[vtkusers] Catching arrow keys in linux

[David Doria]

On Mon, Jan 25, 2010 at 4:18 AM, Liam Kurmos <quantum.leaf at googlemail.com>wrote:

> On Fri, Jan 22, 2010 at 9:17 PM, David Gobbi <david.gobbi at gmail.com>
> wrote:
> > On Fri, Jan 22, 2010 at 2:06 PM, David Doria <daviddoria+vtk at gmail.com<daviddoria%2Bvtk at gmail.com>>
> wrote:
> >> 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
> >
> > Print out the keycode of the mystery key as a hexidecimal value.  My
> > guess is that you're seeing an output from the arrow key in both the
> > OnKeyPress and in OnChar.  The KeyCode values aren't guaranteed to be
> > ascii.
> >
> >   David
>
> off topic, but I found it interesting to learn that sending a
> non-ascii char to cout can cause the <<endl not to function without
> throwing an error.
>
> Liam
>

I can confirm that behavior. That was part of my initial confusion.

Thanks,

David
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