmp or something.
>
>  - David
>
>
> On Fri, Jan 22, 2010 at 1:36 PM, David Doria <daviddoria+vtk at gmail.com<daviddoria%2Bvtk at gmail.com>>
> wrote:
> > On Fri, Jan 22, 2010 at 3:21 PM, David Gobbi <david.gobbi at gmail.com>
> wrote:
> >>
> >> I'm not sure what #defines you are talking about, but why not use the
> >> interactor "GetKeySym" method to detect arrow keys?  They have the
> >> names "Up", "Down", "Left", "Right".
> >>
> >>    David
> >>
> >>
> >> On Fri, Jan 22, 2010 at 1:18 PM, David Doria <daviddoria+vtk at gmail.com<daviddoria%2Bvtk at gmail.com>
> >
> >> wrote:
> >> > It seems that for win32, there are some #defines for arrow keys like
> >> > VK_RIGHT. I can't seem to find what should be done for non win32 - any
> >> > thoughts?
> >> >
> >> > Thanks,
> >> >
> >> > David
> >>
> >
> > So typically I do this from inside my InteractorStyle subclass:
> >
> >     virtual void OnChar()
> >     {
> >       vtkRenderWindowInteractor *rwi = this->Interactor;
> >
> >       char ch = rwi->GetKeyCode() ;
> >       switch (ch)
> >       {
> >         case 's':
> >           cout << "Pressed s." << endl;
> >           break;
> >         case 'a':
> >           cout << "Pressed a." << endl;
> >           break ;
> >         default:
> >           cout << "Pressed an unhandled key: " << rwi->GetKeyCode() <<
> endl;
> >           break;
> >       }
> > The problem is that OnChar() doesn't fire when the arrow keys are
> pressed. I
> > tried to use
> >     virtual void OnKeyDown()
> >     {
> >       vtkRenderWindowInteractor *rwi = this->Interactor;
> >
> >       if(rwi->GetKeySym() == "Up")
> >       {
> >         cout << "Pressed up." << endl;
> >       }
> >
> >       // forward events
> >       vtkInteractorStyleTrackballCamera::OnKeyDown();
> >     }
> > But it doesn't seem to compare to true. It also doesn't seem to flush the
> > buffer when I would expect?
> > Also, what is the difference between KeyPress and KeyDown? The
> documentation
> > is kind of broken
> > here:
> http://www.vtk.org/doc/nightly/html/classvtkInteractorStyle.html#a65fcd9765c162a6021434386037ca641
> > Thanks,
> >
> > David
>

Yes, that was certainly a bug, but not as confusing as the following
problem.

With these two functions:


    virtual void OnKeyPress()
    {
      vtkRenderWindowInteractor *rwi = this->Interactor;

      std::string key = rwi->GetKeySym();
      if(key.compare("Up") == 0)
        {
        cout << "Pressed up." << endl;
        }

      // forward events
      vtkInteractorStyleTrackballCamera::OnKeyPress();
    }

    virtual void OnChar()
    {
      vtkRenderWindowInteractor *rwi = this->Interactor;

      char ch = rwi->GetKeyCode() ;

      switch (ch)
      {
        case 's':
          cout << "Pressed s." << endl;
          break;
        case 'a':
          cout << "Pressed a." << endl;
          break ;
        default:
          cout << "Pressed an unhandled key: " << ch << endl;
          break;
      }
  // forward events
      vtkInteractorStyleTrackballCamera::OnChar();
    }

The output of pressing:
a, b, up, a

Is:

Pressed a.
Pressed an unhandled key: b
Pressed up.
Pressed an unhandled key: Pressed a.

You can see that there is an "unhandled key" in the mix when there was
actually no unhandled key. There were only 4 keypresses, and 5 outputs.

Thanks,

David
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