[vtkusers] Catching arrow keys in linux

[David Gobbi]

On Fri, Jan 22, 2010 at 2:06 PM, David Doria <daviddoria+vtk 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>
>> 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>
>> >> 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